Synthetic and Structural Studies of Phenylenes and ...

Synthetic and Structural Studies of Phenylenes and DehydrobenzannulenesbyOgnjen Scepan MiljanicDiploma (University of Belgrade) 2000A dissertation submitted in partial satisfaction of therequirements for the degree ofDoctor of PhilosophyinChemistryin theGRADUATE DIVISIONof theUNIVERSITY OF CALIFORNIA, BERKELEYCommittee in charge:Professor K. Peter C. Vollhardt, ChairProfessor Robert G. BergmanProfessor Ronald GronskyFall 2005

The dissertation of Ognjen Scepan Miljanic is approved:ChairDateDateDateUniversity of California, BerkeleyFall 2005

Synthetic and Structural Studies of Phenylenes and DehydrobenzannulenesCopyright 2005byOgnjen Scepan Miljanic

AbstractSynthetic and Structural Studies of Phenylenes and DehydrobenzannulenesbyOgnjen Scepan MiljanicDoctor of Philosophy in ChemistryUniversity of California, BerkeleyProfessor K. Peter C. Vollhardt, ChairThis dissertation documents the findings on the syntheses of largerdehydrobenzannulenes and [N]phenylenes and the exploration of their physical andchemical properties.Chapter One. This chapter summarizes the previous synthetic work on[N]phenylenes. Their structural, magnetic, and energetic properties, as well as chemicalreactivity are reviewed, and comparisons are made between different phenylenetopologies.Chapter Two. The synthesis of syn-doublebent [5]phenylene is presented.Approaches to three novel phenylenes, U-shaped [7]- and [9]phenylenes and C-shaped[7]phenylene are also discussed.Chapter Three. The topic of this chapter is the development of a novel alkynemetathesis-based route to ortho-dehydrobenzannulenes. Additionally, the application ofmicrowave irradiation to Sonogashira couplings with gaseous propyne is described.Chapter Four. A versatile synthetic route based on a sequence of Sonogashiracouplings is described to access substituted dehydrobenzannulenes. CpCo-mediated1

cycloisomerizations of these materials that produced partially cyclized phenylenes aresummarized.Chapter Five. The finding that dehydrobenzannulenes substituted withsufficiently bulky silyl-groups are conformationally locked at ambient temperatures ispresented. This result inspired the synthesis of the first chiral diphenylacetylene.Variable-temperature NMR studies of both of these systems were undertaken todetermine the corresponding racemization barriers.Chapter Six. The final chapter details the experimental procedures of the studiespresented in Chapters 2–5.2

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Table of ContentsChapter One[N]Phenylenes: a Novel Class of Cyclohexatrienoid Hydrocarbons1.1 Introduction......................................................................................................... 11.2 Preparation of Phenylenes................................................................................... 91.2.1 Early Synthetic Strategies ........................................................................... 91.2.2 Syntheses of New Phenylenes................................................................... 151.2.2.1 Angular and Helical Phenylenes ........................................................... 151.2.2.2 Zigzag Phenylenes ................................................................................ 191.2.2.3 Phenylenes with Mixed Topology: the “Bent” Isomers........................ 221.2.2.4 Branched Phenylenes ............................................................................ 271.2.2.5 Circular Phenylenes .............................................................................. 311.3 Comparative Reactivity of the Phenylenes ....................................................... 341.3.1 Hydrogenation........................................................................................... 341.3.2 Oxacyclopropanation and Cyclopropanation............................................ 371.3.3 [4+2]Cycloadditions.................................................................................. 411.3.4 Flash Vacuum Pyrolysis............................................................................ 461.3.5 Interaction with Organometallic Fragments.............................................. 481.4 Physical Properties of the Phenylenes .............................................................. 521.4.1 Structural Properties.................................................................................. 521.4.2 Magnetic Properties .................................................................................. 631.4.3 Energetic Properties .................................................................................. 671.5 Thesis Summary................................................................................................ 72ii

Chapter FourSynthesis of Octaalkynylated Dehydrobenz[18]annulenes andAttempted Cycloisomerization into Circular [8]Phenylene and Derivatives4.2 Retrosynthetic Analysis of Circular [8]Phenylene.......................................... 1264.3 Previous Attempts to Synthesize Circular [8]Phenylene ................................ 1294.4 Synthesis and Properties of Octaalkynylated Dehydrobenz[18]annulenes 156and 171b–c.................................................................................................................. 1334.5 Attempted Cycloisomerization of 156 and 171b-c into Circular [8]Phenylenes121 and 170b-c............................................................................................................ 1374.6 Properties of Novel Phenylenes ...................................................................... 1424.7 Summary and Future Directions ..................................................................... 143Chapter FiveConsequences of Steric Crowding Around Triple Bonds in Acyclicand Cyclic Systems5.1 Introduction..................................................................................................... 1445.2 Previous Examples of Hindered Rotation in Phenylene Precursors ............... 1495.3 Synthesis and Properties of the First Chiral 2,2’,6,6’-TetrakisalkynylDiphenylacetylene....................................................................................................... 1515.4 Stereochemical Properties of 171c.................................................................. 1545.5 Proposed Mechanism of Interconversion between the Conformers of 171c .. 1595.6 Summary and Future Directions ..................................................................... 174Chapter SixExperimental and Computational Details6.1 General Considerations................................................................................... 175iv

6.2 Experiments and Calculations Related to Chapter 2....................................... 1776.2.1 Calculated Structures of 60 and 118–120 ............................................... 2036.3 Experiments Related to Chapter 3 .................................................................. 2096.3.1 Crystallographic Information for 159 ..................................................... 2266.4 Experiments Related to Chapter 4 .................................................................. 2316.4.1 Calculated Structures of 121, 156, and 191–195 .................................... 2546.5 Experiments Related to Chapter 5 .................................................................. 2766.5.1 Calculated Structures of Transition States for the Inversion of 171c and213–216 ................................................................................................................. 280v

Abbreviations and Acronyms2DASCBTMSABuCpCp*DFTDMFDMADDMDODMSODMTSDMTSAEtethFVPHOMOICIRISCLDAtwo dimensionalalgebraic structure countbis(trimethylsilyl)acetylenebutylcyclopentadienylpentamethylcyclopentadienyldensity functional theorydimethylformamidedimethyl butynedioatedimethyldioxiranedimethylsulfoxidedimethylthexylsilyl(dimethylthexylsilyl)acetyleneethyletheneflash vacuum pyrolysishighest occupied molecular orbitalinternal conversioninfraredintersystem crossinglithium diisopropylamidevi

LUMOMeMMNICSNMRPAHPrPhTBAFTBCTCNETHFTIPSTMSTMSAUVVTlowest unoccupied molecular orbitalmethylmolecular mechanicsnucleus independent chemical shiftnuclear magnetic resonancepolycyclic aromatic hydrocarbonpropylphenyltetrabutylammonium fluoridetribenzocyclynetetracyanoethenetetrahydrofurantrisisopropylsilyltrimethylsilyltrimethylsilylacetyleneultravioletvariable temperaturevii

AcknowledgementsAlmost five years have passed since I set foot on American soil, intent tocommence this adventure that I am now finishing. Looking back at those years, I realizehow different my life has become, and I am enjoying the changes that have occurred.Living and working in a place as diverse, as vibrant, and as intellectually stimulating asBerkeley, brought about a part of these changes. The other, greater, part was precipitatedby the interaction with many amazing people, most of whom I met in Berkeley.The person that undoubtedly deserves to be mentioned first is Professor PeterVollhardt, my doctoral advisor. Only now do I realize how risky was his decision to bringme here, and I sincerely hope that some of that risk paid off. The influence Peter exertedover me was, and still is, tremendous. Always approaching me as an advisor, rather thana boss, he created a relaxed, yet stimulating atmosphere to work in. In such anenvironment, absorbing some of his knowledge, as well as gaining my own, was aseamless process. From him, I learned how to approach things systematically and withscientific rigor. I learned to be open to new ideas and critical of them at the same time. Itis my firm intention to implement many of these principles in my independent career,regardless of the direction in which it develops.The faculty of the Department of Chemistry of the University of California atBerkeley is an impressive collection of outstanding scientists and, simply put, pleasantpeople. Clearly, I did not interact with all of them equally. First among those to be notedis Professor Bob Bergman, whose fair judgment and sound advice helped to keep mycourse straight during the times of doubt. Professors Dirk Trauner and Dean Toste wereviii

of great help in questions of synthetic methods and catalysis (causing me to nicknamethem “walking SciFinders”). Professor Ken Raymond was the first to incite in me acertain level of appreciation for inorganic chemistry (the scope of which I used to limit toNaCl and CsF) and he is the one who placed the doctoral hood on my shoulders. Finally,thanks are due to Professor Jeff Long for a primer of (American) football.The staff scientists in the Department made everyday routine work exactly that –routine. This is often taken for granted, although it certainly shouldn’t be. Trying tocorrect this, I here express my deep gratitude to Kathy Durkin (Graphics Facility), FredHollander and Allen Oliver (X–Ray), Rudi Nunlist and Herman van Halbeek (NMR) andUlla Andersen (Mass Spectral Facility).A university is not a University without students, and Berkeley should certainlybe proud of its share. Several great guys shared my fate of a graduate student in theVollhardt group: Glenn Whitener, Michael Eichberg, Peter Dosa, David Barry, PhilLeonard, Eli Rodriguez, Stephanie Chan, Mitch Garcia, Ken Windler, and Miles Carter. Ikeep Glen and Dave in particularly fond memory, as great friends, drinking partners,roommates (well, just Dave), and crystallographers (just Glenn).Two dedicated undergraduate students, Sang-Yeul Lee and Nicole Plath, workedwith me for several months each. I sincerely hope they learned something and wish themall the very best in their future careers. Renaud Paubelle, Hiu Fung Chu, and NicolasAgenet did not work with me, but were fun to have around nevertheless.As I prepare myself for the carefree life of a postdoc, I cannot but remember someof the postdocs that worked in the Vollhardt group. Yamato Miura and Sangdon Hangave me the know-how on phenylenes, early in my work; Christian Cremer did the sameix

for organometallic chemistry and glove box work. Jürg Lehmann gave me his old TV onone occasion, a present that I enjoyed until very recently. Patrick Betschmann was quite aguide to the clubs of San Francisco. Yong Yu, Tobias Aechtner, Heiko Oertling, andElisa Paredes were good company in many outings, both in Berkeley and in SanFrancisco. Ichiro Hisaki showed me a good time in Japan; I hope I reciprocated inBerkeley. Kaspar Schärer, in whose capable hands I am leaving 640 Latimer, turnedwriting this thesis into a fun, beer-filled, experience.The above classification breaks down when it comes to the people that wereclosest to me. Rebecca Abergel and Dorothea Fiedler, my long-time roommates, wereresponsible for innumerable parties, lasagna dinners, and trips. They made our house on1612 Edith St. my “home away from home”, and I will miss them greatly. The incrediblyeducated Jens Röder opened my eyes in many ways, took me places (I probably shouldn’thave been taken to), watched a million movies with me, and remains a good friend to thisday. Thomas Godet spiced up Jens’ and my life with the constant flow of on-the-edge-ofgood-tastejokes. Alex Shafir drank many a gallon of wine and tea with me, and spentnumerous evenings in heated discussions about science and other things. He also servedas a great liaison between my old Eastern European and new American identities. EmilyDertz and Didier Pomeranc had a taste for alternative music and movies that made mefeel like I was in Belgrade again. Stefan Gradl was that nice guy on your floor youalways wish for. Mircea Dincă kept the Eastern European spirit alive, not the least bysupplying vişinată, Romanian sour-cherry brandy.A number of my other friends, here, back in Belgrade, and around the world,made my stay here even more pleasant through the time I spent with them, their letters,x

emails and phone calls. The space required to mention them all could easily betransformed into another chapter; that’s why I will limit myself to an (incomplete) list:Vladimir Šobajić, Nikola Mihajlović, Dejan Jovanović, Žarko Aćimović, KatarinaVučićević, Mladen Marinković, Peđa Srejić, Ljubodrag Vujisić, Dejan Gođevac, IvanVučković, Milica Počuča, Bojana Rakić, Jens Freese, María Proupín, Noemi Perez,Alejandro Lago, Klara Štefflova, Jan Šmidrkal, Blake Farington, Ol'ga Medvedeva,Adelina Smirnova, Pilar Vizcaíno, Marine Champsaur, Guillermo Rein, José MaríaGonzalez, Tatjana Bolić, Vesna Rodić, Željka Čabrilo, Velimir Mimo Radmilović,Vojislav and Tamara Stamenković, Radu Mihăescu, Ivana Ostojić, Vojislav and GordanaSrdanov, Ivana Veljković, Petar Milošević, Carsten Dosche, Marina Rotanov, AlexKrajete, Alessandro Pinto, Andrea Trave, Adam Shellhorse, Natalya Didenko, and others.Somewhere in the midst of all this, I met a girl with the name of OliviaMăciuceanu. This intelligent, attractive, cheerful, and kind person stood by me eversince. Her company has been a true blessing, and I joyfully look forward to the years tocome by her side.At last, but definitely not least, I need to thank my parents, Šćepan and FatimaMiljanić, and my sister Bojana Miljanić. Their support, sometimes financial, but alwaysmoral, was constant and fierce. Without them, I probably wouldn’t have written thisthesis; and even if I had done it, it would have had no meaning.*This work was sponsored by the National Science Foundation (CHE-0071887)and the Director, Office of Energy Research, Office of Basic Energy Sciences, Chemicalxi

Sciences Division, of the U.S. Department of Energy, under Contract DE-AC03-76SF00098. The Center for New Directions in Organic Synthesis is supported by Bristol-Myers Squibb as a Sponsoring Member and Novartis as a Supporting Member.I also acknowledge gratefully Arnold Schwarzenegger, the governor of the stateof California, for finding the time to carefully read this thesis and sign my doctoraldiploma.xii

VITAJuly 8th, 1978 – Born – Belgrade, Yugoslavia2000 Diploma in Chemistry, University of Belgrade2000–2005 Research/Teaching Assistant, University of California, Berkeley2005 Doctor of Philosophy in Chemistry, University of California, BerkeleyPublicationsFiedler, D.; Miljanić, O. Š.; Welch, E. J. “Dichlorooxo(N,N’,N”-trimethyl-1,4,7-triazacyclononane–κ 3 N)vanadium(IV)” Acta Cryst., Sect. E 2002, E58, m347.Miljanić, O. Š.; Vollhardt, K. P. C.; Whitener, G. D. “An Alkyne Metathesis-BasedRoute to ortho-Dehydrobenzannulenes” Synlett 2003, 29.Dosche, C.; Kumke, M. U.; Ariese, F.; Bader, A. N.; Gooijer, C.; Dosa, P. I.; Han, S.;Miljanić, O. Š.; Vollhardt, K. P. C.; Puchta, R.; van Eikema Hommes, N. J. R.“Shpol’skii Spectroscopy and Vibrational Analysis of [N]Phenylenes” Phys. Chem.Chem. Phys. 2003, 5, 4563.xiii

Bong, D. T.-Y.; Chan, E. W. L.; Diercks, R.; Dosa, P. I.; Haley, M. M.; Matzger, A. J.;Miljanić, O. Š.; Vollhardt, K. P. C.; Bond, A. D.; Teat, S. J.; Stanger, A. “Syntheses ofSyn and Anti Doublebent [5]Phenylene” Org. Lett. 2004, 6, 2249.Kumaraswamy, S.; Jalisatgi, S. S.; Matzger, A. J.; Miljanić, O. Š.; Vollhardt, K. P. C.“Anatomy of a Cyclohexatriene: Chemical Dissection of the π and σ Frame of Angular[3]Phenylene” Angew. Chem., Int. Ed. 2004, 43, 3711; Angew. Chem. 2004, 116, 3797.Dosche, C.; Kumke, M. U.; Löhmannsröben, H.-G.; Ariese, F.; Bader, A. N.; Gooijer, C.;Miljanić, O. Š.; Iwamoto, M.; Vollhardt, K. P. C.; Puchta, R.; van Eikema Hommes; N. J.R. “Deuteration effects on the vibronic structure of the fluorescence spectra and theinternal conversion rates of D 3h [4]phenylene: Α case for excited state π symmetrizationof a cyclohexatriene” Phys. Chem. Chem. Phys. 2004, 6, 5476.Miljanić, O. Š.; Vollhardt, K. P. C. “[N]Phenylenes: a Novel Class of CyclohexatrienoidHydrocarbons”, in Carbon-rich Compounds: From Molecules to Materials (Eds.: Haley,M. M.; Tykwinski, R. R.), Wiley-VCH, Weinheim, 2005, in press.Miljanić, O. Š.; Han, S.; Holmes, D.; Schaller, G. R.; Vollhardt, K. P. C. “HinderedRotation in an “Exploded” Biphenyl” Chem. Commun. 2005, 2606.xiv

Miljanić, O. Š.; Holmes, D.; Vollhardt, K. P. C. “1,3,6,9,12,14,17,20-Octaethynyltetrabenz[a,b,f,j,k,o]-4,5,10,11,15,16,21,22-octadehydro[18]annulene:aCarbon Rich Hydrocarbon” Org. Lett. 2005, 7, in press.Zhu, B.; Miljanić, O. Š.; Vollhardt, K. P. C.; West, M. J. “Synthesis of 2,2’,3,3’-Tetramethyl- and 2,2’,3,3’-Tetra-t-butylfulvalene: Attractive Platforms for DinuclearTransition Metal Fragments, as Exemplified by (η 5 :η 5 -2,2’,3,3’- t Bu 4 C 10 H 4 )M 2 (CO) n (M =Fe, Ru, Os, W). First X-ray Crystal Structures of Fulvalene Diiron and DiosmiumComplexes” Synthesis 2005, submitted.xv

Chapter One[N]Phenylenes: a Novel Class of Cyclohexatrienoid Hydrocarbons 11.1 IntroductionAromaticity is one of the most frequently employed concepts in organicchemistry. 2 Despite the omnipresent use of the term, a unique definition is lacking to thisday. Aromaticity is most commonly viewed through the prisms of structural, 2a,3energetic, 2a,4 and magnetic 2a,5 properties of the systems under study. Structurally,aromatic bond lengths lie between those of normal single and double bonds. Aromaticrings are more stable than their open-chain counterparts, and their unusual magneticcharacteristics are reflected in the specific values of magnetic susceptibilities and 1 HNMR chemical shifts. Experimentalists often use qualitative chemical reactivity asanother measure of aromatic character. A unifying characteristic of aromatic compoundsis the preference for substitution versus addition reactions, which is a manifestation oftheir tendency to retain the π-electronic skeleton. However, attempts to quantify thiseffect have met with limited success. 6 Krygowski and Cyrañski describe aromaticity asan excess property, a deviation from an additive scheme. 3 While there is a certain degreeof correlation between the various criteria given above, 7the issues are sufficientlycomplex to have induced practitioners to treat aromaticity as a “multidimensionalphenomenon”. 7,8Two simple hydrocarbons, benzene and cyclobutadiene, stand at opposite ends ofthe aromaticity continuum, regardless of the criterion chosen. All six C–C bonds in1

enzene are equal in length (1.398 Å), 9 contrasted by the distinctly single (1.526, 1.581Å) and double (1.441, 1.359 Å) bonds in the crystallographically characterizedperalkylated and persilylated cyclobutadienes, respectively. 10 The resonance energies ofthese two compounds are also drastically different: relative to an isolated double bond,benzene is stabilized by 32 kcal mol –1 , cyclobutadiene destabilized by 48 kcal mol –1 . 11The vastly different stabilities of the two molecules are reflected in the fact that benzenehas been known since Faraday’s times, 12 whereas the first isolation of cyclobutadiene (inan argon matrix) was reported only in 1973. 13 This behavior, as well as the correspondingalternating properties of the higher annulenes, 14 is in accord with Hückel’s rule, 15 whichstates that fully conjugated systems with 4n+2 π-electrons should share the stabilizationof benzene, whereas those with 4n π-electrons should not be stabilized by cyclicconjugation.In light of this divergence, the juxtaposition of the benzene and cyclobutadienestructural motifs fused in a single molecule is an intriguing topology. The simplest stablesystem to have such a fusion is biphenylene (1, Figure 1.1), the five resonance forms ofwhich range from “[12]annulenoid” to increasingly “cyclobutadienoid”. Originallyprepared by Lothrop in 1941 by reacting 2,2’-dibromobiphenyl with Cu 2 O at 350 °C, 16biphenylene has since been synthesized in a multitude of ways 17 and is now1Figure 1.1 The resonance forms of biphenylene (1).2

commercially available. 18Most biphenylene syntheses can be classified into threecategories (Scheme 1.1, left): (i) dimerizations of arynes, 17 (ii) oxidative dehalogenationsof 2,2’-dihalobiaryls, 16,17,19 and (iii) small molecule extrusions from bridged biaryls. 17,20Despite the presence of cyclobutadienoid circuits, the chemical reactivity of 1(Scheme 1.1, right) reflects considerable aromatic character: biphenylene undergoeselectrophilic substitution, rather than addition, almost exclusively at the β-positions andat a rate that is comparable to that of naphthalene. 17The four-membered ring isthermolyzed, most likely to the 2,2’-biphenyldiyl diradical, which dimerizes totetrabenzocyclooctatetraene. 21 The aryl–aryl C–C bond in biphenylene is also readilyattacked by a number of metal complexes, and the organometallic intermediates thusobtained can lead to a variety of ring-opened and insertion products. 17,22 Biphenylene isrelatively inert in the Diels-Alder reaction: it does not react with tetracyanoethene, 23benzyne, 24 or maleic anhydride. 17a However, it functions as a dienophile with respect tothe more electron-deficient tetrachloro- and tetrafluorobenzynes, producingmonoadducts. 233

RR = -N=N-, -SO 2 -, -CO-∆∆EAE + [M]BA = NH 2 , B = COOHA = Br, B = Iox.X 4[M]productsX XX = Br, IX = F, ClX 4Scheme 1.1 General modes of biphenylene preparation (left) and reactivity (right).The above reactivity notwithstanding, there are strong indications that thecyclobutadienoid ring has a profound influence on the properties of the system. Thus, acrystal structure 25 highlights the reluctance of 1 to allow conjugation between the twobenzene nuclei, with relatively long aryl–aryl bonds (1.514 Å) and noticeably shorterfused bonds (1.426 Å). Conversely, the six-membered rings are distorted in such afashion as to minimize cyclobutadienoid character in the center, exhibiting pronouncedbond alternation (long bonds 1.426 and 1.423 Å, short bonds 1.372 and 1.385 Å). Inshort, the first resonance form in Figure 1.1 is a strong contributor to the description ofthe molecule. Despite these distortions, the electronic spectrum of 1 26 is distinctivelydifferent from that of biphenyl, with peaks that are strongly shifted bathochromically,signaling a substantial narrowing of the HOMO–LUMO gap. Cross conjugation is alsoevidenced by substituent effects on reactivity and IR absorptions. 17aPerhaps most4

informative, the 1 H NMR spectrum of 1 exhibits relatively shielded resonances at δ =6.60 (α-hydrogens) and 6.70 ppm (β-hydrogens), 27 ascribed to the presence of aparamagnetic ring current in the cyclobutadiene ring. 13 C NMR spectroscopy isdiagnostic of σ-strain effects and reveals peaks at 117.8 (α-carbon), 128.4 (β-carbon) and151.7 ppm (quaternary). 28The cumulative experimental data on 1 are to be viewed within the context ofrecent advances in the understanding of how both σ- and π-effects impinge on thearomaticity of benzene. 29To what extent are these effects operational in 1? Shaik,Hiberty and coworkers have suggested that the D 6h structure of benzene is the result of aσ-π balance: while π-electrons tend to distort the molecule into the D 3h symmetry ofcyclohexatriene, the rigidity of the σ-framework acts to enforce higher symmetry. 30Recently, Schaefer and Schleyer 31showed that, as a general rule, π-distortivityovercomes σ-rigidity in higher annulenes - benzene is thus a fortuitous exception, ratherthan a prototype! In this context, 1 is not readily classified as aromatic, non-, orantiaromatic. Hückel’s rule seemingly does not apply to it 2,32as it would predict acyclically delocalized 12π-electron system to be unstable. In addition, the strain of thefour-membered ring complicates the picture, consequently making 1 an excellent subjecton which to study π- and σ-strain in polycyclic compounds.Biphenylene is the simplest member of a novel class of polycyclic hydrocarbonsin which benzene rings are fused to cyclobutadiene moieties in an alternating manner.The name [N]phenylenes was coined for these molecules, in which N equals the numberof benzene rings. Higher phenylenes exist as several isomers, 33 due to the different modes5

of fusion between the individual rings. A phenylene can be linear, angular, zigzag,branched, or circular, based on the mode of fusion, and mixed topologies are possible.Figure 1.2 exemplifies these designations.(a) (b) (c) (d) (e) (f)Figure 1.2 Simple phenylene topologies: (a) linear [4]–, (b) angular [4]–, (c) zigzag [4]–,(d) branched [4]–, (e) (mixed) bent [4]–, and (f) circular [6]phenylene.The various topologies of the [N]phenylenes offer the opportunity to test thehypotheses advanced for the understanding of 1, significantly expand the range ofavailable strained ring aromatics in a systematic manner, and provide the opportunity toexplore new avenues in the area of electronic materials. For example, appropriate design,as in angularly fused derivatives, should provide compounds in which benzene ringdistortion is enhanced compared to 1. Alternatively, linear fusion would enforce adifferent, bisallylic type deformation, due to symmetry constraints. Moreover, Trinajstićhas suggested that the HOMO–LUMO gap along the linear series should drop rapidly, 34whereas the isomeric zigzag relatives should show much attenuated electronic activation.Apart from the anticipated unusual physical properties, the reactivity of the phenylenes is6

expected to be unique, due to the combination of electronic and ring-strain factors.Synthetically, these structures pose a challenge, in large part due to the presence ofmultiple cyclobutadiene rings, the cumulative ring strain of which (on the order of 50kcal mol –1 per cyclobutadiene ring) 35 seems prohibitive.Phenylenes are closely related to the much larger family of the polycyclicaromatic hydrocarbons (PAHs). The chemistry of PAHs has been studiedcomprehensively with respect to synthesis, 36 theory, 32 and material science. 37 Eachphenylene is correlated to a unique PAH (its “hexagonal squeeze”) 38 by formal removalof the cyclobutadiene cycles through fusion of the attached benzene rings. 39Thistopological connection (Figure 1.3) is general, as it exists in one (linear phenylenes –acenes), two (e.g., circular [6]phenylene sheets – graphite), and three dimensions (e.g.,archimedene – fullerene). There are important differences, however, starting with theincremental change in the number of π-electrons along the respective series. For example,PAHs increase this count in increments of four, thus maintaining their 4n+2 π-character.Phenylenes, on the other hand, are homologated by the addition of a C 6 fragment andaccordingly alternate between (4n+2) and 4n π-electrons. Circular phenylenes preservethe π-electron count of their open counterparts, whereas PAHs lose two electrons in thisformal transformation and switch from 4n+2 to 4n. Finally, both fullerenes 40 and thethree-dimensional phenylenes alternate between 4n+2 and 4n electron count.Gutman associated several theoretical parameters of the phenylenes with those ofthe analogous PAHs. 41 He showed that the algebraic structure count (ASC) 42 ofphenylenes equals the number of Kekulé structures (K) of their hexagonal squeezes. 38ASC and K serve as measures of stability in nonbenzenoid and benzenoid hydrocarbons,7

espectively. 32,43 The stability of phenylenes therefore appears to parallel that of theircorresponding PAHs. The Wiener index, used to predict the boiling points ofhydrocarbons based on their structures, 44 correlates linearly between the two classes. 45 It(a)nn(b)nn(c)(d)Figure 1.3 Phenylenes and topologically related PAHs: a) linear [N]phenylenes andpolyacenes; b) angular/zigzag [N]phenylenes and polyphenanthrenes/helicenes; c)“circular [6]phenylene sheet” and graphite; d) archimedene (C 120 ) and fullerene (C 60 ).8

has been proposed that six-membered rings in phenylenes follow the anti-Clar’s rule: if acertain ring in phenylene is conjugated strongly, its analogue in the hexagonal squeeze isconjugated weakly (i.e. is “empty” in Clar’s terminology) and vice versa. 46 However, aslater Sections will show, this is not a general trend. The list of analogies is not exhaustedhere, 41,46 and future research may reveal new ties between the two classes.This introductory Chapter will describe progress in the synthesis and theexploration of the chemical and physical properties of the phenylenes, in that order. It iswritten with the aim of placing all presently known members of this class ofhydrocarbons, including 1, on some comparative footing. 471.2 Preparation of Phenylenes1.2.1 Early Synthetic Strategies 47Although 1 had been constructed in a variety of ways 17 attempts to extend thesemethods to the synthesis of higher phenylenes either failed 48or were limited.Nevertheless, Barton and coworkers managed to apply the extrusion of nitrogen frombenzodicinnolines by flash vacuum pyrolysis (FVP) (precedented for biphenylene) 20 tothe relatively low-yielding preparation of angular and linear [3]phenylene. 49 Applicationof this technique to the isolation of branched [4]phenylene was unsuccessful, 50 possiblyindicating the limits of this methodology.The breakthrough that enabled the chemistry described in this account camethrough the discovery of a new versatile biphenylene synthesis based on the9

cyclotrimerization of alkynes catalyzed by [CpCo(CO) 2 ]. 51 Thus, a variety of substitutedbiphenylenes could be made by the cocyclization of 1,2-diethynylbenzene (2) withalkynes, in the case of bis(trimethylsilyl)acetylene (BTMSA) yielding 3 in a remarkable96% yield (Scheme 1.2). 52 Exploiting the silyl substituents as masked ethynyl groups andusing tin instead of silicon, as appropriate, 47 gave access to 4 and 6 and, hence, the linearhomologs 5 53 and 7 54 by iterative sequences involving up to three separatecooligomerization steps (for 7). These linear [N]phenylenes were targeted first forsynthesis, because they are distinct from their angular isomers, as this topology (in whichcyclobutadienoid circuits cannot be completely avoided) imparts relative electronicactivation. 552, N = 24, N = 36, N = 4N-2+TMSTMS(i)TMSTMSN-13, N = 25, N = 37, N = 4Scheme 1.2 The last step in the preparation of linear [N]phenylenes 3, 5, and 7 by an(iterative) single cocyclization strategy: N = 2, (i) [CpCo(CO) 2 ], hν, ∆, 96%; N = 3, (i)[CpCo(CO) 2 ], hν, ∆, 36%; N = 4, (i) [CpCo(CO) 2 ], THF, hν, ∆, 9h, 30%, then CO (1atm), 90 °C, 16 h, 100%.The increasingly long linear sequences necessitated by the single cocyclizationapproach were significantly shortened by employing more convergent doublecocyclizations (Scheme 1.3). In this variant, a tetraethynylated arene precursor undergoesbiscycloadditions to generate four rings in a single operation, leading to 9, 53,56 11, 54 and10

13. 57 The power of the transition-metal-based approach is evident, when one recognizesthat eight of the nine rings in 13 are made by [CpCo(CO) 2 ].(a)TMSTMSTMSR(i)RTMS8 9a, R = TMS9b, R = H(ii)RR(b)TMSTMSTMS(i), (ii)TMSTMSTMS10 11TMSTMSTMSTMS(c)TMS12TMS(i), (ii)TMSTMSTMS13TMSScheme 1.3 The last step in the preparation of linear [N]phenylenes 9b, 11, and 13 by adouble cocyclization strategy: (a) N = 3, (i) [CpCo(CO) 2 ], PhCH 3 /DMF, hν, ∆, 6 h, 71%;(ii) t-BuOK, t-BuOH, THF/DMSO, 85 °C, 6 h, 79%; (b) N = 4, (i) [CpCo(CO) 2 ], THF,hν, ∆, 13 h, 30%; (ii) CO (1 atm), 120 °C, 72 h, 99%; (c) N = 5, (i) [CpCo(CO) 2 ], THF,hν, ∆, 16 h, 20%; (ii) CuCl 2 •2H 2 O (4 equiv), 1,2-diethoxyethane, H 2 O/NEt 3 , 0 °C, 3 h,40%.11

The second topology addressed in this early work was the angular frame. Incontrast to their linear counterparts, angular [N]phenylenes possess one, presumablydominant, resonance form that completely avoids double bonds in the four-memberedrings (Scheme 1.4). This simple representation should translate into increased bondlocalization and alkene-like reactivity of the internal nuclei. Retrosynthetically, theprototype angular [3]phenylene (15) can be unraveled by retrocyclization of the terminalor the internal rings (Scheme 1.4a). The former strategy, while successful for derivativesof 15, 58 is not readily extendable to the higher homologs of 15, therefore only the latter isdescribed. This approach is distinct, in as much as it requires an intramolecular alkynecyclotrimerization (a cycloisomerization), initially deemed a dubious propositionconsidering the large amount of ring strain that is generated during the process. In theevent, however, 15 could be made from 14 by [CpCo(CO) 2 ]-mediated cyclization in 30%yield. 59The generality of this transformation was evident with the biphenylenylsubstituted analogs of 14, namely 16 and 18, which isomerized successfully to angular[4]– (17), and [5]phenylene (19), in 30 and 5% yield, respectively. 60Investigations since these early syntheses have brought about a markedimprovement in yields through a stepwise protocol. Thus, exposure of 14 61 or 16 62 to[CpCo(eth) 2 ] 63 at low temperatures gave the correspondingcobaltacyclopentadiene(alkyne) complexes, which, when heated in the presence of aCpCo trap (e.g. 1,3-cyclohexadiene), furnished 15 and 17 in 70 and 51%, respectively.The reasons for these improvements may be the use of stoichiometric cobalt at lowtemperatures which serves to bind all the alkyne units, thus obviating adversepolymerization or other processes, and the subsequent isomerization-demetallation under12

conditions that bind CpCo irreversibly, thus avoiding strained ring opening by cobaltfragments (see Section 1.3.5).(a)(i)14 15(b)(i)16 17(c)(i)18 19Scheme 1.4 Preparation of angular [N]phenylenes 15, 17, and 19: (a) (i) [CpCo(CO) 2 ],hν, ∆, 30% or [CpCo(eth) 2 ], THF, –30 °C, followed by CO (8 atm), 100 °C, 70 %; (b)[CpCo(CO) 2 ], m-xylene, hν, ∆, 30% or [CpCo(eth) 2 ], THF, –25 °C, 16 h, followed by1,3-cyclohexadiene, THF, 100 °C, 2 h, 51 %; (c) [CpCo(CO) 2 ], m-xylene, hν, ∆, 5%.13

The third topology to be targeted early was the branched frame of 21b (Scheme1.5). The central benzene ring of this system was expected to be maximally bondlocalized, perhaps representing the first example of a 1,3,5-cyclohexatriene - a longsoughtexperimental model for the estimation of the resonance energy in benzene. Thepreparation of 21b was achieved via an ambitious triple cocyclization strategy, in which20 64 added three molecules of BMTSA to provide 21a in 39% yield, which could bereadily protodesilylated to the parent 21b. 65The construction of 21a is remarkable,considering the explosive nature of 20, the regioselectivity of the individualcotrimerizations, the fact that six rings are generated in one step, and, again, the strain inthe product.RR(i)RR20 21a, R=TMS21b, R=HR(ii)RScheme 1.5 Preparation of branched [4]phenylene (21b) by triple cocyclization: (i)BTMSA, [CpCo(CO) 2 ], hν, ∆, 39%; (ii) CF 3 COOH, CHCl 3 , 77%.14

1.2.2 Syntheses of New PhenylenesThe previous section summarized the essence of what was known at the time ofthe last review of the subject. 47a Since then, twelve new phenylenes of increasing size andtopological complexity have been prepared. With the exception of the linear series, forayshave been made into the assembly of all types of phenylenes depicted in Figure 1.2. Thefollowing five subsections will describe, in order, the syntheses of angular [5] –[9]phenylene, also dubbed ‘heliphenes”, because of their helical configuration; 66thepreparation of zigzag [4]– and [5]phenylene, through both intra- and intra/intermolecularcyclizations; the construction of three phenylenes with new mixed topologies; newbranched phenylenes; and synthetic efforts towards the (still) elusive class of circularphenylenes.1.2.2.1 Angular and Helical PhenylenesMolecular models indicate that, starting with angular [6]phenylene, the two endsof the angular phenylenes suffer steric interactions that renders them helical, anexpectation that was quantified theoretically. 67 The hexagonal squeezes of these helicalphenylenes (heliphenes) are helicenes, a class of PAHs that has received much scrutiny. 68As described in Section 1.2.1, the key step in the preparation of angular [3]– to[5]phenylene employed a single cobalt-catalyzed cycloisomerization of the respectiveprecursor triynes 14, 16, and 18. Such a strategy was no longer feasible for the higheranalogs, as suitable building blocks based on functionalized angular [3]phenylene15

derivatives are not (yet) readily available. Hence for the higher systems, multiplecycloisomerizations had to be designed using the same building blocks. The alreadyknown angular [5]phenylene (19) was chosen as a testing ground for a double cyclizationscheme (Scheme 1.6). 66 Crucial for the success of the preparation of starting material 24was the discovery that 1,2,3,4-tetrabromobenzene can be selectively alkynylated at the 1-and 4-positions to give 22. 69 Sonogashira coupling of 22 to the previously reported 23 60produced 24a (57%). The deprotected 24b was cyclized to 19 in 33% yield. 66RRBrBr+2R(i)RRR R(iii)1922, R = DMTS23, R = DMTS24a, R = DMTS24b, R = H(ii)Scheme 1.6 Preparation of angular [5]phenylene (19) by double intramolecularcyclization: (i) [PdCl 2 (PPh 3 ) 2 ], CuI, NEt 3 , ∆, 57%; (ii) TBAF, THF, (95%); (iii)[CpCo(CO) 2 ], m-xylene, hν, ∆, 33%.Replacing the terminal benzene substituents in 24b once and twice by biphenylenylgroups, in a manner analogous to that employed in the extension of the synthesis of 15 to17 and 19 (Scheme 1.4), furnished hexaynes 25 and 27, respectively, both of which16

underwent double cycloisomerization to [6]– (26, 12%) and [7]heliphene (28, 8%),respectively (Scheme 1.7). 66 25(a)(i)26(b)(i)2728Scheme 1.7 Preparation of heliphenes 26 and 28 by double intramolecular cyclization:(a) (i) [CpCo(CO) 2 ], m-xylene, hν, ∆, 30 min, 12%; (b) (i) [CpCo(CO) 2 ], m-xylene, hν,∆, 30 min, 8%.With the synthesis of 28, we have reached the limits of the double intramolecularcyclization approach, and access to the next higher homologs required the execution ofeven more ambitious triple cyclizations. The viability of such reactions was tested with28 (Scheme 1.8). 7017

RRI(i), (ii)(iii), (iv)R R29, R = DMTSR R30, R = DMTS31(v)Scheme 1.8 Preparation of helical [7]phenylene (28) by triple intramolecular cyclization:(i) TMSA, [PdCl 2 (PPh 3 ) 2 ], CuI, NEt 3 , 85 °C, 14 h 52%; (ii) K 2 CO 3 , THF/MeOH, 30 min,92%; (iii) 29, [PdCl 2 (PPh 3 ) 2 ], CuI, NEt 3 , 65 °C, 14 h, 41%; (iv) TBAF, THF, 23 °C,(95%); (v) [CpCo(CO) 2 ], m-xylene, hν, ∆, 1 h, 2%.28Thus, starting with tetrayne 29, 66Sonogashira coupling with TMSA and selectivedeprotection provided 30. This alkyne was reacted with another equivalent of 29 and theresulting nonayne completely desilylated to give 31. Cobalt-catalyzed cyclization thenafforded 28 in 2% yield. While this yield is low, the reaction generates nine rings in onestep, including six four-membered rings with an estimated strain of over 300 kcal mol –1 .Having demonstrated the feasibility of triple cycloisomerizations, syntheticschemes were once again developed that replaced the terminal benzene moieties withbiphenylene, giving rise to 32 and 34, respectively. The former then provided 33, thelatter 35 (both in 2% yield; Scheme 1.9). 70 These two compounds represent the largestphenylenes known.18

(a)(i)3233(b)(i)3435Scheme 1.9 Preparation of heliphenes 33 and 35 by triple intramolecular cyclization: (a)(i) [CpCo(CO) 2 ], m-xylene, hν, ∆, 30 min, 2%; (b) (i) [CpCo(CO) 2 ], m-xylene, hν, ∆, 20min, 2%.1.2.2.2 Zigzag PhenylenesThe family of zigzag phenylenes is closely related to the angular isomers, in asmuch as it has the same repeating angular fusion of benzocyclobutadiene units, although“helical strain” is absent. 67 The electronic properties of its members are thus expected tobe fairly similar. These phenylenes are also interesting as models for the one-dimensionalzigzag-phenylene polymer, with properties different from the infinite linear19

[N]phenylene. 71 Finally, both archimedene (Figure 1.2d) 55a,72 73and the octahedral C 48contain zigzag phenylene subunits.The topological analogy between the angular and the zigzag family of phenylenesis reflected in the resemblance of the synthetic strategies to the two classes. The parentzigzag [4]phenylene (38) was approached via 37, a regioisomer of 16 (Scheme 1.4), inwhich the two alkynyl substituents on the biphenylene nucleus have traded places(Scheme 1.10a). Compound 37 was in turn made via a three-step elaboration of 1,2-diiodobiphenylene (36). 60 Cobalt then converted 37 into 38 in 31% yield. 74 An alternativeroute (Scheme 1.10b) constituted the first example of a combination of intra- andintermolecular cyclizations in a single reaction step. It started with tetrabromobenzene39, which was elaborated with 23 (Scheme 1.6), followed by three-fold coupling withTMSA and full deprotection, ultimately giving 41. This pentayne was cocyclized withTMSA and subsequently protodesilylated to afford 38. This method was extended to thesynthesis of the bent [4]phenylenes (Section 1.2.2.3) and could, in principle, be used alsoon a simplified route to angular [4]phenylene (17), a task yet to be tackled.20

(a)II(i), (ii), (iii)3637(iv)38(iv), (v)(b)BrBrBrBr(i)BrBr(ii), (iii)BrR39 40, R = DMTS 41Scheme 1.10 Two syntheses of zigzag [4]phenylene (38): (a) intramolecular approach, (i)23, [PdCl 2 (PPh 3 ) 2 ], CuI, Et 3 N, 23 °C, 15 h; (ii) TMSA, [PdCl 2 (PPh 3 ) 2 ], CuI, Et 3 N, 50 °C,2 d, 62% (over 2 steps); (iii) TBAF, THF, 23 °C, 40 min; (iv) [CpCo(CO) 2 ], m-xylene,hν, ∆, 18 h, 29% (over 2 steps); (b) mixed intra/intermolecular approach, (i) 23,[Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 50 °C, 24 h, 66%; (ii) TMSA, [Pd(PPh 3 ) 2 Cl 2 ], CuI, piperidine,100 °C, 7 d; (iii) TBAF, THF, 33% (over 2 steps); (iv) [CpCo(CO) 2 ], BTMSA, hν, ∆, 10h, 15%; (v) CF 3 CO 2 H/CHCl 3 , 23 °C, 12 h, 74%.21

A variant of the double cycloisomerization route to angular [5]phenylene (Scheme1.6) was used to prepare zigzag [5]phenylene (44, Scheme 1.11). 74 Starting once morewith 39, double alkynylation with 23 assembled tetrayne 42, which was furthersubstituted with TMSA. Removal of all the silyl protecting groups provided 43, aregioisomer of 24b (Scheme 1.6). Compound 43 was then cyclized to 44 in 2% yield. 74R39(i)BrBr(ii), (iii)(iv)R42, R = DMTS 43 44Scheme 1.11 Synthesis of zigzag [5]phenylene (44): (i) 23, [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 23°C, 5 d, 66%; (ii) TMSA, [Pd(PPh 3 ) 2 Cl 2 ], CuI, piperidine, 80 °C, 3 d; (iii) TBAF, THF,23 °C, 2 h, 80% (over 2 steps); (iv) [CpCo(CO) 2 ], m-xylene, hν, ∆, 2 h, 2%.1.2.2.3 Phenylenes with Mixed Topology: the “Bent” IsomersAll the phenylene topologies discussed so far contained only one mode ofrepeating fusion: either linear or angular. The smallest molecule with mixedlinear/angular connectivity is bent [4]phenylene (48, Scheme 1.12), the last [4]phenyleneisomer to be made. 54,60,65,74 This isomer is intriguing, in particular because of the unusual22

nature of the two juxtaposed internal six-membered rings and their surroundings. Itssynthesis entailed application of a regioisomeric variation of the intramolecular approachto 17, through 46 (Scheme 1.12a), formed by reaction of 2,3-diiodobiphenylene (45) 53with 23. Further ethynylation eventually resulted in triyne 47, which was cyclized to 48in 33% yield. 75The 9,10-bis(trimethylsilyl) derivative of 48, 52, was made by thecombination of intramolecular cyclization and cocyclization with BTMSA, precedentedfor 38 (Scheme 1.12b). 74 The starting 1,2,4,5-tetrabromobenzene (49) wasdesymmetrized into 50. A sequence of two Sonogashira couplings, first with 23 and thenwith TMSA, was followed by the full deprotection to give 51. Cyclization proceeded in19% yield, producing 52. 7523

I(i)IIR4546, R = DMTS(a)(ii), (iii)(iv)4847BrBr(i)BrI(ii), (iii), (iv)BrBrBrBr49 5051(b)(v)TMSTMSScheme 1.12 The syntheses of bent [4]phenylenes 48 and 52: (a) (i) 23, [Pd(MeCN) 2 Cl 2 ],CuI, PPh 3 , piperidine, 90 °C, 40 h, 16%, (ii) TMSA, [Pd(PPh 3 ) 2 Cl 2 ], CuI, piperidine, 44h, 93%, (iii) TBAF, THF, 20 min, (95%), (iv) [CpCo(CO) 2 ], m-xylene, hν, ∆, 15 h, 33%;(b) (i) BuLi, Et 2 O, –78 °C, followed by I 2 , Et 2 O, –78 °C, 93%, (ii) 23, [Pd(PPh 3 ) 2 Cl 2 ],5224

CuI, PPh 3 , Et 3 N, 23 °C, 15 h, (iii) TMSA, [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 120 °C, 2.5 d, 29%(over two steps), (iv) TBAF, THF, 2 h, (95%), (v) [CpCo(CO) 2 ], BTMSA, hν, ∆, 16 h,19%.The success of Scheme 1.12 encouraged approaches to the higher homologues of48, anti- (56, Scheme 1.13), and syn-doublebent [5]phenylene (60, Scheme 1.14). Thesesystems would allow an investigation of the effect of increasing bond localization of thetermini of the linear [3]phenylene fragment on the properties of the center piece.Strategically, the approach to both systems was modeled after Schemes 1.6 (for 19) and1.12, utilizing regioisomeric double intramolecular cyclizations.RIBr(i)Br(ii), (iii)(iv)BrIBrR5354 5556Scheme 1.13 The synthesis of anti-doublebent [5]phenylene (56): (i) 23, [Pd(PPh 3 ) 2 Cl 2 ],CuI, Et 3 N, 72%; (ii) TMSA, [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 120 °C, 70%; (iii) TBAF, THF, 2h, (95%); (iv) [CpCo(eth) 2 ], THF, –25 °C, 16 h, followed by 1,3-cyclohexadiene, THF,110 °C, 2 h, 7%.25

The synthesis of anti-doublebent [5]phenylene (56) 76commenced with thetetrahalogenated C 2h -symmetric 53. 77 Another use of the versatile building block 23provided 54. Subsequent coupling with TMSA and deprotection afforded 55. Thecyclization failed initially when attempted with [CpCo(CO) 2 ] as the catalyst, but waslater rendered successful by the application of the milder [CpCo(eth) 2 ] conditions. 76 In ananalogous (but slightly altered) manner, the synthesis of 60 (Scheme 1.14) started with1,3-dibromo-4,6-diiodobenzene (57) 78 as a C 2v -symmetric template. Reaction with TMSAand deprotection gave 1,3-dibromo-4,6-diethynylbenzene. Another Sonogashira coupling,this time with 1-bromo-2-iodobenzene, provided the tetrabrominated 58. This materialunderwent a four-fold exchange of bromides with TMSA and, after fluoride-assisteddeprotection, yielded hexayne 59. The cyclization to 60 proceeded smoothly under theconditions of [CpCo(eth) 2 ] catalysis.BrIBr(i), (ii), (iii)Br(iv), (v)(vi)IBrBrBr5758 5960Scheme 1.14 The synthesis of syn-doublebent [5]phenylene (60): (i) TMSA,[Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 23 °C, 2 h, 96%; (ii) KOH, Et 2 O/EtOH, (iii) 1-bromo-2-iodobenzene, [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 120 °C, 44% (over 2 steps); (iv) TMSA,26

[Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 120 °C, 47%; (v) TBAF, THF, 2 h, (95%); (vi) [CpCo(eth) 2 ],THF, –25 °C, 16 h, followed by 1,3-cyclohexadiene, THF, 110 °C, 2 h, 14%.1.2.2.4 Branched PhenylenesTwo other types of mixed topology are the branched/linear and branched/angularmotifs. To what extent can the bond localization of the central cyclohexatriene in thebranched [4]phenylene (21b) be manipulated by additional fusions? One might expectlinear fusion to increase it, whereas angular fusion should effect the opposite. To validatethis expectation, branched [5]phenylene 64b (Scheme 1.15), C 3h -symmetric branched 66(Scheme 1.16), and its D 3h -symmetric isomer 71 (Scheme 1.17) were constructed.The preparation of 64b relied on a modification of the iterative cocyclizationstrategy to linear [N]phenylenes (Section 1.2.1). 79 Thus, diyne 61 65 was cocyclized withbis(trisisopropylsilyl)-1,3,5-hexatriyne (62). 57The resulting 63 was deprotected andsubjected to a second cocyclization, this time with BTMSA, providing the Y-shaped 64ain 33% yield (over 2 steps). Acid-catalyzed removal of the silyl groups produced theparent branched [5]phenylene (64b, Scheme 1.15). 7927

TIPSTIPS(i)TIPSTIPS6162 63(ii), (iii)RR64a, R = TMS64b, R = H(iv)Scheme 1.15 The synthesis of branched [5]phenylene (64b): (i) [CpCo(CO) 2 ], PhCH 3 ,hν, ∆, 16 h, 32%; (ii) TBAF, THF, 23 °C, 2 h, (95%), (iii) BTMSA, [CpCo(CO) 2 ], THF,hν, ∆, 16 h, 33%; (iv) CF 3 CO 2 H, CH 2 Cl 2 , 23 °C, 16 h, 65%.The synthesis of C 3h -symmetric branched 66 (Scheme 1.16) represents anextension of Scheme 1.16. It starts with hexaethynylbenzene (20), 64which wascocyclized with 62 in 38% yield. The resulting hexaalkynyl substituted 65a was treatedwith TBAF to afford 65b. This material was cocyclized with BTMSA in 37% yield (over2 steps), producing the C 3 -symmetric hexakis(trimethylsilyl)[7]phenylene (66). 7928

RR20(i)RRRR65a, R = TIPS65b, R = H(ii)(iii)TMSTMSTMSTMS66TMSTMSScheme 1.16 The synthesis of C 3h -symmetric branched 66: (i) 62 (7 equiv),[CpCo(CO) 2 ], PhCH 3 , hν, ∆, 16 h, 38%; (ii) TBAF, THF, 23 °C, 30 min, (95%); (iii)BTMSA, [CpCo(CO) 2 ], THF, hν, ∆, 16 h, 37%.For the preparation of 71 (Scheme 1.17), a strategy was necessary thatdesymmetrized the sixfold symmetry of 20 to allow for the generation of angular fusion.It started with trialdehyde 67, 80 which was coupled with TMSA in 97% yield, to give 68.A Corey-Fuchs dibromoolefination, followed by treatment with LDA provided the29

hexayne 69. The remaining three benzene rings of 70 were introduced by reacting 69with 1-iodo-2-(TMSethynyl)benzene. 81 Base-catalyzed removal of all six TMS groupswas followed by threefold [CpCo(CO) 2 ]-mediated cycloisomerization to 71 (2% yield). 82TMSTMSOBrHOHHO(i)HO(ii), (iii), (iv)BrOHBrTMS TMS TMSTMSO H67 68 69(v)TMS TMS(vi), (vii)TMSTMSTMS TMS7170Scheme 1.17 The synthesis of 71: (i) TMSA, [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, THF, 97%; (ii)CBr 4 , Zn, PPh 3 , CH 2 Cl 2 , 99%; (iii) LDA, THF, –78 °C; (iv) aq. NH 4 Cl, 95% (over 2steps); (v) 1-iodo-2-(TMSethynyl)benzene, [Pd(PPh 3 ) 2 Cl 2 ], CuI, i-Pr 2 NH, THF, 77%; (vi)K 2 CO 3 , MeOH/THF, 61%; (vii) [CpCo(CO) 2 ], m-xylene, hν, ∆, 1.2%.Compound 71 has the distinction of representing the largest synthesized subunit of the“Archimedean solid” archimedene (C 120 , Figure 1.2d). 55,72 The successful conversion of30

the nonayne precursor to 71 provides a valuable additional example of a tripleintramolecular cyclization, differing topologically from those employed on route to 28,33, and 35 by the fact that six (of nine) reacting triple bonds reside on a single benzenering.1.2.2.5 Circular PhenylenesCircular phenylenes have the distinguishing characteristic of a resonance picturethat includes forms that encompass both the inner and outer peripheral loops, aphenomenon described as superdelocalization. 83This class of phenylenes remainselusive. 69,84 The simplest member of this series that does not suffer from additional“circular” strain is [6]phenylene 77d (Scheme 1.18), also christened antikekulene 59 tohighlight its relationship to kekulene, its all-benzenoid relative with an equal number ofrings. 85 In antikekulene, avoidance of (benzo)cyclobutadienoid local circuits is expectedto enhance the contribution of the potentially superdelocalized resonance form depictedfor the structure in Scheme 1.18, albeit with the added and destabilizing feature that bothinside and outside peripheries contain a 4n electron count.An oligoalkyne polycyclization route to any circular phenylene is conceptuallydifferent from those developed for the other topologies, as it requires the elaboration of asuitably functionalized dehydrobenzannulene, a significant synthetic enterprise in its ownright. This is witnessed by the fact that even the preparation of the parentdehydrobenz[12]annulene (also known as tribenzocyclyne, TBC) remains a challengingtask, 84b,86 almost forty years after its original synthesis by Staab and Graf. 87 In the case of31

77d, the appropriate tribenzocyclyne is 74d (Scheme 1.18). Its synthesis commencedwith 39, which was manipulated into bromide 72a. Bromine–iodine exchange, followedRRR RTMS39(i), (ii)Br(iii), (iv)I(v), (vi)RRR72a, R = DMTS72b, R = CH 2 C 6 H 1172c, R = PrR73a, R = DMTS73b, R = CH 2 C 6 H 1173c, R = PrR R74a, R = DMTS74b, R = CH 2 C 6 H 11 (vii)74c, R = Pr74d, R = H(viii)RRRRRRRRRR(ix)RRRRRRR R77b, R = CH 2 C 6 H 1177c, R = Pr77d, R = H76b, R = CH 2 C 6 H 1176c, R = Pr76d, R = H75b, R = CH 2 C 6 H 1175c, R = Pr75d, R = HScheme 1.18 Attempted syntheses of circular [6]phenylenes 77b–d: (i) RC≡CH,[Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 23–60 °C, 3 d, 80% (72a), 58% (72b), 51% (72c); (ii) TMSA,[Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 100 °C, 4 h–2.5 d, 49% (72a), 31% (72b), 27% (72c); (iii)BuLi, Et 2 O, –78 °C, 30 min; (iv) I 2 , Et 2 O, from –78 °C to 23 °C; (v) K 2 CO 3 , CH 3 OH, 1 h,91% (73a), 86% (73b), 73% (73c); (vi) CuCl, NH 4 OH, EtOH, 1 h, followed by pyridine,∆, 6 h, 20% (74a), 36% (74b), 32 % (74c); (vii) TBAF, THF, CH 3 CN, 5 h, 95%; (viii)32

[CpCo(CO) 2 ], m-xylene, hν, ∆, 20 min, 45% (75b), 14% (75c), 0% (75d); (ix)[CpCo(CO) 2 ], 1,2,4-trichlorobenzene, hv, ∆, 20 min, 40% (76b), 14% (76c).by TMS group removal delivered 73a in 91% overall yield. Attempted cyclocouplingunder Sonogashira conditions was complicated by irreproducibility. Switching to theStephens-Castro reaction gave better results, and cyclyne 74a emerged in 20% yield.Deprotection with TBAF gave 74d in 95% yield. 69Compound 74d is the largestsynthesized substructure of the novel carbon allotrope 88 graphyne 89 and organizes into aremarkable supramolecular framework in the crystal. 84aUnfortunately, attempted threefold cobalt-mediated cyclization of 74d gave onlyinsoluble dark brown materials. Suspecting that the insolubility of intermediates or 77ditself might be the problem, the cyclohexylmethyl- and propyl-substituted materials wereprepared (74b and 74c, respectively; Scheme 1.18). Application of standard cyclizationconditions to these derivatives furnished the singly cyclized 75b and c, respectively.Resubjecting these materials to the reaction conditions in the higher-boiling 1,2,4-trichlorobenzene afforded the products of the double cyclization 76b and c, respectively.Despite extensive efforts, the third cyclization did not take place even in sulfolane(reaction temperature ~ 200 °C). This result is puzzling, especially in view of the readymetallacycle formation from triyne 14 and [CpCo(eth) 2 ]. 61 A possible explanation mightbe the increasing distance between the reacting triple bonds along the series 74b–75b–76b (all of which were crystallographically characterized). The notion that the problemsof the final cyclization are kinetic in nature is supported by the finding that the33

conversion of 76d into 77d is calculated to be exothermic by –45.50 kcal mol –1(B3LYP/6–31G*). 69To summarize this section, to date nineteen phenylenes have yielded to synthesis.They can be divided broadly into 5 families (# of examples): linear (3), angular/helical(7), zigzag (2), bent (3), and branched (4). Their topologies have been accessed through26 different routes, 15 of which involved in the crucial step an all-intramolecular cobaltcatalyzedcyclization, nine used intermolecular variants, and two a combination of thetwo strategies.1.3 Comparative Reactivity of the PhenylenesThe presence of strained cyclobutadiene moieties 35 and cyclohexatrienoid ringsrenders the phenylenes susceptible to various reactions. Thus, hydrogenation, metalcomplexation, ring openings, and cycloadditions are all feasible. Early work focused onthe chemistry of linear [3]– 53,90 and branched [4]phenylene 65,91 and has been reviewed. 47aThe following sections will concentrate on selected recent examples featuring thecomparative reactivity of angularly fused cyclohexatrienoid rings.1.3.1 HydrogenationWith the caveat of the mechanistic complexities of heterogenous catalytichydrogenations, 92 the relative ease of hydrogenation of the cyclohexatrienoid rings in the34

phenylenes (Scheme 1.19) can be used as a qualitative measure of reactivity. Thus, while9b 53 and 21b 91 could be hydrogenated readily (Pd/C, 1 atm H 2 ), 15 required morestringent conditions (Pd/C, 10 atm H 2 ), 59 and 1 was inert or underwent hydrogenolyticfour-membered ring opening. 17a(a)9b(i)HHHH78(b)15(i)HHH H79(c)21b(i)HHHHH H80Scheme 1.19 Hydrogenation of phenylenes 9b, 15, and 21b: (a) (i) Pd/C, H 2 (1 atm),THF, 23 °C, 3 h, 74%; (b) (i) Pd/C, H 2 (10 atm), THF, 23 °C, 99%; (c) (i) Pd/C, H 2 (1atm), THF, 23 °C, 18 h, 87%.Preliminary observations thus suggested a reactivity order of 9b ≥ 21b > 15 > 1. Theambiguities in the kinetics notwithstanding, thermodynamic measurements clearly pointto the fact that the central ring in 21b is more cyclohexatrienic than that in 15. Thus, themeasured heats of hydrogenation, corrected for the strain present in the respective all-cis-35

hexahydroderivatives 80 and 79 (Scheme 1.19), are –(83.0 to 84.2) kcal mol –1 and –(68.1to 73.6) kcal mol –1 , respectively, revealing that the central ring in 15 enjoys moreresonance stabilization than that in 21b by at least ~ 10 kcal mol –1 . Perhaps even moreinterestingly, the corrected ∆H hyd of 21b is remarkably close to that estimated for threecyclohexene double bonds (–84.8 kcal mol –1 ), suggesting that the central ring is a truecyclohexatriene, possibly devoid of any resonance interaction between the π bonds. Sucha picture has also been painted employing other methods. 93 Finally, the estimated ∆H hydof biphenylene (1), corrected for strain in the product, using a similar approach to thatdescribed for 15 and 21b, has a value of –64.8 kcal mol –1 , attesting to its expectedattenuated activation relative to the other two phenylenes, although still featuring benzenerings that are less aromatic than benzene itself (∆H hyd = –49.1 kcal mol –1 ). 35The relatively higher reactivity of 9b compared to 15 made the hydrogenation ofbent [4]phenylene (48) an interesting proposition: which one of the two internal rings isthe more reactive? On the basis of simple resonance arguments, the fusion of anadditional benzocyclobutadiene fragment should stabilize the linear and destabilize theangular component of 48, and thus possibly invert the reactivity order observed for theparents 9b and 15. Because 48 was not available in sufficient quantities, the problem wasaddressed with its bis(trimethylsilyl) derivative 52 (Scheme 1.20). 75 Upon subjecting 52to the reaction conditions previously used on 9b and 21b (Pd/C, 1 atm H 2 ), the B ringwas hydrogenated cleanly to give 81. This result was clearly in consonance withexpectation, even though the effect of the presence of the remote silyl groups in 52 mayhave contributed to its outcome. More experimentation is in order to corroborate thesefindings.36

TMSTMSD C BA(i)TMSTMSH HHH5281Scheme 1.20 The hydrogenation of 52: (i) H 2 (1 atm), Pd/C, Et 2 O, 10 min, 44%.In syn-doublebent [5]phenylene (60), the central linear moiety is stabilized evenfurther compared to 48, due to the presence of two angular fusions. The angularcomponents, in turn, are still destabilized compared to the parent 15, but to a lesser extentthan in 48 (since they “share” the destabilization caused by the linear fusion). An overalldecrease in reactivity of all rings, relative to 48 (or 52) is thus expected. Preliminaryresults confirm this prediction, since, in contrast to 52, 60 remains inert to hydrogenation(Pd/C, 1 atm H 2 , 2 h). 94 Similarly, dipropyl substituted zigzag [5]phenylene resistedhydrogenation even at increased pressures (Pd/C, 12.2 atm H 2 ), 74 in agreement with thenotion that extension of the angular/zigzag phenylene frame causes an (at least initial)decrease in cyclohexatrienoid character of the internal rings. 47a,601.3.2 Oxacyclopropanation and CyclopropanationIn light of the difficulty to attach meaning to the relative kinetic reactivities of thephenylenes in catalytic hydrogenations, it would be instructive to inspect their directreactions with electrophilic species capable of attacking the activated six-memberedrings. Indeed, and further corroborating the cyclohexatrienic character of the phenylenes,37

it was possible to effect oxacyclopropanations of 1, 15, and 21b. Usingdimethyldioxirane (DMDO) 95 as the oxidant, biphenylene (1) was converted sluggishlyinto the corresponding trisoxacyclopropane 82 (Scheme 1.21a). Its stereochemistry wasO(a)1(i)OO82RRRRTMSTMSOO(b)(i)(ii)OOORRRRTMSTMS15, R = H83, R = TMS84a, R = H84b, R = TMS85(c)21b(i)OOO86Scheme 1.21 Oxacyclopropanation of 1, 9b, 83, and 21b: (a) (i) DMDO, acetone, 23 °C,24 h, 30%; (b) (i) for 9b: DMDO, acetone, 23 °C, 30 min, (100%), for 83: DMDO,acetone, 23 °C, 1 h, (100%); (ii) for 84b only: DMDO, acetone, 23 °C, 6 h, 26%; (c) (i)DMDO, acetone, 23 °C, 84%.38

assigned as trans on mechanistic grounds; however, a cis-geometry would also beconsistent with the spectral data. 96 In contrast to the slow conversion of 1, angular[3]phenylene (15) was oxidized comparatively quickly under these conditions, but only tothe moisture-sensitive (and hence difficult to completely characterize)bisoxacyclopropane 84a (Scheme 1.21b). Switching to tetrakis(trimethylsilylated) 83provided the more stable 84b, the connectivity of which could be proven by NMRspectroscopy. Only on renewed oxidation of this compound was the trisoxacyclopropane85 obtained in 26% yield. 97 In the latter, the asymmetry of the trans,trans,cis-arrangementmanifests itself diagnostically in the 1 H NMR spectrum. This stereochemical assignmentalso corroborates the proposed trans-geometries of 84a and b, for which NMR data werenot definitive, 97 and possibly provides further support for the proposed structure of 82.Finally, and to complete the series, 21b underwent complete, but now all-cis,oxacyclopropanation to 86 during the course of just one hour (84% yield; Scheme1.21c). 91 Its structure was ascertained by an X-ray crystallographic analysis (Figure 1.4).The different stereochemical outcome of the oxidations of 1 and 15 compared to21b may be a consequence of the unique all-benzofusion in 86, resulting in significantsteric hindrance to trans attack due to the outside rings, even after the firstoxacyclopropanation and pronouncedly so after the second.39

Figure 1.4 X-ray crystal structure of 86 (thermal ellipsoids are shown at 50%probability).Compared to the results of the above oxidations, the picture is less clear for thetopologically seemingly analogous cyclopropanations. Thus, 1 transforms in the presenceof ethyl diazocarboxylate to 88 only at elevated temperature (Scheme 1.22a), presumablythrough intermediate adduct 87. 17a,98 On the other hand, while angular [3]phenylene (15)was inert to modified Simmons-Smith conditions (Et 2 Zn, PhCH 3 , 60 °C), 97,99 branched21a,b responded to this reagent by providing the triscyclopropanated 89a and b inexcellent yields (Scheme 1.22b). 91 In analogy to the trisoxacyclopropanation of 21b(Scheme 1.21c), carbene addition occurs all-cis, as rigorously ascertained by an X-raycrystal structure of 89a.40

(a)1(i)COOEtCOOEt8788RR(b)21a,b(i)RRRR89a, R = TMS89b, R = HScheme 1.22 Cyclopropanation of 1, 21a, and 21b: (a) (i) ethyl diazoacetate(N 2 CHCOOEt), 165 °C, 15%; (b) (i) Et 2 Zn, PhCH 3 , 60 °C, 78% (89a), 97% (89b).1.3.3 [4+2]CycloadditionsAnother measure of the degree of diene character of phenylenes is their relativesusceptibility to undergo [4+2]cycloadditions. Such reactions would lead to highlystrained products, which might be expected to be labile. In addition, cycloadditionsshould be regiocontrolled by the desire to avoid ensuing cyclobutadienoid circuits. In thisrespect, singlet oxygen 100 has proven to be an interesting dienophile. For example, theoxidation of 1 with this species (Scheme 1.23a) 96 was proposed to generate intermediateendoperoxide 90, which underwent ring-opening to 91, followed by a series of skeletalrearrangement and an ene-reaction with the reagent, ultimately giving hemiacetalhydroperoxide 92 in 56% yield. Tetrasilylated linear [3]phenylene (9a) reacted withatmospheric oxygen through an analogous endoperoxidation-ring opening sequence41

giving the diketone 94. Interestingly, no irradiation, or added sensitizer were required forthis reaction to proceed; it has been proposed that phenylenes themselves act assensitizers for oxygen. 101 Unlike the related 91, this compound could be isolated andcharacterized (along with its E-isomer). 101 In both cases, the regioalternative mode ofinitial cycloaddition, which would have generated one (for 1) or two (for 9a)benzocyclobutadiene subunits, was avoided.(a)1(i)OOOOHOOOOH909192O(b)9a(i)TMSTMSOOTMSTMSTMSTMSOTMSTMS9394Scheme 1.23 Reactions of 1 and 9a with singlet oxygen: (a) (i) O 2 ,tetraphenylporphyrine, hν, acetone, –40 °C, 5 d, 56%; (b) (i) O 2 , hν, C 6 H 6 , 23 °C, 1–2 h,80% (Z:E = 3:1, by NMR).On the basis of the above results, analogous endoperoxidation of the angular 15was expected to be even more facile, as the subsequent skeletal rearrangement shouldallow the opening of both four-membered rings. This expectation was confirmed by thereaction of 15 with singlet oxygen (now requiring irradiation in the presence of asensitizer), which produced Z-dione 96 in 70% yield (Scheme 1.24a). 97The42

corresponding conversion of dipropyl-substituted zigzag [5]phenylene 97 (again withoutadded sensitizer; Scheme 1.24b) provided 98, the structure of which was confirmedO(a)15(i)O OO9596Pr Pr Pr PrO O(b)(i)9798Scheme 1.24 Reactions of 15 and 97 with singlet oxygen: (a) (i) O 2 , methylene blue, hν,CH 2 Cl 2 , 23 °C, 70%; (b) (i) O 2 , 23 °C, 12 h, 9%.crystallographically (Figure 1.5). 74 Unfortunately, no data are available that would allowfor an estimate of the relative reactivity of 1, 9a, 15, and 97. However, it is interesting tonote that the branched 21b, although containing the most highly cyclohexatrienic ring,was recovered unchanged under these conditions. The reason must be that there is nopathway available that does not generate a benzocyclobutadiene derivative.43

Figure 1.5 X-ray crystal structure of 98 (thermal ellipsoids are shown at 50%probability).Considering the success of singlet oxygen cycloadditions, it seemed logical toextend this chemistry to carbon-based dienophiles. Indeed, biphenylene, while generallyinert, even in the presence of o-benzyne, transforms to isolated Diels-Alder adducts withmore reactive benzyne derivatives (Scheme 1.1). 17a,23,24 Angular phenylene 15 appears tobe more reactive, as expected, but undergoes further rearrangements driven by the releaseof ring strain in the cycloadducts. 97 Thus, on exposure to tetracyanoethene (TCNE), 15formed a green charge-transfer complex, which, on heating, resulted in thedibenzodehydro[10]annulene 99 (Scheme 1.25a). Mechanistically, this transformationcan be envisaged to proceed by a process similar to that leading to 96, except that doublebond isomerization has occurred (possibly during work-up).44

(a)(b)CNNC(i)15(i)CO 2 MeCO 2 MeNCCNCO 2 MeCO 2 Me99100101Scheme 1.25 Cycloaddition reactions of 15: (a) (i) TCNE (1 equiv), CH 3 CN, ∆, 8 h,78%; (b) (i) DMAD (1.6 equiv), AlCl 3 (1 equiv), PhCH 3 , 23 °C, 1 h, 74%.Remarkably, changing the dienophile to the alkyne dimethyl butynedioate (DMAD),activated by added AlCl 3 , did not alter the course of the reaction, even though a highlystrained product is generated via 100 in the form of 101 (Scheme 1.25b). Theextraordinary structure of 101, the most distorted fully unsaturated [6]paracyclophane,was confirmed by X-ray crystallography (Figure 1.6). 97In contrast, and again asexpected, branched 21b was unreactive to these reagents, with the exception of TCNE,which produced a charge-transfer complex.Figure 1.6 X-ray crystal structure of 101 (thermal ellipsoids are shown at 50%probability).45

1.3.4 Flash Vacuum PyrolysisThe remarkable ring opening reactions in the preceding section herald thephenylenes as “loaded springs”, not surprising in light of their ring strain and hence highheat of formation (Section 1.3.1). One might therefore anticipate that, much like otherstrained hydrocarbons, 102 they would enter isomerization manifolds, ultimately ending inPAHs as thermodynamic minima. Indeed, under flash-vacuum pyrolysis (FVP)conditions, 1 had been shown to isomerize to acenaphtylene (104) as the major (Scheme1.26a) and transient as-indacene (103) as a minor product, the existence of the latterinferred through the isolation of a Diels-Alder adduct to 104 (Scheme 1.26a). 103 Isomers103 and 104 are derived from a common intermediate, benzopentalene 102, in thiscascade, which is generated by a sequential hydrogen shift/ring contraction from 1, asindicated summarily in its structural drawing. A second such process leads to 103.Acenaphthylene (104), in turn, is the result of a vinylidene carbenedeinsertion/reinsertion sequence from benzopentalene (wavy lines). 104These resultsprompted an investigation of the behavior of the two isomeric [3]phenylenes 9b and 15under these conditions. Aside from probing the kinds of PAHs that might be formed, itwas of interest to see whether the two compounds would interconvert prior to furtherconversion, a possibility that, if realized, would shed experimental light on their relativestability, a much debated issue. 34,55 Recent calculations suggest that 15 is slightly morestable than 9b. 5546

(a)H(i)+HHH1102103 104(b) 9b(i)105 (10 %) 106 (4 %) 107 (1 %) 108 (1 %) 15 (1 %)(c) 15(i)105 (24 %) 106 (11 %) 107 (3 %) 108 (7 %)Scheme 1.26 FVP of 1, 9b, and 15: (a) (i) 900 °C, vacuum, 45% (104), 55% (adduct of103 to 104); (b) (i) 1000 °C, 5x10 –7 Torr; (c) (i) 1000 °C, 5x10 –7 Torr.In fact, 9b 105 and 15 105,106 gave not only the same mixture of PAHs on FVP, butthe linear isomer could be shown to isomerize to its angular relative at 1000 °C (Scheme1.26b and c). A mechanism for this isomerization is patterned after a relatedisomerization in the literature 107 and proposes a four-membered ring opening, followedby hydrogen shifts in the resulting biradical and ring closure. 13 C-Labeling experimentsnarrowed considerably the number of mechanistic pathways leading to the PAHs. Details,too lengthy to be presented here, are reported in the original publication, 105 and allsuggest initial hydrogen or carbon shift/ring contraction from 15.47

1.3.5 Interaction with Organometallic FragmentsAs σ and π activated hydrocarbons, phenylenes should be susceptible tointeraction with metal fragments. This notion is already borne out with 1, which readilyundergoes metal-promoted ring openings 17a,22,108 and π complexation. 17a,109 A systematiccomparison of the reactivity of higher phenylenes with transition metal complexes is yetto be executed. Therefore, the following provides simply a summary of what has beendone so far.TMSTMS9a(i)TMS(OC) 3 FeTMSTMS(OC) 3 FeTMSFe(CO) 3TMSFe(CO) 3TMSFe(CO) 3109TMSTMS110Fe(CO) 3TMSFe TMS(CO) 3Scheme 1.27 Reaction of 9a with [Fe 2 (CO) 9 ]: (i) [Fe 2 (CO) 9 ] (5.5 equiv), C 6 H 6 , ∆, 24 h,67% (109), 18% (110), 14% (111).111In the linear phenylenes, the increased cyclobutadienoid character of the fourmemberedrings manifests itself already in their synthesis, since both 11 and 13 wereformed initially as CpCo complexes. The use of an external ligand 54 or oxidation of thecobalt center 57 was necessary to release the free phenylene (Scheme 1.3b and c). While48

not recorded for CpCo, the C(aryl)–C(aryl) bond in 9a can be activated with [Fe 2 (CO) 9 ]to give rise to dibenzoferroles 109 and 110, as well as the bisallylic complex 111(Scheme 1.27). 53The angular [3]phenylene (15) underwent double C–C activation by [CpCo(eth) 2 ]to afford 112 in 71% yield (Scheme 1.28a). 97 The formation of an η 4 -complex betweenthe central benzene ring in 15 and CpCo was not observed in this reaction. This finding issurprising, considering that the Cp*Co complex 113 can be prepared via a stepwisesequence from the cyclization precursor 14 (Scheme 1.28b). In 113, the cobalt is attachedin such a way as to minimize cyclobutadienoid circuits (Scheme 1.28b, Figure 1.7, left). 61(a)15(i)CpCoCpCoCo CoCp Cp112CoCp*(b)14(i), (ii)113Scheme 1.28 (a) C(aryl)–C(aryl) activation in 15: (i) [CpCo(eth) 2 ] (10 equiv), C 6 H 6 , 70°C, 6 h, 71%. (b) Preparation of the η 4 -complex of 15 to a Cp*Co-fragment: (i)[Cp*Co(eth) 2 ], THF, –20 °C, 16 h; (ii) ∆.Finally, like biphenylene, 109a,110 phenylenes appear to be readily complexed bychromium tricarbonyl. For example, exposure of 15 to [Cr(CO) 3 (NH 3 ) 3 ] produced49

complex 114 (Scheme 1.29a). 111 The crystal structure of 114 (Figure 1.7, right) showedthat the three Cr–C–O axes are perpendicular to those of the formal single bonds of 15. 112Similarly, the branched skeleton of 21a is susceptible to metalation by Cr(CO) 3 , however,Figure 1.7 X-ray crystal structures of 113 (left) and 114 (right). Thermal ellipsoids areshown at 50% probability.here giving rise to two regioisomeric complexes (Scheme 1.29b). Treatment with[Cr(CO) 3 (NH 3 ) 3 ] resulted in the (so-called) exo-complex 115, while naphthalene–Cr(CO) 3 provided the endo isomer 116. The latter appears to be a kinetic product, as itcould be converted thermally to 115. Further complexation of 115 generated thebischromium complex 117. 113 It is clear from these cursory experiments that phenylenesshould be a rich source of new organometallic compounds.50

(a)15(i)Cr(CO) 3114TMSTMSTMSTMS(b)21a(i)(ii)TMSTMSTMSTMSTMSCr(CO) 3TMS115(iii)TMSCr(CO) 3TMS(ii)TMSTMSCr(CO) 3117TMSCr(CO) 3TMSTMSTMS116Scheme 1.29 Complexation of six-membered rings in 15 and 21a: (a) (i)[Cr(CO) 3 (NH 3 ) 3 ], dioxane, 100 °C, 4–5 h; (b) (i) [Cr(CO) 3 (NH 3 ) 3 ], dioxane, 100 °C, 14h, 57%; (ii) naphthalene–Cr(CO) 3 , THF/Et 2 O, 60 °C, 14 h, 89% (116), 43% (117); (iii)90 °C, (99%).51

1.4 Physical Properties of the PhenylenesAs a novel class of hydrocarbons, an important aspect of the phenylenes lies intheir physical properties. The following sections will compare (to the extent that it ispossible) structural, spectroscopic, and calculated aspects of the known 19 phenylenes.1.4.1 Structural PropertiesAs mentioned repeatedly in previous sections, the unique interplay of the π and σframe in the phenylenes gives rise to unusually distorted benzene rings, a feature thatmanifests itself in experimental and calculated structural parameters. Generally, twotypes of distortion are observed. The first is typical of linearly annulated systems, inwhich, for reasons of symmetry, the inner six-membered rings cannot adopt acyclohexatrienoid configuration. Rather, the effect of fusion is to impart bisallyliccharacter, with long fused and shorter adjacent bonds. This is accompanied by a changein the fusion angles in the six-membered rings to more obtuse.The second and, at this point, more frequently encountered distortion of innerrings is typical of angular and branched topologies and easier to understand, namelycyclohexatrienoid bond alternation. Here, a simple descriptor of average bond lengthalternation, i.e. (Σ 3 long bonds – Σ 3 short bonds)/3, can be employed for comparativepurposes. This number can also be expressed as the degree of bond alternation (in %), byassigning a 0% value to benzene and choosing the exocyclic diene unit in 1,2-dimethylenecyclobutene as the 100% standard. The difference between the 1.497 Å long52

ond and 1.338 Å short bond in this reference equals 0.159 Å. 114 This model was chosenbecause of its appropriate geometry and the fact that the two exocyclic bonds showalmost no interaction, thus minimizing cyclobutadienoid resonance.Keeping in tune with the experimental tenor of this Chapter, Figure 1.8summarizes the available experimental 1 H NMR and structural data (bond alternationpercentages) for all known parent phenylenes. Exceptions are 11, 13, and 66, for whichthe parent systems have not been made. In these cases, calculated bond lengths of theparent systems were employed in determining the extent of bond alternation. For 38, 44,and 48, for which X-ray data could not be collected, the experimental geometries ofsubstituted derivatives were used, in conjunction with calculated data (parent) for thesubstituted rings. Finally, the missing X-ray information for 60, 64b, and 71 has beenreplaced by calculated values. Justification for blending experimental with calculatedinformation comes from the finding that the latter reproduces experimental trendsperfectly, although it tends to underestimate slightly bond alternation percentages. Figure1.8 also lists NICS values (vide infra) for the parent systems. The following discussionattempts to place these data on a comparative footing, focusing on selected illustrativeexamples. As will be seen, a fairly consistent picture emerges.53

6.606.426.246.815.897.028%-8.06.706.6333%-7.5 7.3N/A-4.7TMSTMS31%*-7.3 7.6N/A-5.27.5TMSTMS19b11, C 6 D 66.31TMSTMS6.8132%*-7.3 7.65.90N/A-5.17.75.56N/A-5.1TMSTMS64%6.186.96-3.3 4.23.124%22%-9.56.98-9.16.906.990.86.8253%-4.76.936.316.896.9413, C 6 D 615176.496.426.296.936.517.017.021.568%-4.34.031%-9.26.9948%-6.26.876.346.346.496.84-6.8255%-2.811.114.651%-4.515%-7.912.47.00-6.956.886.84-6.826.496.326.496.2747%-4.711.153%-2.612.050%-3.914.323%-8.46.776.63 6.646.541926286.446.436.476.496.446.1352%-4.412.054%-4.111.0 6.9214.454%-3.15.9811.729%-8.16.546.696.696.396.236.396.0648%*-3.812.048%*-5.011.76.0449%*-4.210.9 14.453%*-3.06.95 6.615.9923%*-8.26.596.616.86-6.906.77-6.8223%*-9.14.36.77-6.826.2757% a-4.70.855% a-4.76.344.326% a-9.133 35386.79-6.866.266.2354%*-4.33.91.528% b-9.249% b-6.26.89-6.936.79-6.866.516.856.466.68 6.6829%*-7.57.5N/A-6.46.506.395.966.526.0466%-2.92.9N/A-7.56.782.517%-9.76.866.866.73N/A-7.56.582.62.96.976.9023% c-9.82.36.9067% c-2.944, CD 2 Cl 2 4856, 1,2-dichlorobenzene-d 46.075.947.016.9722%*-9.72.56.926060%*-2.96.126.0654

7.15-7.217.316.657.2497% 20%92%* N/A-0.4-1.4-1.1 -10.7-1.1 -7.0-0.917%*-10.921b, acetone-d 664b7.7 27%*-7.66.55-6.596.71-6.75TMSTMS6.566.92115%-1.4-2.3N/A-7.57.6 29%*-7.6TMSTMS76%*-3.6-0.36.4950%*-5.36.42TMS6.80-6.854.924%*-8.86.80-6.856.90-6.95TMS6671Figure 1.8 Experimental 1 H NMR chemical shifts (CDCl 3 , unless mentioned otherwise),measured bond localization percentages (from X-ray data), and calculated NICS(1)values [NICS(0) for heliphenes] of known phenylene topologies. All NICS values refer tothe parent compounds. An asterisk denotes a calculated bond localization percentage forthe parent system. Double bonds are omitted for clarity. a For the 2,3-bis(trimethylsilyl)derivative; b for 97; c for 52.Inspection of the terminal rings of all the phenylenes in Figure 1.8 shows that theyare the least localized (average value 26.8%), and thus, based on this structural criterion,the most aromatic. For comparison, 1 shows 28% bond-localization (Figure 1.8). 25Formal linear fusion of a benzocyclobutadiene fragment to 1 gives rise to 9b. Onthe basis of the simple bond localization picture developed for biphenylene (Section 1.1),this mode of fusion should increase the cyclobutadienoid character of the four-membered55

ing and, in turn, force the terminal benzene ring of 9b to become more localized. This isindeed the case, albeit subtly so: the termini of 9b are 33% localized. 115 The core in 9bhas D 2h symmetry, imposed upon it by the “conflicting” fusion of the adjacentcyclobutadiene rings. In such cases, the bond localization analysis is not applicable, sinceit assumes pseudo-three fold symmetry of the system. The central ring instead exhibitsthe expected bisallylic character (Figure 1.9): two symmetric C 3 fragments (bond lengths1.392 Å) are connected by two long bonds (1.417 Å). 115 Skeletal elongation in the linearseries apparently has little effect on bond alternation in the terminal rings, judged by thecalculated values of 31% (11) and 33% (13).In contrast to 9b, 15 evolves from 1 by formal angular fusion of abenzocyclobutadiene unit. This alteration acts to dramatically increase bond localizationin the center (64%), 59 in turn decreasing the cyclobutadienoid character of the fourmemberedrings and hence increasing delocalization of the terminal benzene nuclei(24%). The effect of further angular fusions on the termini is quite small, ascorresponding values average 23.9% (Figure 1.8). However, such elongation imposes adistinct pattern of oscillating bond alternation values on the internal rings in the angularand, to the extent of available members, also the zigzag series. 74 A simple rationale forthis phenomenon is that the most delocalized terminus enforces the highest degree ofbond localization in the first internal ring, which then allows for some “relaxation” of thesecond internal ring, which in turn increases relative localization in the third and so on.This pattern seems to be attenuating with size, as judged by the heliphene series, 70perhaps approaching a limiting value of ~ 50% in the corresponding polyheliphene.56

The fusion of three benzocyclobutadienes to benzene, as in branched 21b,maximizes its cyclohexatriene character (97% bond alternation), thus allowing thetermini to be maximally delocalized (20%). 58The bond-alternation approach can be used to evaluate the effects of mixedfusions. For example, the skeleton of 48 can be built formally from 15 by linearbenzocyclobutadieno fusion. This change, by relay, appears to lead to increasedlocalization of the angularly fused six-membered ring (67% vs. 64% in 15).Alternatively, regarding 48 as built by angular terminal benzocyclobutadieno fusion to9b, the effect of increasing bond alternation in one of the termini of 9b “relaxes” theother (29% of the linear end in 48 vs. 33% in 9b). Similar effects are observed in 56. 76While the numbers are small, the trends are consistent.In the mixed branched examples, the elongation of 21b either linearly (as in 64bor 66) or angularly (as in 71) has the expected localizing and delocalizing effects,respectively, on the centers of branching. For example (experimentally), whereas thecentral ring of 21b exhibits 97% localization, in 66, this value is increased to 115% -larger than the reference 1,2-dimethylenecyclobutene! Taking recourse to calculatedstructures for the other members in the branched family (and, for the sake of consistency,using calculated numbers also for 21b and the parent of 66) confirms the experimentaltrend: 89% (21b) – 92% (64b) – 92% (parent of 66) – 76% (71). 76,82 One notes that thejuxtaposition of branched and angular fusion in 71 delocalizes not only the center (vs.21b), but also the penultimate six-membered rings (50%, vs. 64% in 15). 8257

Figure 1.9 X-ray structures of selected [N]phenylenes - top and side views. Hydrogenatoms omitted for clarity, thermal ellipsoids shown at 50% probability.58

Figure 1.9 shows the X-ray structures of some of the phenylenes discussed. While9b and 56 are essentially planar, 21b and the substituted 52, 66, 38(TMS) 2 , and 97 shownoticeable deplanarization. Such deplanarization is general and independent of topology,size, and substitution pattern and is thought to be due to crystal-packing effects that arecomparable in energy to deformation energies (several kcal mol –1 ). 58VT NMRexperiments on a derivative of 21b bearing prochiral substituents revealed the absence ofdecoalescence at the experimental low temperature limit of –93 °C, indicating either avery low barrier to planarization, or a planar structure in solution, as indeed alsocalculated for 21b. In addition, calculations showed that the phenylenes are moredeformable than their hexagonal squeezes. This flexibility was ascribed to readypyramidalization of the four-membered ring carbons as a result of two phenomena:hyperconjugation of the low lying σ antibonding orbitals of the strained bonds with theHOMO of the π system 116and minimization of antiaromatic overlap in thecyclobutadiene nuclei. 117 The observation of such facile deplanarization is encouraging inview of projected syntheses of archimedene 55,72 and circular [5]phenylene (the phenyleneanalog of corannulene). 55In light of the preceding discussion, it is instructive to view the compilation of X-ray structures of the heliphenes (Figure 1.10). Even in the absence of non-bondedinteractions, angular [5]phenylene (19) already shows a small, prehelical deviation fromplanarity. The higher angular [N]phenylenes (N > 5) can no longer adopt planar structuresand are helical. 66,70 The “helical strain” is not large, as determined by calculations, forexample, only 3.2, 5.4, and 7.0 kcal mol –1 for 26, 28, and 33, respectively. 67 Table 1.1summarizes some of the structural parameters of the heliphenes, highlighting the steady59

increase in the helix climb and in-plane turn in the series. The angle between the planesof the terminal benzene rings is the highest in [7]heliphene. The inner helix of the [6]–and [7]helicene (hexagonal squeezes of 26 and 28) climbs more steeply than that in theirheliphene counterparts, due to the smaller diameters of the PAH systems. 118,119MoleculeTerminal ringTerminal ringInnerInnerRacemiza-Helicalcentroidinterplanarhelixhelix in-tion barrierstraindistance (Å)angle (°)climb (Å)plane turn(kcal mol –1 )(kcal mol –1 )(°)26 5.62 (5.87) a 22.8 (27.2) a 2.1628 4.07 (4.54) a 30.1 (40.6) a 3.2933 4.41 (5.49) c 23.6 (41.1) c 3.3535 N/A (7.48) c N/A (33.2) c N/A(2.30) a 337.3(332.4) a N/A (3.6) b (3.2) b(3.64) a 361.3(361.6) a 12.6±0.5 a(17.0) a (5.4) b(4.24) c 393.0(389.1) c 13.4±0.4 c (7.0) b(5.07) c N/A(415.7) c

As the heliphenes are chiral, the possibility of enantiomer separation is intriguing.Because of their extensive delocalization, the heliphenes should show remarkablechiroptical properties. 68c–d,120 In an attempt to probe the feasibility of their resolution,configurational stability was probed by NMR experiments. For this purpose, a series ofheliphene derivatives bearing potentially diastereotopic substituents (isopropyl andmethoxymethyl, respectively) was prepared. 66,70 In accord with the calculated low barrierto enantiomerization of 26, 67 decoalescence of the methyl group signals for an isopropylderivative was not evident at the limiting temperature of –75 °C. Turning tomethoxymethyl [7]heliphene, methylene decoalescence was recorded at –27 °C,indicating a barrier of 12.6±0.4 kcal mol –1 for helix flipping 66 - less than a third of thevalue for the corresponding helicene. 68c–d,120Surprisingly, the analogous barrier formethoxymethyl [8]heliphene was only slightly higher, 13.4±0.4 kcal mol –1andmethoxymethyl substituted 35 showed no signal splitting for the methylene hydrogens oncooling to its solubility limit at –45 °C. 66,70 The flexibility of these systems is thereforeextraordinary, a consequence of both ready in- and out-of-plane deformations (vide supraand infra).61

Figure 1.10 X-ray structures of [N]heliphenes - top and side views. Hydrogen atomsomitted for clarity, thermal ellipsoids shown at 50% probability.62

1.4.2 Magnetic PropertiesProton NMR chemical shifts are highly diagnostic of whether a compound isaromatic or not. 5 Hydrogens located on the inside of aromatic rings exhibit relatively highfield chemical shifts, while those on the outside are relatively deshielded. Antiaromaticcircuits have the opposite effect. In the phenylenes, the generally observed shielding ofall protons (relative to alkylbenzenes) is the result of the simultaneous operation of twoeffects: the decreased diatropism of the six-membered rings and the shielding influenceof the cyclobutadiene nuclei on the protons in their vicinity.To better understand the relative contributions of the component rings to theobserved chemical shifts in the phenylenes, recourse was taken to nucleus-independentchemical shift (NICS) 121 calculations, which provide such data (in ppm) for a pointnucleus at any given position in a molecule. For cyclic polyenes this is typically 1.0 Åabove the center of the ring, chosen to minimize local perturbations. 122 Negative NICSvalues denote an aromatic ring (NICS(1) benzene = –12.5), whereas positive values indicatean antiaromatic circuit (NICS(1) cyclobutadiene = 15.1). 123 Used together, NICS and NMR areuseful tools in the following analysis of the corresponding entries in Figure 1.8. As willbe seen, in the phenylenes, the magnetic data correlate well with the structural criterion of(anti)aromaticity.As mentioned previously, the α- and β-protons in 1 resonate at δ 6.60 ppm and6.70 ppm, respectively. The relative shielding of the α-proton is a consequence of theresidual paratropicity of the neighboring four-membered ring, applicable to allphenylenes, with the exception of the branched isomers. The corresponding NICS values63

are –8.0 and 7.0 for the six- and four-membered rings, respectively. In general, theterminal rings exhibit the most negative NICS values and, correspondingly, the highestNMR chemical shifts, in consonance with the occurrence of the smallest extent of bondalternation.In going from 1 to 9b, the paratropism (antiaromaticity) of the cyclobutadienes(NICS = 7.3) is subtly increased, while the diatropism (aromaticity) of the terminalbenzene rings decreases, as evidenced by the lower NMR chemical shifts (δ = 6.42 and6.63 ppm) and less negative NICS value (–7.5). The diatropic character is lowest in thecentral ring (NICS = –4.7), which, in conjunction with the paratropism of the twoadjacent cyclobutadiene fragments, leads to strong shielding of its hydrogen (δ = 6.24ppm). 123 While the NICS values for the internal six-membered rings fluctuate somewhatalong the linear series 9b–11–13, the cyclobutadienes appear to become increasinglyparatropic, providing an explanation for the observation of incremental shielding of thecentral hydrogens. 123The angular mode of fusion in 15 further reduces the diatropism of the center(NICS = –3.3; δ = 6.18 ppm), in conjunction with decreased paratropism of thecyclobutadienes (NICS = 3.1). As a consequence, the termini are more diatropic than inbiphenylene (NICS = –9.5 vs. –8.0). 123In the remainder of the angular series, thearguments advanced previously for the rationalization of the trends in bond-localizationsare clearly augmented by the magnetic data. Thus, 19, as an example, shows thealternation of diatropism of the six-membered rings: NICS = –9.2, –4.3, –6.2. Theparatropism of the cyclobutadiene moieties also oscillates: it is high in the outer ring(NICS = 4.0) and less so in the inner one (NICS = 1.5), reflecting the interplay with the64

neighboring six-membered rings and their respective aromaticity. For the heliphenes, theuse of NICS(1) values was abandoned, since the areas above and below the rings are nowinequivalent. Instead, NICS(0) data were computed, which, although numerically notdirectly comparable with NICS(1) numbers, showed the same alternating trends, inagreement with experimental NMR chemical shifts and bond localization numbers. 66,70The NMR and the NICS values of angular [4]– and [5]phenylene are essentially identicalto those of their zigzag counterparts, highlighting the similarity between the twotopologies.In the branched 21b, the central six-membered ring becomes essentially atropic(NICS = –1.1), as do the adjacent cyclobutadienes (NICS = –0.4), allowing for maximumdiatropism of the three terminal cycles (NICS = –10.7; δ = 7.24, 7.31 ppm). As such, thesystem can be described essentially as an extended stilbene. 123 In support of this view, thesignal for H α (δ = 7.31 ppm) and H β (δ = 7.24 ppm) have traded their “normal” places,appearing in the order observed for ordinary benzocycloalkanes, such as indane: H α δ =7.06 ppm, H β δ = 6.99 ppm. 124For the mixed topologies realized in 48 and 56/60, a component analysis is inaccord with the calculated magnetic behavior. Thus, if these systems are viewed asperturbed linear [3]phenylenes, the added angular fusions serve to increase thecyclohexatrienoid character of one or both termini of the linear substructure,consequently reducing their diatropism, as observed. At the same time, the paratropism ofthe four-membered rings (of the linear substructure) is also reduced, thus rendering thecenter ring more diatropic (aromatic). The trends in the NICS values of the latter agreewith this analysis: –4.7 (9b), –6.4 (48), –7.5 (56/60), as do NMR chemical shifts δ 6.2465

(9b), – 6.39 (48), – 6.58 (60) ppm. Along the same lines, completely removing thediatropism of one terminus of 9b, as it occurs in 64b and 66, should have a similarpronounced effect on the diatropism of the central benzene, as reflected by thecorresponding numbers for 64b (δ = 6.65 ppm, NICS = –7.0) and 66 (δ = 6.56 ppm,NICS = –7.5). Turning to the mixed system 71 and viewing it as a perturbed 15, thereduced diatropism of the core (the “perturbed” end of 15) goes with reduced paratropismof the adjacent four-membered rings and increased diatropism of the next six-memberedcycle (δ average = 6.58 ppm, NICS = –3.6). Alternatively, viewing 71 as a perturbed 21b,the effect of reduced diatropism of the terminal rings of the substructure of branched[4]phenylene is to increase the diatropism of the core (NICS = –3.6 vs. –1.1).Carbon-13 NMR spectroscopy is not usefully diagnostic of ring currents, and atypical 13 C NMR spectrum of a phenylene exhibits four groups of signals. At the highestchemical shifts (δ ~ 145–155) are the signals corresponding to the four-membered ringcarbon atoms without adjacent other four-membered rings. Those that are adjacent to asecond four-membered ring are relatively shielded 125 and absorb at δ ~ 133–140 ppm.The remaining carbons, namely the non-quaternary nuclei of the six-membered rings, arealso split into two categories - those adjacent to a cyclobutadiene (δ ~ 113–120 ppm) andthose distant from it (δ ~ 125–130 ppm). The averaged δ (over all six carbons) for theinternal six-membered rings in angular [3]–, [4]– and [5]phenylene changes very littleand lies between 132.5 and 134.5 ppm.66

1.4.3 Energetic PropertiesThe determination of the ground-state energies of the [N]phenylenes is of crucialimportance in the evaluation of their aromaticity 4 and strain. On the other hand, theirfrontier orbital separation constitutes a measure of their kinetic stability 126 and is centralto organic conductor applications. 127 The excited states of the phenylenes are also ofinterest for probing the changes in aromaticity that occur upon excitation and foridentifying the nature of radiative relaxation pathways (fluorescence and/orphosphorescence).Experimental enthalpies of formation for members of the series have beenobtained only for 1, 128 15, and 21b, and the agreement between the calculated andobserved ∆H° f data is remarkable. 35For other phenylenes, only calculated data areavailable, and the following will highlight some key findings.Although the conjugated-circuit model 34 suggested that the linear [N]phenylenesare more stable than their angular isomers, the application of ab initio methods proved theopposite. 129 Schulman and Disch’s examination of the problem by modern DFT methodsplaced the stabilization of 15 vs. 9b at 2.4 kcal mol –1 . 55 Branched [4]phenylene (21b) isthe most stable of the five [4]phenylenes, followed by 38 (relative energies: +4.1 kcalmol –1 ), 17 (+4.3 kcal mol –1 ), 48 (+ 4.8 kcal mol –1 ), and linear [4]phenylene (+8.5 kcalmol –1 ). The energies of zigzag [4]– (38) and [5]phenylene (44) are almost identical tothose of their angular isomers. 55 A comparison of the relative energies of the twelve[5]phenylenes reveals the same general trends: the linear isomer is the least (+10.7 kcalmol –1 ), the branched 64b the most stable (0.0 kcal mol –1 ), surprisingly more stable than67

the other branched isomer (+0.9 kcal mol –1 ), which is devoid of a linear [3]phenylenesubstructure. Similarly, among the nonbranched [5]phenylenes, the two doublebentisomers (56 and 60) have the lowest energies (+3.8 kcal mol –1 ), despite the presence ofthe linear fragment. 67 This disagreement with expectation, albeit associated with smallnumbers, was attributed to the opposing energetic contributions of the σ- (stabilizing) andπ- (destabilizing) components of the linear frame. 76The “helical strain” in the smaller heliphenes is relatively small (Table 1.1), butbecomes substantial for larger systems. Thus, in order to model the limiting properties oflarger phenylenes, calculations have been executed on various illustrative topologies of[19]phenylene. 71 The results indicate that the helical topology is 26.9 kcal mol –1 (1.4 kcalmol –1 per ring) less stable than its zigzag counterpart. Linear [19]phenylene is the leaststable, 40.4 kcal mol –1 (2.1 kcal mol –1 per ring) more energetic than the zigzag isomer.The electronic spectra of the phenylenes feature two typical sets of bands: one atlower wavelengths, with relatively large ε values, and a second at higher wavelengths,with lower exctinction coefficients. The exact position of these absorptions, however,depends on the phenylene topology (Table 1.2). In the linear series, the λ max valueincreases dramatically in going from 1 to 9a (∆λ max = 75 nm), 11 (∆λ max = 54 nm), andthen 13 (∆λ max = 38 nm). 47a,53,54,57 The extrapolation of this limited set of experimentaldata to infinite N provides λ max = 662 nm, corresponding to a small band gap of 1.87 eVfor the linear polymer, boding well for potential electronic applications.68

λ max (nm)HOMO–LUMO gap (eV)N Angular Zigzag Linear Angular Zigzag Linear2 363 a (isooctane) 363 a 363 a 3.42 3.42 3.423 428 b (THF) 428 b 438 b,d (THF) 2.90 2.90 2.834 448 b (THF) 465 c (THF) 492 b,d (THF) 2.77 2.67 2.525 470 b (THF) 484 c (CH 2 Cl 2 ) 530 b,d (THF) 2.64 2.56 2.346 491 e (CH 2 Cl 2 ) – – 2.53 – –7 503 e (CH 2 Cl 2 ) – – 2.47 – –8 515 f (CH 2 Cl 2 ) – – 2.41 – –9 524 f (CH 2 Cl 2 ) – – 2.37 – –∞ 578 f 587 g 662 g 2.14 2.11 1.87Table 1.2 HOMO–LUMO gaps and λ max values in angular, zigzag and linear phenylenes.a Ref. 47a; b Ref. 60; c Ref. 74; d for tetrasilylated compounds; e Ref. 66; f Ref. 70; g Ref.130 .In contrast to the linear frame, the λ max values of angular phenylenes attenuatemore rapidly (N = ∞, λ max = 578 nm, band gap = 2.14 eV). 47a,59,60,66,70 The same seems tobe true for the zigzag isomers, again with the caveat that only four experimental valuesare available (N = ∞, λ max = 587 nm, band gap = 2.11 eV). 74 The so-estimated band gapsfor the linear, angular, and zigzag family conform with theoretical predictions. 34,71In agreement with the virtual absence of antiaromatic circuits, the UV spectrum ofbranched 21b, while still exhibiting the diagnostic phenylene pattern, is69

hypsochromically shifted, with a highest wavelength absorption at 379 nm, reflecting aHOMO–LUMO gap of 3.28 eV - the highest among the [4]phenylenes. 65The electronic spectra of the “mixed” phenylenes are strongly influenced by thepresence of the linear substructures, which cause strong bathochromic shifts. Thus, 48exhibits a λ max of 486 nm, which is almost exactly equal to that of its linear relative andhigher than that of the remaining isomers. 75 Doublebent [5]phenylenes 56 and 60 absorbat 505 and 507 nm, respectively, at energies significantly lower than their isomers 19, 44,and 64b, but higher than the all-linear 13 (Table 1.1). 76 Finally, in the series of branchedphenylenes, the effect of the presence of linear annelation is highlighted by the changesin λ max when going from 21b to 64b (∆λ max = 107 nm), 64b to 66 (∆λ max = 37 nm), 79 and,particularly, 71 to 66 (∆λ max = 67 nm). 81The exploration of the photophysics of the phenylenes, still in its infancy, hasfocused on the smaller linear, angular, and branched systems, as well as 1. On the basis oftheir rates of internal conversion of the first excited state (S 1 ), the systems studied havebeen labeled as either “fast IC compounds”, with k IC > 10 9 s –1 , or “slow IC compounds”,with k IC ≈ 10 7 s –1 . 131 Fast IC compounds, biphenylene and 9b, relax their S 1 statepredominantly through internal conversion (Φ IC > 99%), since the rates of this reactionare significantly greater than those of the competing intersystem crossing andfluorescence processes. In angularly fused, slow IC compounds 15, 38, and 44, otherrelaxation mechanisms gain in importance and become dominant in zigzag [5]phenylene44, which releases 21% of its excited state energy through fluorescence and crosses overefficiently (Φ ISC = 45%) to the triplet state (T 1 ). The corresponding quantum yields forthe branched 21b are Φ F = 15% and Φ ISC = 3%. 13170

Shpol’skii spectroscopy 132 of the phenylenes, together with DFT calculations,have provided significant insights into the vibrational characteristics of their excitedstates. The resemblance between the fluorescence emission and excitation spectra,observed for 15 and 44, has indicated that, in phenylenes with angular substructures, theS 0 and S 1 states have similar geometries. 133 Studies performed on deuterated derivativesof 21b allowed for the distinction between C–C and C–H vibrational modes in the S 1state and demonstrated that, while the terminal rings of 21b are essentially unperturbed inthe excited state, the central cyclohexatrienoid ring partly delocalizes, suggestingrearomatization. 134 This is an important result, in view of the fact that the opposite effect- dearomatization of benzene in the first excited state - is well known. 2a Photophysicalstudies confirmed the presence of a theoretically invoked 55,67 low-frequency (~ 35 cm –1 )out-of-plane vibration and also revealed a new in-plane vibration in angular phenylenes(~ 100 cm –1 ), notably absent from the spectra of corresponding PAHs. The first vibrationdeplanarizes the angular fragment by moving the terminal rings out of the molecularplane in opposite directions. The second increases the angle between the centroids of thethree successive six-membered rings of an angular fragment, in turn pushing the terminalrings away from each other. 133Both of these distortions have been proposed asoperational in the transition state for the racemization of [6]heliphene 67and theirmagnitude provides a convincing rationale for the ease by which this process occurs forthe other heliphenes studied so far.71

1.5 Thesis SummaryThis dissertation will document the progress achieved in the syntheses of largerdehydrobenzannulenes and novel [N]phenylenes with mixed modes of fusion. Alongthese lines, the following Chapter 2 will present the synthesis of syn-doublebent[5]phenylene and advances toward the (still elusive) U-shaped [7]– and [9]phenylenes, aswell as the C-shaped [7]phenylene. Building upon these results, an approach to circular[8]phenylene will be described. As part of this effort, two routes todehydrobenzannulenes were developed. The first one, described in Chapter 3, utilizedalkyne metatheses of propynylated benzenes to produce dehydrobenzannulenes.Although simple, this method was somewhat limited in scope, thus necessitating adifferent strategy for the preparation of extensively substituted dehydrobenzannulenicsystems. An alternative procedure, to be presented in Chapter 4, relied on a sequence ofSonogashira couplings to assemble a variety of substituted dehydrobenzannulenes. Someof these systems, due to the appreciable bulk of their pendant substituents, wereconformationally constrained. This intriguing property will be more thoroughly discussedin Chapter 5. This chapter will also feature the synthesis and stereochemical evaluation ofthe first chiral diphenylacetylene. Finally, Chapter 6 will provide the experimental detailsof the studies performed.72

Chapter TwoSynthetic Approaches to Novel Phenylenes with Mixed Angular and Linear Fusion2.1 IntroductionAt the beginning of the work described in this dissertation only two phenyleneswith mixed angular and linear topologies were known: bent [4]phenylene (48, Section1.2.2.3) 75 and anti-doublebent [5]phenylene (56, Section 1.2.2.3). 76 This chapter willfocus on the continued exploration of this mode of fusion through the attemptedsyntheses of the four novel mixed phenylenes shown in Figure 2.1.60 118 119 120Figure 2.1 Novel phenylenes with mixed angular/linear fusion: syn-doublebent[5]phenylene (60), C-shaped [7]phenylene (118), U-shaped [7]– (119), and [9]phenylene(120).Syn-doublebent [5]phenylene (60) and C-shaped [7]phenylene (118) feature acentral linear [3]phenylene fragment, extended by the double benzocyclobutadieno- and73

iphenylenocyclobutadienofusion, respectively. Conversely, U-shaped phenylenes 119and 120 share the central angular [5]phenylene unit, which is elongated by annelation oftwo benzocyclobutadienes (119) or two biphenylenocyclobutadienes (120). Thesekinships, between 60 and 118 on one, and 119 and 120 on the other side are reflected intheir proposed syntheses and expected properties.The relevance of the investigations of 60 and 118–120 is manifold.Methodologically, and as will be seen later, they represent a significant extension of theCpCo-mediated approach to phenylenes. In terms of modes of fusion, syn-doublebent[5]phenylene 60 is completely equivalent to its anti-relative 56, but with the addedfeature of the “super-bay” region flanked by two benzocyclobutadieno groups. Fusingbenzocyclobutadienes to the termini of 60, as in 118, converts them from terminal(relatively delocalized) into central rings of an angular fragment (relatively localized).This modification is also expected to affect the terminal two rings of the linear fragment,allowing them to delocalize relative to 60. Consequently, attenuation of “activity” of allinternal six-membered rings of 118 is expected, relative to the internal rings of linear andangular [3]phenylene. In this context, the juxtaposition of 119 with its helical isomer 28is particularly intriguing: switching the mode of fusion of the termini from angular (28) tolinear (119) is expected to invert the localization trends observed in 28, making thecentral ring relatively delocalized and inverting the alternation of properties of thesubsequent rings. Finally, in addition to adopting the same features as those predicted for119, 120 is hypothesized to adopt a helical conformation, thus opening up access to anew class of chiral phenylenes, possibly with properties different from the heliphenesmade so far.74

In the context of this dissertation, phenylenes 60, 118, and 119 have another,common property: they constitute formally subunits of circular [8]phenylene (121, Figure2.2). The structure of this elusive circular phenylene (Section 1.2.2.5) encompasses aninternal [18]annulene and an external [30]annulene circuit (shown in bold, Figure 2.2).Both of these π-loops have 4n+2 electrons, and, according to Hückel’s rule, are thereforearomatic. On the basis of the properties of the substructures in 121, one would anticipatethat the resonance structure shown in Figure 2.2 would contribute strongly to theresonance picture of this molecule, thus enabling superdelocalization. The internalprotons of 121 would be an excellent probe for this phenomenon, as they should berelatively shielded, as in [18]annulene itself. 5 A more thorough treatment of the expectedproperties of 121 is deferred until Chapter 4.121Figure 2.2 Circular [8]phenylene (121).The topological resemblance between the above mentioned novel phenylenes and121 makes the former ideal models for comparisons of physical properties discussed inSection 1.4. Synthetically, they would enable the evaluation of the viability of preparativeroute(s) to 121, including the stability and solubility of advanced precursors and75

intermediates. Finally, the strategy to compound 120, which requires an unprecedentedfour-fold CpCo-mediated cycloisomerization of an appropriate oligoalkyne precursor(vide infra), would present a test for the viability of a similar approach to 121.2.2 Retrosynthetic Approach to 60, 118, 119, and 120Conceptually, 60 and 118 were targeted through a regioisomeric version of thedouble intramolecular cyclization developed for angular [5]phenylene (19, Scheme 1.6) 66and helical [7]phenylene (28, Scheme 1.7b). 66Thus, while the 1,2,3,4-tetraalkynylsubstitution pattern of the heliphene precursors 24b and 27 translated into the angularcenter of the products, the requirement for the central linear fragment in 60 and 118dictated a related 1,2,4,5-relationship. This suggested 59 and 122 as plausible ultimatecyclization precursors for these molecules (Scheme 2.1).(a)60(b)11859122Scheme 2.1 Retrosynthetic analysis of 60 (a) and 118 (b).76

Similarly, a topological variant of 27, namely attachment of 2,3-diethynylbiphenyleneunits rather than their 1,2-alkynylated isomers, would suggest 123 as an ideal precursor to119 (Scheme 2.2).119123Scheme 2.2 Retrosynthetic analysis of 119.Alternatively, 119 could be pursued through the more ambitious four-fold interandintramolecular cyclization of 124, creating 10 rings in one step (Scheme 2.3a). In thisvariant, the double-cyclization precursor to angular [5]phenylene, 24b, would have to befunctionalized by four additional ethynyl groups. The significance of this synthesis lies inits potential extendibility, as exemplified by a possible access to 120 (Scheme 2.3b).The remainder of Chapter 2 will discuss the attempted synthetic execution of theabove proposals, in the order in which they were introduced.77

(a)119124(b)120Scheme 2.3 Inter- and intramolecular retrosynthetic analysis of 119 (a) and theretrosynthetic analysis of 120 (b).1252.3 Synthesis of Doublebent [5]Phenylene 60Syn-doublebent [5]phenylene (60) has been targeted previously by our group,through hexayne 59 as the ultimate cyclization precursor. The synthesis of 59 wasstraightforward (Scheme 2.4): starting with the 1,5-dibromo-2,4-diiodobenzene (57) 78 asa C 2v -symmetric template, treatment with 23 60and subsequently TMSA underSonogashira conditions provided tetrayne 126a. The complete, fluoride-assisted,deprotection of this material yielded hexayne 59. Disappointingly, attempted cyclization78

to 60 failed when [CpCo(CO) 2 ] was used as the catalyst, prompting speculation that thelow solubility of 60 (imparted by its planar structure) plagued this synthetic route. 135RTMSRRIBr(i), (ii)(iii)(iv)IBrTMSRRR57126a, R = DMTS126b, R = Pr59, R = H127, R = Pr60, R = H128, R = PrScheme 2.4 The attempted synthesis of syn-doublebent [5]phenylene (60) and thesuccessful synthesis of its dipropyl derivative 128: (i) 23 (for 126a) or 1-ethynyl-2-(pent-1-ynyl)benzene (for 126b), [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 23–50 °C, 24–36 h, 65% (126a),83% (126b); (ii) TMSA, [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 120–135 °C, 18–72 h, 70% (126a),86% (126b); (iii) for 59: TBAF, THF, 23 °C, 45 min, (95%); for 127: NaOH,THF/MeOH, 23 °C, 30 min, 85%; (iv) [CpCo(CO) 2 ], m-xylene, hν, ∆, 2 h, 0% (60), 1%(128).Such speculation gained some credibility through the successful completion of thesynthesis of 128, a derivative of 60 substituted with two solubilizing propyl groups(Scheme 2.4). The preparation of 128 followed the same strategy as that projected for 60,but employing 1-ethynyl-2-(pent-1-ynyl)benzene instead of 23 to install the propyl79

substituents. Final cyclization of 127 proceeded successfully, albeit in a low 2% yield, togive 128.Subsequent to this preliminary work, investigations of the synthesis of otherphenylenes showed that [CpCo(eth) 2 ], 63when used under certain conditions, couldprovide a more successful catalytic system. 61,62 Specifically, this complex allowed thepreparation of the parent anti-doublebent [5]phenylene 56 (Section 1.2.2.3, Scheme 1.13),an effort that failed when using [CpCo(CO) 2 ]. 76 Consequently, the synthesis of 60 wasrevisited, including a new, more convergent, synthesis of 59 (Scheme 2.5). Starting againBrBr57(i), (ii), (iii)(iv), (v)(vi)BrBr58 5960Scheme 2.5 The synthesis of syn-doublebent [5]phenylene (60): (i) TMSA,[Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 23 °C, 2 h, 96%; (ii) KOH, Et 2 O/EtOH; (iii) 1-bromo-2-iodobenzene, [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 120 °C, 44% (over 2 steps); (iv) TMSA,[Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 120 °C, 47%; (v) TBAF, THF, 23 °C, 2 h, (95%); (vi)[CpCo(eth) 2 ], THF, –25 °C, 16 h, followed by 1,3-cyclohexadiene, THF, 110 °C, 2 h,14%.80

with 57, Sonogashira coupling and base-assisted deprotection provided 1,5-dibromo-2,4-diethynylbenzene. Another Sonogashira reaction between this material and 1-bromo-2-iodobenzene gave the tetrabromide 58, the X-ray crystal structure of which is shown inFigure 2.3. 136The molecule has a pseudo-C 2 axis that passes through the twounsubstituted carbons of the central benzene ring. The bromines are located anti, withdihedral angles of 148.7 and 162.2 °, respectively. Compound 58 crystallizes in the P2 1 /nspace group with four molecules in the unit cell.Figure 2.3 ORTEP diagram of 58. Thermal ellipsoids shown at the 50% probabilitylevel.The use of 58 as an intermediate on route to 60 avoided the superfluousdifferential silyl substitution of 126a. Reaction of 58 with an excess of TMSA, andsubsequent deprotection to 59 proceeded in a satisfactory 45% overall yield. Exposure of59 to [CpCo(eth) 2 ] was followed by treatment with 1,3-cyclohexadiene as an externalCpCo-trap and heating. Gratifyingly, the desired 60 was isolated in 14% yield (37% percyclization step).81

2.4 Attempted Synthesis of C-Shaped [7]Phenylene (118)Encouraged by the results described in Section 2.3, we embarked on the pursuit of118, formally a derivative of 60 with two additional benzocyclobutadieno-fusions. Asdiscussed previously (Section 2.2), hexayne 122 was deemed a suitable precursor. Itspreparation could follow either of the two strategies precedented for 60, substituting asuitable biphenylenyl building block for the corresponding phenyl fragment. However,1,2-difunctionalized biphenylenes need several steps for their synthesis and are toovaluable to be introduced early in the synthesis. Therefore, the alternative Schemes 2.6and 2.7 were executed. The central benzene ring of 122 was elaborated from 57 by twoDMTSTMSDMTS57(i), (ii)(iii)DMTSTMSDMTS129130Scheme 2.6 The synthesis of 130: (i) DMTSA, [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 23 °C, 48 h,92%; (ii) TMSA, [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 110 °C, 48 h, 81%; (iii) K 2 CO 3 , Et 2 O/EtOH,97%.consecutive Sonogashira couplings. The first, with DMTSA, targeted the more reactiveiodinated positions; the second functionalized the brominated sites with TMSA. Thusobtained tetrayne 129 was selectively deprotected into 130 (Scheme 2.6). Compound 13082

underwent twofold Sonogashira coupling with biphenylene 131, 60 giving the hexayne 132in 54% yield (Scheme 2.7).DMTSRRDMTSI+(i)DMTSRR130131118x(iii)132, R = DMTS122, R = H(ii)Scheme 2.7 The attempted synthesis of 118: (i) [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 120 °C, 16 h,54%; (ii) TBAF, THF, 23 °C, 2 h, (95%); (iii) [CpCo(eth) 2 ], THF, –25 °C, 16 h, followedby 1,3-cyclohexadiene, THF, 100 °C, 90 min.Bearing in mind the poor performance of [CpCo(CO) 2 ] in the attemptedpreparation of 60, we decided to use exclusively [CpCo(eth) 2 ] in our efforts to produce118. As precedented for 60, precursor 132 was subjected to an in-situ fluoride-assisteddeprotection into 122, which was followed by treatment with [CpCo(eth) 2 ] at lowtemperatures, and then with 1,3-cyclohexadiene at 100 °C. Although 1 H NMRspectroscopy indicated the formation of CpCo-cyclohexadiene, it could not detect anyphenylenic products. Additionally, neither mass spectral (EI, 70 eV), nor TLC analysisshowed indications of the presence of the desired material in the crude reaction mixture.83

2.5 Attempted Syntheses of U-Shaped [7]Phenylene (119)2.5.1 Intramolecular ApproachThe intramolecular route to 119 bears close resemblance to the one developed forthe regioisomeric helical [7]phenylene (28). 66 The hexayne 123 (Scheme 2.2), designedas the ultimate precursor to 119, differs from its isomer 27 only in the substitution modeof the biphenylenyl groups. It is understandable, therefore, that the most challenging partof the preparation of 123 was the development of an efficient route to unsymmetrical 2,3-substituted biphenylenes.It was hoped that 2-alkynyl-3-iodobiphenylenes (134) could be prepared throughthe exposure of the previously described 2,3-diiodobiphenylene (133) 53 to one equivalentof the alkyne (Scheme 2.8). In practice, almost statistical mixtures of the startingII(i)IR+RR133134a, R = TMS134b, R = DMTS134c, R = Hex135a, R = TMS135b, R = DMTS135c, R = HexScheme 2.8 Attempted monoalkynylations of 2,3-diiodobiphenylene (133): (i) R–C≡CH(1 equiv), [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 23 °C, 12 h. Yields: for R = TMS: 31% (133), 25%(134a), 34% (135a); for R = DMTS: 31% (133), 25% (134b), 34% (135b); for R = Hex:20% (133) 46% (134c), 9% (135c).84

material, the desired product, and the dialkynylated derivative 135 were obtained. Thisresult was fairly independent of the nature of alkyne, indicating that the reactivity of themonoalkynylated 134 is equal to, if not greater than, that of 133. This unsatisfactoryoutcome suggested the use of (unknown) 2-bromo-3-iodobiphenylene (138) as analternative substrate for monoalkynylation. The preparation of 138 (Scheme 2.9)followed closely that employed in the preparation of 2-bromo-3-iodobenzocyclobutenefrom 2,3-bis(trimethylsilyl)benzocyclobutene. 137 In such systems, steric strain rendersone silyl group much more reactive than the other in electrophilic aromatic substitutions.Therefore, bis(trimethylsilyl)biphenylene (136) 52 was treated briefly with bromine to givemonobrominated 137 as the major product (59%). The remaining TMS group was thenexchanged for iodide by treatment with ICl. 137TMS(i)TMS(ii)ITMSBrBr136137138Scheme 2.9 Preparation of 2-bromo-3-iodobiphenylene (138): (i) Br 2 , pyridine, CH 2 Cl 2 ,0 °C, 3 min, 59%; (ii) ICl, CH 2 Cl 2 , 0 °C to 23 °C, 5 h, 99%.Bromoiodide 138 behaved as expected in the Sonogashira reactions with TMSA,DMTSA, or 1-octyne: no dialkynylation was observed and only a minor portion of thestarting material was left unreacted. The remaining bromine in the desired products85

139a–c was converted successfully to iodide through halogen–lithium–halogen exchange(Scheme 2.10).R138(i)Br(ii), (iii)134a, R = TMS134b, R = DMTS134c, R = Hex139a, R = TMS139b, R = DMTS139c, R = HexScheme 2.10 Stepwise preparation of 2-iodo-3-alkynylbiphenylenes (134): (i) R–C≡CH,[Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 23 °C, 12 h, 75% (for 139a, 78% converted yield), 60% (for139b, 85% converted yield), 67% (for 139c, 91% converted yield); (ii) BuLi, Et 2 O, –45°C, 30 min; (iii) I 2 , Et 2 O, from –45 °C to 23 °C, 2 h, 78 % (for 134a, over two steps),82% (for 134b, over two steps), 85% (for 134c, over two steps).With 134 in hand, the stage was set for the final couplings toward 123, namelywith 140, used previously in the synthesis of heliphenes (Scheme 2.11). 66,69 While thistransformation worked reproducibly, the yields were disappointing, never exceeding30%. Hexaynes 141 were deprotected (using methanolic K 2 CO 3 for 141a and TBAF/THFfor 141b and c) into the ultimate cyclization precursors 142a and b, and the parent 123(Scheme 2.12).86

DMTSDMTSDMTS RDMTSR+134a, R = TMS134b, R = DMTS134c, R = Hex(i)140141a, R = TMS141b, R = DMTS141c, R = HexScheme 2.11 Preparation of 141a–c: (i) [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 120 °C, 36–48 h, 23%(141a), 28% (141b), 30% (141c).The parent 119 was targeted first: 123 was treated with [CpCo(eth) 2 ] at lowtemperature, followed by heating and exposure to 1,3-cyclohexadiene. As in the case of118 (Scheme 2.7), analysis of the crude reaction mixture (by 1 H NMR, MS, TLC) gaveno indication of the presence of the phenylene targets. At first, solubility problems wereinvoked as a possible explanation for this failure. Since [5]phenylenes 56 and 60 are onlysparingly soluble in most of the common organic solvents, it was reasonable to assumethat the (presumably planar) [7]phenylene 119 would be even less soluble. However,subjecting the two substituted precursors, 142a and b (bearing solubilizing DMTS andhexyl groups, respectively) to [CpCo(CO) 2 ] failed to produce even traces of phenylenes143a and b, respectively (Scheme 2.12).87

R' RR'RR'R'RR(ii)x141a, R = TMS141b, R = DMTS141c, R = Hex(i)142a, R' = DMTS, R = H123, R = R' = H142b, R' = H, R = Hex143a, R' = DMTS, R = H119, R = R' = H143b, R' = H, R = HexScheme 2.12 Attempted preparation of 119 and 143a–b: (i) for 123 and 142b: TBAF,THF, 23 °C, 1 h, (95%); for 142a: K 2 CO 3 , MeOH/Et 2 O, 23 °C, 1 h, (95%); (ii) for 119,143a and b: [CpCo(CO) 2 ], m-xylene, hν, reflux, 1 h, 0%; for 119 only: [CpCo(eth) 2 ],THF, –25 °C, 16 h, followed by 1,3-cyclohexadiene, THF, 90 min, 110 °C.The failure of the synthetic routes to 119 and 118 (Section 2.4) is puzzling,especially in view of the fact that the preparation of phenylenes by double CpCocycloisomerizationhas precedence, most relevantly for the isomeric 28 (Section 1.2.2.1,Scheme 1.7) 66 and syn-doublebent [5]phenylene 60 (Section 2.3, see also Chapter 4).During efforts to optimize the problematic Sonogashira coupling to 141 (Scheme2.11), an unexpected result was obtained. Performing the reaction between 140 and 134cin undried commercial piperidine provided the aldehyde 144 (Figure 2.4) as the soleisolable product in 34% yield. Thus, while one of the reactive sites of 140 had beenfunctionalized in the expected Sonogashira fashion, the other terminal triple bond hadbecome hydrated in an anti-Markovnikov manner. The aldehyde was formed as an88

exclusive product; not even a trace of Markovnikov-type methyl ketone could be detected(by 1 H NMR). This observation suggests stereochemical, rather than electronic control ofselectivity.To place these results within the context of the literature, there are reports of anti-Markovnikov palladium-catalyzed alkyne hydroesterification 138 andhydroalkoxylation, 138a,139but not of hydration. On the other hand anti-Markovnikovalkyne hydrations have been catalyzed by other transition metals. 138,140Moreover,Sonogashira reactions occur in water, 141 suggesting that the formation of 144 was anR R'OR144, R = DMTS, R' = HexFigure 2.4 Aldehyde 144.anomaly. Nevertheless, we tested our catalyst system in this respect by treatingphenylacetylene with iodobenzene in piperidine in the presence of added water (100equivalents). The only product was diphenylacetylene. In addition, exposing simplealkynes (1-octyne, phenylacetylene, TMSA, and DMTSA) to a 100-fold excess of waterand [Pd(PPh 3 ) 2 Cl 2 ]/CuI in piperidine at 120 °C. Again, hydration was not observed–themain products (in the complex mixture) were the alkyne homocoupling dimers of the89

type R–≡–≡–R. It is possible that steric hindrance in the singly coupled intermediate ofthe reaction of 140 with 134c (Scheme 2.11) slows further reaction sufficiently to allow ahydration pathway to take place. It remains to be tested whether other hindered alkynesbehave in the same way.2.5.2 Intermolecular ApproachThe intramolecular approach to 119 has biphenylene building blocks incorporatedinto the final cyclization precursors 141. A more convergent synthetic alternative can beenvisioned, in which decayne 124 undergoes both intra- and intermolecular cyclizationsto generate all component four-membered rings in one step (Scheme 2.3a). This methodhas been used previously in the syntheses of phenylenes 38 (Section 1.2.2.2, Scheme1.10b) 74 and 52 (Section 1.2.2.3, Scheme 1.12b). 75DMTSDMTS57(i), (ii), (iii)BrI(iv), (ii), (iii)IDMTSDMTSTMS145146Scheme 2.13 The synthesis of 146: (i) DMTSA, [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 23 °C, 48 h,92%; (ii) BuLi, Et 2 O, –50 °C, 45 min; (iii) I 2 , Et 2 O, from –50 °C to 23 °C, 12 h, 99 %90

(for 145, over two steps), 75% (for 146, over two steps); (iv) TMSA, [Pd(PPh 3 ) 2 Cl 2 ], CuI,Et 3 N, 23 °C, 1 h, 79%.To required dodecayne 124 was built through a Sonogashira coupling of 140 with1,2,4,5-functionalized arene fragment 146 (Scheme 2.13). The latter was prepared asshown in Scheme 2.13, starting with 57 via 145. The coupling between 140 and 146R RRRRR140+146(i)R'R'147, R = DMTS, R' = TMS124, R = R' = H(ii)(iii)TMSTMSTMSTMSScheme 2.14 Preparation of 148: (i) [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, reflux, 16 h, 87%; (ii)TBAF, THF, 23 °C, 1 h, followed by EtOH, 23 °C, 1 h, (95%); (iii) BTMSA,[CpCo(CO) 2 ], m-xylene, hν, reflux, 1 h, traces.14891

proceeded uneventfully, providing 147 in 87% yield. The ensuing deprotection gave 124,which was immediately subjected to the cobalt-mediated cocyclization with BTMSA(Scheme 2.14). Analysis of the reaction mixture by thin-layer chromatography revealedat least four products, the polarities of which were similarly low – possibly indicating thatall components of the mixture contained silyl groups. The 1 H NMR spectrum wasdifficult to interpret, as it showed at least six signals in the silyl region (δ 0–0.5 ppm) andmore than 15 weak signals between δ 6.4 and 7.6 ppm. The mass spectrum (EI, 70 eV)was somewhat more insightful, as it revealed the presence of several weak ions in theregion of interest (m/z > 800), at m/z values of 810, 840, 923 and 934. The first one ofthese signals is consistent with the presence of 148 (m/z 810), while the peak at m/z 934can be interpreted as 148·CpCo. Repeated separation attempts by ordinary columnchromatography and HPLC failed to produce pure 148.2.6 Attempted Synthesis of U-Shaped [9]Phenylene (120)The last phenylene to be targeted as part of these investigations was the helical U-shaped [9]phenylene 120, only the second [9]phenylene to be pursued to date. 70 Itsproposed synthesis relied on the four-fold intramolecular cyclization of 125 (Scheme2.3b).As indicated in Section 2.2, 125 was built formally from 124 by tethering twoadditional alkynes via an o-phenylene linker. For this purpose, the TMS groups of 147(the synthetic equivalent of 124) were selectively deprotected. The resulting diterminal92

alkyne was treated with 1-iodo-2-[(trimethylsilyl)ethynyl]benzene 142 under Sonogashiraconditions, producing 149, the protected version of 125 (Scheme 2.15).RRRR R'R RRRRRRRR'R'R'(i), (ii)147, R = DMTS, R' = TMS120x(iv)149, R = DMTS, R' = TMS125, R = R' = H(iii)Scheme 2.15 Attempted preparation of 120: (i) K 2 CO 3 , MeOH/Et 2 O, 23 °C, 90 min,(95%); (ii) 1-iodo-2-(TMSethynyl)benzene, [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, reflux, 16 h, 88%;(iii) TBAF, THF, 23 °C, 2 h, (95%); (iv) [CpCo(eth) 2 ], THF, –25 °C, 16 h, followed by1,3-cyclohexadiene, THF, 100 °C, 90 min.In-situ fluoride-assisted deprotection of 149 was followed by the application of the[CpCo(eth) 2 ] cyclization conditions. Disappointingly, again no cyclization products wereobserved. Given the ambitiousness of the four-fold CpCo-mediated cyclization and thelow yields (0.2–3.5%) observed in triple cyclizations (Section 1.2.2.1, Schemes 1.8 and1.9), 70,82 this negative outcome is perhaps not surprising. Additionally, the probableinstability of the octaterminal dodecayne 125 might have contributed to this negativeoutcome.93

2.7 Calculated and Measured Properties of 60, 118, 119, and 120This section will focus on the experimentally observed properties of 60, as well ason the calculated structural and energetic data for all the phenylenes discussed in thischapter. Comparisons will be made, where applicable, between the novel phenylenes andtheir previously synthesized homologues.Syn-doublebent [5]phenylene (60) is an orange-red material, which decomposeswhen exposed to air, both in the solid state and (significantly faster) in solution. Thesystem seems to be more inert to hydrogenation than either 9b or 15, as it remained intactunder comparable conditions (Pd/C, 1 atm H 2 , 5 h). Increasing the pressure of hydrogengas led to decomposition. Over the course of a few days, 60 reacted with atmosphericoxygen (both as a solid and in CHCl 3 solution). The mass spectrum of the productmixture showed molecular ions consistent with the addition of one and two molecules ofoxygen, suggesting oxidation via initial single and double endoperoxidation. Analogousresults were observed in the oxidations of 15 and 97 (Section 1.3.3, Scheme 1.24, Figure1.5). 74,97 In an attempt to activate C(aryl)–C(aryl) bonds (as precedented for 15, Section1.3.5, Scheme 1.28), 97 60 was treated with an excess of [CpCo(eth) 2 ], but this procedurefailed to produce any isolable products. No further experiments were carried out, becauseof the small amounts of 60 prepared. A more efficient synthesis will be required to fullyassess its chemical reactivity.Since it was impossible to obtain a sample of 60 suitable for X-ray analysis and118–120 could not be made, a discussion of their structures has to rely on calculated94

(B3LYP/6–31G*) data (Figure 2.5). Such calculations have been shown to reproduceexperimental values faithfully, most recently in the example of anti-doublebent[5]phenylene 56 (with deviations ∆ avg = 0.008 Å, ∆ max = 0.016 Å, Section 1.4.1, Figure1.8). 76 In addition, since calculated bond lengths for 56 and 60 are essentially identical,the extrapolation of the experimental bond lengths of the former to those of the latter isjustified. 76The central ring of 60 is calculated to adopt the characteristic bisallylic pattern(average allyl bond length 1.393 Å), previously observed in 9b (1.392 Å, Section1.4.1), 115 bis(silyl)bent [4]phenylene 52 (1.389 Å, Section 1.4.1), 75 and 56 (1.387 Å,Section 1.4.1). 76 The same is true for the central rings in the linear fragments of 118–120,with the corresponding averaged allyl bond lengths being virtually identical (118: 1.395Å, 119: 1.394 Å, 120: 1.394 Å).Conversely, the angularly fused benzene ring in 60 is predicted to exhibit evenmore bond fixation (experimentally in 56 - 66%, calculated in 60 - 60%) than the centerof 15 (64%, Section 1.4.1. Figure 1.8), 35 but the same as the corresponding ring ofsilylated 52 (67% Section 1.4.1. Figure 1.8). The localization in the first (50%) andsecond (53%) internal cyclohexatriene ring of the C-shaped 118 is expected to be lowercompared to 60; this result is expected, since the replacement of a localized benzene ringwith a biphenylene moiety allows relative delocalization in the six-membered rings of thelatter. In 119, the central six-membered ring should be relatively delocalized (44%),while the neighboring rings should show increased bond-alternation (56%). Phenylene95

6.636.4233%-7.5 7.36.24N/A-4.764%-3.36.183.124%-9.56.966.989b156.906.996.68 6.6829%*6.85-7.56.507.56.46-6.46.392.66.90 67%-2.95.942.323%-9.8 6.076.976.9048 a N/A5.966.526.0466%-2.92.9N/A-7.56.782.517%-9.76.866.8656, 1,2-dichlorobenzene-d 47.016.976.7322%*-9.72.56.9260N/A-7.52.960%*-2.96.126.586.0650%*21%*53%* 23%* 28%*58%*56%*54%*44%* 44%*118 119 120Figure 2.5 Measured bond localization percentages (from X-ray data), experimental 1 HNMR chemical shifts (CDCl 3 , unless mentioned otherwise), and calculated NICS(1)values of phenylenes relevant to discussion in Section 2.6. All NICS values refer to theparent compounds. An asterisk denotes a calculated bond localization percentage for theparent system. Double bonds are omitted for clarity. a Localization values of 23% and67% were crystallographically determined for the unsubstituted rings of 52 (the silylatedderivative of 48).96

119 should thus feature the central angular [3]phenylene substructure with invertedlocalization parameters compared to its counterpart in 28. 66 The central [3]phenylene unitin 120 behaves in the same way (44% and 54%, respectively). The terminal rings in allsystems are minimally distorted, with a somewhat higher localization predicted for 119(28%), because of the linear fusion at the terminus. This expectation is in accord with thehigher localization of terminal rings in 9b vs. 15.The calculated structures of phenylenes 60 and 118–120 are shown in Figure 2.7.Compounds 60, 118, and 119 are predicted to be essentially planar. A structural featurethat is of interest in 119 and 120 is the “wing”-angle, defined as the angle between thevertical projections of two linear[3] fragments onto the plane of the central ring(equivalent to analyzing artificially flattened structures of the above mentionedphenylenes). Because of the inherent distortion of the angular [3]phenylene frame, thecalculated value of this angle is not 0 °, but 11.2 ° (119) and 14.9 ° (120). The structure ofangular [3]phenylene (Figure 2.6) offers insight into the origins of this deformation.Thus, focusing just on the bond angles of the central “bay” region, moving from thecenter to the terminal ring, the first two neutralize each other’s effects (153 and 147 °).However, the third is larger (123 °) than normal, a consequence of strain-inducedrehybridization, typical of phenylenes (Section 1.4.1). 116,117 This widening effectivelymoves the terminal rings of 15 away from each other, thus expanding the “bay” region.As a consequence, the vectors (dashed lines in Figure 2.6) between the centroids of the97

H123 o147 o 153 oFigure 2.6 X-Ray structure of angular [3]phenylene 15 with bond angles responsible forthe “wing”-angle deformation in higher angular and U-shaped phenylenes.terminal rings and the bonds shown in bold in Figure 2.6 are at an angle of 2.3 °. Thesame distortion is evident in the crystal structure of the parent angular [5]phenylene (19,9.1 °). 66 Forcing 119 into a structure in which the “wing”-angle is 0 ° destabilizes thesystem by 10.75 kcal mol –1 . This result suggests that circular [8]phenylene (121) mightsuffer from an additional form of strain caused by the constrained parallel arrangement ofthe linear [3]phenylene fragments.The calculated structure for 120 highlights its inherent helical nature (Figure 2.7).A comparison between [7]heliphene (28) and 120 is particularly instructive, since thelatter can be viewed as 28 with “linear phenylene” spacers. The distance between thecentroids of the terminal rings is higher in 120 (5.23 Å, 28: 4.54 Å). On the other hand,the corresponding interplanar angle is significantly larger in 28 (40.6 °, 120: 29.7 °),hinting at the fact that the helix turns more sharply in 28. Indeed, analysis of the innerhelix shows that while the absolute climb is comparable (120: 3.51 Å, 28: 3.64 Å), the inplaneturn has a much larger value in 28 (361.6 °, 120: 338.3 °). 66Clearly, the98

displacement of the linear fragments in 120 away from each other (reflected in the“wing” angle) also acts to separate the termini of the helix.Figure 2.7 Calculated structures of phenylenes 60 and 118–120, top and side views.The relatively low solubility of 60 precluded 13 C NMR measurements. Its 1 HNMR spectrum, however, is revealing, especially in comparison with related phenylenes(Figure 2.5). The assignments given in Figure 2.5 were made on the basis of signal99

multiplicity, including the simplification of the spectra of the dipropyl derivative 128,comparison to the NMR spectra of 9b, 15 and 48, and calculated chemical shifts. 76 Theeffect of additional annelation onto 48 (and 9b) is noticeably larger δ values (relative to9b and 48) for the hydrogens attached to the central ring, in accord with the changes inNICS values. Thus, the central protons in the linear fragment experience increasingdeshielding along the series 9b (δ = 6.24 ppm, NICS = –5.4) – 48 (δ = 6.46, 6.39 ppm,NICS = –6.4) – 60 (δ = 6.73, 6.58 ppm, NICS = –7.5), the result of consecutive bondfixation in the terminal rings, in turn subtly increasing aromaticity in the central ring andattenuating paratropism of cyclobutadienoid nuclei. In contrast, the central protons of theangular fragment, which are slightly shielded in 48 (δ = 5.94 and 6.07 ppm, NICS = –2.9)relative to 15 (δ = 6.12 ppm, NICS = –3.3, also vide supra), seem to be unchanged in 60(δ = 6.06 and 6.12 ppm, NICS = –2.9). The deshielding effect of the evolving “bayregion” manifests itself in the increased ∆δ of two protons on the central ring: 0.07 ppmin 48, 0.15 ppm in 60. Finally, a long range effect of symmetrization in going from 48 to60 seems absent, as indicated by the essentially identical NMR and NICS data for theterminal and first internal rings.Calculations of the heats of formation of the entire family of [5]phenylenes 76reveal that 56 and 60, despite the presence of the linear substructure, are not destabilizedrelative to their all-angular isomers 19, 44 and 150 (Figure 2.8). This phenomenon hasbeen traced to the opposing effects of the σ- (relatively stabilizing) and π-frames(relatively destabilizing) on the energetics of linear versus angular fusion. 82 Since NICS(1.0) values are reflective primarily of the properties of the π system, total NICS (i.e. thesum of all NICS values) 143 should rectify the relative ordering of these isomers. Indeed100

(Figure 2.9), such is found, the entire series exhibiting a fairly good linear correlationbetween ∆H f and total NICS (R 2 = 0.9816). Calculations on [7]phenylenes 118 and 119favor the former by 1.56 kcal mol –1 , understandably so in view of the fact that 118possesses just one linear fusion, whereas 119 has two.19, 0.65 (-22.12)44, 0.36 (-22.30) 150, 0.48 (-22.29)56, 0.01 (-21.96)60, 0.00 (-21.91)Figure 2.8 Calculated energies (relative to 60, in kcal mol –1 ) and total NICS values (inparenthesis) of selected [5]phenylenes.The electronic spectrum of 60 exhibits the typical two sets of absorptions athigher (λ max ~ 340–390 nm) and lower energy (highest wavelength λ max = 507 nm). Thereare no significant indications of the topological differences between the two doublebent[5]phenylene isomers, unlike for the series of angular vs. zigzag phenylenes. 60 In tunewith a trend emerging in the electronic spectra of the lower phenylenes, i.e. λ max101

(branched/angular) < λ max (linear), 1,47 these bands are at higher energy than that for thelinear [5]phenylene frame (530 nm), 57 but bathochromically shifted from those in thezigzag- (484 nm), 74 Y-shaped (C 2v ) branched (486 nm), 79 and angular isomers (470nm). 602.8 SummaryFour new phenylenes were targeted by CpCo-mediated cyclization; to this end,five routes–four of which were all-intramolecular, and one mixed intra/intermolecular–were developed to access the corresponding oligoyne precursors. Unfortunately, only oneof the envisioned cyclizations was successful.Syn-doublebent [5]phenylene (60) showed properties that closely parallel thosepreviously reported for its anti-relative 56. The expected stabilization of linear [3]- anddestabilization of angular [3]phenylene fragments (relative to their parent molecules) wasindeed observed. The calculated structures and relative energies of 118–120 seem tosupport predictions based on the arguments borne out in Section 1.4.Future studies should focus on renewed attempts to synthesize 118–120. In thisrespect, particularly appealing is the mixed intra/intermolecular route to 119, theexecution of which led to traces of compound that could be tetrasilylated 119.102

Chapter ThreeA Novel Alkyne Metathesis-Based Route to Dehydrobenzannulenes 84b3.1 IntroductionIn an alkyne metathesis 144 reaction, two triple-bonded carbon atoms swap theirsubstituent groups (Scheme 3.1). The first reports of a homogeneous catalytic version ofthis transformation date back to the mid 1970’s, when Mortreux and coworkers 145showed that exposure of alkynes to mixtures of [Mo(CO) 6 ] 146 and resorcinol led to astatistical scrambling of alkyl groups on the acetylene.R 1R 2+R 1R 1catalyst+R 2 R 1R 2R 2Scheme 3.1 Schematic representation of alkyne metathesis.It was not before the 1990’s, though, that the groups of Bunz and othersdeveloped more practical variants of this reaction 147and started applying itsynthetically. 148 In a typical example, a methyl alkyne (Scheme 3.1, R 1 = Me) is treatedwith an off-the-shelf mixture of [Mo(CO) 6 ] and p-chlorophenol, in o-dichlorobenzene asa solvent, at temperatures of 150–170 ºC. The use of methyl alkynes is crucial since itleads to the formation of 2-butyne as the other product of the reaction. This material isgaseous under the reaction conditions, and as such easily removed, either by a stream ofnitrogen, or by performing the reaction under a slight vacuum.103

While the ease of manipulation certainly speaks in favor of the in situ[Mo(CO) 6 ]/phenol catalytic system, long reaction times and high temperatures requiredare often incompatible with the sensitive functionalities of the starting materials. Thisproblem was particularly pronounced in natural product syntheses, necessitating thedevelopment of a more gentle reaction system. A well-defined tungsten-alkylidynecomplex [(Me 3 CO) 3 W≡CCMe 3 ] (151), first prepared by Schrock, 149was found tocatalyze alkyne metathesis under milder conditions (several hours, 80 ºC, toluene).Fürstner’s group 144a,150 was the first to apply 151 in synthesis. Because the resultingalkynes can be reduced stereoselectively to cis- or trans-alkenes, an alkynemetathesis/reduction sequence provides a solution to the problem of the poor E/Zselectivity in the related alkene metathesis reaction. 150a,c–e Other reports of use soonfollowed. 151 In 2005, 151 was made commercially available, 152 paving the way for itsmore extensive utilization in organic synthesis.Recently, a third catalytic system, based on the mixture of [Mo{N(t-Bu)Ar} 3 ] andmethylene chloride, was reported. 153 This and related combinations constitute the mostactive alkyne metathesis catalysts disclosed to date, 154 although they have the drawbackof cumbersome preparation and low stability.The general mechanism that is widely accepted as an explanation of the observedtrends in alkyne metathesis mediated by 151 (and related alkylidyne species) is given inScheme 3.2. It involves metallacyclobutadiene 152 as the key intermediate, which104

RRRRRRRRMR'MR'152MR'MR'Scheme 3.2 Proposed general mechanism of the alkyne metathesis.decomposes in solution to regenerate the reactive carbyne complex and yield themetathesis product. The dissociation of an alkyne from the metallacyclobutadiene is oftenthe slowest step of the reaction. 155The mechanism of action of the [Mo(CO) 6 ]/phenol catalytic system remainslargely obscure. Although it is tempting to speculate on the intermediacy of ametallacarbyne as the active catalyst, recent investigations have suggested trinuclearalkylidyne clusters as possible intermediates. 144c,1563.2 Retrosynthetic Approach to DehydrobenzannulenesThis chapter will disclose the potential of alkyne metathesis in the construction ofdehydrobenzannulenes, 157as exemplified in Scheme 3.3. It was postulated that thedehydrobenz[12]annulenes 153 might be constructed by the metathetic cyclotrimerizationof o-di(prop-1-ynyl)benzenes (154). Those would, in turn, be assembled from the readilyaccessible diiodides 155.105

R 2R 1R 1R 2R 2RR 21 R 1R 1R 1R 2R 2R 2R 2 R 1R 1R 1R 1R 2R 2II153a-g154a-ga: R 1 = R 2 = Hb: R 1 = CH 3 , R 2 = Hc: R 1 = CH 3 O, R 2 = Hd: R 1 = R 2 = CH 3e: R 1 = Br, R 2 = Hf: R 1 = H, R 2 = Brg: R 1 = H, R 2 = Cl155a-gScheme 3.3 Retrosynthetic analysis of dehydrobenz[12]annulenes 153a–g.The class of dehydrobenzannulenes is interesting in several respects - it providesattractive ligands to transition metal complexes, 158 models for subunits of graphyne - anovel allotrope of carbon, 88,89 precursors to ordered carbon nanostructures, 159 scaffoldsfor molecules on which to study supramolecular phenomena, 160and materials withinteresting photophysical properties. 161Our need for an efficient synthetic entry into substituted derivatives stems fromour quest for the first members of the circular phenylenes (Section 1.2.2.5, Scheme 1.18),such as antikekulene 77d 69 and circular [8]phenylene (121, Figure 2.2). 162 The synthesisof these elusive phenylenes relies heavily on all-ortho alkynylated dehydrobenzannulenesas precursors (exemplified for 121 in Scheme 3.4). Approaching circular phenylenesthrough this method takes advantage of their higher symmetry (relative to other106

phenylenes), and is therefore more elegant than the alternative based on Sonogashiracouplings (presented for 77d in Section 1.2.2.5, Scheme 1.18).121156Scheme 3.4 Retrosynthetic analysis of circular [8]phenylene 121.Prior to the work described here, Bunz and coworkers reported the preparation ofa series of meta-fused dehydrobenz[30]annulenes (exemplified by 158, Scheme 3.5) by[Mo(CO) 6 ]/p-chlorophenol catalyzed alkyne metathesis. The desired products wereisolated in 0.5–6% yields. 148e A recent improvement (Scheme 3.5) used molybdenumamidocomplexes in a precipitation-driven alkyne metathesis to produce 158 in a muchhigher 61% yield (on a mg scale). 154a107

(i)157 158Scheme 3.5 An example of the preparation of meta-fused dehydrobenz[30]annulenes byalkyne metathesis: (i) [Mo(CO) 6 ], p-chlorophenol, 170 °C, 20 h, 6%, 148eor[EtC≡Mo{N(t-Bu)Ar} 3 ], p-nitrophenol, 30 °C, 22 h, 61%. 154aAs representative targets, we directed our initial efforts to examples oftribenzocyclynes 153 (Scheme 3.3), and subsequently the more challengingtetrabenzocyclyne 159, as well as the fused systems 160 and 161 (Figure 3.1). The parent153a and its derivatives have received considerable attention, 157 whereas a substitutedversion of 159 160f and parent 160 163 have been prepared for the first time only recently,and through relatively long sequences.108

159 160161Figure 3.1 Dehydrobenzannulenes targeted via alkyne metathesis.The following sections will detail the synthetic execution of the proposal given inScheme 3.3. The preparation of the requisite iodobenzenes will be described first,followed by the Sonogashira coupling to the propynylated precursors. Finally, the resultsof the desired metathesis reaction will be presented.109

3.3 Preparation of Iodinated PrecursorsAs Scheme 3.3 outlines, a facile access to the iodides 155a–g was essential for theevaluation of the proposed route. If successful, this initial pool of iodoarenes was to beextended to several other systems (162–164, Figure 3.2) that would enable us to test theviability of cross metathesis leading to targets 159–161.IIIIIIIXXIII162163a: X = H163b: X = I57: X = Br164Figure 3.2 Additional iodoarene starting materials.Most of the starting materials were either available commercially (155a, 163a, 164) ordescribed previously in the literature. 78,164 Simple iodination of 1,2-dibromobenzene withI 2 /H 5 IO 6 , 164d provided 1,2-dibromo-4,5-diiodobenzene (155e). The desymmetrized 1,2-diiodo-3,5-dimethylbenzene (162) required utilization of 3,5-dimethylanthranilic acid inan aprotic diazotization/iodination sequence, which proceeded through a substitutedbenzyne intermediate (Scheme 3.6). 165 An analogous sequence furnished 155g.110

NH 2 162(i)(ii)ICOOHIScheme 3.6 Preparation of 1,2-diiodo-3,5-dimethylbenzene (162): (i) isoamyl nitrite,dioxane, 80 °C, 2 h; (ii) I 2 , 76% (over 2 steps).In contrast, 1,4-dibromo-2,3-diiodobenzene (155f) had to be prepared by a significantlymore complicated synthetic route (Scheme 3.7). 166 It started with 2,5-dibromoaniline,which was converted into the corresponding isonitrosoacetanilide by treatment withBrBrNH 2BrBrBrHHN ONNH 2(i) (ii) (iii) (iv)ONCO 2 HBr OH Br OBrBrBrII155fScheme 3.7 Preparation of 1,4-dibromo-2,3-diiodobenzene (155f): (i) NH 2 OH·HCl,Cl 3 CCHO·H 2 O, H 2 O, EtOH, reflux, 12 h, 84%; (ii) 86% H 2 SO 4 , 100 °C, 15 min, 47%;(iii) NaOH, H 2 O 2 , 50 °C, 1 h, 47%; (iv) I 2 , isoamyl nitrite, ClCH 2 CH 2 Cl, 1 h, reflux,58%.chloral hydrate and hydroxylamine. Acid-catalyzed cyclization to 3,6-dibromoisatineproceeded uneventfully 167 and was followed by basic hydrolysis in aqueous hydrogenperoxide to yield 3,6-dibromoanthranilic acid. 168 Finally, the acid was converted to 155fby employing an aprotic diazotization procedure. 165 The overall yield of the reaction111

sequence is a modest 11%, a fact that is compensated for by the simple workup, as nopurification of intermediates was needed.3.4 Classical and Microwave-Assisted PropynylationsThe requisite diynes 154a–g for the metathetical cyclization were accessed bySonogashira reaction of appropriately substituted iodoarenes (Scheme 3.8, Table 3.1).The respective couplings of otherwise unsubstituted and of alkyl- or alkoxy-substitutediodoarenes proceeded cleanly, in good to excellent yields (entries 1–4, 7–10, 12 in Table3.1). Entry 12 in Table 3.1 deserves special mention as one of the rare examples of sixfoldSonogashira coupling to hexaiodobenzene. 169I 2-6 2-6Scheme 3.8 Propynylation reactions: (i) propyne (1–2.5 atm), [PdCl 2 (PPh 3 ) 2 ], CuI, NEt 3 ;specific conditions for individual substrates are given in Table 3.1.Entry Iodoarene Product Conditions Yield (%)1 155a 154a 25 °C, 22 h 952 155b 154b 25 °C, 26 h 573 155c 154c 25 °C, 48 h 814 155d 154d 25 °C, 96 h 915 a 155e 154e 110 °C, 3.75 min, microwave 71112

Entry Iodoarene Product Conditions Yield (%)6 a 155f 154f 110 °C, 20 min, microwave 607 155g 154g 110 °C, 16 h 688 16216525 °C, 44 h 769 163a166a25 °C, 22 h 9310 163b166b90 °C, 36 h 7711 a 57Br166cBr100 °C, 2 min, microwave 6412 b 16490 °C, 60 h 28167Table 3.1 Propynylation reactions. a DMF (10%) was used as a cosolvent. b Penta(prop-1-ynyl)benzene was obtained as a side product in 32% yield.To retain the potential of subsequent introduction of further alkyne substituents, 69,162tribenzocyclynes bearing bromine 170 substituents were also of interest. Their preparationrequired the selective alkynylation of bromoiodoarenes (entries 5,6,11 in Table 3.1).While such is often achievable at room temperature, 171113we noticed significant

overalkynylation in systems 155e, 155f, and 57. Monitoring the course of the reaction tothe point of optimal conversion proved difficult because of the use of closed systemsunder the positive pressure of propyne (closed systems were chosen in order to ensureeconomic use of the relatively expensive propyne gas).We therefore turned our attention to microwave-assisted Sonogashira couplings 172executed in a Smith Synthesizer. 173Application of this technique allowed thedipropynylation of three isomers of dibromodiiodobenzene at 100–110 °C (entries 5,6,11in Table 3.1) with excellent selectivity in less than 20 minutes. Monitoring the change inpressure during the course of the reaction (Figure 3.3) provided a convenient gauge of itsFigure 3.3 Pressure changes as a function of reaction time in Pd-catalyzedpropynylations of 155e in a Smith Synthesizer. There is an initial pressure increase, asheating commences. The reaction starts at t ~ 5 min, causing the propyne pressure todrop, and ends at t ~ 15 min. The heater was turned off at t ~ 44 min.progress. The instrumental setup (heavy-walled sealed Smith Process vials, 5–10 mLvolume, pressurized with gaseous propyne) enabled this reaction to be performed only on114

a relatively small scale; this procedure was thus restricted to the preparation ofpropynylated benzenes for which classical conditions proved to be too hard to control.The results of all propynylation reactions, both “classical” and microwaveassisted,are summarized in Table 3.1.3.5 Dehydrobenzannulenes by Alkyne MetathesisWith the well-developed route to o-dipropynylated benzenes in hand, thefeasibility of alkyne metathesis to tribenzocyclynes could be tested. Due to the simplicityof the [Mo(CO) 6 ]/p-chlorophenol system, this catalyst was used in our first experimentswith 154a as the substrate. Under a variety of conditions - performing the reaction atdecreased pressure, under a constant stream of nitrogen (both of which served to remove2-butyne formed), or with variable catalyst loading - not even trace amounts of 153a(GC/MS) were detectable. The only occasional product was the metathesis dimer, 1,1’-(1,2-ethynediyl)bis[2-(prop-1-ynyl)benzene, generated in approximately 2% yield (byGC/MS analysis).Gratifyingly, turning to 151 174 as the catalyst, the reaction proceeded cleanly togive 153a in 54% yield as the only isolable product (Scheme 3.9, entry 1 in Table 3.2).This preparation is superior in terms of yield and simplicity compared to other recentlypublished approaches that, for the most part, rely on sequences of Pd-catalyzed crosscouplings and proceed in yields ranging from 15% to 40%. 86c,d,158a,b,175115

R 2R 1R 1R 1R 2(i)R 2R 1R 2R 1R 2R 1R 2R 2R 2R 1R 1Scheme 3.9 Dehydrobenz[12]annulenes by alkyne metatheses: (i) 151 (20 mol%),PhCH 3 , 80 °C, specific conditions for individual substrates given in Table 3.2.Entry Starting material Cyclyne Reaction time (h) Yield (%)1 a 154a 153a 8 542 b 154b 153b 24 273 c 154c 153c 140 284 154d 153d 96 05 154e 153e 120 126 154f 153f 96 07 154g 153g 36 0Table 3.2 Dehydrobenz[12]annulenes by alkyne metatheses catalyzed by 151. a Ref. 176 . bRef. 177 . c Ref. 158a,d.Encouraged by this result, scope and limitations were investigated, summarized inTable 3.2. A rather simple trend was observed - sterically more crowdedbisorthosubstituted precursors did not undergo cyclization (entries 4,6,7 in Table 3.2),whereas bismetasubstituted ones did (entries 2,3,5 in Table 3.2). This outcome was not116

particularly dependent on electronic effects - both electron withdrawing (Br) and electrondonating (OMe and Me) substituents were tolerated as long as they were located in metapositions; interestingly, substrates with resonance donors as substituents (Br and OMe)reacted more slowly (~ 2–4 times) than their unsubstituted or alkylsubstitutedcounterparts.To provide an intramolecular test for the proposed steric trend, substrate 165 wasinvestigated, in which the two alkyne units are differentiated by bearing an ortho- and ameta-methyl group, respectively. It should react only once, to give the product ofmetathesis of the sterically less crowded triple bond. Indeed, the system produced solely168 in 55% yield (Scheme 3.10).(i)165 168Scheme 3.10 Regioselective alkyne metathesis reaction: (i) 151, PhCH 3 , 80 °C, 72 h,55%.While the yields of the products depicted in Table 3.2 are modest, the simplicityand straightforward execution of the method would seem to make it that of choice for therapid synthesis of specific derivatives, in particular when such are endowed withinteresting novel topologies. As a consequence, and to explore the possibility of ringclosure cross metathesis, we targeted the parent hydrocarbons 159–161. To our delight,117

equimolar proportions of 154a and 166a converted directly to the new tetrabenzocyclyne159 in 19% yield (Scheme 3.11a)! Even more impressive was the finding that 154a and166b (4:1) underwent six-fold metathesis to furnish 160 in 6% yield (Scheme 3.11b).This compound, as previously reported, 163 was extremely insoluble in common organicsolvents, probably to the detriment of the isolated yield. Finally, not unexpectedly in lightof the results described above, hexapropynylbenzene 165 was inert to metathesis with154a (on route to 161) and even simple propynylbenzenes.(a)154a+166a(i)159(b)154a+166b(i)Scheme 3.11 Alkyne metathesis to 159 and 160: (i) 151, PhCH 3 , 80 °C, 60–84 h, 19%(159), 6% (160).160118

3.6 Properties of Novel DehydrobenzannulenesCyclyne 159 constitutes the parent of a di-tert-butyl derivative synthesized as partof a series of phenylacetylene macrocycles adorned with solubilizing substituents. 160f Itis, nonetheless, quite soluble in common organic solvents, exhibiting strong, purplefluorescence. Its 1 H NMR spectrum contains a characteristic peak due to the proton insidethe macrocycle at δ = 8.05 ppm (CDCl 3 ). The less benzofused system 169 (Figure 3.4)shows the analogous absorption at δ 7.82 ppm (CDCl 3 ), possibly (but not necessarily) areflection of increased dehydro[18]annulenoid diatropism. 178 The aromaticity of cyclynesas measured by the ring current criterion is a topic of renewed current scrutiny. 23169Figure 3.4 Cyclyne 169.The X-ray crystal structure of 159, 179 shown in Figure 3.5, is only slightly distorted fromideal planarity–the dihedral angle between the planes of the respective meta- and orthofusedrings is 7.1 °. The intraannular hydrogen–hydrogen distance is 2.29 Å; incomparison, in 169 this distance is 2.57 Å–a possible indication of the greater flexibilityof the system. 178 The compound crystallizes in the C2/c space group, with four moleculesof 159 in the unit cell.119

Figure 3.5 ORTEP diagram of 159. Thermal ellipsoids shown at the 50% probabilitylevel.Although 160 was described previously, 163 its 1 H NMR spectrum could not beobtained due to seemingly poor solubility. We have found 160 sufficiently soluble inCDCl 3 to allow for such a measurement. The molecule gives rise to an AA’BB’ multipletfor the peripheral aromatic hydrogens at δ = 7.19 and 7.44 ppm, instead of the expectedABCD pattern, reflecting local symmetry, and a singlet at δ = 7.34 ppm for the protonson the central benzene ring. These appear shielded relative to the corresponding ringhydrogens in 1,2,4,5-tetraethynylbenzene, which resonate at δ 7.63 ppm (CDCl 3 )–anindication of the effect of the two neighboring paratropic cyclyne moieties. 180120

3.7 SummaryWe have shown that alkyne metathesis holds promise as a general tool for theconstruction of benzocyclynes. Although some of the reactions proceed in relativelymodest yields, this is compensated for by a synthetic approach that is short andstraightforward. The feasibility of the reaction is dependent on the substitution pattern ofthe starting materials; this effect is presumably steric in nature and could be explored interms of regioselective alkyne metathesis reactions. Furthermore, it is possible that someof the systems we found unreactive in the presence of 151 will yield themselves tometathesis with the new, more active, molybdenum-based catalysts.121

Chapter FourSynthesis of Octaalkynylated Dehydrobenz[18]annulenes and AttemptedCycloisomerization into Circular [8]Phenylene and Derivatives 1814.1 Introduction: Circular [8]PhenyleneNotably missing among the simple phenylene topologies synthesized are thecircular isomers. As mentioned in Section 1.2.2.5, this class of phenylenes differs fromother topologies by the potential for delocalization not just within the six-memberedrings, but also of the internal and the external annulenoid loops. This phenomenon isknown as superdelocalization 83 and has not been observed in hydrocarbons so far. 85Synthetically, our group has pursued actively circular [6]phenylene (77d,antikekulene, Figure 4.1, Section 1.2.2.5). In addition to this system, circular [4]-, [5]-,and [7]phenylenes have been theoretically scrutinized. 55 The former two molecules arebowl-shaped and significantly strained (e.g. circular [5]phenylene is destabilized by 46.8kcal mol –1 due to its bowl shape). 55 Circular [7]phenylene is planar, but still strainedrelative to 77d.The next higher strain-free homologue is circular [8]phenylene (121, Figure 4.1),formally a derivative of 77d with two linear phenylene spacers. Both 77d and 121 are 4nspecies (Section 1.1), with π-electron counts of 36 and 48, respectively. In 77d, theinternal and the external supercircuits also have 4n π-counts–12 and 24, respectively.Each of the extra linear fragments present in 121 contributes one additional atom to theinternal and one less atom to the external loop, switching the respective π-counts to 18122

and 30, both of which are 4n+2. Thus, while both superloops in 77d are formallyantiaromatic, in 121 they are aromatic, which is expected to impart some additionalstability to the system.77d121Figure 4.1 Circular [6]- (77d) and [8]phenylene (121).If annulenoid aromaticity of the 18- and 30-electron supercircuits were indeed tobe present, it could manifest itself in the accentuation of the resonance form depictedabove for 121. For example, one might expect bonds shared between the six-memberedrings and each one of the supercircuits to become increasingly “double”, while radialbonds connecting two supercircuits might become increasingly “single”. A comparisonbetween the calculated structures of 121 and non-circular models 118–120 (Section 2.7)is given in Figure 4.2. The effects of the superloops appear to be too subtle to be visible,at least structurally. For example, going from 119 to 121, one would expect a decrease inthe bond alternation in the peripheral six-membered rings of the linear fragment, since thebond-localizing effect of the linear moiety is shared by two angular fragments in 121(analogous to comparison between 48 and 56/60, Section 1.4.1, Figure 1.8). 75,76123

50%21%53% 23% 28%58%56%54%44% 44%118 119 12056%46%121Figure 4.2 Bond localization percentages for 121 and some non-circular analogs(calculated values, B3LYP/6-31G*).However, this behavior is not observed, as both 119 and 121 show 56% localization. Thecentral ring in 119 is 2% more localized than its counterpart in 121. Seemingly inagreement with the annulene-enforced localization is a comparison between 120 and 121.In the former, the central ring is 44% localized, its neighbor 54%. The values foranalogous rings of 121 are 46 and 56%, respectively, although the first point of differencebetween the two molecules is four (relative to the center of 121) six-membered ringsaway!124

The structure of 121 is shown in Figure 4.3. The molecule is almost planar, themost significant deviations being in the positions of two internal hydrogen atoms. Theseare oriented in a way that maximizes their interatomic distance (to 1.80 Å) – one of themlying above the average molecular plane, the other positioned below it. These distortionsgo hand in hand with a deformation of the carbon skeleton. Thus, the angle between theplanes of the central six-membered rings of the linear fragment of 121 and the central sixmemberedrings of the angular [5]phenylene subunit (the “most right”/”most left” rings inFigure 4.3) is 3.9 °. Previous molecular mechanics calculations placed this angle at 7.1 °and the internal H–H distance at 2.30 Å. 162 Finally, the bisallylic pattern calculated forthe central linear rings of 60 and 118–120 (Section 2.7) is predicted for 121 as well.Curiously, the bonds of the linearly fused ring that are also part of the [18]annulenecircuit are much shorter (1.385 Å) than those shared with its [30]annulene counterpart(1.401 Å). In 60, these values are virtually identical (1.393 and 1.394 Å, respectively).Figure 4.3 Calculated structure of 121 (B3LYP/6-31G*, top and side views).125

A much more sensitive probe of aromaticity are 1 H NMR chemical shifts. 2,5Therefore, the potential superaromaticity of the aromatic superloops might manifest itselfin relative deshielding of the outside hydrogens and, most diagnostically, shielding of theinside ones. 5 In [18]annulene itself, the latter value is –2.88 ppm (THF-d 8 , –59.5 °C), 182 anumber large enough to lead to the anticipation that even a strongly attenuated effect ofsuperdelocalization would be measurable.This chapter will detail the synthesis of dehydrobenzannulenic precursors to 121and substituted versions thereof. The discussion of the results of the attempted conversionof these materials by CpCo-cycloisomerization will follow. The chapter will concludewith the presentation of the properties of some new phenylenes prepared during theseattempts.4.2 Retrosynthetic Analysis of Circular [8]PhenyleneDue to their unique structures devoid of terminal six-membered rings, circular[N]phenylenes can be accessed only by intramolecular CpCo-mediated cyclizations of thecorresponding precursors (Section 1.2). Focusing on circular [8]phenylene (121) as thetarget, the choice of potential precursors is even more limited, since the central rings oflinear [3]phenylene fragments in 121 have to be included in the structure of theprecursors (Section 1.2.1). Based on this notion, dehydrobenz[18]annulenes 156 and171a–c (Scheme 4.1) were chosen as precursors to 121 (and its derivatives 170a–c).Successful conversion into circular phenylenes would require an unprecedented four-foldCpCo-cycloisomerization. 183126

RRRRRRRRRRRRRR R R170a, R = Pr170b, R = Hex170c, R = DMTS121, R = H171a, R = Pr171b, R = Hex171c, R = DMTS156, R = HScheme 4.1 Retrosynthetic analysis of 121 and its derivatives.Consideration of simpler cycloisomerization substrates suggested two alternativesto 156/171, shown in Figure 4.4. In 172 (Figure 4.4, left), five of the eight six-memberedrings of 121 are already preformed, requiring only a triple cobalt-catalyzedcyclization. 70,82In 173 (Figure 4.4, right), six of these rings are already present,necessitating only a double cyclization. 66,74,76 While these routes may seem tempting,neither the 1,2,8,9-tetrahalogenated biphenylenes required for the assembly of 172, norappropriately substituted linear [3]phenylenes on route to 173 are known and are in factnot easily accessible by current art. Thus, only the 121 → 156 disconnection wasconsidered.127

172 173Figure 4.4 Alternative (but impractical) precursors to 121.The results presented in Chapter 3 indicated that the direct formation of all-orthobrominated dehydrobenz[18]annulenes (followed by per-alkynylation) would not bepossible due to the steric limitations of alkyne metathesis. Therefore, an alternativestepwise approach was envisioned, which produces 171 by the formal dimerization of174 (Scheme 4.2). Compound 174, in turn, would be made through a Sonogashiracoupling of 1,2,4,5- and 1,2,3,4-substituted arene fragments 175 and 176. Thisretrosynthetic proposal allowed for the easy modification of the nature of the substituentsR, which might become necessary as both solubilizing and protecting units.128

RRRRRR R RRRRIR171a, R = Pr171b, R = Hex171c, R = DMTS156, R = H174a, R = Pr174b, R = Hex174c, R = DMTSRRR+BrITMSR175a, R = Pr175b, R = Hex175c, R = DMTS176a, R = Pr176b, R = Hex146, R = DMTSScheme 4.2 Retrosynthetic analysis of 171.4.3 Previous Attempts to Synthesize Circular [8]PhenyleneA route to circular [8]phenylene had been executed previously along theguidelines outlined in Section 4.2. In anticipation of solubility problems, the focus was onthe octapropylated derivative 170a via 171a. Thus, starting with 57, 78 triyne 177 wasmade in three steps (with the exception of the last step, the preparation paralleled that for146, Section 2.5.2, Scheme 2.13). 162,181 This material was deprotected and coupled with129

the previously described 2-iodo-1,4-di(pent-1-ynyl)-3-[(trimethylsilyl)ethynyl] benzene 69to give the elaborated diphenylacetylene 178 in 72% yield (Scheme 4.3).PrPrPrPrPr(i), (ii)BrBrTMSTMSPr177178Scheme 4.3 The synthesis of 178: (i) TBAF, THF, 23 °C, 30 min, (95%); (ii) 2-iodo-1,4-di(pent-1-ynyl)-3-[(trimethylsilyl)ethynyl]benzene, [Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 70 °C, 16h, 72%.Half of the so-produced 178 was deprotected to 179, while the other was subjected tobromine-iodine exchange that produced 180. These two fragments were coupled to 181(Scheme 4.4).130

PrPrPrBrPrPrPrPr Pr(i)179178(ii), (iii)PrPrPr(iv)TMSBrPrIPrPrPrTMS181Pr180Scheme 4.4 The synthesis of 181: (i) TBAF, THF, 23 °C, 30 min, 66%; (ii) BuLi, Et 2 O, –78 °C, 30 min; (iii) I 2 , Et 2 O, –78 °C, 10 min, 94% (over two steps); (iv) [Pd(PPh 3 ) 2 Cl 2 ],CuI, Et 3 N, 70 °C, 14 h, 80%.So-obtained 181 was subjected to another bromine-iodine exchange, deprotection of theTMS group and intramolecular Sonogashira reaction to provide the octa(pent-1-ynyl)dehydrobenz[18]annulene 171a in 30% overall yield (Scheme 4.5). Cobaltcatalyzedcycloisomerization of 171a stopped at doubly-cyclized 182 and 183,derivatives of doublebent [5]- and angular [3]phenylene, respectively. These twoproducts were formed exclusively – not even traces of mono- or triscyclized phenyleneswere observed (by 1 H NMR). Curiously, although a third double-cyclization product was131

possible, it was not generated in these experiments. Resubjecting 182 and 183 to thecatalyst in higher-boiling solvents either left the starting materials unaffected (1,2-dichlorobenzene) or completely destroyed them (1,2,4-trichlorobenzene). The synthesisof octapropyl circular [8]phenylene 170a and 121 was abandoned at this point, 162,181 untilthe work to be described next commenced.PrPrPrPrPrPrPrPr(i), (ii), (iii), (iv)180 171a(v)182+PrPrPr PrPrPrPrPrScheme 4.5 The synthesis of 171a and its cycloisomerization into 182 and 183: (i) BuLi,Et 2 O, –78 °C, 30 min; (ii) I 2 , Et 2 O, –78 °C, 10 min; (iii) TBAF, THF, 23 °C, 30 min; (iv)[Pd(PPh 3 ) 2 Cl 2 ], CuI, Et 3 N, 65 °C, 14 h, 30% (over 4 steps); (v) [CpCo(CO) 2 ], m-xylene,reflux, 45 min, 10% (182), 35% (183).183132

4.4 Synthesis and Properties of Octaalkynylated Dehydrobenz[18]annulenes 156and 171b–cThe failure to reach 170a via 171a could be due to a variety of reasons. Amongthem were still insufficient solubility of the target as well as the penultimate cyclizationintermediates derived from 182 and 183, and steric hindrance to cobalt-catalyzedcyclization imparted by the terminal alkyl substituents. To probe the validity of theseconsiderations, the synthesis of 156 and 171b–c was planned, 171b as a system in whichsolubility problems were thought to be truly irrelevant, and 171c as a protected precursorto 156, the latter providing the opportunity to tackle the parent 121.Within the context of a bigger picture, the dehydrobenzannulenes of the type 171were of interest also as novel members of this class of hydrocarbons. As Chapter 3mentioned, such constructs are subject to intense scrutiny because of their potentialapplications as optoelectronic, liquid crystalline, conducting, and sensing materials, asbuilding blocks in the construction of allotropes of carbon, as scaffolds forsupramolecular assemblies, and as monomers in topochemical and otherpolymerizations. 157 In this connection, the novelty of compounds 171 lies in their newtopology, combining the 1,2,3,4- with the 1,2,4,5-tetraethynylbenzene motifs in anelaborated octaalkynylated tetrabenz[a,b,f,j,k,o]-4,5,10,11,15,16,21,22-octadehydro[18]annulene, 84b endowed with internal hydrogens that can serve as probesfor the effect of peripheral alteration on the aromaticity of the central core. Parent 156 isalso the only second hydrocarbon of composition C 48 H 16 to be targeted for synthesis. 184133

The triynes 184b–c, reported previously, 69,185 were chosen as the precursors forthe 1,2,3,4-substituted moieties of 171b–c (Scheme 4.6). Selective TMS removal from184b–c generated the corresponding terminal alkynes, which were coupled with iodides176b/146 to give the highly functionalized diarylacetylenes 185b–c. Compounds 185b–cwere the source of both pieces needed to assemble 171b–c. Protodetrimethylsilylationprovided 186b–c; alternatively, another bromine-iodine exchange led to 187b–c (Scheme4.7). Sonogashira coupling of 186b–c and 187b–c created 188b–c, possessing all thecarbon atoms of 171b–c. Finally, bromine-iodine exchange, followed by TMSdeprotection and an intramolecular Sonogashira coupling afforded 171b–c (Scheme 4.7).In situ deprotection of 171c (TBAF/SiO 2 ) provided the parent 156, which decomposedwithin minutes, even in dilute solutions.RRRRTMSBr(i)175b175c+ 176b146(ii)BrTMSRR184b, R = Hex184c, R = DMTS185b, R = Hex185c, R = DMTSScheme 4.6 The synthesis of 185b–c and its cycloisomerization into 182 and 183: (i)K 2 CO 3 or KOH, MeOH/Et 2 O, 23 °C, 1 h; (ii) [Pd(PPh 3 ) 2 Cl 2 ], CuI, NEt 3 , reflux, 16 h,90% (185b, over two steps), 95% (185c, over two steps).134

The approach to 156 and 171b–c is a topological alternative to the schemeexecuted on route to 171a, as the roles of the coupling partners in Schemes 4.3 and 4.6were switched. The yields of the two routes are comparable.Dodecaynes 171b and c are yellow-brown waxy solids, stable to air, both neat andin solution. On the other hand, parent 156 decomposed quickly, even in solution, thusprecluding its isolation and full characterization. The electronic spectra are characterizedby a lowest-energy band (λ max = 369–377 nm) that is significantly shiftedbathochromically relative to that of the parent dehydrobenz[18]annulene (λ max = 341 nm),a reflection of the extensive alkynyl substitution. The NMR spectra show thecharacteristically deshielded intracyclic hydrogen signals at δ ~ 7.8 ppm 84band theappropriate number of 1 H and 13 C peaks. An exception is 171c, which featured four(instead of the expected two) sets of resonances of the methyl groups in the DMTSresidue. This was a consequence of conformational rigidity of 171c which rendered theDMTS methyl groups diastereotopic, and thus inequivalent in the NMR. A more detailedtreatment of this phenomenon will be presented in Chapter 5.135

RBrRRRRRRR185b185c(i)(ii), (iii)186b, R = Hex186c, R = DMTS(iv)BrRRRTMSRRTMSIRR188b, R = Hex188c, R = DMTS187b, R = Hex187c, R = DMTSR(i), (ii), (iii), (iv)156(v)171b171cScheme 4.7 The synthesis of 156 and 171b-c: (i) K 2 CO 3 or KOH, MeOH/Et 2 O, 23 °C, 1h, 98% (186b), 87% (186c); (ii) BuLi, Et 2 O, –45 °C, 30 min; (iii) I 2 , Et 2 O, –45 °C to 23°C, 2 h, 94% (187b, over two steps), 92% (187c, over two steps); (iv) [Pd(PPh 3 ) 2 Cl 2 ],CuI, Et 3 N, reflux, 16 h, 78% (188b), 78% (188c); (v) TBAF/SiO 2 , THF, 23 °C, 1 h. Theoverall yield of steps (i)–(iv) for 171b and c was 62% and 45%, respectively.136

4.5 Attempted Cycloisomerization of 156 and 171b-c into Circular [8]Phenylenes121 and 170b-cWith systems 156 and 171b-c available, experiments were executed aimed ataccessing circular [8]phenylene (121), and its derivatives 170b and c. The parent 156 wastreated with [CpCo(eth) 2 ] at low temperatures, followed by heating with 1,3-cyclohexadiene–a procedure analogous to the one employed in the successful synthesis ofsyn-doublebent [5]phenylene 60 (Section 2.3, Scheme 2.5). 76 Disappointingly, even whenusing in situ deprotection protocols, 157 complete decomposition of 156 was observed.Silyl-substituted 171c proved inert to [CpCo(CO) 2 ], not surprisingly in light of the stericbulk of the DMTS groups. Therefore, our efforts focused on the isomerizations of 171b(Scheme 4.8). Unfortunately, only double cyclizations were achieved to the deep-reddouble bent [5]- and yellow angular [3]phenylene derivatives 189 and 190, respectively.The polarities of the two products were virtually identical, precluding their separation.However, we were able to obtain 189 as the exclusive product by increasing the amountof [CpCo(CO) 2 ] to 6 equiv. These results parallel essentially those obtained with thecorresponding propyl system 171a, ruling out solubility as an issue. It is clear that somefactor is precluding complete cycloisomerization of the dodecaynes, in the case of 171astopping at 182 and 183, in the case of 171b at 189 and 190. It is possible that the parentsystem 156 suffers the same fate, but that in this case the dangling terminal triple bondsundergo intermolecular oligomerizations.137

RRRRRRR R171b(i)+RRRRRRRR189, R = Hex190, R = HexScheme 4.8 Cycloisomerization of 171b: (i) [CpCo(CO) 2 ], PhCH 3 , reflux, hν, 19%(inseparable mixture of 189 and 190). Isomer 189 was the only product (11%), when 6equiv of [CpCo(CO) 2 ] were used.Stymied by the above failures, calculational efforts were made aimed at gaining adeeper understanding of the reasons for them. Specifically, DFT calculations (B3LYP/6-31G*) of all possible cyclization products derived from 156 were performed (Figure 4.5).The most stable forms of all these compounds were predicted to be non-planar, althoughplanarization was energetically cheap. The respective energies and some of the important(vide infra) structural results are summarized in Figure 4.5 and Tables 4.1 and 4.2 (forplanar and deplanarized structures, respectively). The data predict that a) thecycloisomerization sequence is quite exothermic, ~ 50 kcal mol –1 per step; b) as thecyclization progresses, the resulting phenylenes planarize more easily (evidenced bysmaller ∆E values), and c) the inner 18-membered ring becomes more compact (judgedby the internal hydrogen separation). Particularly diagnostic for our purposes is thechange in the geometry of the triple bonds in the series 156 → 191 → 192–4 → 195: asthe cyclization proceeds, the remaining triple bonds in each intermediate product are138

Figure 4.5 Calculated structures of in the products of the cyclization of 156.139

calculated to become increasingly separated, thus likely retarding the normally facilecobaltacyclopentadiene(alkyne) formation. 61To some extent, the origins of thisdistancing are in the “opening” of the phenylenic frame, analogous to that observed inangular [3]- (15) and U-shaped phenylenes 119 and 120 (Section 2.7, Figures 2.6 and2.7). This deformation moves the terminal triple bond on the phenylene into an “emptyspace”, rather than towards the other uncyclized triple bonds. A similar phenomenon hadfrustrated an approach to circular [6]phenylene. 69RelativeDistance betweenDistance betweenCompoundenergyinternal hydrogensterminal triple bonds[kcal/mol][Å][Å] a156 0.000 2.101 3.352–4.2203.393–4.269191 –50.557 2.0043.471–4.3693.374–4.240192 –100.292 1.907 3.545–4.446193 –101.557 1.871 3.508–4.406194 –99.026 2.002 3.420–4.296195 –148.908 1.853 3.578–4.481121 –195.507 1.753 N/ATable 4.1 Comparison of calculated structural parameters for planar forms of 121 and itsalkyne isomers. a Terminal carbon atoms–internal carbon atoms. For 191, which contains140

three sets of different triyne units, the order is top right, bottom left, bottom right, whenviewing the preceding structural drawing.CompoundEnergy a[kcal/mol]Distance betweeninternal hydrogens[Å]Distance betweenterminal triple bonds[Å] b156 –2.221 2.321 3.522–4.291191 –1.829 2.1143.531–4.3583.822–4.5373.688–4.410192 –0.054 1.907 3.560–4.445193 –1.036 2.026 3.741–4.508194 –0.173 2.002 3.479–4.324195 +0.019 1.882 3.612–4.483121 –0.013 1.800 N/ATable 4.2 Comparison of calculated structural parameters for nonplanar forms of 121 andits alkyne isomers. a Relative to the corresponding planar conformer. b Terminal carbonatoms–internal carbon atoms. For 191, which contains three sets of different triyne units,the order is top right, bottom left, bottom right, when viewing the preceding structuraldrawing.141

4.6 Properties of Novel PhenylenesDespite the failure of the final two cyclization steps, phenylene systems 189 and190 (and their octapropyl relatives 182 and 183) represent the only third and fourthexamples of phenylenocyclynes. In these systems, the terminal rings of a phenylene arelinked by a conjugating bridge, and the changes in their properties as a result of thisfeature are of interest. Indeed, the molecules appear more air sensitive than theircomponent phenylenes (Section 1.3.3), and solutions (CHCl 3 ) of, e.g., 189 in airdecomposed within hours. In this case, the mass spectra of the complex product mixturerevealed molecular ions consistent with the addition of one and two molecules of oxygen,and the IR spectrum exhibited a strong band at 1645 cm –1 , suggesting oxidation via initialsingle and double endoperoxidation, as observed for angular [3]- (15) and dipropylzigzag [5]phenylene (97, Section 1.3.3, Scheme 1.24). 74,97 The electronic spectrum of 189is, as expected, very similar to that of 182 and it provides a quantitative measure ofincreased delocalization in longest wavelength maxima, which are shifted to lowerenergies when compared to the parent phenylene substructures by ∆λ max = 37 nm(Section 1.4.3). 76,181 A similar comparison of the 1 H NMR spectra of 189 and 190 withthose of their component phenylenes and of 171b illustrates the absence of anysignificant “super ring current” effects. For example, the two relatively sharp singlets at δ= 7.69 (inner H) and 7.49 ppm (outer H) of the tetraalkynylbenzene ring hydrogens in189, compare well with the corresponding signals in 171b: δ = 7.81 and 7.43 ppm. Themore coupled 186 central phenylene hydrogens at δ = 6.67 (inner H) and 6.47 ppm (outerH) have counterparts in the parent [5]phenylene at δ = 6.73 and 6.58 ppm. The142

assignments in 189 were corroborated by NOE experiments. Polarization was cleanlytransferred from the inner benzenoid proton at δ = 7.69 ppm to the phenylenic one at δ =6.67 ppm. No such correlation was observed for the other pair.4.7 Summary and Future DirectionsA convergent and robust synthetic route to the octaalkynylateddehydrobenz[18]annulenes 156 and 171b–c was developed. Compound 171b was partlycyclized to the cyclically delocalized phenylenes 189 and 190 in which the remainingalkyne units seem too distant to undergo CpCo-catalyzed cyclotrimerization to circular[8]phenylene 170b. Future work will aim to modify chemically the phenylene skeletonsof 189 and 190, in order to circumvent this problem.143

Chapter FiveConsequences of Steric Crowding Around Triple Bonds in Acyclic and CyclicSystems 181,1875.1 IntroductionThe three-dimensional structures of molecules are not unambiguously defined bycomposition and configuration alone. A complete description requires information aboutthe torsional angles around all of the single bonds in a molecule - a quality known asconformation. Since torsional angles are defined by four points, any system with an A–B–C–D arrangement can have multiple conformers. The simplest such stable molecule ishydrogen peroxide (H–O–O–H) in general, and ethane (CH 3 –CH 3 ) among organicmolecules. In a large majority of systems, the rotation around single bonds is unrestricted.However, adequate crowding can increase the barrier to rotation to the point where therate of the interconversion of conformers becomes comparable to the time scale ofanalytical techniques. To allow the observation of this hindered rotation, the conformerscannot be superimposable images of each other; this translates into the necessity ofdifferential substitution around the single bond that is considered. For example, even ifrotation in ethane were to be completely shut down, conformers would have identicalstructures, thus making hindered rotation unobservable. 188Atropisomerism (from Greek: α = not, and τροποσ = to turn) is a type ofrotational isomerism in which detection and even isolation of rotamers is possible due toa sufficiently hindered rotation around a chirogenic axis of the molecule. Atropisomeric144

systems have been conveniently classified on the basis of the identity of the chirogenicaxis. As Table 5.1 shows, the phenomenon has been observed with bonds to all types of–C(sp 3 ) –C(sp 2 ) –C(sp)COOCH 3BrH19619733.2 kcal mol –1aC(sp 3 )– COOCH 319827.1 kcal mol –1b 15.6 kcal mol –1cC(sp 2 )–HOOH20013.0 kcal mol –1d 18.0 kcal mol –1eC(sp)– –Table 5.1 Examples of atropisomeric molecules for which rotational barriers have beenmeasured, classified by the identity of the chirogenic axis (shown in bold in thestructures). Numbers below the structures are the corresponding ∆G ‡ values. a Ref. 189. bRef. 190. c Ref. 191. d Ref. 192. e Ref. 193.199145

hybridized carbons. In this area of investigation, tetrasubstituted biphenyls exemplifiedby 199 (Table 5.1) have attracted the most attention. 188,194Rotation around bonds to an sp-carbon is special, in as much as this nucleus doesnot bear any substituents but only another such carbon at a 180 ° angle, generating a largespacer (~ 4.0 Å) that requires unusually bulky groups at the termini for this motion to besufficiently retarded to be measurable. Thus, rotation around the –C≡C– unit is normallyessentially “free” - for example, in the parent diphenylacetylene the barrier is less than 1kcal mol –1 . 195 The idea that appropriate substitution may hinder this motion 195b has beenverified only rarely: for example, in ditriptycenyl- (198, Table 5.1), 191,196 tritylphenyl-(202, Figure 5.1), 197 dianthryl- (200, Table 5.1), 193 and constrained macrocyclicacetylenes (203, Figure 5.1). 198These efforts notwithstanding, observable hinderedrotation in a simple diphenylacetylene has remained elusive. Notably, a 2,2’,6,6’-tetra-ptolylderivative retained conformational mobility on the NMR time scale at temperaturesas low as –100 ºC. 199Rotational isomerism in diaryl– and other alkynes is of interestfundamentally, 191,192,196,199as well as in applications. Examples of novel moleculardevices 197,198,200 that contain this structural fragment include Glass’s molecular “sensors”(201, Figure 5.1), 200a,b Garcia-Garibay’s gyroscopes (202), 197,200d,e and Moore’s“turnstiles” (203). 198 Deplanarized diphenylacetylenes also constitute an essential modelfor the novel phenyleneethynylene polymers. 201146

RRRRFOORFR201 202 203Figure 5.1 Examples of molecular devices that feature a –C≡C– unit: “sensors” (left),“gyroscopes” (center), and “turnstiles” (right). R = receptor moiety.The following two sections will deal with the NMR-detection of hindered rotationaround the –C≡C– unit in alkynylated diphenylacetylenes, notably core 205b (Figure 5.2,center), the first member of the class of chiral 2,2’,6,6’-tetrakisalkynyldiphenylacetylenes (205a). 202 These compounds relate to chiral biphenyls by the insertionof a C≡C fragment into all five of the single bonds that bring about the chirality of 204and are thus, in Houk-Scott terminology, 203 “exploded” biphenyls. Constructs of the type205a function as building blocks in the assembly of carbon rich materials, such as planarmetallacycles, 202 substructures of graphyne and its relatives, 163,204 and nanotubes. 159Previous chapters have amply demonstrated the importance of elaborated variants of205a in the syntheses of the phenylenes. 1,47 Additionally, they might also be viable asnew scaffolds for chiral atropisomeric ligand construction. 205147

RRσRRRRRRR'R'R'R'RRRR204 205a205b, R = TMS, R' = DMTS171c, R = DMTSDMTS =HSiFigure 5.2 General structures of chiral biphenyls (204), diphenylacetylenes (205a), andthe structure of a conformationally locked dehydrobenzannulene 171c.Section 5.4 will focus on the stereochemical properties of the macrocycle 171c(Section 4.4, Figure 5.2, right). Overall, 171c is achiral, since it possesses a plane ofsymmetry (σ in Figure 5.2, vide infra); however, its structure encompasses the chiral2,2’-dialkynyldiphenylacetylene motif. As will be seen, steric hindrance around the triplebonds in 171c shuts down the free conformational equilibration of the molecule. This isan example of a conformationally locked dehydrobenzannulene in which the rigidity isinduced by substituents, rather than the macrocyclic skeleton itself. 159c,206148

5.2 Previous Examples of Hindered Rotation in Phenylene PrecursorsThe occurrence of atropisomerism in 205a first became apparent during thecourse of the synthesis of the [N]heliphenes, N = 7–9, by triple cobalt-catalyzedcycloisomerization of the corresponding nonaynes (Section 1.2.2.1, Schemes 1.8 and1.9). 70 In particular, the 500 MHz 1 H NMR spectrum of the advanced intermediate 206(Figure 5.3) on route to methoxymethyl [9]heliphene revealed two doublets (δ = 4.08,4.15 ppm; AB, 2 J = 15 Hz) for the methylene hydrogens at room temperature (500 MHz,CDCl 3 ), clearly signaling the presence of a configurationally stable chiral conformation.Furthermore, gradual cooling of the sample to –53 °C in toluene-d 8 , caused furtherdecoalescence and the appearance of several broad signals for these hydrogens. At thistemperature, the corresponding methoxy singlet separated into two distinct peaks (∆ν =36 Hz), the combined data indicating the rotational restriction of a second (and perhapsthird) stereogenic axis in the molecule giving rise to two, or perhaps three, diastereomers.Because of the complexity of the NMR signals of unsymmetrical 206 and toelucidate the nature of these dynamic processes, we turned to the symmetrical 207 66 and208, 70 the former as a model for probing the hindered rotation of the “outside”diphenylacetylene axis (●), the latter for doing so with respect to its inside counterpart(■). In these molecules, the signals for the potentially diastereotopic pairs of methyls ofthe DMTS group, especially the distinct silylmethyl absorptions, were sufficiently wellresolved to allow for variable temperature NMR studies.149

OCH 3RRRRRRRRRRRRRRR206, R = DMTS207, R = DMTS208, R = DMTSFigure 5.3 Precursors to helical [N]phenylenes that exhibit hindered rotation around“internal” (■) and “external” (●) chirogenic axes (see text for details).In 207, a precursor to [7]heliphene by double cyclization, 66 restricted rotation maygive rise to only two diastereomers: the syn form, in which the biphenylenyl substituentsface each other (as shown in Figure 5.3, C s symmetry), and the anti rotamer (C 2 ), inwhich they point in opposite directions. Molecular mechanics calculations favor theformer energetically by ~ 1 kcal mol –1 . At room temperature, the 1 H NMR spectrum of207 displayed two sets of resonances for the two inequivalent DMTS groups, without anyindication of hindered rotation. Specifically, only two silylmethyl singlets were visible atδ = 0.12 and 0.16 ppm (400 MHz, CD 2 Cl 2 ). Upon cooling to –54 ºC, the latterdecoalesced into two singlets, while the former started to broaden. The aromatic region ofthe spectrum remained unchanged. Similarly, at this temperature, the 13 C signals for thethree types of methyl carbons appeared as four lines each, while the remaining carbonsgave rise to single resonances. These observations are consistent with the occurrence ofhindered rotation around the biphenylenyl-phenyl alkyne bond and the presence of only150

one of the two possible diastereomers of 207, presumably the syn isomer. Simple peakcoalescence analysis provided a ∆G ‡ of 11.5 kcal mol –1 for this process, 207 its facilitysuggesting that it is also responsible for the lower energy restricted movement(s) takingplace in 206 (● axes).To support this hypothesis, a similar analysis was performed on 208. Indeed,decoalescence of the three silylmethyl singlets (δ = 0.04, 0.10, 0.16 ppm, 40 ºC)associated with the three distinct DMTS groups to six singlets occurred already at 28 ºC(400 MHz, CDCl 3 ). Analysis of the decoalescence of the low field signal furnished anapproximate activation barrier of 15.6 kcal mol –1 . 207 It therefore seems that thesubstructure 205a is responsible for the higher energy conformational process observedin 206 (■ axis).5.3 Synthesis and Properties of the First Chiral 2,2’,6,6’-TetrakisalkynylDiphenylacetyleneThe observations summarized in Section 5.2 provided the impetus for thesynthesis of 205b, devoid of all the unessential elements present in 206–208. In thissystem, there is only one stereogenic axis, and a variable temperature NMR analysiswould provide unambiguous data addressing the possibility of hindered rotation around adiphenylacetylene triple bond. The preparation of 205b (Scheme 5.1) commenced withthe previously described 2,2’,6,6’-tetrabromodiphenylacetylene (209), 202which wasdesymmetrized to 2,2’-dibromo-6,6’-diiodo-diphenylacetylene (210) by bromine–iodineexchange. The selectivity of this exchange is rather remarkable, as the reaction proceeded151

to give only the desired product, without even traces of singly or triply exchangedmaterial. 208 The iodinated positions in 210 were alkynylated with DMTSA 209 understandard Sonogashira coupling conditions 171 to furnish triyne 211 in 52% yield. A secondbromine–iodine exchange afforded the doubly iodinated 212, thetrimethylsilylethynylation of which proceeded with great difficulty to give only 15% of205b, after a laborious purification sequence that involved column chromatography,Kugelrohr distillation, and HPLC.XBrDMTS(i)Br X209, X = Br210, X = I(ii)XXDMTS(i)211, X = Br212, X = I(iii)205bScheme 5.1 Synthesis of 205b: (i) BuLi, Et 2 O, –45 °C, 1 h, then I 2 , Et 2 O, –45 °C to 23°C, 2 h, 75% (for 210), 92% (for 212); (ii) DMTSA, [PdCl 2 (PPh 3 ) 2 ], CuI, NEt 3 , 23 °C, 20h, 52%; (iii) TMSA, [PdCl 2 (PPh 3 ) 2 ], CuI, NEt 3 , 100 °C, 72 h, 15%.Remarkably, restricted rotation in 205b was evident already at room temperaturein both the 1 H and 13 C NMR spectra. The former featured a doubling of all the signalsdue to the diastereotopic methyls of the DMTS group, observable in dioxane-d 8 (Figure5.4a), CDCl 3 , and THF-d 8 . The latter (CDCl 3 ) revealed such behavior only for thecarbon-bound methyl groups, the silylmethyl carbons apparently being accidentally152

isochronous. In both cases, the remainder of the spectrum was as expected for a singlespecies.Figure 5.4 1 H NMR (500 MHz) spectra of 205b (methyl group region). Conditions: a)dioxane-d 8 , 22 °C; b) THF-d 8 , –82 °C; c) dioxane-d 8 , 109 °C, sealed tube.For the purpose of evaluating the barrier to rotation, the most diagnostic isopropyldoublets (marked with “x” in Figure 5.4) were chosen. Unfortunately, a solvent coveringthe entire temperature range within which spectral changes were occurring could not befound. Thus, toluene did not provide clear peak separations and DMF did not dissolve205b. Therefore, low temperature NMR measurements were undertaken in THF-d 8 ,whereas dioxane-d 8 was employed at high temperatures. An example of a clearlyresolved low temperature spectrum is shown in Figure 5.4b. Coalescence of the isopropyl153

signals occurred at 96 ºC, and increasing the temperature generated eventually a singleset of DMTS peaks above 100 ºC (Figure 5.4c). The ∆G ‡ for the enantiomerization in205b was calculated to be 18.7(±0.4) kcal mol –1 .The rotational barrier in 205b is remarkably high, in the high range of thosereported for more complex diarylacetylene systems. For example, the ∆G ‡ values forToyota’s bis(1-phenyl-9-anthryl)acetylenes ranges between 10 and 18 kcal mol –1 , 193while Moore’s “molecular turnstiles” have corresponding values of 13–20 kcal mol –1 , 198depending on the size of substituents on the aryl rings. On the other hand, theconformationally mobile 2,2’,6,6’-tetrakisaryldiphenylacetylene frame exhibits barriersbelow 8 kcal mol –1 , 199 less than a half of that in 205b.This work constitutes the first observation of hindered rotation in a simplesubstituted diphenylacetylene. It also attests to the power of substituted alkyne units inexerting remote steric influence, in spite of the ready deformability of the carbon–carbontriple bond.5.4 Stereochemical Properties of 171cAs the preceding work showed, sufficient encumbrance around –C≡C– units canhinder rotation about these axles as observed in diphenylacetylenes (Section 5.3) and themore complex acyclic oligo(phenyleneethylene)benzenes (Section 5.2). This section willextend the above notion to the octaalkynyl dehydrobenz[18]annulenes 171a–c, whichwere the focus of Chapter 4. The basic structural feature of these cyclic systems is a 2,2’-dialkynyldiphenylacetylene, a close relative of the 2,2’,6,6’-motif in acyclic systems.154

However, the four-fold incorporation of this structural moiety into the cyclic skeleton ofdehydrobenzannulenes complicates the conformer equilibration mechanism significantly.Molecular mechanics studies aimed at probing this mechanism will be the subject ofSection 5.6.Figure 5.5 Line-bond (left) and calculated (right) structures of 156.DFT calculations presented in Section 4.5 revealed the nonplanar conformation ofthe parent 156 as the most stable (Figure 5.5). In this conformation, the 1,2,4,5-substituted benzene rings are distorted out of the plane defined by the 1,2,3,4-substitutedrings, in opposite directions (Figure 5.5, right). The shallow conformation energy curveof 156 features a negligible (~ 2 kcal mol –1 ) barrier to planarization. Appropriatesubstitution at the termini of the triple bonds in 156 was expected to exacerbate theenergy differences between the conformers, possibly rendering the equilibration processobservable by NMR. This expectation was supported by the preliminary molecularmechanics calculations on 171c (the MM was chosen over the DFT method because ofthe size of 171c, see Section 5.5), which singled out the two most stable conformers,shown in Figure 5.6. In the C 2h -symmetric structure (left), analogous to that calculated for155

RσRRRRRRσ 1σ 2RC 2RRRRRRRRFigure 5.6 Two possible diastereomers of 171c, shown with their key symmetryelements: C 2h -isomer (left) and C 2v -isomer (right).the parent, the two benzene rings intersected by the σ plane lie in parallel planes.Alternatively, the same two rings could be oriented in a roof-like formation, forming thesecond symmetry plane in the now C 2v -symmetric molecule (σ 2 in Figure 5.6, right). Thelatter conformer was favored by a significant 12 kcal mol –1 , somewhat surprisinglyconsidering that the C 2h -structure was favored for the parent system.Experimentally, compounds 171a–c (Sections 4.3 and 4.4) served as ideal NMRprobesof conformational (in)flexibility, since all three compounds bore potentiallydiastereotopic substituents (propyl, hexyl, and DMTS, successively). The 1 H NMRspectra of octapentynyl– and octaoctynyl-substituted dehydrobenz[18]annulenes 171aand b (Section 4.3 and 4.4) featured three singlets in the aromatic region and two sets ofresonances corresponding to the propyl and hexyl groups, respectively. This observationwas consistent with structures that are either planar, or nonplanar but conformationallymobile on the NMR time scale. On the other hand, the DMTS spectral region of theanalogously built 171c revealed not two, but four sets of resonances for each of the threemethyl groups, illustrated for the silylmethyls on top of Figure 5.7. In accord with the156

calculations, the aromatic region of the spectrum confirmed the presence of a singleconformer (presumably C 2v ). Equilibration of this conformer with its superimposablemirror image (and hence coalescence) appeared remarkably sluggish, as measured by VTNMR at 62 and 90 ºC, respectively (Figure 5.7, bottom). Phenomenologically, the rapidequilibration of the two degenerate conformers is equivalent to an averaged planarstructure; in the acyclic analogy, this would translate into the free rotation around thecore diarylalkyne bonds. 187Figure 5.7 Silylmethyl 1 H NMR spectra (dioxane-d 8 ) and the corresponding schematicrepresentations of 171c at 22 ºC (top) and 99 ºC (bottom), respectively. The black andwhite spheres represent the (potentially) diastereotopic methyl substituents. A = DMTS–C≡C–, B = (CH 3 ) 2 CH(CH 3 ) 2 C–.Peak-shape analysis 207 provided an activation barrier of 19.4(±0.4) kcal mol –1 ,almost ten times greater than the one calculated for the parent! In contrast, both the157

acyclic precursor analogs 147 (Figure 5.8, left, also Section 2.5.2, Scheme 2.14) and 149(Figure 5.8, center, also Section 2.6, Scheme 2.15), and the related hexaalkynylateddehydrobenz[12]annulene 74a (Figure 5.8, right, also Section 1.2.2.5, Scheme 1.18) 69remained mobile conformationally at temperatures as low as –80 ºC. 210RRRR TMSR RRRRRRRTMSR RRRTMSTMSRR147, R = DMTS149, R= DMTS74a, R = DMTSFigure 5.8 Acyclic (147 and 149) and cyclic (74a) models for the behavior of 171c.Rotation around –C≡C– axes shown in bold in 147 and 149 remained free on cooling tothe limiting temperature of –80 °C. Similarly, in 74a, the macrocyclic skeleton stayedflexible at this temperature.The incorporation of a hindered diarylalkyne into a cyclic environment ofdehydrobenz[18]annulenes led to the unprecedented restriction of the conformationalfreedom of the latter system. The following section will deal with the energetic and themechanistic intricacies of the conformer equilibration at elevated temperatures.158

5.5 Proposed Mechanism of Interconversion between the Conformers of 171c 211The unique stereochemical behavior of 171c kindled our interest in themechanism through which the interconversion of its conformers occurs. Severalquestions were addressed: a) what is the calculated inversion barrier; b) are themovements of the four quadrants of 171c (Figure 5.6): independent, somewhat correlated,or completely synchronized; c) which parts of the system “take the load” in the transitionstate of inversion - the macrocyclic skeleton, the pendant substituted triple bonds, orsomething else? Experimental models suitable for addressing these concerns werelacking, prompting us to turn to calculations for guidance. Due to the appreciable cost ofDFT calculations for 171c, molecular mechanics (MM) was selected as the computationalmethod, a choice justified by the purely steric nature of the problem. This section willdescribe the results of the calculations performed. To best depict the relevant issues,graphics and colors will be used, deviating from the format of the preceding chapters andsections.In order to separate the movements within the individual quadrants, we performedcalculations on 171c and 213–216 (Figure 5.9), constructed formally from 171c by thesequential removal of pairs of adjacent alkynyl substituents (within the context of thissection, “adjacent” signifies the closest alkynyl group on a different benzene ring). Theoverall strategy of the calculations assumed that the change in the torsion angle a–b–c–d(shown for 213 in Figure 5.9) featured as crucial in the inversion process. This angle wasconstrained successively to a set of predetermined values and the remainder of themolecule was optimized for each. The so-obtained energies were plotted against the159

SiSiSiaSibdcSiABSi213 214SiSiSiSiASiABSiSiBSiCSiSi215 216SiSiSiABSiSiDCSiSiSi171cFigure 5.9 Molecules analyzed by MM methods. The torsion angles a–b–c–d (defined in213) were constrained in all systems. Capital letters A–D are used to denote molecularquadrants.160

torsion angle in the search for a meaningful transition state. Such was deemedaccomplished if an energy maximum was traversed as the geometrical constraints werevaried. Pathways that led to continually increasing energy were discarded asnonproductive.Ground-state calculations of 171c and 213–216 indicated that only theorientations of the rings bearing DMTSethynyl groups are predicted to influence theoverall energy of the molecule. In other words, the unsubstituted rings could adopt anumber of different arrangements with miniscule energetic consequences (the conformersof 213 and 214 in Figure 5.9 are therefore arbitrarily chosen). For 171c, 215, and 216, inwhich both meta-fused rings are substituted, the roof-shaped conformation (pseudo-C 2v ,Figure 5.6, right) was predicted to be more stable than the pseudo-C 2h alternative (Figure5.6, left), by ~ 6.5, 9, and 12.5 kcal mol –1 , respectively.The first studied molecule was 213 (Figure 5.9), with only two adjacent alkynylgroups. Table 5.2 and Figure 5.10 show the dependence of the energy of the system onthe torsion angle. As expected, the calculations predict that the initial increase in energyis followed by a sudden decrease, establishing this movement as a possible pathway forinversion. The barrier was estimated at ~ 15 kcal mol –1 .161

Torsion angle a–b–c–d [°] Energy [kcal mol –1 ]50.7 0.0044.8 0.2439.1 0.7233.5 1.4327.7 2.6321.9 4.0616.0 5.7310.0 7.653.7 9.80–3.0 12.19–6.7 13.62–10.9 14.81–14.7 15.05–55.7 –0.24–56.2 –0.24Table 5.2 Calculated dependence of the total energy on torsion angle a–b–c–d in 213.162

161412Energy [kcal mol -1 ]1086420-2-60 -40 -20 0 20 40 60Torsion angle a-b-c-d [ o ]Figure 5.10 Graphical representation of the calculated dependence of the total energy ontorsion angle a–b–c–d in 213. The red curve shows a Gaussian fit of the calculated datapoints.Figure 5.11 depicts the conformation that corresponds to the energy maximum of thecurve given in Figure 5.10. This structure should closely resemble the predicted transitionstate for the inversion. This model suggests that the benzene rings invert first, leaving theDMTSethynyl groups behind. A consequence of this facet is a significant increase in thestrain energy of the transition state. Accordingly, the release of this strain causes theDMTSethynyl groups to “flip over”, precipitating the inversion of the overall system.163

Figure 5.11 Calculated structure of the transition state for the inversion of 213.Out of the three possible isomers with two pairs of adjacent alkynyl substituents,two were examined (Figure 5.9): 214, with two DMTSethynyl substituents on the orthofusedbenzene ring, and 215, possessing two of the four DMTSethynyl group on its metafusedring. In order to minimize the constraints imposed on the system, only one of thetwo possible torsion angles in 214/215 was changed (denoted as A in Figure 5.8). Table5.3 and Figure 5.12 show the dependence of the other angle (B) and the overall energy ofthe system on the constraint imposed on angle A.164

Torsion angle A [°] Torsion angle B [°] Energy [kcal mol –1 ]57.9 –54.9 0.00 a48.1 –51.2 0.4842.9 –48.9 1.1937.8 –46.9 2.3932.8 –44.9 3.8227.8 –42.9 5.5022.9 –41.1 7.6518.0 –39.3 10.0413.3 –37.7 12.668.6 –36.4 15.773.9 –35.3 18.88–0.9 –34.1 22.22–5.5 –33.4 26.05–10.1 –32.4 29.63–14.8 –31.7 33.69–83.6 70.8 –0.48Table 5.3 Calculated dependence of the total energy and the torsion angle B in 214 onthe torsion angle A. a Simulation started with the pseudo-C 2h structure.165

806040Torsion angle B [ o ]Energy [kcal mol -1 ]200-20-40-60-100 -80 -60 -40 -20 0 20 40 60Torsion angle A [ o ]Figure 5.12 Graphical representation of the calculated dependence of the total energyand the torsion angle B in 214 on the torsion angle A. The red curve shows a Gaussian fitof the calculated data points.Changes in the torsion angle A were reflected in the angle B, causing both quadrants toinvert simultaneously, rather than independently. The inversion barrier was estimated at ~34 kcal mol –1 . The presumed structure of the transition state (shown in Figure 5.13)indicated that the motion of the central benzene ring preceded that of the attachedsubstituents. In other words, the benzene rings “overshot” by ~ 15 ° before theDMTSethynyl groups inverted.166

Figure 5.13 Calculated structure of the transition state for the inversion of 214. Hydrogenatoms omitted for clarity.In an alternative arrangement of 215 (Figure 5.9), the ortho-fused ring bears twoDMTSethynyl groups. Analysis analogous to the one elaborated for 214 shows that thetwo units are now calculated to move independently. The constraints imposed on A areinfluencing B (Table 5.4, Figure 5.12), but not dramatically; more significantly, theinversion of A does not cause one in B. Relative to the more stable conformer, theinversion barrier is calculated to be ~ 16 kcal/mol, fairly close to the value obtained for213.167

Torsion angle A [°] Torsion angle B [°] Energy [kcal mol –1 ]40.1 43.1 6.45 a34.5 44.4 6.6929.0 45.9 7.1723.4 47.2 7.8817.6 48.6 9.0811.6 50.0 10.515.1 51.4 11.18–1.8 52.8 14.10–9.9 54.7 16.01–52.6 59.6 0.00Table 5.4 Calculated dependence of the total energy and the torsion angle B in 215 onthe torsion angle A. The inversion of one quadrant produced a different diastereomer ofthe material, hence the different values for energies before and after the inversion. aSimulation started with the pseudo-C 2h structure.168

8060Torsion angle B [ o ]Energy [kcal mol -1 ]400-80 -60 -40 -20 0 20 40 60Torsion angle A [ o ]Figure 5.14 Graphical representation of the calculated dependence of the total energyand the torsion angle B in 215 on the torsion angle A. As a consequence of theirdefinition, the initial signs of the two angles are different. The inversion of one quadrantproduced a different diastereomer of the material, hence the different values for energiesbefore and after the inversion. The red curve shows a Gaussian fit of the calculated datapoints.In 216 and 171c, the systems with three and four pairs of adjacent alkynyl groups,a change in just one of the torsion angles failed to model the inversion. Conformations ofunreasonable geometries and very high energies were obtained, suggesting a moreordered transition state. To address this requirement, we decided to change169

simultaneously two of the torsion angles in the same direction and by the sameincrements. 212In the triply substituted system 216 (Figure 5.9), three possiblecombinations of the angles could, in principle, be restrained: A-B, A-C, and B-C. Theformer two were examined. Constraining angles A and C simultaneously gave rise tohigh-energy conformers. On the other hand, a simultaneous change in A and B provedproductive, as these calculations predicted that the two units should invert synchronouslywith an energy barrier of ~ 40 kcal mol –1 (relative to the more stable conformer) and,significantly, without causing the inversion of C (Table 5.5).170

Torsion angle [°]A B C Energy [kcal mol –1 ]42.1 –43.4 44.4 8.84 a35.5 –36.1 45.6 9.3229.9 –30.6 46.4 10.5124.2 –25.2 47.1 12.4218.3 –19.8 47.9 14.8112.1 14.2 48.8 17.684.3 –7.9 50.7 21.03–1.6 –25 51.5 25.09–7.8 2.7 52.3 29.63–14.1 8.0 53.2 34.65–20.7 13.4 54.1 39.90–64.3 65.3 56.2 0.00Table 5.5 Calculated dependence of the total energy and the torsion angle C in 216 onthe torsion angles A and B. The inversion of quadrants A and B produced a differentdiastereomer of the material, hence the different values for energies before and after theinversion. a Simulation started with the pseudo-C 2h structure.Finally, the fully substituted 171c (Figure 5.9) had three possible combinations ofthe angles to be constrained: A-B, A-C, and A-D. While constraint in the A-C and A-Dpairs gave rise only to high-energy maxima, the simultaneous change of A and B gave a171

clean inversion of these two quadrants (inversion barrier ~ 42 kcal mol –1 ), leaving C andD fairly intact in their ground state geometries (Table 5.6, Figure 5.15).Torsion angle [°]A B C D Energy [kcal mol –1 ]40.9 –40.6 –51.7 52.5 12.43 a35.2 –35.0 –52.0 52.8 12.9129.9 –29.6 –52.1 53.0 13.8624.6 –24.3 –52.2 53.1 15.5419.2 –19.0 –52.2 53.1 17.9313.9 –13.6 –52.2 53.1 20.037.2 –3.8 –56.0 54.8 23.901.8 2.4 –56.7 55.0 27.72–3.5 8.6 –57.3 55.0 32.26–8.9 15.1 –58.1 55.2 37.04–15.1 23.2 –59.1 55.5 42.30–66.5 68.0 –71.6 68.8 0.24–61.3 63.8 –71.9 68.6 0.00Table 5.6 Calculated dependence of the total energy and the torsion angles C and D in171c on the torsion angles A and B. The inversion of quadrants A and B produced adifferent diastereomer of the material, hence different values for energies before and afterthe inversion. a Simulation started with the pseudo-C 2h structure.172

Figure 5.15 Calculated structure of the transition state for the inversion of A and Bquadrants in 171c. Hydrogen atoms omitted for clarity.With the caveat of the inaccuracy of absolute numbers produced by MM methods,our calculations strongly suggest that the inversion of theocta(DMTSethynyl)dehydrobenz[18]annulene 171c occurs via a stepwise “2+2”mechanism. Of the four molecular quadrants, only pairs connected through the 1,2,4,5-substituted rings can cooperate productively. Thus, using Figure 5.6 as reference, the C 2v -conformer (right) inverts its upper half first with a ~ 42 kcal mol –1 barrier, giving rise tothe energetically loaded (+12 kcal mol –1 ) C 2h -isomer. This intermediate now inverts thebottom two quadrants (+30 kcal mol –1 ), producing a superimposable mirror image of theC 2v -conformer.173

In the transition state, both the triple bonds of the pendant DMTSethynyl groupsand the –C≡C– linkages in the macrocycle are significantly distorted. The transition stategeometries also reveal an interesting “catapult” behavior: The DMTSethynyl groups arelagging behind the benzene ring to which they are attached as the system undergoesinversion. Of course, it is likely that adding more flexibility to the structures employed inthese calculations will change the energetic values obtained and lead to more favorabletransition states. However, such optimizations were not pursued and probably would notchange the basic conclusions drawn in this section.5.6 Summary and Future DirectionsThe first cases of hindered rotation around the triple bond in simplediphenylacetylenes have been observed, including that in the simple chiral tetraethynylsystem 205b. The conformational barriers can be substantial, leading to the observationof restricted rotation by NMR at room temperature. In cyclic systems, such as 171c, stericcrowding around triple bonds caused the loss of the conformational freedom. Molecularmechanics calculations proposed a stepwise “2+2” mechanism for inversion of 171c atelevated temperatures.Future work will aim to gain insight into the effect of substituent size on theflexibility of 205a with the ultimate goal of achieving resolution of suitable derivatives.These investigations may lead to the development of 205a as a viable new tool in chiralscaffold construction.174

Chapter SixExperimental and Computational Details6.1 General ConsiderationsAll reactions, except base-catalyzed silyl-group deprotections, the preparations ofstarting iodoarenes, and microwave-assisted reactions, were performed under nitrogenatmosphere in oven-dried glassware. Solvents were dried by distillation over thecorresponding drying agents: triethylamine (KOH pellets), ether (Na-benzophenone,purple solution), THF (Na-benzophenone, purple solution), toluene (Na-benzophenone,purple solution), and degassed by a 15 min nitrogen purge prior to use. All othermaterials and solvents, unless noted otherwise, were purchased from commercialsuppliers and used without further purification. Bis(triphenylphosphine)palladium(II)chloride 213was prepared according to previously published procedures. Flashchromatography used silica gel, according to Still’s procedure. 214 Microwave-assistedreactions were run in a Smith Synthesizer single-mode microwave cavity, producingcontinuous radiation at 2450 MHz. All manipulations of [(Me 3 CO) 3 W≡CCMe 3 ] werecarried out in a glove box. Irradiation in [CpCo(CO) 2 ]-mediated cyclizations was doneusing a GE 300 W projector lamp, positioned ~ 5 cm away from the flask.The identity of products was established by 1 H NMR, 13 C NMR, IR, and massspectrometry. Purity was confirmed by melting point and elemental analyses; in somecases, due to the small amounts or the consistency (viscous oils) of prepared materials,purity was assessed by NMR and high-resolution mass spectrometry, along with a175

distillation/gas chromatography sequence (for some volatile compounds). Melting pointswere taken in open capillary tubes, using a Thomas Hoover Unimelt apparatus, and areuncorrected. Mass spectral measurements (FAB, EI of GC/MS incompatible compoundsand high resolution) and elemental analyses were supplied by the Micro Mass Facility ofthe College of Chemistry, University of California at Berkeley, California. Forcompounds containing polyisotopic elements, mass spectra give data only for the mostabundant isotopomer. In compounds that contain an odd number of bromines the twomost abundant isotopomers exist in roughly equal ratios, and data for both are given (inM( 81 Br) + /M( 79 Br) + format). NMR spectra were recorded on Bruker DRX-500, AVB-400,AVQ-400, and AV-300 spectrometers, with working frequencies (for 1 H nuclei) of 500,400, 400, and 300 MHz, successively. All 13 C NMR spectra were recorded withsimultaneous decoupling of 1 H nuclei. 1 H NMR chemical shifts are reported in ppm units,relative to the residual signal of the solvent (CDCl 3 –7.26 ppm; C 6 D 6 –7.15 ppm; CD 2 Cl 2 –5.32 ppm). IR measurements were performed on a Perkin Elmer System 2000 FT–IRspectrometer. UV measurements were executed on an HP 8450A diode arrayspectrometer and are reported in nm (logε). Gas chromatography utilized an HP 5890Series II chromatograph. Column chromatography was carried out on silica gel 60, 32–63mesh. Analytical TLC employed Merck aluminum-backed silica gel plates.All calculations were carried out at the Molecular Graphics Facility in the Collegeof Chemistry, University of California at Berkeley. DFT calculations employed the abinitio electronic structure software package Jaguar 5.5, while molecular mechanicscomputations used MacroModel 8.1, both as modules of the Maestro 6.5 suite. 215 AllDFT calculations were done at the B3LYP level, using the 6–31G* basis set. 216 In most176

cases, the geometries submitted to DFT scrutiny were preoptimized using molecularmechanics, in order to minimize the time required for the higher level calculations.6.2 Experiments and Calculations Related to Chapter 21,5-Dibromo-2,4-bis[(2-bromophenyl)ethynyl]benzene (58):BrBrTMSTMS1,5-Dibromo-2,4-bis[(trimethylsilyl)ethynyl]benzene. A suspension of 1,5-dibromo-2,4-diiodobenzene (57) 78 (0.69 g, 1.40 mmol), TMSA (0.50 mL, 3.50 mmol),[Pd(PPh 3 ) 2 Cl 2 ] (49.0 mg, 0.07 mmol), and CuI (13.0 mg, 0.07 mmol) in 100 mL oftriethylamine was stirred for 2 h at 23 °C. After removing the solids by filtration, thesolvent was evaporated in vacuo and the resulting crude product purified by columnchromatography (hexanes) to yield 1,5-dibromo-2,4-bis[(trimethylsilyl)ethynyl]benzeneas a yellow oil (581 mg, 96 %). UV-VIS (cyclohexane) λ max (logε) 254 (4.29), 275(3.95), 284 (sh, 3.88), 306 (3.23), 335 (2.86) nm. IR (NaCl film): ~ ν = 2960, 2898, 2159,2068, 1451, 1340, 1250, 1174, 1058, 977, 843, 760, 696 cm –1 . MS (EI, 70 eV) m/z (relintensity) 428 (M + , 33), 413 (100), 199 (21). 1 H NMR (400 MHz, CDCl 3 ) δ 7.81 (s, 1H),7.61 (s, 1H), 0.28 (s, 18H). 13 C NMR (100 MHz, CDCl 3 ) δ 137.4, 135.6, 125.6, 124.5,101.4, 101.3, –0.3. HR-MS Calcd for C 16 H 20 Br 2 Si 2 : 427.9450. Found: 427.9448. Anal.Calcd for C 16 H 20 Br 2 Si 2 : C, 44.87; H, 4.71. Found: C, 44.51; H, 5.07.177

BrBr1,5-Dibromo-2,4-diethynylbenzene. A solution of 1,5-dibromo-2,4-bis[(trimethylsilyl)ethynyl]benzene (520 mg, 1.21 mmol) in a mixture of ethanol (20 mL)and ether (30 mL) was treated with solid KOH (800 mg). The mixture was stirred at 23°C for 1 h and then filtered through a short plug of silica. After removal of the solvent,white crystals of 1,5-dibromo-2,4-diethynylbenzene were obtained; since they appearedto decompose quickly (darkened within 5 min), the material was used without anypurification in the subsequent step.BrBrBrBr1,5-Dibromo-2,4-bis[(2-bromophenyl)ethynyl]benzene (58). A mixture of 1,5-dibromo-2,4-diethynylbenzene (345 mg, 1.21 mmol), 1-bromo-2-iodobenzene (1.64 g,5.80 mmol), [Pd(PPh 3 ) 2 Cl 2 ] (42.0 mg, 0.06 mmol), and CuI (12.0 mg, 0.06 mmol) intriethylamine (100 mL) was stirred overnight at 23 °C. The solvent was removed invacuo and the desired material isolated by column chromatography (hexanes) as offwhitecrystals, mp 156–158 °C (321 mg, 45 %). UV-VIS (cyclohexane) λ max (logε) = 299(3.87), 308 (3.80), 320 (sh, 3.80), 354 (3.02), 371 (3.00), 406 (2.98) nm. MS (EI, 70 eV)m/z (rel intensity) 594 (M + , 100), 516 (5), 514 (5), 434 (11), 274 (28), 137 (18). 1 H NMR(400 MHz, CDCl 3 ) δ 7.92 (s, 1H), 7.81 (s, 1H), 7.63 (br t, J = 7.9 Hz, 4H), 7.33 (br t, J =7.3 Hz, 2H), 7.23 (br t, J = 7.3 Hz, 2H). 13 C NMR (100 MHz, CDCl 3 ) δ 137.1, 136.0,178

133.7, 132.6, 130.1, 127.1, 125.7, 125.6, 124.7, 124.6, 93.7, 90.7. HR-MS Calcd forC 22 H 10 Br 4 : 593.7475. Found: 593.7467. Anal. Calcd for C 22 H 10 Br 4 : C, 44.49; H, 1.70.Found: C, 44.78; H, 1.65.1,5-Bis(ethynyl)-2,4-bis[(2-ethynylphenyl)ethynyl]benzene (59):TMSTMSTMSTMS1,5-Bis[(trimethylsilyl)ethynyl]-2,4-bis[{(2-trimethylsilyl)ethynylphenyl}ethynyl]benzene. A mixture of 58 (135 mg, 0.23 mmol), TMSA (0.32 mL, 2.27 mmol),[Pd(PPh 3 ) 2 Cl 2 ] (8.0 mg, 0.011 mmol), and CuI (2.0 mg, 0.011 mmol) in triethylamine (40mL) was sealed in a 200 mL Schlenk tube and heated at 100 °C for 8 d. The solvent wasremoved in vacuo and the residue subjected to column chromatography(hexanes/CH 2 Cl 2 ), yielding 1,5-bis[(trimethylsilyl)ethynyl]-2,4-bis[{(2-trimethylsilyl)ethynylphenyl}ethynyl]benzene contaminated by incompletely alkynylatedmaterial, as a pale yellow oil (71 mg, 47 %), used as such in the subsequent steps. MS(EI, 70 eV) m/z (rel intensity) 662 (M + , 28), 73 (100). 1 H NMR (400 MHz, CDCl 3 ) δ 7.74(s, 1H), 7.66 (s, 1H), 7.52–7.49 (m, 4H), 7.30–7.26 (m, 4H), 0.24 (s, 18H), 0.23 (s, 18H).13 C NMR (100 MHz, CDCl 3 ) δ 135.7, 135.3, 132.1, 131.7, 128.2, 128.0, 125.94, 125.86,125.7, 125.0, 103.2, 102.3, 101.1, 99.1, 94.0, 90.8, 0.0, –0.2.179

1,5-Bis(ethynyl)-2,4-bis[(2-ethynylphenyl)ethynyl]benzene (59). A solution of 1,5-bis[(trimethylsilyl)ethynyl]-2,4-bis[{2-(trimethylsilyl)ethynylphenyl}ethynyl]benzene(39 mg, 0.059 mmol) in THF (10 mL) was treated with 0.20 mL of 1M TBAF solution inTHF (0.20 mmol). The mixture turned brown immediately and was stirred at 23 °C for 1h, after which water (0.20 mL) was added. The resulting solution was stirred for anadditional 20 min and subsequently filtered under N 2 through a short plug of silica into a50 mL Schlenk tube. The pad of silica was washed with two additional portions of dryTHF and the combined filtrates concentrated to 25 mL volume in vacuo.syn-Doublebent [5]phenylene (60):A solution of 59 was cooled to –25 °C, and [CpCo(eth) 2 ] 63 was added as anethereal solution (23.4 mg, 0.130 mmol; 10 mL of ether). The mixture was kept at –25 °Cfor 18 h and then allowed to slowly warm. As soon as the temperature reached –10 °C,1,3-cyclohexadiene (0.50 mL, 0.42 g, 5.25 mmol) was added in one portion. The Schlenktube was closed and heated at 100 °C for 90 min. The mixture was then preadsorbed onsilica and purified by column chromatography (hexanes/CH 2 Cl 2 ) to elute a first, greenfluorescent fraction of 60 (3.0 mg, 14%), providing orange crystals, mp >220 °C (no180

decomposition). UV-VIS (cyclohexane) λ max (logε) 304 (sh, 4.57), 312 (4.59), 329 (sh,4.54), 343 (sh, 4.62), 355 (4.69), 373 (4.63), 393 (4.57), 414 (sh, 4.18), 442 (sh, 3.92),475 (3.95), 507 (3.90) nm. IR (NaCl film): ~ ν = 2921, 2850, 1739, 1635, 1464, 1262,1106, 1091 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 374 (M + , 100), 187 (9), 186 (6). 1 HNMR (400 MHz, CDCl 3 ) δ 7.03–6.99 (m, 4H), 6.97 (m, 2H), 6.92 (m, 2H), 6.75 (d, 5 J =1.5 Hz, 1H), 6.60 (d, 5 J = 1.6 Hz, 1H), 6.14 (d, 3 J = 6.8 Hz, 2H), 6.06 (d, 3 J = 6.8 Hz,2H). HR-MS Calcd for C 30 H 14 : 374.1096. Found: 374.1093.1,5-Bis[(dimethylthexylsilyl)ethynyl]-2,4-bis[(trimethylsilyl)ethynyl]benzene (129):SiSiBrBr1,5-Dibromo-2,4-bis[(dimethylthexylsilyl)ethynyl]benzene. A suspension of 57 78(2.84 g, 5.80 mmol), [Pd(PPh 3 ) 2 Cl 2 ] (0.20 g, 0.29 mmol), and CuI (55.0 mg, 0.29 mmol)in triethylamine (100 mL) was degassed, and DMTSA 209 (2.69 g, 16.0 mmol, 2.8 equiv)was injected. The mixture was left to stir at 23 °C for 48 h. The suspension was filteredand the filtrate concentrated in vacuo. The resulting crude oil was dissolved in hexanesand passed through a short column of silica. Removal of the solvent in vacuo gave 3.04 g(92%) of 1,5-dibromo-2,4-bis[(dimethylthexylsilyl)ethynyl]benzene as a yellow oil. IR(NaCl film): ~ ν = 2958, 2866, 2158, 1450, 1340, 1251, 1174, 1059, 838, 818, 776, 699cm –1 . MS (EI, 70 eV) m/z (rel intensity) 568 (M + , 2), 525 (3), 483 (100), 399 (31), 84(44). 1 H NMR (500 MHz, CDCl 3 ) δ 7.79 (s, 1H), 7.56 (s, 1H), 1.72 (sept, 3 J = 6.9 Hz,2H), 0.97 (s, 12H), 0.94 (d, 3 J = 6.9 Hz, 12H), 0.24 (s, 12H). 13 C NMR (125 MHz,181

CDCl 3 ) δ 137.24, 135.50, 125.54, 124.62, 102.06, 101.23, 34.49, 23.48, 20.66, 18.66, –2.65. HR-MS Calcd for C 26 H 40 Br 2 Si 2 : 568.1015. Found: 568.1021. Anal. Calcd forC 26 H 40 Br 2 Si 2 : C, 54.92; H, 7.09. Found: C, 54.53; H, 7.19.SiSiTMSTMS1,5-Bis[(dimethylthexylsilyl)ethynyl]-2,4-bis[(trimethylsilyl)ethynyl]benzene (129). Amixture of 1,5-dibromo-2,4-bis[(dimethylthexylsilyl)ethynyl]benzene (1.97 g, 3.47mmol), TMSA (1.13 mL, 8.00 mmol), [Pd(PPh 3 ) 2 Cl 2 ] (24 mg, 0.035 mmol), and CuI (7.0mg, 0.035 mmol) in triethylamine (100 mL) was sealed in a 200 mL Schlenk tube andheated at 110 °C for 48 h. The solvent was removed in vacuo and the residue subjected tocolumn chromatography (hexanes/ether), yielding 129 as a dark brown oil (1.69 g, 81 %).IR (NaCl film): ~ ν = 2959, 2164, 2070, 1480, 1378, 1250, 1186, 998, 876, 761, 674, 641cm –1 . MS (EI, 70 eV) m/z (rel intensity) 602 (M + , 29), 519 (80), 517 (88), 434 (38), 252(62), 235 (50), 196 (66), 140 (88), 123 (100). 1 H NMR (500 MHz, CDCl 3 ) δ 7.56 (s, 1H),7.48 (s, 1H), 1.71 (sept, 3 J = 6.7 Hz, 2H), 0.98 (s, 12H), 0.94 (d, 3 J = 6.7 Hz, 12H), 0.25(br s, 30H). 13 C NMR (125 MHz, CDCl 3 ) δ 136.72, 136.11, 125.23, 125.02, 102.81,102.12, 100.66, 100.39, 34.50, 23.44, 20.85, 18.68, –0.13, –2.41.182

1,5-Bis[(dimethylthexylsilyl)ethynyl]-2,4-bis(ethynyl)benzene (130):SiSiA solution of 129 (105 mg, 0.174 mmol) in a mixture of methanol (30 mL) andether (30 mL) was treated with K 2 CO 3 (74 mg, 0.533 mmol). The mixture was left to stirat 23 °C for 2 h. The suspension was then filtered and the filtrate concentrated in vacuo.The resulting crude oil was dissolved in hexanes and passed through a short column ofsilica. Removal of the solvent in vacuo gave (80 mg, 97%) of 130 as a brown oil. Thecrude material was used in the next step.Compound 132:DMTSDMTSDMTSDMTSA mixture of 130 (77 mg, 0.168 mmol), 1-iodo-2-[(dimethylthexylsilyl)ethynyl]biphenylene 60 (155 mg, 0.348 mmol), [Pd(PPh 3 ) 2 Cl 2 ] (6.3mg, 0.009 mmol), and CuI (1.7 mg, 0.009 mmol) in triethylamine (15 mL) was sealed ina 20 mL Schlenk tube and heated at 120 °C for 16 h. The solvent was removed in vacuoand the residue subjected to column chromatography (hexanes/CH 2 Cl 2 ), yielding 132 as a183

dark brown oil (103 mg, 54 %). IR (NaCl film): ~ ν = 2958, 2866, 2154, 1458, 1417,1250, 1157, 873, 822, 775, 740 cm –1 . MS (FAB) m/z (rel intensity) 1092 ([M+2H] + , 3),1091 ([M+H] + , 3), 1090 (M + , 2), 960 (1), 765 (1), 252 (80), 235 (42), 140 (100), 124 (82).1 H NMR (400 MHz, CDCl 3 ) δ 7.67 (s, 1H), 7.60 (s, 1H), 6.96 (d, 3 J = 7.1 Hz, 2H), 6.83–6.76 (m, 6H), 6.67–6.60 (m, 2H), 6.54 (d, 3 J = 7.1 Hz, 2H), 1.72–1.51 (m, 4H), 0.90 (s,12H), 0.88 (s, 12H), 0.86 (d, 3 J = 6.8 Hz, 12H), 0.84 (d, 3 J = 6.8 Hz, 12H), 0.20 (s, 12H),0.17 (s, 12H). 13 C NMR (100 MHz, CDCl 3 ) δ 153.35, 150.65, 149.97, 149.73, 136.02,135.92, 133.26, 129.29, 128.99, 125.39, 124.70, 124.12, 118.60, 117.98, 116.60, 114.41,104.29, 103.11, 101.06, 98.05, 92.49, 89.97, 34.57, 34.54, 23.51, 23.44, 20.73, 20.70,18.66, 18.63, –2.25, –2.42. HR-MS Calcd for C 74 H 90 Si 4 : 1090.6120. Found: 1090.6100.2-Iodo-3-[(trimethylsilyl)ethynyl]biphenylene (134a):IMethod A. 2,3-Diiodobiphenylene (133) 53 (1.40 g, 3.47 mmol) was dissolved in amixture of triethylamine (40 mL) and THF (10 mL). The solution was degassed in a 50mL Schlenk flask, and [Pd(PPh 3 ) 2 Cl 2 ] (121 mg, 0.17 mmol) and CuI (34 mg, 0.17 mmol)were added. The mixture was left to stir overnight at 80 °C (~ 16 h). After the reactionwas complete, solvent was removed in vacuo and the mixture chromatographed on silica(hexanes) to give the starting material (436 mg, 31%), followed by the desired 134a (320mg, 25%) as yellow crystals, mp 100 °C. The last fraction contained 413 mg (34%) of2,3-bis(trimethylsilylethynyl)biphenylene (135a). 53 IR (NaCl film): ~ ν = 2959, 2152,1422, 1250, 1154, 999, 876, 843, 739, 717 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 374184TMS

(M + , 100), 359 (65), 248 (16), 233 (24), 179 (18), 124 (6). 1 H NMR (400 MHz,CDCl 3 ) δ 7.09 (s, 1H), 6.84–6.78 (m, 2H), 6.71 (s, 1H), 6.71–6.67 (m, 2H), 0.27 (s, 9H).13 C NMR (100 MHz, CDCl 3 ) δ 151.66, 150.41, 149.92, 149.79, 129.37, 128.96, 128.66,127.12, 120.50, 118.61, 118.57, 107.57, 101.18, 99.42, –0.15. HR-MS Calcd forC 17 H 15 ISi: 373.9988. Found: 373.9988.Method B. A solution of 139a (vide infra, 450 mg, 1.38 mmol) in THF (30 mL)was cooled to –45 °C, and BuLi (0.70 mL of 2.5 M solution in hexane, 1.75 mmol) wasadded via syringe. The dark brown solution was stirred at –45 ºC for 30 min. After thattime, a THF (20 mL) solution of iodine (508 mg, 2.00 mmol) was added dropwise viasyringe. The color of the solution lightened gradually with the addition of iodine. Themixture was left to warm to 23 °C overnight, extracted with ether (2 x 100 mL), andwashed with aq. Na 2 S 2 O 3 and then brine. Drying over MgSO 4 , followed by removal ofsolvent in vacuo, gave 134a as a yellow oil (399 mg, 78%).2-[(Dimethylthexylsilyl)ethynyl]-3-iodobiphenylene (134b):ISiMethod A. 2,3-Diiodobiphenylene (133) 53 (100 mg, 0.25 mmol) was dissolved intriethylamine (50 mL). The solution was degassed, and [Pd(PPh 3 ) 2 Cl 2 ] (9 mg, 0.013mmol), CuI (3 mg, 0.016 mmol), and DMTSA 209 (45 mg, 0.27 mmol) were added. Themixture was stirred at 23 °C for 7 h, after which time an additional portion of DMTSA(49 mg, 0.29 mmol) was injected through the septum. After an additional 2 h of stirring,185

solvent was removed in vacuo and the mixture chromatographed on silica (hexanes) togive the starting material (12 mg, 12%), followed by 134b (23 mg, 21%) as a yellow oil.The last fraction contained 135b (74 mg, 63%) as yellow crystals, mp 106–108 °C. IR(NaCl film): ~ ν = 2958, 2154, 1735, 1464, 1378, 1248, 1113, 872, 830, 738 cm –1 . MS(EI, 70 eV) m/z (rel intensity) 444 (M + , 19), 359 (100), 283 (9), 233 (28), 161 (18), 123(12). 1 H NMR (400 MHz, CDCl 3 ) δ 7.08 (s, 1H), 6.82–6.79 (m, 2H), 6.71 (s, 1H), 6.71–6.66 (m, 2H), 1.75 (sept, 3 J = 6.9 Hz, 1H), 0.97 (s, 6H), 0.95 (d, 3 J = 6.9 Hz, 6H), 0.25 (s,6H). 13 C NMR (100 MHz, CDCl 3 ) δ 151.50, 150.36, 149.95, 149.83, 129.34, 128.94,127.12, 120.80, 118.57, 118.55, 108.19, 100.65, 100.01, 99.28, 34.63, 23.65, 20.84,18.80, –2.42. HR-MS Calcd for C 22 H 25 ISi: 444.0770. Found: 444.0771.SiSiSpectral data for 135b: IR (NaCl film): ~ ν = 2959, 2865, 2147, 1465, 1424, 1249,1108, 912, 874, 841, 773, 733 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 484 (M + , 33), 399(8), 329 (78), 315 (100), 241 (17), 73 (55). 1 H NMR (400 MHz, CDCl 3 ) δ 6.83–6.81 (m,2H), 6.69–6.67 (m, 2H), 6.67 (s, 2H), 1.72 (sept, 3 J = 6.9 Hz, 2H), 0.97 (s, 12H), 0.96 (d,3 J = 6.9 Hz, 12H), 0.23 (s, 12H). 13 C NMR (100 MHz, CDCl 3 ) δ 150.14, 150.04, 128.13,126.01, 120.40, 118.35, 105.04, 99.17, 34.67, 23.57, 20.93, 18.79, –2.28. HR-MS Calcdfor C 32 H 44 Si 2 : 484.2982. Found: 484.2990.Method B. A solution of 139b (vide infra, 350 mg, 0.88 mmol) in THF (30 mL)was cooled to –45 °C, and BuLi (0.50 mL of 2.5 M solution in hexane, 1.25 mmol) was186

added via syringe. The dark brown solution was stirred at –45 ºC for 30 min. After thattime, a THF (20 mL) solution of iodine (508 mg, 2.00 mmol) was added dropwise viasyringe. The color of the solution lightened gradually with the addition of iodine. Themixture was left to warm to 23 °C overnight, extracted with ether (2 x 100 mL), andwashed with aq. Na 2 S 2 O 3 and then brine. Drying over MgSO 4 , followed by removal ofsolvent in vacuo, gave 134b as a yellow oil (320 mg, 82%).2-Iodo-3-(oct-1-ynyl)biphenylene (134c):IMethod A. 2,3-Diiodobiphenylene (133) 53 (105 mg, 0.26 mmol) was dissolved intriethylamine (5 mL). The solution was degassed, and [Pd(PPh 3 ) 2 Cl 2 ] (18 mg, 0.026mmol), CuI (5 mg, 0.026 mmol), and 1-octyne (29 mg, 38 µL, 0.26 mmol) were added.The mixture was stirred at 23 °C for 12 h, after which time the solvent was removed invacuo and the mixture was chromatographed on silica (hexanes) to give the starting 133(21 mg, 20%), followed by 134c (46 mg, 46%) as a yellow oil. The last fractioncontained 135c (9 mg, 9%) as a yellow oil. IR (NaCl film): ~ ν = 2927, 2855, 2225, 1567,1423, 1377, 1346, 1256, 1155, 1112, 974, 872, 739 cm –1 . MS (EI, 70 eV) m/z (relintensity) 386 (M + , 100), 315 (26), 260 (63), 216 (42), 202 (65), 189 (82), 165 (20). 1 HNMR (400 MHz, CDCl 3 ) δ 7.07 (s, 1H), 6.80–6.79 (m, 2H), 6.70–6.65 (m, 3H), 2.44 (t,3 J = 7.0 Hz, 2H), 1.66–1.59 (m, 2H), 1.54–1.48 (m, 2H), 1.34–1.26 (m, 4H), 0.91 (t, 3 J =7.0 Hz, 3H). 13 C NMR (100 MHz, CDCl 3 ) δ 150.67, 150.45, 149.99, 149.97, 129.61,129.09, 128.84, 127.05, 120.64, 118.46, 118.30, 100.15, 95.60, 84.02, 31.40, 28.67,187

28.51, 22.63, 19.71, 14.14. HR-MS Calcd for C 20 H 19 I: 386.0532. Found: 386.0535. Anal.Calcd for C 20 H 19 I: C, 62.19; H, 4.96. Found: C, 62.87; H, 5.23.Spectral data for 135c: IR (NaCl film): ~ ν = 2929, 2857, 2221, 1466, 1427, 1378,1327, 1279, 1154, 1112, 879, 739 cm –1 . MS (FAB) m/z (rel intensity) 368 (M + , 33), 252(100), 235 (56), 140 (89), 123 (73). 1 H NMR (400 MHz, CDCl 3 ) δ 6.79–6.77 (m, 2H),6.67–6.65 (m, 2H), 6.62 (s, 2H), 2.44 (t, 3 J = 7.1 Hz, 2H), 1.64–1.55 (m, 2H), 1.50–1.43(m, 2H), 1.36–1.26 (m, 4H), 0.91 (t, 3 J = 7.0 Hz, 3H). 13 C NMR (100 MHz,CDCl 3 ) δ 150.24, 149.38, 128.78, 126.36, 120.05, 117.97, 94.94, 80.45, 31.49, 28.85,28.66, 22.62, 19.82, 14.13. HR-MS Calcd for C 28 H 32 : 368.2504. Found: 368.2495.Method B. A solution of 139c (vide infra, 400 mg, 1.18 mmol) in THF (30 mL)was cooled to –45 °C, and BuLi (0.60 mL of 2.5 M solution in hexane, 1.50 mmol) wasadded via syringe. The dark brown solution was stirred at –45 ºC for 30 min. After thattime, a THF (20 mL) solution of iodine (508 mg, 2.00 mmol) was added dropwise viasyringe. The color of the solution lightened gradually with the addition of iodine. Themixture was left to warm to 23 °C overnight, extracted with ether (2 x 100 mL), andwashed with aq. Na 2 S 2 O 3 and then brine. Drying over MgSO 4 , followed by removal ofsolvent in vacuo, gave 134c as a yellow oil (388 mg, 85%).188

2-Bromo-3-(trimethylsilyl)biphenylene (137):Br2,3-Bis(trimethylsilyl)biphenylene 52 (3.62 g, 12.3 mmol) and pyridine (0.97 mL,12.1 mmol) were dissolved in methylene chloride (35 mL), and the solution was cooledto 0 °C. Neat bromine (0.65 mL, 12.7 mmol) was added via syringe. The originallyorange mixture immediately turned dark brown. The solution was stirred at 0 °C for 3min and then treated with aq. NaHCO 3 , followed by dilution with ether and washing withaq. Na 2 S 2 O 3 . The organic layer was dried over MgSO 4 , and the solvent was subsequentlyremoved in vacuo to give the crude material as an oily solid. Washing the solid withhexanes extracted a yellow oil that contained 137 (2.20 g, 59%) that was used in thefollowing reaction without further purification. The remaining white crystals weretentatively identified as impure 2,3-dibromobiphenylene (970 mg, 25%), which was notfully characterized. IR (NaCl film): ~ ν = 3066, 2955, 2898, 1932, 1653, 1587, 1418,1322, 1248, 1196, 1075, 854, 739, 647 cm –1 . 1 H NMR (500 MHz, CDCl 3 ) δ 6.81 (s, 1H),6.79–6.77 (m, 2H), 6.69 (s, 1H), 6.68–6.66 (m, 2H), 0.36 (s, 9H). 13 C NMR (125 MHz,CDCl 3 ) δ 153.36, 151.23, 149.93, 148.89, 140.05, 130.18, 128.93, 128.32, 123.42,122.30, 118.28, 117.75, –0.40.TMS2-Bromo-3-iodobiphenylene (138):BrCompound 137 (2.20 g, 7.26 mmol) was dissolved in CH 2 Cl 2 (30 mL) and thesolution cooled to 0 °C. To this solution, ICl (1.19 g, 7.30 mmol) in CH 2 Cl 2 (20 mL) was189I

added slowly via syringe. The mixture changed color from yellow to reddish-brown. Thesolution was stirred for 2 h at 0 °C and an additional 3 h at 23 °C. Subsequently, it wastreated with aq. NaHCO 3 , followed by dilution with ether and washing with aq. Na 2 S 2 O 3 .The organic layer was dried over MgSO 4 , and the solvent was removed in vacuo to givethe crude material, which was purified by column chromatography on silica (eluting withhexanes). Final purification was achieved by Kugelrohr sublimation (250 °C, 0.3 Torr) togive 138 as yellow crystals, mp 122–124 °C (2.57 g, 99%). MS (EI, 70 eV) m/z (relintensity) 358/356 (M + , 98/98), 312/310 (18/18), 229 (16), 150 (100), 75 (24). 1 H NMR(400 MHz, CDCl 3 ) δ 7.04 (s, 1H), 6.85 (s, 1H), 6.82–6.80 (s, 2H), 6.69–6.65 (m, 2H). 13 CNMR (100 MHz, CDCl 3 ) δ 152.29, 150.67, 149.63, 149.40, 129.28, 129.20, 128.60,128.27, 121.79, 118.89, 118.64, 99.21. HR-MS Calcd for C 12 H 79 6 BrI: 355.8698. Found:355.8694. Anal. Calcd for C 12 H 6 BrI: C, 40.37; H, 1.69. Found: C, 40.30; H, 1.82.2-Bromo-3-[(trimethylsilyl)ethynyl]biphenylene (139a):BrA thoroughly degassed solution of 138 (700 mg, 1.96 mmol) in triethylamine (50mL) was treated with [Pd(PPh 3 ) 2 Cl 2 ] (68 mg, 0.098 mmol), CuI (19 mg, 0.098 mmol),and TMSA (0.35 mL, 2.50 mmol). After stirring for 12 h at 23 °C, an additional portionof TMSA (0.30 mL, 2.14 mmol) was added. The mixture was left to stir for an additional24 h, and the solvent was then removed in vacuo. Column chromatography of the residueprovided the starting material (29 mg, 4%), followed by the desired product (480 mg,75%) as a yellow oil. IR (NaCl film): ~ ν = 2958, 2153, 1868, 1489, 1250, 882, 844, 740190TMS

cm –1 . MS (EI, 70 eV) m/z (rel intensity) 328/326 (M + , 100/92), 313/311 (85/83), 231 (15),217 (18), 202 (31), 189 (76), 156 (15). 1 H NMR (400 MHz, CDCl 3 ) δ 6.84 (s, 1H), 6.84–6.80 (m, 2H), 6.72–6.66 (m, 3H), 0.26 (s, 9H). 13 C NMR (100 MHz, CDCl 3 ) δ 151.99,149.81, 149.45, 149.33, 129.47, 128.99, 126.16, 123.82, 121.62, 121.13, 118.60, 118.38,103.94, 100.23, –0.11. HR-MS Calcd for C 17 H 81 15 BrSi: 328.0106. Found: 328.0103.Anal. Calcd for C 17 H 15 BrSi: C, 62.39; H, 4.62. Found: C, 61.90; H, 4.96.2-Bromo-3-[(dimethylthexylsilyl)ethynyl]biphenylene (139b):BrSiA thoroughly degassed solution of 138 (700 mg, 1.96 mmol) in triethylamine (50mL) was treated with [Pd(PPh 3 ) 2 Cl 2 ] (68 mg, 0.098 mmol), CuI (19 mg, 0.098 mmol),and DMTSA (505 mg, 3.00 mmol). After stirring for 24 h at 23 °C, the solvent wasremoved in vacuo. Column chromatography of the residue provided the starting material(203 mg, 29%), followed by the desired product (467 mg, 60%) as a yellow oil. Thecrude material was used in subsequent steps. IR (NaCl film): ~ ν = 2959, 2866, 2152,1421, 1250, 1010, 877, 818, 775, 739 cm –1 . 1 H NMR (500 MHz, CDCl 3 ) δ 6.83 (s, 1H),6.85–6.80 (m, 2H), 6.69 (s, 1H), 6.70–6.67 (m, 2H), 1.74 (sept, 3 J = 6.9 Hz, 1H), 0.97 (s,6H), 0.95 (d, 3 J = 6.9 Hz, 6H), 0.24 (s, 6H). 13 C NMR (125 MHz, CDCl 3 ) δ 151.75,149.74, 149.39, 149.22, 129.37, 128.99, 125.96, 124.01, 121.56, 121.19, 118.50, 118.27,104.63, 99.97, 34.63, 23.50, 20.70, 18.69, 18.57, –2.51.191

2-Bromo-3-(oct-1-ynyl)biphenylene (139c):BrA thoroughly degassed solution of 138 (700 mg, 1.96 mmol) in triethylamine (50mL) was treated with [Pd(PPh 3 ) 2 Cl 2 ] (68 mg, 0.098 mmol), CuI (19 mg, 0.098 mmol),and 1-octyne (0.37 mL, 2.50 mmol). After stirring for 12 h at 23 °C, an additional portionof 1-octyne (0.4 mL, 2.70 mmol) was added. The mixture was left to stir for an additional24 h, and the solvent was then removed in vacuo. Column chromatography of the residueprovided the starting material (182 mg, 26%), followed by the desired 139c (446 mg,67%) as a yellow oil. IR (NaCl film): ~ ν = 3058, 2930, 2857, 2228, 1656, 1424, 1351,1258, 1207, 1155, 1113, 1013, 872, 739 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 340/338(M + , 100/100), 269/267 (34/34), 230 (21), 216 (48), 202 (38), 190 (66), 187 (62), 57 (10).1 H NMR (400 MHz, CDCl 3 ) δ 6.81 (s, 1H), 6.81–6.79 (s, 2H), 6.68–6.64 (s, 2H), 6.64 (s,1H), 2.45 (t, 3 J = 7.0 Hz, 2H), 1.65–1.60 (m, 2H), 1.54–1.49 (m, 2H), 1.39–1.30 (m, 4H),0.94 (t, 3 J = 7.1 Hz, 2H). 13 C NMR (100 MHz, CDCl 3 ) δ 150.97, 149.89, 149.63, 149.41,129.20, 128.88, 125.26, 124.79, 121.60, 121.26, 118.34, 118.24, 96.31, 80.45, 31.48,28.68 (2C), 22.72, 19.81, 14.22. HR-MS Calcd for C 20 H 79 19 Br: 338.0670. Found:338.0664. Anal. Calcd for C 20 H 19 Br: C, 70.80; H, 5.64. Found: C, 71.10; H, 5.81.192

Compound 141a:TMSDMTSDMTSTMSIn a 25 ml Schlenk flask, compounds 134a (331 mg, 0.885 mmol) and 140 66 (196mg, 0.428 mmol), along with [Pd(PPh 3 ) 2 Cl 2 ] (18 mg, 0.026 mmol) and CuI (5.1 mg,0.026 mmol), were suspended in triethylamine (120 mL). The suspension was degassedand the tube closed. The mixture was heated at 120 °C for 48 h. The solvent was removedin vacuo and the mixture purified by column chromatography (hexanes/CH 2 Cl 2 ) to give141a as a yellow oil (93 mg, 23%). IR (NaCl film): ~ ν = 2959, 2866, 2150, 1653, 1250,1164, 942, 885, 841, 775, 761, 739 cm –1 . MS (FAB) m/z (rel intensity) 950 (M + , 4), 877(3), 307 (21), 154 (100), 136 (80). 1 H NMR (500 MHz, C 6 D 6 ) δ 7.11 (s, 2H), 6.79 (s,2H), 6.54 (s, 2H), 6.42–6.41 (m, 4H), 6.30–6.29 (m, 2H), 6.19–6.17 (m, 2H), 1.73 (sept,3 J = 6.8 Hz, 2H), 1.01 (s, 12H), 0.94 (d, 3 J = 6.9 Hz, 12H), 0.31 (s, 12H), 0.26 (s, 18H).13 C NMR (125 MHz, CDCl 3 ) δ 150.16, 150.05, 150.00, 149.97, 131.10, 128.98, 128.95,128.49, 126.75, 126.11, 125.96, 119.96, 119.83, 118.20, 118.19, 104.42, 103.71, 100.74,99.69, 97.20, 91.21, 34.51, 23.44, 20.71, 18.65, –0.13, –2.37. HR-MS Calcd forC 64 H 70 Si 4 : 950.4555. Found: 950.4560.193

Compound 141b:DMTSDMTSDMTSDMTSIn a 25 ml Schlenk flask, compounds 134b (23 mg, 0.052 mmol) and 140 66 (12mg, 0.025 mmol), along with [Pd(PPh 3 ) 2 Cl 2 ] (3.5 mg, 0.005 mmol) and CuI (1.0 mg,0.005 mmol), were suspended in triethylamine (20 mL). The suspension was degassedand the tube closed. The mixture was heated at 120 °C for 48 h. The solvent was removedin vacuo and the mixture purified by column chromatography (hexanes/CH 2 Cl 2 ) to give141b as a yellow oil (8 mg, 28%). IR (NaCl film): ~ ν = 2958, 2866 , 2151, 1462, 1250,1165, 943, 883, 838, 820, 775, 739 cm –1 . MS (FAB) m/z (rel intensity) 1090 (M + , 4), 252(82), 140 (100). 1 H NMR (500 MHz, C 6 D 6 ) δ 7.15 (s, 2H), 6.85 (s, 2H), 6.51 (s, 2H),6.44–6.41 (m, 4H), 6.32–6.31 (m, 2H), 6.21–6.19 (m, 2H), 1.75 (sept, 3 J = 6.8 Hz, 2H),1.74 (sept, 3 J = 6.8 Hz, 2H), 1.01 (s, 12H), 1.00 (s, 12H), 0.95 (d, 3 J = 6.9 Hz, 12H), 0.94(d, 3 J = 6.9 Hz, 12H), 0.33 (s, 12H), 0.30 (s, 12H). 13 C NMR (125 MHz,CDCl 3 ) δ 150.12, 150.05, 150.01, 149.77, 130.82, 128.90, 128.87, 128.86, 126.59,126.22, 125.95, 119.96, 119.93, 118.11, 118.10, 105.07, 103.66, 100.62, 99.15, 97.10,90.86, 34.50, 34.43, 23.41, 23.31, 20.64, 20.59, 18.63, 18.55, –2.35, –2.40. HR-MS Calcdfor C 74 H 90 Si 4 : 1090.6120. Found: 1090.6116.194

Compound 141c:DMTSDMTSIn a 25 ml Schlenk flask, compounds 134c (388 mg, 1.01 mmol) and 140 66 (359mg, 0.57 mmol), along with [Pd(PPh 3 ) 2 Cl 2 ] (35 mg, 0.05 mmol) and CuI (5.0 mg, 0.025mmol), were suspended in triethylamine (10 mL). The suspension was degassed and thetube closed. The mixture was heated at 120 °C for 36 h. The solvent was removed invacuo and the mixture purified by column chromatography (hexanes/CH 2 Cl 2 ) to give141c as a brown oil (291 mg, 30%). IR (NaCl film): ~ ν = 2958, 2866, 2225, 2155, 1717,1458, 1428, 1378, 1250, 1157, 1120, 819, 776, 740 cm –1 . MS (EI, 70 eV) m/z (relintensity) 976 (M + , 1), 252 (100), 235 (70), 140 (95), 123 (73). 1 H NMR (400 MHz,CDCl 3 ) δ 7.33 (s, 2H), 6.81–6.79 (m, 6H), 6.70–6.65 (m, 6H), 2.24 (t, 3 J = 7.3 Hz, 4H),1.72 (sept, 3 J = 6.8 Hz, 2H), 1.49–1.41 (m, 4H), 1.33–1.27 (m, 4H), 1.18–1.10 (m, 8H),0.95 (s, 12H), 0.92 (d, 3 J = 6.8 Hz, 12H), 0.79 (t, 3 J = 7.1 Hz, 6H), 0.24 (s, 12H). 13 CNMR (100 MHz, CDCl 3 ) δ 150.34, 150.27, 150.16, 148.77, 131.29, 128.99, 128.81,128.56, 127.47, 126.19, 125.62, 120.46, 120.17, 118.18, 117.95, 103.97, 100.50, 97.92,195

96.63, 90.79, 80.16, 34.63, 31.53, 28.88, 28.84, 23.56, 22.57, 20.82, 19.92, 18.71, 14.11,–2.33. HR-MS Calcd for C 70 H 78 Si 2 : 974.5642. Found: 974.5650.Compound 144:DMTSODMTSIn a 25 mL Schlenk flask, compounds 134c (129 mg, 0.334 mmol) and 140 66 (77mg, 0.168 mmol), along with [Pd(PPh 3 ) 2 Cl 2 ] (12 mg, 0.017 mmol) and CuI (3.2 mg,0.017 mmol), were suspended in piperidine (15 mL). The suspension was degassed andthe tube closed. The mixture was heated at 120 °C for 24 h. The solvent was removed invacuo and the mixture purified by column chromatography (hexanes/CH 2 Cl 2 ) to give 144as a yellow oil (55 mg, 34%). IR (NaCl film): ~ ν = 2958, 2927, 2860, 2153, 1728, 1465,1428, 1379, 1250, 1157, 878, 822, 775, 739 cm –1 . MS (FAB) m/z (rel intensity) 735([M+H] + , 5), 734 (M + , 5), 252 (100), 235 (70), 140 (95), 123 (73). 1 H NMR (400 MHz,CDCl 3 ) δ 9.70 (s, 1H), 7.38 (br s, 2H), 6.84–6.82 (m, 2H), 6.76 (s, 1H), 6.72–6.68 (m,2H), 6.68 (s, 1H), 4.23 (s, 2H), 2.43 (t, 3 J = 7.1 Hz, 2H) 1.75–1.67 (m, 2H), 1.61–1.54(m, 2H), 1.45–1.37 (m, 2H), 1.26–1.22 (m, 4H), 0.96–0.92 (m, 24H), 0.87 (t, 3 J = 6.9 Hz,2H), 0.26 (s, 6H), 0.23 (s, 6H). 13 C NMR (100 MHz, CDCl 3 ) δ 198.09, 150.77, 150.10,150.03, 149.26, 137.22, 131.49, 131.42, 129.16, 129.02, 127.03, 126.90, 126.44, 124.70,124.21, 120.41, 119.99, 118.42, 118.11, 104.16, 103.24, 101.62, 100.62, 98.37, 96.14,196

89.98, 80.55, 47.85, 34.61 (2C), 31.42, 28.75, 28.73, 23.57, 23.50, 22.56, 20.83, 20.73,19.88, 18.71, 18.66, 14.10, –2.29, –2.54. HR-MS Calcd for C 50 H 62 OSi 2 : 734.4367.Found: 734.4358.1-Bromo-2,4-bis[(dimethylthexylsilyl)ethynyl]-5-iodobenzene (145):SiSiBrIA solution of 1,5-dibromo-2,4-bis[(dimethylthexylsilyl)ethynyl]benzene (2.90 g,5.11 mmol) in ether (200 mL) was cooled to –50 °C, and BuLi (4.4 mL of 2.4 M solutionin hexane, 10.3 mmol) was added via syringe. The orange solution was stirred at –50 ºCfor 45 min. After that time, an ethereal solution (100 mL) of iodine (3.45 g, 13.5 mmol)was added dropwise via syringe. The color of the solution lightened gradually withaddition of iodine. The mixture was left to warm to 23 °C overnight, extracted with ether(2 x 100 mL), and washed with aq. Na 2 S 2 O 3 and then brine. Drying over MgSO 4 ,followed by removal of solvent in vacuo, gave 145 as a yellow oil (3.11 g, 99%). IR(NaCl film): ~ ν = 2962, 2865, 2156, 1462, 1445, 1378, 1336, 1250, 1174, 1046, 970, 873,818, 775, 690 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 616/614 (M + , 1/1), 601/599 (1/1),573/571 (2/2), 531/529 (100/92), 451 (32), 405 (20), 319 (24), 85 (26). 1 H NMR (500MHz, CDCl 3 ) δ 8.03 (s, 1H), 7.51 (s, 1H), 1.82–1.70 (m, 2H), 0.97 (s, 6H), 0.96 (s, 6H),0.94 (d, 3 J = 6.9 Hz, 6H), 0.94 (d, 3 J = 6.9 Hz, 6H), 0.25 (s, 6H), 0.24 (s, 6H). 13 C NMR(125 MHz, CDCl 3 ) δ 141.44, 136.37, 129.04, 125.40, 125.32, 105.42, 102.21, 101.48,100.48, 100.28, 34.49 (2C), 23.53, 23.48, 20.73, 20.67, 18.71, 18.67, –2.61, –2.64. HR-197

MS Calcd for C 26 H 40 81 BrISi 2 : 616.0876. Found: 616.0867. Anal. Calcd for C 26 H 40 BrISi 2 :C, 50.73; H, 6.55. Found: C, 50.99; H, 6.92.1-Iodo-2,4-bis[(dimethylthexylsilyl)ethynyl]-5-[(trimethylsilyl)ethynyl]benzene(146):SiSiBrTMS1-Bromo-2,4-bis[(dimethylthexylsilyl)ethynyl]-5-[(trimethylsilyl)ethynyl]benzene.A suspension of 145 (1.45 g, 2.36 mmol), [Pd(PPh 3 ) 2 Cl 2 ] (83.0 mg, 0.12 mmol), and CuI(23.0 mg, 0.12 mmol) in triethylamine (60 mL) was thoroughly degassed.Trimethylsilylacetylene (4.00 mL, 28.3 mmol) was injected, the mixture stirred at 23 °Cfor 1 h, the solids filtered off, the solvent removed in vacuo, and the resulting crudemixture filtered through a short pad of silica (hexanes) to yield 1-bromo-2,4-bis[(dimethylthexylsilyl)ethynyl]-5-[(trimethylsilyl)ethynyl]benzene as a yellow oil (1.03mg, 75%). IR (NaCl film): ~ ν = 2959, 2866, 2158, 1467, 1356, 1250, 1153, 862, 841, 775cm –1 . MS (EI, 70 eV) m/z (rel intensity) 586/584 (M + , 100/98), 518 (41), 485 (14), 405(11). 1 H NMR (500 MHz, CDCl 3 ) δ 7.66 (s, 1H), 7.51 (s, 1H), 1.76–1.68 (m, 2H), 0.97(br s, 12H), 0.94 (d, 3 J = 6.8 Hz, 6H), 0.93 (d, 3 J = 6.8 Hz, 6H), 0.25 (s, 9H), 0.24 (s, 6H),0.24 (s, 6H). 13 C NMR (100 MHz, CDCl 3 ) δ 136.71, 135.97, 126.25, 125.28, 124.73,124.69, 102.66, 102.24, 101.92, 101.54, 101.36, 99.97, 34.51, 34.48, 23.50, 23.41, 20.83,20.67, 18.68, 18.66, –0.17, –2.45, –2.61. HR-MS Calcd for C 31 H 81 49 BrSi 3 : 586.2305.198

Found: 586.2313. Anal. Calcd for C 31 H 49 BrSi 3 : C, 63.55; H, 8.43. Found: C, 63.23; H,8.58.SiSiITMS1-Iodo-2,4-bis[(dimethylthexylsilyl)ethynyl]-5-[(trimethylsilyl)ethynyl]benzene(146). A solution of 1-bromo-2,4-bis[(dimethylthexylsilyl)ethynyl]-5-[(trimethylsilyl)ethynyl]benzene (60.0 mg, 0.11 mmol) in ether (10 mL) was cooled to –50 °C, and BuLi (0.2 mL of 2.34 M solution in hexane, 0.48 mmol) was added viasyringe. The orange solution was stirred at –50 °C for 45 min. After that time, an etherealsolution (10 mL) of iodine (127 mg, 0.50 mmol) was added dropwise via syringe. Thecolor of the solution lightened gradually with addition of iodine. The mixture was left towarm to 23 °C overnight, extracted with ether (2 x 10 mL), and washed with aq. Na 2 S 2 O 3and then brine. Drying over MgSO 4 , followed by removal of solvent in vacuo, gave 146as a yellow oil (51.0 mg, 79%). IR (NaCl film): ~ ν = 2958, 2867, 2157, 2068, 1463,1378, 1350, 1250, 1191, 1149, 1036, 861, 775, 683 cm –1 . MS (EI, 70 eV) m/z (relintensity) 632 (M + , 5), 589 (2), 547 (100), 421 (68). 1 H NMR (500 MHz, CDCl 3 ) δ 7.92(s, 1H), 7.47 (s, 1H), 1.77–1.68 (m, 2H), 0.98 (s, 6H), 0.97 (s, 6H), 0.95 (d, 3 J = 6.9 Hz,6H), 0.94 (d, 3 J = 6.9 Hz, 6H), 0.26 (s, 6H), 0.25 (s, 9H), 0.24 (s, 6H). 13 C NMR (100MHz, CDCl 3 ) δ 142.23, 135.76, 129.64, 126.11, 125.43, 106.04, 102.39, 101.38, 101.30,101.07, 100.25, 99.53, 34.53, 34.50, 23.59, 23.44, 20.86, 20.76, 18.73, 18.71, –0.13, –2.42, –2.55. HR-MS Calcd for C 31 H 49 ISi 3 : 632.2187. Found: 632.2185. Anal. Calcd forC 31 H 49 ISi 3 : C, 58.53; H, 7.80. Found: C, 58.84; H, 7.99.199

Compound 147:DMTSDMTSDMTSTMSTMSDMTSDMTSDMTSIn a 250 ml Schlenk flask, compounds 140 66 (343 mg, 0.75 mmol) and 146 (946mg, 1.50 mmol), along with [Pd(PPh 3 ) 2 Cl 2 ] (26 mg, 0.04 mmol), and CuI (7.0 mg, 0.04mmol) were suspended in triethylamine (100 mL). The mixture was set to reflux and leftto stir, with heating, overnight (~ 16 h). After the reaction was complete, solvent wasremoved in vacuo and the mixture filtered through a short plug of silica (hexanes/EtOAc)to give the desired product (950 mg, 87%) as a yellow oil. IR (NaCl film): ~ ν = 2959,2932, 2158, 1484, 1463, 1380, 1250, 1188, 930, 867, 840, 776, 673 cm –1 . 1 H NMR (400MHz, C 6 D 6 ) δ 7.84 (s, 2H), 7.57 (s, 2H), 7.09 (s, 2H), 1.71–1.59 (m, 6H), 0.97 (s, 12H),0.92 (s, 12H), 0.91 (d, 3 J = 6.9 Hz, 12H), 0.88 (s, 12H), 0.87 (d, 3 J = 6.9 Hz, 12H), 0.84(d, 3 J = 6.9 Hz, 12H), 0.28 (s, 9H), 0.25 (s, 6H), 0.25 (s, 6H), 0.16 (s, 6H). 13 C NMR (100MHz, CDCl 3 ) δ 136.06, 135.82, 131.11, 128.77, 125.89, 125.58, 125.54, 125.19, 124.99,103.41, 103.18, 103.07, 102.40, 101.10, 100.87, 100.31, 100.07, 95.23, 91.78, 34.64,34.56, 34.50, 23.53, 23.46, 23.38, 20.93, 20.66, 20.64, 18.78, 18.68, 18.60, 0.00, –2.32, –2.37, –2.40.200

Attempted preparation of compound 148:TMSTMSTMSA solution of 147 (90 mg, 0.061 mmol) in THF (50 mL) was treated with TBAF(0.6 mL of 1.0 M THF solution, 0.60 mmol). The dark-colored mixture was stirred at 23°C for 90 min, after which time ethanol (3 mL) was added via syringe. After anadditional 40 min of stirring, the solution was diluted with ether and washed with water.The organic layer was dried over MgSO 4 . m-Xylene (20 mL) was added, and the volumeof the solution was reduced in vacuo to ~ 25 mL. The resulting solution was mixed with[CpCo(CO) 2 ] (0.2 mL) and injected over 5 min into a refluxing mixture of m-xylene andBTMSA (with irradiation). Irradiation and heating were continued for 45 min. Aftercooling, solvents were removed in vacuo, and the crude material was filtered through aplug of silica (hexanes/CH 2 Cl 2 ) to provide a complicated mixture of products. MS (EI, 70eV) m/z (rel intensity) 933 (0.5), 922 (0.5), 840 (0.5), 810 (0.5, possibly 148), 711 (25),623 (27), 294 (33), 125 (31), 111 (48), 97 (68), 83 (62), 71 (72), 57 (100).TMS201

Compound 149:DMTSDMTSDMTS TMSDMTSDMTSDMTSTMSIn a 100 mL round-bottom flask, compound 147 (475 mg, 0.324 mmol) wasdissolved in a mixture of ether (20 mL) and methanol (20 mL). Potassium carbonate (138mg, 1.0 mmol) was added and the mixture left to stir at 23 °C for 90 min. Solids werefiltered off and the solvent removed in vacuo. The crude product was redissolved inmethylene chloride and the solution filtered through a short pad of silica. Solvent wasremoved in vacuo. The resulting diterminal alkyne was transferred into a 250 mL Schlenkflask and dissolved in triethylamine (100 mL). This solution was treated with[Pd(PPh 3 ) 2 Cl 2 ] (11.2 mg, 0.016 mmol), CuI (3.0 mg, 0.016 mmol), and 1-iodo-2-[(trimethylsilyl)ethynyl]benzene 142 (203 mg, 0.700 mmol). The mixture was thoroughlydegassed, set to reflux, and left to stir, with heating, overnight (~ 16 h). After the reactionwas complete, solvent was removed in vacuo and the mixture filtered through a shortplug of silica (hexanes/EtOAc) to give the desired product (468 mg, 88%) as a yellow oil.IR (NaCl film): ~ ν = 2959, 2932, 2158, 1489, 1464, 1379, 1250, 930, 902, 874, 840, 776,674 cm –1 . MS (FAB) m/z (rel intensity) 1670 (M + , 58), 1585 (100), 1500 (71), 1416 (62).1 H NMR (500 MHz, C 6 D 6 ) δ 7.97 (s, 2H), 7.72 (s, 2H), 7.49 (dd, 3 J 1 = 7.8 Hz, 4 J 2 = 0.6Hz, 2H), 7.37 (dd, 3 J 1 = 7.8 Hz, 4 J 2 = 0.6 Hz, 2H), 7.12 (s, 2H), 6.84 (dt, 3 J 1 = 7.7 Hz, 4 J 2202

= 1.2 Hz, 2H), 6.75 (dt, 3 J 1 = 7.7 Hz, 4 J 2 = 1.2 Hz, 2H), 1.70–1.63 (m, 6H), 0.94 (s, 12H),0.92 (s, 24H), 0.89 (d, 3 J = 6.9 Hz, 12H), 0.87 (d, 3 J = 6.9 Hz, 12H), 0.86 (d, 3 J = 6.9 Hz,12H), 0.32 (s, 9H), 0.27 (s, 6H), 0.23 (s, 6H), 0.22 (s, 6H). 13 C NMR (125 MHz,CDCl 3 ) δ 135.69, 134.98, 131.85, 131.75, 131.21, 128.22, 128.04, 127.85, 126.37,126.07, 125.97, 125.85, 125.61, 128.28, 125.25, 103.41, 103.21 (2C), 103.06, 101.11,100.98, 100.52, 99.26, 94.93, 93.49, 91.68, 91.05, 34.47 (2C), 34.39, 23.39, 23.34, 23.25,20.69, 20.64, 20.59, 18.61 (2C), 18.54, –0.09, –2.38, –2.42 (2C). The high molecularmass of 149 precluded HR-MS measurements.6.2.1 Calculated Structures of 60 and 118–120Calculated positional parameters for 60:Atom x y zC1 –0.0413513298 0.5413477993 5.8636121223C2 –0.3092033702 3.2809890496 5.9994865076C3 –0.1332418660 1.3270481111 4.6791300864C4 –0.0809106068 1.1063130814 7.1202535966C5 –0.2190847435 2.5130990264 7.1607367892C6 –0.2682156736 2.6972635208 4.7120887729C7 0.0308396940 –0.5551416246 1.1544397841C8 0.1762396501 –1.9748646358 –1.1569207288C9 0.1762396501 –1.9748646358 1.1569207288C10 –0.0488828124 0.2199865013 0.0000000000C11 0.0308396940 –0.5551416246 –1.1544397841C12 0.2556451598 –2.7488282192 0.0000000000C13 –0.1332418660 1.3270481111 –4.6791300864C14 –0.2190847435 2.5130990264 –7.1607367892C15 –0.0413513298 0.5413477993 –5.8636121223C16 –0.2682156736 2.6972635208 –4.7120887729C17 –0.3092033702 3.2809890496 –5.9994865076C18 –0.0809106068 1.1063130814 –7.1202535966C19 0.0752217707 –0.7109205642 5.0499839975C20 0.1839570514 –1.9897099744 2.6526961077203

C21 0.2140845876 –2.0681281615 5.0597906218C22 –0.0185658986 0.0964210650 3.8385174058C23 0.0354448344 –0.5411344328 2.6468986291C24 0.2723310826 –2.7496877988 3.7827235826C25 0.0752217707 –0.7109205642 –5.0499839975C26 0.1839570514 –1.9897099744 –2.6526961077C27 0.2140845876 –2.0681281615 –5.0597906218C28 –0.0185658986 0.0964210650 –3.8385174058C29 0.0354448344 –0.5411344328 –2.6468986291C30 0.2723310826 –2.7496877988 –3.7827235826H1 –0.0114672594 0.5259443880 8.0356174416H2 –0.2560068873 3.0123736343 8.1252459797H3 –0.1573752676 1.2998562463 0.0000000000H4 0.3676986583 –3.8284323108 0.0000000000H5 –0.0114672594 0.5259443880 –8.0356174416H6 –0.2560068873 3.0123736343 –8.1252459797H7 0.2819511805 –2.6420634789 5.9793310759H8 0.3838560298 –3.8296237156 3.7532110711H9 0.2819511805 –2.6420634789 –5.9793310759H10 0.3838560298 –3.8296237156 –3.7532110711H11 –0.3378598434 3.3099217750 –3.8180129970H12 –0.4148014510 4.3588903003 –6.0870107319H13 –0.3378598434 3.3099217750 3.8180129970H14 –0.4148014510 4.3588903003 6.0870107319Calculated positional parameters for 118:Atom x y zC1 1.8190162296 3.8598612631 0.4107420789C2 2.9861222185 1.4100948500 0.3891866579C3 3.1792765798 3.8018811710 0.5447765123C4 0.9531544545 2.7063972912 0.2561901512C5 1.5358910221 1.4780120245 0.2467054493C6 3.7996027622 2.5013676200 0.5330518469C7 –0.4534051883 –1.9831390690 –0.1325966739C8 –1.7081555290 –4.4214111753 –0.3784292891C9 0.2985986114 –3.1919972798 –0.1223174403C10 –1.8230707838 –1.9710546873 –0.2636675256C11 –2.4432586562 –3.2382107108 –0.3885740304C12 –0.2985215803 –4.4272022193 –0.2429339644C13 2.9275046915 –0.0748805783 0.3010819304C14 1.5729570327 –2.4162087475 0.0429344977C15 1.4823615908 –0.0128786502 0.1600466305C16 3.6516394497 –1.2394630083 0.3110514742204

C17 2.9350209135 –2.4789164099 0.1743188961C18 0.8080584911 –1.1864685740 0.0316059838C19 –1.2024564763 6.1682212563 0.2357174281C20 –2.0687213758 5.0478683123 0.0759256651C21 –1.6229975685 3.7247746269 0.0454662351C22 –0.2370854226 3.6257348674 0.1858329940C23 0.6227753556 4.7516741300 0.3405601958C24 0.1804480264 6.0721950126 0.3735354789C25 –4.1693958147 8.6905345016 0.0744322141C26 –5.0136927439 7.6254009146 –0.0854891204C27 –4.5826110276 6.2322483537 –0.1265599802C28 –3.2541006355 5.9737516121 0.0041197380C29 –2.3628973581 7.1060150237 0.1706153052C30 –2.7621201680 8.4136572039 0.2096391312C31 –8.7383363647 6.6022032447 –0.5789399064C32 –8.3350045685 5.2937706700 –0.6196979169C33 –6.9603801414 4.8575675041 –0.4882169238C34 –6.0027242231 5.8068460205 –0.3144150483C35 –6.4267421123 7.1964484932 –0.2717657407C36 –7.7287305691 7.6096928494 –0.3944110110C37 –9.4324737913 1.6042638852 –1.0083269543C38 –8.1101128036 1.1847852530 –0.8795304801C39 –7.0499156971 2.1045267383 –0.6887072676C40 –7.4074592423 3.4324358809 –0.6384727493C41 –8.7587508832 3.8613023749 –0.7688141481C42 –9.7942823627 2.9725113988 –0.9552448245H1 4.8772122391 2.4126435163 0.6366687650H2 0.2569464199 –5.3606958918 –0.2366272956H3 –2.2330051075 –5.3682840752 –0.4772296660H4 4.7325920102 –1.2484197860 0.4188601290H5 3.4748539907 –3.4216415461 0.1784117829H6 3.7892774471 4.6935825324 0.6574908467H7 –2.2802458238 2.8691443545 –0.0743855838H8 0.8376110624 6.9278431352 0.4928846520H9 –4.5261782597 9.7161687859 0.1001651794H10 –2.0579341198 9.2309542653 0.3372590454H11 –9.7805417468 6.8914112358 –0.6817950574H12 –8.0103321362 8.6582370103 –0.3577960225H13 –2.4119828374 –1.0582505996 –0.2729888745H14 –3.5238427429 –3.2895906764 –0.4950063144H15 –10.2099345277 0.8585511665 –1.1540160999H16 –7.8864761415 0.1222626782 –0.9274970797H17 –6.0240868339 1.7608364492 –0.5906470725H18 –10.8313013993 3.2792815595 –1.0580793730205

Calculated positional parameters for 119:Atom x y zC1 2.2552637652 3.7124088815 0.3938557760C2 2.4476658018 1.0030523814 0.2877885071C3 3.5008783042 3.1592088607 0.4837226979C4 1.0266715358 2.9509936287 0.2445382669C5 1.1189357743 1.5992069443 0.1884969107C6 3.6030708977 1.7195780054 0.4279026405C7 –2.0046956608 –0.8750344317 –0.2222010830C8 –4.0662839769 –2.8416810904 –0.5049255426C9 –1.7327445313 –2.3093106852 –0.2481139274C10 –3.2952365837 –0.4744704022 –0.3416644409C11 –4.3159187962 –1.4991180704 –0.4828974113C12 –2.6934915976 –3.2723111436 –0.3805838689C13 1.8420541908 –0.3526478711 0.1747772997C14 –0.2780761471 –2.0317012945 –0.0941353372C15 0.5227947524 0.2342873127 0.0727169445C16 2.0916416121 –1.7053437115 0.1463586018C17 0.9760908421 –2.5886752900 0.0055763745C18 –0.5421677446 –0.6087302195 –0.0658431611C19 0.2383624007 6.9433578405 0.3876919351C20 –0.9681210043 6.1998258069 0.2436395641C21 –1.0198742096 4.8132603671 0.1639889413C22 0.2489829904 4.2321429428 0.2404669370C23 1.4519263332 4.9747016365 0.3850649288C24 1.5010163631 6.3701511976 0.4652680945C25 –6.9907121059 1.2039622746 –0.6861287107C26 –6.7221036406 –0.1587877241 –0.6977659034C27 –5.3565235230 –0.4274630615 –0.5579457923C28 –4.3610995898 0.5772697399 –0.4202618243C29 –4.6361931373 1.9476719018 –0.4106581709C30 –5.9936706527 2.2122057298 –0.5489630054C31 –9.7157297145 3.9491830888 –0.9091656219C32 –8.7449351330 4.9323516729 –0.7747350378C33 –7.3667479683 4.6124431561 –0.6320591210C34 –7.0594558508 3.2751845821 –0.6352827827C35 –8.0551729256 2.2676666795 –0.7727159135C36 –9.3877194664 2.5652628275 –0.9114355535C37 –1.8069112522 10.2336850659 0.4034968563C38 –2.9833468417 9.5105983152 0.2625226336C39 –2.9868567398 8.0908600691 0.1808690571C40 –1.7580817058 7.4841145956 0.2492697727C41 –0.5524179941 8.2260538418 0.3932496948C42 –0.5381001235 9.5955705595 0.4737364650206

H1 4.5773485994 1.2444354319 0.4988816701H2 –2.4560688904 –4.3321819008 –0.3959757186H3 –4.8572584751 –3.5782731271 –0.6136483985H4 3.0974625622 –2.1078100951 0.2273289374H5 1.1331557460 –3.6632962377 –0.0207084630H6 4.3979020619 3.7616285597 0.5963163818H7 –1.9386624903 4.2449156005 0.0572982838H8 –7.4819154654 –0.9266102425 –0.8041968758H9 –3.8753816521 2.7154986642 –0.3089243193H10 –10.7563162648 4.2444875733 –1.0158738285H11 –9.0454198286 5.9769692153 –0.7787567893H12 –6.6217872574 5.3966057947 –0.5289618862H13 –10.1610336747 1.8099833417 –1.0179097479H14 2.4195771503 6.9377678728 0.5771211467H15 –1.8554267547 11.3179704282 0.4621216157H16 –3.9294093325 10.0435140475 0.2133905572H17 –3.9185626230 7.5427962562 0.0716937797H18 0.3721685341 10.1780541437 0.5846218227Calculated positional parameters for 120:Atom x y zC1 2.4432614782 3.6747979008 1.0437363054C2 2.5539152919 0.9955562378 0.6740020788C3 3.6313725584 3.0498572809 1.2977469025C4 1.2324795062 3.0090995997 0.5927874592C5 1.2782992480 1.6600268343 0.4300146268C6 3.6918852194 1.6249065148 1.0959829787C7 –1.7996593675 –0.6697127913 –0.7231820603C8 –3.7840086704 –2.5553293523 –1.5726929853C9 –1.5014047215 –2.0708363683 –1.0006484283C10 –3.0916596325 –0.2654363044 –0.8459614290C11 –4.0662328115 –1.2486892956 –1.2878224429C12 –2.4205144125 –2.9946170100 –1.4152424341C13 1.9607762955 –0.3003994928 0.2580004576C14 –0.0857116669 –1.8472715647 –0.6111311663C15 0.6791967718 0.3405855467 0.0424682539C16 2.2151723080 –1.6341148977 0.0407879229C17 1.1369617141 –2.4481125984 –0.4260502492C18 –0.3614353619 –0.4467974513 –0.3624485146C19 0.7438174657 7.0564429600 0.7053296124C20 –0.4431972986 6.4244454392 0.2301337556C21 –0.5937210594 5.0411957153 0.1084834471C22 0.5529702928 4.3479264632 0.4971227672207

C23 1.7438095351 4.9874021425 0.9532943133C24 1.8930578478 6.3655677709 1.0831528160C25 –6.8605495321 1.2928943491 –0.8533031761C26 –6.5131859885 0.0031703685 –1.2506345157C27 –5.1430324222 –0.2258799341 –1.1539953463C28 –4.1977555640 0.7450694568 –0.7083201502C29 –4.5481534749 2.0331763350 –0.3015542732C30 –5.9228959792 2.2633580558 –0.3918179548C31 –9.8682150094 3.6961513641 –0.2371850793C32 –8.9787769280 4.6250525850 0.2179659296C33 –7.5355863597 4.4212274501 0.2808106698C34 –7.0426028310 3.2326060368 –0.1453174640C35 –7.9916616684 2.2393568602 –0.6255832067C36 –9.3425353539 2.4244783854 –0.6842215418C37 –0.7509835364 10.6107022144 0.1234411590C38 –1.8826967055 10.0112792972 –0.3473762824C39 –2.0763964080 8.5676513477 –0.4251727674C40 –1.0705642046 7.7673992540 0.0026862818C41 0.1398034533 8.4057122915 0.4977641892C42 0.3277457815 9.7557318652 0.5709271917C43 –8.5119767863 8.1586380376 1.7135433064C44 –7.1318035422 7.9633608791 1.7768446692C45 –6.5268374696 6.7591154481 1.3465919841C46 –7.3825656653 5.7951359544 0.8591185662C47 –8.7911929265 5.9937236588 0.7942674913C48 –9.3862135518 7.1649552770 1.2148320997C49 –5.5676791891 9.1410867878 –1.9766725842C50 –4.5789004437 8.2320341569 –1.5343040316C51 –3.4305815274 8.7946421954 –1.0212205324C52 –3.2434517017 10.2042999459 –0.9421238260C53 –4.2035219025 11.0948080080 –1.3751228471C54 –5.3852028730 10.5219651137 –1.8999433902H1 4.6222887585 1.0902542155 1.2645157446H2 –2.1566684833 –4.0302921944 –1.6091267812H3 –4.5495522948 –3.2586091084 –1.8881572996H4 3.1959827869 –2.0692247904 0.2099942637H5 1.2936930420 –3.5058594171 –0.6179655238H6 4.5151256016 3.5928995736 1.6204339424H7 –1.4917362764 4.5621426035 –0.2696200698H8 –7.2297431047 –0.7427408421 –1.5801460529H9 –3.8357218346 2.7663746633 0.0641190953H10 –10.9386529062 3.8789957362 –0.2661771372H11 –10.0205939684 1.6559319775 –1.0443881067H12 2.8065983999 6.8463727506 1.4187323889H13 –0.6358283960 11.6902391567 0.1616425594H14 1.2494330890 10.1969200229 0.9393650140208

H15 –8.9262656171 9.1028990679 2.0574064346H16 –6.5026057636 8.7600908447 2.1640605392H17 –5.4502455926 6.6267927668 1.4038433734H18 –6.4966804687 8.7526151904 –2.3849390633H19 –4.7386180515 7.1598499893 –1.6028633123H20 –4.0795041400 12.1730221799 –1.3265645144H21 –6.1768335484 11.1770841180 –2.2547385692H22 –10.4585760540 7.3343169940 1.17457905796.3 Experiments Related to Chapter 31,2-Dibromo-4,5-diiodobenzene (155e):BrBrIIThis compound was prepared by using a modified literature procedure. 78 Periodicacid (2.96 g, 13.0 mmol) was dissolved in concentrated H 2 SO 4 (12 mL). The mixture wascooled to 0 °C, and powdered KI (6.46 g, 39.0 mmol) was slowly added over 15 min.After the addition of KI was complete, 1,2-dibromobenzene (6.00 g, 25.0 mmol) wasadded dropwise. The reaction mixture was stirred at 23 °C for 1 h and then poured ontocrushed ice. The dark precipitate was recrystallized four times from benzene to yield 2.06g (17%) of 155e as white needles, mp 173–175 °C. IR (CS 2 ): ~ ν = 2925, 1408, 1282,1005, 877 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 488 (M + , 100), 361 (32), 234 (17), 153(8), 74 (20). 1 H NMR (400 MHz, CDCl 3 ): 8.03 (s, 2H). 13 C NMR (100 MHz, CDCl 3 ):142.5, 125.4, 106.9. HR-MS Calcd for C 6 H 2 Br 2 I 2 : 487.6592. Found 487.6596. Anal.Calcd for C 6 H 2 Br 2 I 2 : C, 14.78; H, 0.41. Found C, 14.55; H, 0.43.209

1,4-Dibromo-2,3-diiodobenzene (155f):BrIBrIThe preparation of 3,6-dibromoisatine used a slightly modified literatureprocedure: 167 chloral hydrate (9.93 g, 60.0 mmol), 2,5-dibromoaniline (12.6 g, 50.0mmol), hydroxylamine hydrochloride (5.21 g, 75.0 mmol), and sodium sulfate (60.0 g)were suspended in a mixture of water (300 mL) and ethanol (300 mL). The mixture wasstirred and kept at reflux for 12 h; after that time, it was concentrated by evaporation ofthe ethanol and poured onto crushed ice, which caused precipitation of a white solid.After 5 h at 0 °C, the suspension was filtered, and the crystals were air-dried to yield 13.5g (84%) of crude 2,5-dibromoisonitrosoacetanilide. This isonitrosoacetanilide wascyclised by heating at 100 °C in 86% sulfuric acid for 15 min. The resulting dark redsuspension was poured onto crushed ice to yield 5.98 g (47 %) of 3,6-dibromoisatine asbright orange crystals, which were subsequently subjected to basic hydrolysis in aq.H 2 O 2 168to yield 2.72 g (47%) of off-white crystals of 3,6-dibromoanthranilic acid.Finally, 3,6-dibromoanthranilic acid was converted to 1,4-dibromo-2,3-diiodobenzene byemploying the aprotic diazotization procedure of Nakayama. 165After columnchromatography (hexanes) the product was obtained in yield of 2.61 g (58%), as whitecrystals, mp 97–99 °C. Crystals of 155f are stable for several months; however, itssolutions in CHCl 3 and hydrocarbon solvents appear to decompose within days with theloss of iodine. IR (CHCl 3 ): ~ ν = 2920, 1396, 1150, 1002, 810 cm –1 . MS (EI, 70 eV) m/z(rel intensity) 488 (M + , 100), 361 (29), 234 (21), 153 (18), 74 (24). 1 H NMR (400 MHz,CDCl 3 ) δ 7.49 (s, 2H). 13 C NMR (100 MHz, CDCl 3 ) δ 132.8, 127.8, 117.4. HR-MS210

Calcd for C 6 H 2 Br 2 I 2 : 487.6592. Found 487.6596. Anal. Calcd for C 6 H 2 Br 2 I 2 : C, 14.78; H,0.41. Found C, 14.74; H, 0.04.1,4-Dichloro-2,3-diiodobenzene (155g): 165ClIClIA solution of iodine (620 mg, 2.43 mmol) and isoamyl nitrite (396 µL, 2.92mmol) in 1,2-dichloroethane (50 mL) was brought to reflux. 3,6-Dichloroanthranylic acid(500 mg, 2.43 mmol) was added as a dioxane solution (vide infra, 20 mL) over a periodof 20 min and mixture left at reflux for 3 h. After cooling, CH 2 Cl 2 was added and theresulting solution washed with two portions of aq. Na 2 S 2 O 3 , followed by brine. Thesolution was subsequently dried over MgSO 4 ; removal of the solvents in vacuo gave thecrude material, which was purified by column chromatography on silica (hexanes) to give155g as a white powder, mp 96–97 °C (292 mg, 30%). MS (EI, 70 eV) m/z (rel intensity)398 (M + , 100), 271 (21), 144 (18), 74 (11). 1 H NMR (500 MHz, CDCl 3 ) δ 7.42 (s, 2H).13 C NMR (125 MHz, CDCl 3 ) δ 136.83, 129.10, 114.80. HR-MS Calcd for C 6 H 2 Cl 2 I 2 :397.7623. Found: 397.7626. Anal. Calcd for C 6 H 2 Cl 2 I 2 : C, 18.07; H, 0.51. Found: C,17.91; H, 0.45.211

1,2-Diiodo-3,5-dimethylbenzene (160):I3,5-Dimethylanthranilic acid (165 mg, 1.00 mmol) was converted to a colorlessoil of 1,2-diiodo-3,5-dimethylbenzene according to the literature procedure. 165 However,we noticed that the low yield of this reaction–111 mg (31%)–was caused by significantcontamination of product by 1-chloro-2-iodo-3,5-dimethylbenzene and 2-chloro-1-iodo-3,5-dimethylbenzene (by GC/MS). Separation of these side-products was achieved byKugelrohr distillation. We also found that the reaction could be performed successfully indioxane; this avoids the formation of chlorinated by-products, but does not increase theyield significantly (32%). Data for 1,2-diiodo-3,5-dimethylbenzene: IR: reportedpreviously. 217 MS (EI, 70 eV) m/z (rel intensity) 358 (M + , 100), 231 (16), 104 (17). 1 HNMR (400 MHz, CDCl 3 ) δ 7.55 (s, 1H), 6.98 (s, 1H), 2.54 (s, 3H), 2.19 (s, 3H). 13 CNMR (100 MHz, CDCl 3 ) δ 144.0, 139.6, 137.7, 129.8, 110.2, 109.7, 32.5, 20.4. HR-MSCalcd for C 8 H 8 I 2 : 357.8716. Found 357.8721. Anal. Calcd for C 8 H 8 I 2 : C, 26.84; H, 2.25.Found C, 27.10; H, 2.33.IGeneral procedure for propynylations (method A):To a 150 mL Schlenk flask, equipped with a Teflon-coated magnetic stirring bar,aryl iodide (1.67 mmol, in the case of diiodides), [Pd(PPh 3 ) 2 Cl 2 ] (177 mg, 0.25 mmol),CuI (32 mg, 0.17 mmol), and triethylamine (7.50 mL) were added. The flask was thenevacuated and filled with propyne gas to 1.5 atm (approx. 10 mmol, 3 equiv) of pressure.Depending on the system, the reaction mixture was stirred for 22–96 h, at either room or212

elevated temperature (Table 3.1). After that time, the reaction mixture was diluted withether, washed with two portions of aq. NH 4 Cl, and dried over MgSO 4 . Solvent wasremoved in vacuo and the resulting crude product purified by Kugelrohr distillation orsublimation (unless indicated otherwise). The following compounds were prepared usingthis method:1,2-Di(prop-1-ynyl)benzene (154a):Starting from 155a, product was obtained as a pale yellow oil (distilled at 120°C/2 Torr), 244 mg (95%). MS (EI, 70 eV) m/z (rel intensity) 154 (M + , 100), 152 (84), 76(12). 1 H NMR (400 MHz, CDCl 3 ) δ 7.38 (dd, 2H, 4 J 1 = 3.2 Hz, 3 J 2 = 5.7 Hz), 7.18 (dd,2H, 4 J 1 = 3.2 Hz, 3 J 2 = 5.7 Hz), 2.12 (s, 6H). Spectral data are in good agreement withthose reported previously. 2181,2-Dimethyl-4,5-di(prop-1-ynyl)benzene (154b):Starting from 155b, 164a product was obtained as yellow crystals (sublimed at 150°C/2 Torr), mp 92–93 °C, yield 174 mg (57%). IR (CHCl 3 ): ~ ν = 2920, 2261, 1494, 887cm –1 . MS (EI, 70 eV) m/z (rel intensity) 182 (M + , 100), 165 (51), 152 (42). 1 H NMR (400MHz, CDCl 3 ) δ 7.15 (s, 2H), 2.17 (s, 6H), 2.10 (s, 6H). 13 C NMR (100 MHz, CDCl 3 ) δ213

136.1, 133.0, 123.4, 88.3, 78.7, 19.4, 4.7. HR-MS Calcd for C 14 H 14 : 182.1096. Found182.1096. Anal. Calcd for C 14 H 14 : C, 92.26; H, 7.74. Found C, 92.02; H, 7.47.1,2-Dimethoxy-4,5-di(prop-1-ynyl)benzene (154c):OOStarting from 155c, 164a product was obtained as yellow crystals (sublimed at 190°C/2 Torr), mp 164–166 °C (dec), yield 121 mg (34%). The yield was probably lowereddue to some decomposition during sublimation. Purification by column chromatography(hexanes/ethyl acetate) provided the material in 81% yield (289 mg). IR (CHCl 3 ): ~ ν =2919, 2170, 1223, 1155, 862 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 214 (M + , 100), 128(25). 1 H NMR (400 MHz, CDCl 3 ) δ 6.74 (s, 2H), 3.73 (s, 6H), 1.99 (s, 6H). 13 C NMR(100 MHz, CDCl 3 ) δ 148.3, 118.9, 114.2, 87.8, 78.5, 55.8, 4.5. HR-MS Calcd forC 14 H 14 O 2 : 214.0994. Found 214.0994. Anal. Calcd for C 14 H 14 O 2 : C, 78.48; H, 6.59.Found C, 78.21; H, 6.62.1,2,3,4-Tetramethyl-5,6-di(prop-1-ynyl)benzene (154d):Starting from 155d, 164a product was obtained as a very thick yellow oil (distilledat 200 °C/2 Torr), yield 35.0 mg (10%). The yield was probably lowered due to somedecomposition during sublimation. Purification by column chromatography214

(hexanes/ethyl acetate) provided the material in 91% yield (319 mg). IR (CHCl 3 ): ~ ν =2917, 1704, 1214, 773 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 210 (M + , 100), 195 (27),179 (30), 165 (42). 1 H NMR (400 MHz, CDCl 3 ) δ 2.39 (s, 6H), 2.19 (s, 6H), 2.16 (s, 6H).13 C NMR (100 MHz, CDCl 3 ) δ 135.5, 134.5, 123.7, 91.7, 78.9, 18.6, 16.7, 4.8. HR-MSCalcd for C 16 H 18 : 210.1409. Found 210.1415.1,4-Dichloro-2,3-di(prop-1-ynyl)benzene (154g):ClClStarting from 155g, the product was obtained as a yellow oil (252 mg, 68%),which solidified into off-yellow crystals, mp 58–59 °C, upon standing. IR (NaCl film): ~ ν= 2917, 2227, 1542, 1439, 1412, 1376, 1264, 1161, 993, 810, 762, 650 cm –1 . MS (EI, 70eV) m/z (rel intensity) 222 (M + , 100), 186 (33), 152 (94), 75 (18). 1 H NMR (400 MHz,CDCl 3 ) δ 7.19 (s, 2H), 2.19 (s, 6H). 13 C NMR (125 MHz, CDCl 3 ) δ 134.22, 128.39,127.47, 96.97, 75.57, 4.89. HR-MS Calcd for C 12 H 8 Cl 2 : 223.9974. Found: 223.9968.3,5-Dimethyl-1,2-di(prop-1-ynyl)benzene (165):Starting from 162, the product was obtained as a yellow oil (distilled at 220 °C/4Torr), which solidified upon standing (yellow crystals, mp 45–46 °C), 231 mg (76%). IR(NaCl film): ~ ν = 2920, 2246, 1455, 859 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 182215

(M + , 100), 165 (57), 152 (47). 1 H NMR (400 MHz, CDCl 3 ) δ 7.06 (s, 1H), 6.91 (s, 1H),2.36 (s, 3H), 2.24 (s, 3H), 2.16 (s, 3H), 2.11 (s, 3H). 13 C NMR (100 MHz, CDCl 3 ) δ140.2, 136.7, 129.9, 129.6, 126.1, 123.0, 92.8, 88.5, 79.2, 77.4, 21.1, 21.0, 4.8, 4.7. HR-MS Calcd for C 14 H 14 : 182.1096. Found 182.1100.1,3-Di(prop-1-ynyl)benzene (166a):Starting from 163a, the product was obtained as a pale yellow oil (distilled at 120°C/2 Torr), 239 mg (93%). MS (EI, 70 eV) m/z (rel intensity) 154 (M + , 100), 152 (68),115 (16), 76 (12). 1 H NMR (400 MHz, CDCl 3 ) δ 7.40 (s, 1H), 7.27 (d, 2H, 3 J = 7.3 Hz),7.17 (t, 1H, 3 J = 7.4 Hz), 2.03 (s, 6H). Spectral data are in good agreement with thosereported previously. 2191,2,3,4-Tetra(prop-1-ynyl)benzene (166b):Starting from 163b, 164c the product was obtained as brownish crystals (sublimedat 220 °C/1 Torr), mp 168–171 °C (dec), 148 mg (77%). IR (KBr): ~ ν = 2914, 2238,1485, 1396, 902 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 230 (M + , 100), 213 (20), 202(20), 189 (11), 101 (6). 1 H NMR (400 MHz, CDCl 3 ) δ 7.36 (s, 2H), 2.08 (s, 12H). 13 C216

NMR (100 MHz, CDCl 3 ) δ 135.4, 125.1, 91.0, 77.9, 4.7. HR-MS Calcd for C 18 H 14 :230.1096. Found 230.1094.General procedure for microwave-assisted propynylations (method B): 172A heavy-walled Smith process vial was charged with a magnetic stirring bar,triethylamine (0.9 mL), DMF (0.1 mL), [Pd(PPh 3 ) 2 Cl 2 ] (19.6 mg, 0.028 mmol), CuI (5.4mg, 0.028 mmol), and the respective dibromodiiodobenzene (55.0 mg, 0.113 mmol). Thevial was sealed, evacuated, and filled with propyne through a Teflon septum up to 2.5atm pressure. It was then irradiated in the microwave cavity. It is of crucial importance tostop these reactions immediately after irradiation by filtering through a short pad of silicagel (hexanes/ethyl acetate) to remove the catalyst. So-obtained crude products werefurther purified by column chromatography on silica gel (hexanes). The followingcompounds were prepared using this method:1,2-Dibromo-4,5-di(prop-1-ynyl)benzene (154e):BrBrStarting from 155e, the product was obtained as a thick yellow oil, which slowlycrystallizes upon standing (yellow crystals, mp 67–69 °C), 25.1 mg (71%). IR (CHCl 3 ):~ν = 2957, 2363, 2321, 1461, 775 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 312 (M + , 100),233 (11), 231 (11), 152 (80), 76 (18). 1 H NMR (400 MHz, CDCl 3 ) δ 7.60 (s, 2H), 2.09 (s,6H). 13 C NMR (100 MHz, CDCl 3 ) δ 136.3, 126.5, 123.4, 91.9, 76.8, 4.7. HR-MS Calcdfor C 12 H 8 Br 2 : 311.8972. Found 311.8982.217

1,4-Dibromo-2,3-di(prop-1-ynyl)benzene (154f):BrBrStarting from 155f, the product was obtained as a viscous yellow oil, 21.2 mg(60%). IR (CHCl 3 ): ~ ν = 2952, 1437, 1217, 757 cm –1 . MS (EI, 70 eV) m/z (rel intensity)312 (M + , 90), 233 (11), 231 (11), 152 (100), 76 (18). 1 H NMR (400 MHz, CDCl 3 ): 7.29(s, 2H), 2.19 (s, 6H). 13 C NMR (100 MHz, CDCl 3 ): 131.8, 131.7, 124.3, 96.1, 77.7, 4.9.HR-MS Calcd for C 12 H 8 Br 2 : 311.8972. Found 311.8975.1,3-Dibromo-4,6-di(prop-1-ynyl)benzene (166c):BrBrStarting from 57, 78 the product was obtained as pale yellow crystals, mp 78–80°C, 22.5 mg (64%). IR (CHCl 3 ): ~ ν = 2922, 2242, 1454, 1059, 896 cm –1 . MS (EI, 70 eV)m/z (rel intensity) 312 (M + , 100), 233 (11), 231 (11), 152 (75), 76 (22). 1 H NMR (400MHz, CDCl 3 ) δ 7.72 (s, 1H), 7.44 (s, 1H), 2.08 (s, 6H). 13 C NMR (100 MHz, CDCl 3 ) δ137.0, 135.3, 125.2, 124.4, 92.3, 77.2, 4.9. HR-MS Calcd for C 12 H 8 Br 2 : 311.8972. Found311.8976.Utilizing a somewhat modified general propynylation procedure, the followingcompounds were also prepared:218

Hexa(prop-1-ynyl)benzene (167) and penta(prop-1-ynyl)benzene:To a 200 mL Schlenk flask, equipped with a Teflon-coated magnetic stirring bar,hexaiodobenzene (164, 528 mg, 0.63 mmol), [Pd(PPh 3 ) 2 Cl 2 ] (66 mg, 0.094 mmol), CuI(36 mg, 0.189 mmol), and triethylamine (7.50 mL) were added. The flask was evacuatedand filled with propyne gas up to 1.5 atm (approx. 7.60 mmol, 12 equiv) of pressure. Thereaction mixture was stirred for 60 h at 90 °C. After that time, it was diluted with ether,washed with two portions of aq. NH 4 Cl, and dried over MgSO 4 . Solvent was removed invacuo and the resulting crude product chromatographed on silica (hexane/ethyl acetate).The first fraction contained penta(prop-1-ynyl)benzene (54 mg, 32%) and the secondhexa(prop-1-ynyl)benzene (167, 55 mg, 28%), both as dark red oily solids. Theseparation of the two compounds was not complete; repeated efforts gave noimprovement. Therefore, materials were characterized only partly, and 167 was used assuch in further experiments.Spectral data for penta(prop-1-ynyl)benzene: MS (EI, 70 eV) m/z (rel intensity)268 (M + , 100), 250 (34), 239 (10), 226 (13). 1 H NMR (400 MHz, CDCl 3 ) δ 7.28 (s, 1H),2.16 (br s, 9H), 2.09 (s, 6H). HR-MS Calcd for C 21 H 16 : 268.1252. Found 268.1258.Spectral data for 167: MS (EI, 70 eV) m/z (rel intensity) 306 (M + , 100), 289 (40),281 (34), 263 (29), 144 (13), 96 (8). 1 H NMR (400 MHz, CDCl 3 ) δ 2.15 (s, 18H). 13 C219

NMR (100 MHz, CDCl 3 ) δ 127.80, 94.72, 77.71, 5.04. HR-MS Calcd for C 24 H 18 :306.1409. Found 306.1411.General procedure for [(Me 3 CO) 3 W≡CCMe 3 ]-mediated alkyne metatheses:A 25 mL Schlenk flask was charged, under an atmosphere of nitrogen, withpropynylated benzene (0.20–0.35 mmol), [(Me 3 CO) 3 W≡CCMe 3 ] (20–40 mol %), andtoluene (20 mL). The solution was stirred at 80 °C for 8–96 h (Table 3.2). After thereaction was complete, solvent was removed in vacuo and the residue subjected to flashchromatography on silica (hexane/ethyl acetate). Utilizing this procedure, the followingcompounds were prepared:5,6,11,12,17,18-Hexadehydrotribenzo[a,e,i]cyclododecene (153a):The reaction was carried out with 54.0 mg (0.35 mmol) of 154a; isolated yield of153a was 18.7 mg (54%) as pale yellow crystals showing green fluorescence, mp 209 °C(lit. 210–211 °C). 163 MS (EI, 70 eV) m/z (rel intensity) 300 (M + , 100), 149 (18). 1 H NMR(400 MHz, CDCl 3 ) δ 7.33 (dd, 6H, 4 J 1 = 3.3 Hz, 3 J 2 = 5.8 Hz), 7.18 (dd, 6H, 4 J 1 = 3.3 Hz,3 J 2 = 5.8 Hz). Spectral data are in good agreement with those reported previously. 87b,163220

5,6,11,12,17,18-Hexadehydro-2,3,8,9,14,15-hexamethyltribenzo[a,e,i]-cyclododecene(153b):The reaction was performed with 49.0 mg (0.27 mmol) of 154b; isolated yield of153b was 9.2 mg (27%) as pale yellow crystals showing green fluorescence, mp 334–336°C (dec). The extremely low solubility of this compound prevented analysis by 13 C NMRspectroscopy. MS (EI, 70 eV) m/z (rel intensity) 386 ([M+2H] + , 7), 385 ([M+H] + , 33),384 (M + , 100), 192 (M 2+ , 8). 1 H NMR (400 MHz, CDCl 3 ) δ 7.09 (s, 6H), 2.19 (s, 18H).HR-MS Calcd for C 30 H 24 : 384.1878. Found 384.1884. Spectral data are in goodagreement with those reported previously. 86d5,6,11,12,17,18-Hexadehydro-2,3,8,9,14,15-hexamethoxytribenzo[a,e,i]-cyclododecene (153c):OOOOOO221

The reaction was run with 22.5 mg (0.105 mmol) of 154c. Columnchromatography (hexane/ethyl acetate) yielded 13.6 mg (60%) of starting material in thefirst fraction, followed by 153c, 4.7 mg (28%), as yellow crystals showing greenfluorescence. We found this compound to be unstable, both as a solid and in solution–itcompletely decomposed within 24 h (previous reports 158a,d,220 do not indicate similarproblems). MS (EI, 70 eV) m/z (rel intensity) 482 ([M+2H] + , 8), 481 ([M+H] + , 33), 480(M + , 100), 240 (M 2+ , 18). 1 H NMR (400 MHz, CDCl 3 ) δ 6.93 (s, 6H), 4.00 (s, 18H).Performing this reaction for a shorter time (96 h), gave 3.1 mg (16%) of the metathesisdimer as the major product:1,1'-(1,2-Ethynediyl)bis[4,5-dimethoxy-2-(prop-1-ynyl)]benzene:OOOOIsolated as a brownish solid, mp 250–253 °C (dec), 3.1 mg (16%). IR (CHCl 3 ): ~ ν= 2928, 2360, 1464, 1274, 1154 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 375 ([M+H] + ,18), 374 (M + , 100), 187 (M 2+ , 8). 1 H NMR (400 MHz, CDCl 3 ) δ 6.98 (s, 2H), 6.90 (s,2H), 3.94 (s, 6H), 3.88 (s, 6H), 2.12 (s, 6H). HR-MS Calcd for C 24 H 22 O 4 : 374.1518.Found 374.1519.222

5,6,11,12,17,18-Hexadehydro-2,3,8,9,14,15-hexabromotribenzo[a,e,i]-cyclododecene(153e):BrBrBrBrBrBrThe reaction was executed with 33.0 mg (0.106 mmol) of 154e to give 153e, 3.3mg (12%), as brown crystals showing green fluorescence. MS (EI, 70 eV) m/z (relintensity) 774 (M + , 100), 695 (29), 614 (19). 1 H NMR (400 MHz, CDCl 3 ) δ 7.56 (s, 6H).The material decomposed within several hours.Utilizing a somewhat modified general metathesis procedure, the followingcompounds were also prepared:5,6,12,13,18,19,25,26-octadehydro-7,11:20,24-dimethenodibenzo[a,l]-cyclodocosene(159):A 25 mL Schlenk tube was charged with a magnetic stirring bar, 154a (52.6 mg,0.34 mmol), 164a (46.5 mg, 0.30 mmol), [(Me 3 CO) 3 W≡CCMe 3 ] (44.0 mg, 0.092 mmol),223

and dry toluene (25 mL). The mixture was heated at 80 °C for 84 h. After that time,solvent was removed in vacuo and the residue purified by column chromatography(hexane/ethyl acetate) to yield 24.6 mg of a mixture of starting materials as the firstfraction, 5.4 mg (16%) of 153a and, as a third fraction, 5.8 mg (19%) of 159 as ayellowish solid showing green fluorescence, mp 310–315 °C (dec). UV-VIS (CH 2 Cl 2 ):λ max (logε) = 265 (4.03), 272 (4.05), 278 (4.11), 280 (4.10), 317 (3.62), 341 (3.26) nm. IR(CHCl 3 ): ~ ν = 2920, 2219, 1468, 1212, 892 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 401([M+H] + , 31), 400 (M + , 100), 199 (11). 1 H NMR (400 MHz, CDCl 3 ) δ 8.05 (broad t, 4 J =1.5 Hz, 2H), 7.59 (dd, 3 J 1 = 5.7 Hz, 4 J 2 = 3.3 Hz, 4H), 7.54 (dd, 3 J 1 = 7.9 Hz, 4 J 2 = 1.6Hz, 4H), 7.38 (t, 3 J = 8.0 Hz, 2H), 7.32 (dd, 3 J 1 = 5.8 Hz, 4 J 2 = 3.4 Hz, 4H). HR-MSCalcd for C 32 H 16 : 400.1252. Found 400.1248.5,6,11,12,14,15,20,21,26,27,29,30-Dodecadehydrotetrabenzo[e,e',i,i']benzo-[1,2-a:4,5-a']dicyclododecene (160):A 25 mL Schlenk tube was charged with a magnetic stirring bar, 154a (116 mg,0.76 mmol), 164b (35.0 mg, 0.15 mmol), [(Me 3 CO) 3 W≡CCMe 3 ] (36.0 mg, 0.076 mmol),and dry toluene (25 mL). The mixture was heated at 80 °C for 60 h. After that time, thesolvent was removed in vacuo and the residue purified by washing with hexanes, ether,and acetone to yield 5.0 mg (6%) of 160 as an extremely insoluble yellow powder,224

showing green fluorescence, mp 348–351 °C [dec, lit. mp 350 °C (dec)]. 163 Ether andacetone washes contained tribenzocyclyne 153a as the main component, resulting fromthe homometathesis of the excess 154a. The compound was too insoluble to providemeaningful 13 C NMR information. MS (EI, 70 eV) m/z (rel intensity) 524 ([M+2H] + , 10),523 ([M+H] + , 42), 522 (M + , 100), 261 (M 2+ , 25). 1 H NMR (400 MHz, CDCl 3 ) δ 7.44 (dd,3 J 1 = 6.0 Hz, 4 J 2 = 3.6 Hz, 8H), 7.34 (s, 2H), 7.19 (dd, 3 J 1 = 6.0 Hz, 4 J 2 = 3.6 Hz, 8H).HR-MS Calcd for C 42 H 18 : 522.1408. Found 522.1428. Spectral data are in goodagreement with those reported previously. 1631,1'-(1,2-Ethynediyl)bis[3,5-dimethyl-2-(prop-1-ynyl)]benzene (168):A 10 mL Schlenk tube was charged with a magnetic stirring bar, 165 (20.0 mg,0.11 mmol), [(Me 3 CO) 3 W≡CCMe 3 ] (10.0 mg, 0.021 mmol), and dry toluene (7.5 mL).The mixture was heated at 80 °C for 72 h. After that time, solvent was removed in vacuoand the residue filtered through short pad of silica gel (ethyl acetate). The unreactedstarting material (4.0 mg, 20%) was removed by distillation, which left 9.4 mg (55%) ofpure 168 as a brown solid. IR (CHCl 3 ): ~ ν = 2926, 2360, 1601, 1468, 1212 cm –1 . MS (EI,70 eV) m/z (rel intensity) 310 (M + , 100), 295 (32), 280 (65), 263 (21). 1 H NMR (400MHz, CDCl 3 ) δ 7.18 (s, 2H), 6.96 (s, 2H), 2.38 (s, 6H), 2.28 (s, 6H), 2.17 (s, 6H). 13 C225

NMR (100 MHz, CDCl 3 ) δ 140.1, 136.7, 130.3, 130.1, 129.2, 126.5, 109.7, 90.9, 77.2,21.1, 21.0, 4.8. HR-MS Calcd for C 24 H 22 : 310.1722. Found: 310.1721.6.3.1 Crystallographic Information for 159Crystal data and collection parameters:A. Crystal DataEmpirical Formula C 32 H 16Formula Weight 400.48Crystal Color, HabitCrystal DimensionsCrystal SystemLattice Typecolorless, cubic0.16 x 0.17 x 0.17 mmmonoclinicC-centered226

No. of Reflections Used for UnitCell Determination (2θ range) 1520 (3.0–45.0 °)Lattice Parameters a 28.905(4) Åbc4.8000(6) Å18.010(2) Åβ 124.107(2) °V 2068.9(4) Å 3Space Group C2/c (#15)Z value 4D calc 1.286 g cm –3F 000 832.00µ(MoKα) 0.73 cm –1B. Intensity MeasurementsDiffractometerSMARTRadiation MoK α (λ = 0.71069 Å)graphite monochromatedCrystal to Detector Distance60.0 mmTemperature –132.0 °CScan TypeScan Rateω (0.3 ° per frame)25.0 seconds per frame2θ max 50.8 °227

No. of Reflections Measured Total: 4635Unique: 1923 (R int = 0.036)CorrectionsLorentz-polarizationAbsorption (T max = 1.00, T min = 0.64)C. Structure Solution and RefinementStructure SolutionRefinementDirect Methods (SIR92)Full-matrix least-squaresFunction Minimized Σ w (|F o | – |F c |) 2Least Squares Weights 1/σ 2 (F o ) = 4F o 2 /σ 2 (F o 2 )p-factor 0.030Anomalous DispersionAll non-hydrogen atomsNo. Observations (I>3.00σ(I)) 1049No. Variables 145Reflection/Parameter Ratio 7.23Residuals: R; R w ; R all 0.040; 0.047; 0.068Goodness of Fit Indicator 1.29Max Shift/Error in Final Cycle 0.00Maximum peak in Final Diff. Map 0.17 e – /Å 3Minimum peak in Final Diff. Map –0.24 e – /Å 3228

Positional parameters and B(eq):Atom x y z B(eq)C(1) 0.5697(1) –0.5571(5) 0.4550(1) 1.84(8)C(2) 0.62573(9) –0.6578(5) 0.5111(1) 1.61(8)C(3) 0.64472(9) –0.8641(5) 0.4799(1) 1.84(8)C(4) 0.6994(1) –0.9572(5) 0.5318(1) 2.15(9)C(5) 0.73623(9) –0.8473(5) 0.6171(1) 2.00(9)C(6) 0.71804(9) –0.6446(5) 0.6502(1) 1.79(8)C(7) 0.66311(9) –0.5462(4) 0.5982(1) 1.55(7)C(8) 0.64453(8) –0.3358(5) 0.6324(1) 1.59(8)C(9) 0.62866(8) –0.1603(5) 0.6605(1) 1.60(8)C(10) 0.60748(8) 0.0508(4) 0.6903(1) 1.48(7)C(11) 0.63941(8) 0.1522(5) 0.7783(1) 1.65(8)C(12) 0.61777(8) 0.3559(5) 0.8049(1) 1.81(8)C(13) 0.56501(9) 0.4635(5) 0.7461(1) 1.80(8)C(14) 0.53225(8) 0.3642(5) 0.6577(1) 1.60(8)C(15) 0.4772(1) 0.4724(5) 0.5958(1) 1.79(8)C(16) 0.55404(9) 0.1590(5) 0.6307(1) 1.76(8)H(1) 0.6190 –0.9400 0.4208 2.2H(2) 0.7119 –1.1043 0.5094 2.5H(3) 0.7743 –0.9084 0.6534 2.3H(4) 0.7431 –0.5719 0.7095 2.2H(5) 0.6763 0.0797 0.8215 1.8H(6) 0.6396 0.4219 0.8650 2.2H(7) 0.5514 0.6117 0.7654 1.9H(8) 0.5316 0.0913 0.5694 1.9Intramolecular distances involving the nonhydrogen atoms:Atom atom distanceC(1) C(2) 1.429(3)C(1) C(15) 1.203(3)C(2) C(3) 1.394(3)C(2) C(7) 1.419(3)C(3) C(4) 1.383(3)C(4) C(5) 1.392(3)C(5) C(6) 1.389(3)C(6) C(7) 1.398(3)C(7) C(8) 1.434(3)C(8) C(9) 1.199(3)C(9) C(10) 1.435(3)C(10) C(11) 1.400(3)229

C(10) C(16) 1.396(3)C(11) C(12) 1.383(3)C(12) C(13) 1.380(3)C(13) C(14) 1.403(3)C(14) C(15) 1.435(3)C(14) C(16) 1.395(3)Intramolecular bond angles involving the nonhydrogen atoms:Atom atom atom angleC(2) C(1) C(15) 176.8(2)C(8) C(9) C(10) 177.5(2)C(1) C(2) C(3) 120.1(2)C(9) C(10) C(11) 121.4(2)C(1) C(2) C(7) 120.8(2)C(9) C(10) C(16) 119.6(2)C(3) C(2) C(7) 119.1(2)C(11) C(10) C(16) 119.0(2)C(2) C(3) C(4) 121.0(2)C(10) C(11) C(12) 119.9(2)C(3) C(4) C(5) 120.0(2)C(11) C(12) C(13) 121.2(2)C(4) C(5) C(6) 119.9(2)C(12) C(13) C(14) 119.8(2)C(5) C(6) C(7) 120.7(2)C(13) C(14) C(15) 120.5(2)C(2) C(7) C(6) 119.2(2)C(13) C(14) C(16) 119.1(2)C(2) C(7) C(8) 120.2(2)C(15) C(14) C(16) 120.4(2)C(6) C(7) C(8) 120.6(2)C(1) C(15) C(14) 177.8(2)C(7) C(8) C(9) 179.6(2)C(10) C(16) C(14) 121.0(2)230

6.4 Experiments Related to Chapter 42-Bromo-1,4-di(oct-1-ynyl)-3-[(trimethylsilyl)ethynyl]benzene (184b):Br Br2,3-Dibromo-1,4-di(oct-1-ynyl)benzene. 1,2,3,4-Tetrabromobenzene 221 (5.00 g,12.7 mmol), 1-octyne (4.50 mL, 30.5 mmol, 2.4 equiv), [Pd(PPh 3 ) 2 Cl 2 ] (0.89 g, 1.27mmol), and CuI (0.24 g, 1.27 mmol) were suspended in triethylamine (250 mL). Themixture was heated at 60 ºC for 96 h. After that time, the solids were filtered off, thesolvent removed in vacuo and the resulting crude mixture separated by columnchromatography (hexanes) to yield 2,3-dibromo-1,4-di(oct-1-ynyl)benzene as the second,yellow, fraction (4.20 g, 73%). The first fraction consisted predominantly ofmonooctynylated product (1.25 g, 22%), which could be resubjected to the reactionconditions and converted to 2,3-dibromo-1,4-di(oct-1-ynyl)benzene (up to 80%). UV-VIS (cyclohexane): λ max (logε) = 224 (3.94), 232 (3.95), 279 (4.00), 292 (4.12), 371(2.83), 388 (2.75), 422 (2.15) nm. IR (NaCl film): ~ ν = 3583, 2930, 2858, 2230, 1579,1378, 1351, 1330, 1095, 827, 726, 666 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 452 (M + ,100), 409 (25), 302 (32), 294 (57), 165 (52). 1 H NMR (400 MHz, CDCl 3 ) δ 7.26 (s, 2H),2.47 (t, 3 J = 7.0 Hz, 4H), 1.63 (m, 4H), 1.47 (m, 4H), 1.31 (m, 8H), 0.90 (t, 3 J = 7.0 Hz,6H). 13 C NMR (100 MHz, CDCl 3 ) δ 130.96, 128.31, 127.00, 97.47, 79.94, 31.28, 28.52,28.36, 22.53, 19.62, 14.03. HR-MS Calcd for C 22 H 28 Br 2 : 452.0537. Found: 452.0543.231

Br2-Bromo-1,4-di(oct-1-ynyl)-3-[(trimethylsilyl)ethynyl]benzene (184b). Asuspension of 2,3-dibromo-1,4-di(oct-1-ynyl)benzene (4.70 g, 10.4 mmol),[Pd(PPh 3 ) 2 Cl 2 ] (0.13 g, 0.21 mmol), and CuI (35.0 mg, 0.21 mmol) in triethylamine (150mL) was degassed thoroughly in a 250 mL Schlenk tube. Trimethylsilylacetylene (1.60mL, 12.5 mmol) was injected through the septum and the tube closed. The mixture washeated at 90 ºC for 24 h. After that time, the solids were filtered off, the solvent removedin vacuo, and the resulting crude mixture separated by column chromatography (hexanes)to yield the starting material as the first, yellow, fraction (1.89 g, 40%), followed by 184b(1.63 g, 33%) as an orange oil. UV-VIS (cyclohexane): λ max (logε) = 252 (3.82), 260(4.02), 280sh (3.64), 288sh (3.67), 298sh (3.72), 321 (2.91), 336 (2.78) nm. IR (NaClfilm): ~ ν = 2957, 2931, 2859, 2230, 2160, 1579, 1456, 1378, 1329, 1250, 1192, 1133,956, 844, 760, 675 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 470/468 (M + , 58/56), 398(20), 295 (100), 252 (38), 166 (40). 1 H NMR (400 MHz, CDCl 3 ) δ 7.23 (br s, 2H), 2.46(t, 3 J = 7.2 Hz, 4H), 1.61 (m, 4H), 1.48 (m, 4H), 1.32 (m, 8H), 0.90 (t, 3 J = 6.8 Hz, 3H),0.89 (t, 3 J = 6.8 Hz, 3H), 0.29 (s, 9H). 13 C NMR (100 MHz, CDCl 3 ) δ 131.72, 129.93,128.37, 127.79, 127.32, 125.74, 103.49, 102.05, 96.98, 96.93, 79.46, 78.87, 31.25 (2C),28.59, 28.56, 28.45, 28.33, 22.48, 22.43, 19.63, 19.58, 13.97 (2C), –0.22. HR-MS Calcdfor C 27 H 81 37 BrSi: 470.1827. Found: 470.1834. Anal. Calcd for C 27 H 37 BrSi: C, 69.06; H,7.94. Found: C, 68.84; H, 7.90.TMS232

2-Bromo-3-ethynyl-1,4-di(oct-1-ynyl)benzene (175b):BrA solution of 184b (1.63 g, 3.46 mmol) in ether (10 mL) was treated with asaturated solution of KOH in a 1:1 mixture of ether and ethanol (100 mL). The resultingbrown solution was stirred for 1 h at 23 °C. The mixture was diluted with ether (200 mL)and washed with saturated aq. NH 4 Cl. The aqueous layer was extracted with ether (3 x100 mL) and the combined organic phases were washed with brine. After drying overMgSO 4 overnight, removal of solvent in vacuo gave 175b as a brown oil (1.37 g, 99%).UV-VIS (cyclohexane): λ max (logε) = 246sh (4.56), 254sh (4.63), 283sh (4.40), 294sh(4.56), 319 (3.31), 332 (3.29) nm. IR (NaCl film): ~ ν = 3307, 2931, 2858, 2230, 1717,1579, 1522, 1457, 1375, 1329, 1249, 1183, 1132, 1119, 830, 774, 748, 723, 694, 626 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 398/396 (M + , 100), 318 (29), 277 (49), 189 (48). 1 HNMR (400 MHz, CDCl 3 ) δ 7.20 (d, 3 J = 8.4 Hz, 1H), 7.17 (d, 3 J = 8.4 Hz, 1H), 3.49 (s,1H), 2.38 (t, 3 J = 6.8 Hz, 2H), 2.37 (t, 3 J = 7.2 Hz, 2H), 1.53 (m, 4H), 1.40 (m, 4H), 1.24(m, 8H), 0.82 (t, 3 J = 6.8 Hz, 6H). 13 C NMR (100 MHz, CDCl 3 ) δ 132.16, 130.09,128.50, 127.78, 126.80, 125.86, 97.31, 97.22, 85.23, 81.11, 79.34, 78.72, 31.28, 31.24,28.47, 28.45, 28.39, 28.33, 22.49 (2C), 19.59 (2C), 13.99 (2C). HR-MS Calcd forC 24 H 81 29 Br: 398.1432. Found: 398.1433. Anal. Calcd for C 24 H 29 Br: C, 72.54; H, 7.36.Found: C, 72.71; H, 7.49.233

2-Bromo-1,4-bis[(dimethylthexylsilyl)ethynyl]-3-ethynylbenzene (175c):SiSiBrA solution of 184c 69 (1.50 g, 2.56 mmol) in a mixture of ether (150 mL) andmethanol (150 mL) was treated with solid K 2 CO 3 (352 mg, 2.56 mmol). The resultingorange solution was stirred for 3 h at 23 °C. After the reaction was complete, the mixturewas diluted with ether (200 mL) and washed with saturated aq. NH 4 Cl. The aqueous layerwas extracted with ether (2 x 100 mL), and the combined organic phases were washedwith brine. The solution was dried over MgSO 4 overnight. Removal of solvent in vacuogave 175c as an orange oil (1.30 g, 99%). IR (NaCl film): ~ ν = 3310, 2958, 2866, 2159,1449, 1372, 1251, 1129, 1091, 962, 860, 836, 814, 776, 673 cm –1 . MS (EI, 70 eV) m/z(rel intensity) 514/512 (M + , 0.8), 499 (0.8), 471/469 (1.6), 429/427 (100/92), 346 (30). 1 HNMR (400 MHz, CDCl 3 ) δ 7.35 (d, 3 J = 8.1 Hz, 1H), 7.33 (d, 3 J = 8.1 Hz, 1H), 1.73 (brsept, 3 J = 6.9 Hz, 2H), 0.97 (s, 6H), 0.96 (s, 6H), 0.94 (d, 3 J = 6.9 Hz, 6H), 0.93 (d, 3 J =6.9 Hz, 6H), 0.25 (s, 6H), 0.24 (s, 6H). 13 C NMR (100 MHz, CDCl 3 ) δ 132.53, 130.47,128.96, 127.78, 127.44, 126.09, 103.44, 102.99, 101.90, 101.83, 86.14, 80.81, 34.59,34.55, 23.62, 23.57, 20.76 (2C), 18.75, 18.73, –2.48, –2.55. HR-MS Calcd forC 28 H 79 41 BrSi 2 : 512.1930. Found: 512.1920.234

1-Iodo-2,4-di(oct-1-ynyl) -5-[(trimethylsilyl)ethynyl]benzene (176b):BrBr1,5-Dibromo-2,4-di(oct-1-ynyl)benzene. A suspension of 57 78 (6.72 g, 13.7mmol), 1-octyne (4.50 mL, 30.5 mmol), [Pd(PPh 3 ) 2 Cl 2 ] (0.49 g, 0.69 mmol), and CuI(0.13 g, 0.69 mmol) in triethylamine (150 mL) was degassed in a 250 mL Schlenk tube.The tube was closed and the mixture heated at 120 ºC for 2.5 h. After that time, solidswere filtered off, solvent was removed in vacuo, and the resulting crude product purifiedby column chromatography (hexanes) to yield 1,5-dibromo-2,4-di(oct-1-ynyl)benzene asa pale yellow oil (5.98 g, 96%). UV-VIS (cyclohexane): λ max (logε) = 248sh (4.54),268sh (4.23), 277sh (4.17), 296sh (3.87), 395 (2.80) nm. IR (NaCl film): ~ ν = 3583,2955, 2931, 2858, 2233, 1455, 1363, 1326, 1060, 893, 869, 725, 666 cm –1 . MS (EI, 70eV) m/z (rel intensity) 452 (M + , 100), 409 (27), 344 (14), 302 (21), 165 (24). 1 H NMR(400 MHz, CDCl 3 ) δ 7.76 (s, 1H), 7.45 (s, 1H), 2.43 (t, 3 J = 6.8 Hz, 4H), 1.63 (m, 4H),1.47 (m, 4H), 1.30 (m, 8H), 0.90 (t, 3 J = 6.8 Hz, 6H). 13 C NMR (100 MHz,CDCl 3 ) δ 136.69, 135.15, 125.15, 124.28, 96.83, 78.06, 31.25, 28.45, 28.30, 22.49, 19.51,13.98. HR-MS Calcd for C 22 H 28 Br 2 : 452.0537. Found: 452.0550.BrI1-Bromo-5-iodo-2,4-di(oct-1-ynyl)benzene. A solution of 1,5-dibromo-2,4-di(oct-1-ynyl)benzene (2.78 g, 6.15 mmol) in ether (100 mL) was cooled to –45 ºC, and BuLi(3.2 mL of 2.5 M solution in hexane, 8.00 mmol) was added via syringe. The dark brown235

solution was stirred at –45 ºC for 30 min. After that time, an ethereal solution (100 mL)of iodine (2.54 g, 10.0 mmol) was added dropwise via syringe. The color of the solutionlightened gradually with the addition of iodine. The mixture was left to warm to 23 °Covernight, extracted with ether (2 x 100 mL), and washed with aq. Na 2 S 2 O 3 and thenbrine. Drying over MgSO 4 , followed by removal of solvent in vacuo, gave 1-bromo-5-iodo-2,4-di(oct-1-ynyl)benzene as a yellow oil (3.00 g, 97%). UV-VIS (cyclohexane):λ max (logε) = 250 (4.87), 266 (4.53), 274 (4.47), 282 (4.29), 307 (3.38), 363 (3.37) nm. IR(NaCl film): ~ ν = 2929, 2857, 2232, 1449, 1378, 1361, 1326, 1252, 1210, 1111, 1047,892, 871, 819, 724, 605 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 500/498 (M + , 100/100),456/454 (15/15), 421 (23), 374 (50), 295 (55), 165 (50), 91 (73). 1 H NMR (400 MHz,CDCl 3 ) δ 8.00 (s, 1H), 7.40 (s, 1H), 2.43 (t, 3 J = 6.8 Hz, 2H), 2.42 (t, 3 J = 6.8 Hz, 2H),1.61 (m, 4H), 1.47 (m, 4H), 1.32 (m, 8H), 0.90 (m, 6H). 13 C NMR (100 MHz,CDCl 3 ) δ 141.04, 135.72, 129.58, 125.88, 124.24, 99.4, 97.06, 96.00, 81.60, 78.27, 31.31,31.28, 28.58, 28.49, 28.33, 28.30, 22.55, 22.53, 19.58, 19.53, 14.06, 14.03. HR-MS Calcdfor C 22 H 81 28 BrI: 500.0399. Found: 500.0407.BrTMS1-Bromo-2,4-di(oct-1-ynyl)-5-[(trimethylsilyl)ethynyl]benzene. A solution of 1-bromo-5-iodo-2,4-di(oct-1-ynyl)benzene (1.95 g, 3.90 mmol), trimethylsilylacetylene(0.63 mL, 4.50 mmol), PdCl 2 (PPh 3 ) 2 (54.6 mg, 0.08 mmol), and CuI (14.9 mg, 0.08mmol) in triethylamine (100 mL) was stirred for 2 h at 23 °C. After removing the solidsby filtration, the solvent was evaporated in vacuo and the resulting crude product purified236

y column chromatography (hexanes) to yield 1-bromo-2,4-di(oct-1-ynyl)-5-[(trimethylsilyl)ethynyl]benzene as a yellow oil (1.77 g, 96%). UV-VIS (cyclohexane):λ max (logε) = 256 (4.48), 283 (4.06), 288 (4.09), 300 (4.19), 320 (3.09), 334 (3.00) nm. IR(NaCl film): ~ ν = 2930, 2558, 2232, 2157, 1475, 1428, 1376, 1327, 1250, 1178, 1111,1055, 895, 844, 760, 725 cm –1 . MS (EI, 70 eV) m/z (rel intensity) 470/468 (M + , 56/54),398/396 (20/18), 374 (8), 295 (100), 252 (40), 73 (35). 1 H NMR (400 MHz,CDCl 3 ) δ 7.63 (s, 1H), 7.41 (s, 1H), 2.43 (m, 4H), 1.61 (m, 4H), 1.47 (m, 4H), 1.31 (m,8H), 0.90 (m, 6H), 0.26 (s, 9H). 13 C NMR (100 MHz, CDCl 3 ) δ 135.78, 135.25, 125.98,125.79, 125.41, 123.46, 102.06, 100.24, 97.60, 95.99, 78.70, 77.82, 31.29, 31.28, 28.60,28.59, 29.47, 28.34, 22.51, 22.46, 19.55 (2C), 13.99 (2C), –0.23. HR-MS Calcd forC 27 H 81 37 BrSi: 470.1827. Found: 470.1824.ITMS1-Iodo-2,4-di(oct-1-ynyl)-5-[(trimethylsilyl)ethynyl]benzene (176b). A solution of1-bromo-2,4-di(oct-1-ynyl)-5-[(trimethylsilyl)ethynyl]benzene (4.07 g, 8.68 mmol) inether (100 mL) was cooled to –45 °C, and BuLi (8.0 mL of 2.4 M solution in hexane,19.2 mmol) was added via syringe. The dark brown solution was stirred at –45 °C for 30min. After that time, an ethereal solution (50 mL) of iodine (5.59 g, 22.0 mmol) wasadded dropwise via syringe. The color of the solution lightened gradually with addition ofiodine. The mixture was left to warm to 23 °C overnight, extracted with ether (2 x 100mL), and washed with aq. Na 2 S 2 O 3 and then brine. Drying over MgSO 4 , followed by theremoval of solvent in vacuo, gave 176b as a yellow oil (3.98 g, 89%). UV-VIS237

(cyclohexane): λ max (logε) = 260 (4.77), 285 (4.28), 291 (4.30), 297 (4.26), 303sh (4.33),322 (3.47), 337 (3.36) nm. IR (NaCl film): ~ ν = 2957, 2931, 2858, 2231, 2160, 1467,1428, 1371, 1250, 1211, 1176, 1048, 878, 843, 760, 725, 700, 673, 633 cm –1 . MS (EI, 70eV) m/z (rel intensity) 516 (M + , 100), 73 (36). 1 H NMR (400 MHz, CDCl 3 ) δ 7.88 (s,1H), 7.37 (s, 1H), 2.45 (t, 3 J = 6.8 Hz, 2H), 2.42 (t, 3 J = 7.2 Hz, 2H), 1.62 (m, 4H), 1.46(m, 4H), 1.32 (m, 8H), 0.90 (m, 6H), 0.26 (s, 9H).13 C NMR (100 MHz,CDCl 3 ) δ 141.49, 134.77, 130.32, 126.52, 125.32, 101.84, 100.26, 98.46, 96.90, 96.31,82.21, 77.94, 31.28 (2C), 28.59, 28.55 (2C), 28.29, 22.51, 22.45, 19.58, 19.55, 14.03,14.00, –0.21. HR-MS Calcd for C 27 H 37 BrI: 516.1709. Found: 516.1703. Anal. Calcd forC 27 H 37 BrI: C, 62.78; H, 7.22. Found: C, 63.01; H, 7.45.Compound 185b:BrTMSA solution of 175b (1.11 g, 2.79 mmol), 176b (1.57 g, 3.04 mmol),[Pd(PPh 3 ) 2 Cl 2 ] (39.0 mg, 0.06 mmol), and CuI (15.0 mg, 0.09 mmol) in triethylamine(100 mL) was heated at reflux for 16 h. After that time, the solids were filtered off,238

solvent removed in vacuo, and the resulting crude mixture purified by columnchromatography (hexanes/ethyl acetate) to yield 10a as brown, highly fluorescent (at 354nm) fraction (2.00 g, 91%). UV-VIS (cyclohexane): λ max (logε) = 239 (4.41), 268 (4.77),276 (4.87), 290 (4.75), 333 (4.41), 358 (4.23), 371 (3.83) nm. IR (NaCl film): ~ ν = 2956,2858, 2360, 2230, 1577, 1457, 1249, 901, 843, 759, 669 cm –1 . MS (EI, 70 eV) m/z (relintensity) 786 (M + , 100), 706 (8), 678 (8), 73 (13). 1 H NMR (400 MHz, C 6 D 6 ) δ 7.86 (s,1H), 7.74 (s, 1H), 7.11 (d, 3 J = 7.9 Hz, 1H), 7.08 (d, 3 J = 7.9 Hz, 1H), 2.30–2.18 (m, 8H),1.51–1.39 (m, 8H), 1.39–1.27 (m, 8H), 1.26–1.05 (m, 16H), 0.90–0.79 (m, 12H), 0.27 (s,9H). 13 C NMR (100 MHz, CDCl 3 ) δ 135.88, 135.22, 131.90, 130.13, 128.04, 128.03,127.55, 126.74, 126.27, 125.90, 124.24 (2C), 102.77, 99.44, 97.45, 97.33, 97.10, 97.05,95.49, 91.97, 79.55, 79.10, 76.84, 76.82, 31.62, 31.45, 31.40, 31.37, 28.71 (5C), 28.63,28.58, 28.46, 22.69, 22.62, 22.55, 22.54, 20.06, 19.85, 19.75, 19.71, 14.14, 14.10 (3C), –0.07. HR-MS Calcd for C 51 H 79 65 BrSi: 784.4039. Found: 784.4036. Anal. Calcd forC 51 H 65 BrSi: C, 77.93; H, 8.33. Found: C, 78.95; H, 8.53.Compound 185c:DMTSDMTSDMTSTMSBrDMTSIn a 500 mL Schlenk flask, 146 (1.58 g, 2.51 mmol) and 175c (1.29 g, 2.51mmol), along with [Pd(PPh 3 ) 2 Cl 2 ] (88 mg, 0.13 mmol) and CuI (24 mg, 0.13 mmol),239

were suspended in triethylamine (300 mL) and degassed. The mixture was kept at refluxfor 16 h, the solvent removed in vacuo and the crude material filtered through a shortplug of silica (hexanes/ethyl acetate) to give 185c (2.44 g, 96%) as a brownish oil. IR(NaCl film): ~ ν = 2959, 2932, 2865, 2158, 1482, 1404, 1405, 1378, 1250, 1188, 1129,1089, 873, 842, 819, 775, 674 cm –1 . MS (FAB) m/z (rel intensity) 1019 (M + , 58), 849(100). 1 H NMR (500 MHz, C 6 D 6 ) δ 7.78 (s, 1H), 7.76 (s, 1H), 7.00 (AB q, 2H), 1.76–1.62 (m, 4H), 1.02 (s, 6H), 1.01 (s, 6H), 0.98 (d, 3 J = 6.9 Hz, 6H), 0.93 (d, 3 J = 6.9 Hz,6H), 0.91 (br s, 12H), 0.86 (d, 3 J = 6.9 Hz, 6H), 0.86 (d, 3 J = 6.9 Hz, 6H), 0.29 (s, 9H),0.28 (s, 6H), 0.26 (s, 6H), 0.25 (s, 6H), 0.22 (s, 6H). 13 C NMR (100 MHz,CDCl 3 ) δ 136.48, 136.39, 132.16, 130.54, 128.99, 128.17, 127.31, 125.96, 125.53,125.39, 125.08, 124.89, 103.59, 103.18, 102.98, 102.91, 102.12, 101.83, 101.70, 101.22,100.86, 100.52, 95.39, 92.15, 34.60 (2C), 34.54, 34.49, 23.66, 23.54, 23.49 (2C), 20.95,20.73 (3C), 18.77, 18.74, 18.68, 18.62, –0.04, –2.32, –2.36 (2C), –2.55. HR-MS Calcdfor C 59 H 79 89 BrSi 5 : 1016.4994. Found: 1016.5006.240

Compound 186b:BrA solution of 185b (1.00 g, 1.28 mmol) in ether (10 mL) was treated with asaturated solution of KOH in a 1:1 mixture of ether and ethanol (20 mL). The resultingbrown solution was stirred for 1 h at 23 °C. After the reaction was complete, the mixturewas diluted with ether (50 mL) and washed with saturated aq. NH 4 Cl. The aqueous layerwas extracted with ether (3 x 100 mL), and the combined organic phases were washedwith brine. The solution was dried over MgSO 4 overnight. Removal of solvent in vacuogave 186b as a thick brown oil (0.89 g, 98%). UV-VIS (cyclohexane): λ max (logε) = 238(4.54), 265 (4.84), 273sh (4.94), 293 (4.71), 331 (4.50), 355 (4.36), 369 (3.98) nm. IR(NaCl film): ~ ν = 3305, 2930, 2858, 2362, 2229, 1579, 1488, 1457, 1328, 1106, 900, 828,722, 642 cm –1 . MS (FAB) m/z (rel intensity) 714 (M + , 100). 1 H NMR (400 MHz,C 6 D 6 ) δ 7.81 (s, 1H), 7.69 (s, 1H), 7.11 (d, 3 J = 8.2 Hz, 1H), 7.08 (d, 3 J = 8.2 Hz, 1H),3.00 (s, 1H), 2.30–2.18 (m, 8H), 1.49–1.37 (m, 8H), 1.37–1.24 (m, 8H), 1.23–1.05 (m,16H), 0.91–0.79 (m, 12H). 13 C NMR (100 MHz, CDCl 3 ) δ 136.18, 135.36, 131.97,130.15, 128.06, 127.97, 127.54, 126.94, 126.73, 125.91, 124.33, 123.14, 97.52 (2C),241

97.27, 97.14, 95.30, 92.11, 81.69, 81.51, 79.53, 79.03, 78.54, 78.50, 31.44, 31.40 (2C),31.36, 28.75, 28.72 (2C), 28.70, 28.57, 28.55 (2C), 28.45, 22.61 (2C), 22.54 (2C), 20.06,19.87, 19.71 (2C), 14.10 (4C). HR-MS Calcd for C 48 H 79 57 Br: 712.3644. Found:712.3659. Anal. Calcd for C 48 H 57 Br: C, 80.76; H, 8.05. Found: C, 80.83; H, 8.24.Compound 186c:DMTSDMTSDMTSBrDMTSA solution of 185c (1.13 g, 1.11 mmol) in a mixture of ether (70 mL) and ethanol(70 mL) was treated with solid K 2 CO 3 (306 mg, 2.22 mmol). After stirring for 2 h at 23°C, the solvents were removed in vacuo, and the resulting oil was redissolved in 20 mLof CH 2 Cl 2 and filtered through a short plug of silica to give (0.91 g, 87%) of 186c as abrown oil. IR (NaCl film): ~ ν = 3309, 2959, 2867, 2156, 1482, 1464, 1379, 1250, 1129,1090, 837, 776, 675 cm –1 . MS (FAB) m/z (rel intensity) 946 (M + , 0.5), 777 (1.5), 252(100), 235 (58), 140 (98), 123 (83). 1 H NMR (500 MHz, C 6 D 6 ) δ 7.65 (s, 1H), 7.64 (s,1H), 6.99 (AB q, 2H), 2.97 (s, 1H) 1.80–1.56 (m, 4H), 1.00 (s, 6H), 0.98 (s, 6H), 0.94 (d,3 J = 6.9 Hz, 6H), 0.93 (d, 3 J = 6.9 Hz, 6H), 0.89 (s, 6H), 0.88 (s, 6H), 0.83 (d, 3 J = 6.9Hz, 6H), 0.83 (d, 3 J = 6.9 Hz, 6H), 0.24 (s, 6H), 0.24 (s, 6H), 0.22 (s, 6H), 0.19 (s, 6H).13 C NMR (100 MHz, CDCl 3 ) δ 136.16, 136.01, 132.19, 130.51, 128.94, 128.22, 127.38,126.20, 126.03, 125.98, 125.08, 124.39, 103.60, 103.19, 102.78 (2C), 101.89, 101.74,242

101.44, 101.27, 95.27, 92.36, 82.77, 81.10, 34.72, 34.64, 34.60, 34.54, 23.67, 23.56,23.50, 23.48, 20.78 (2C), 20.74, 20.69, 18.78, 18.75, 18.67, 18.62, –2.39 (2C), –2.42, –2.54. HR-MS Calcd for C 56 H 81 79 BrSi 4 : 944.4599. Found: 944.4589.Compound 187b:ITMSA solution of 185b (1.01 g, 1.28 mmol) in ether (40 mL) was cooled to –45 ºC,and BuLi (0.8 mL of 2.4 M solution in hexane, 1.92 mmol) was added via syringe. Thedark brown solution was stirred at –45 ºC for 30 min. After that time, an ethereal solution(20 mL) of iodine (762 mg, 3.00 mmol) was added dropwise via syringe. The color of thesolution lightened gradually with addition of iodine. The mixture was stirred at –45 ºC for10 min, left to warm to 23 °C over 90 min, extracted with ether (2 x 100 mL), andwashed with aq. Na 2 S 2 O 3 and then brine. Drying over MgSO 4 , followed by removal ofsolvent in vacuo gave 187b as a brown oil (1.01 g, 94%). UV-VIS (cyclohexane): λ max(logε) = 271 (4.26), 278 (4.24), 284 (4.20), 291 (4.14), 330 (3.76), 353 (3.64) nm. IR(NaCl film): ~ ν = 2930, 2858, 2229, 2157, 1454, 1329, 1249, 1111, 901, 844, 724, 700243

cm –1 . MS (FAB) m/z (rel intensity) 832 (M + , 100). 1 H NMR (400 MHz, C 6 D 6 ) δ 7.87 (s,1H), 7.74 (s, 1H), 7.13 (d, 3 J = 8.2 Hz, 1H), 7.04 (d, 3 J = 8.2 Hz, 1H), 2.30–2.21 (m, 8H),1.52–1.37 (m, 8H), 1.37–1.05 (m, 24H), 0.91–0.79 (m, 12H), 0.27 (s, 9H). 13 C NMR (100MHz, CDCl 3 ) δ 135.87, 135.27, 132.59, 131.70, 131.00, 130.98, 130.68, 126.71, 126.68,126.18, 124.24, 124.21, 106.82, 102.79, 99.43, 97.24, 97.01, 96.31, 95.69, 94.60, 83.44,79.32, 78.83, 78.63, 31.46, 31.39 (3C), 28.70 (3C), 28.68 (3C), 28.63, 28.41, 22.62, 22.55(2C), 22.52, 20.24, 19.85, 19.74, 19.71, 14.09 (4C), –0.07. HR-MS Calcd for C 51 H 65 SiI:832.3900. Found: 832.3904.Compound 187c:DMTSDMTSDMTSTMSIDMTSA solution of 185c (1.13 g, 1.11 mmol) in ether (100 mL) was cooled to –50 ºC,and BuLi (0.95 mL of 2.34 M solution in hexane, 2.22 mmol) was added via syringe. Thedark brown solution was stirred at –50 ºC for 45 min. After that time, an ethereal solution(100 mL) of iodine (1.02 g, 4.00 mmol) was added dropwise via syringe. The color of thesolution lightened gradually with addition of iodine. The mixture was left to warm to 23°C overnight, extracted with ether (2 x 100 mL), and washed with aq. Na 2 S 2 O 3 and thenbrine. Drying over MgSO 4 , followed by removal of solvent in vacuo, gave 187c as a darkbrown oil (1.09 g, 92%). IR (NaCl film): ~ ν = 2959, 2923, 2864, 2157, 1482, 1463, 1442,244

1249, 869, 839, 775 cm –1 . MS (FAB) m/z (rel intensity) 1066 (M + , 100). 1 H NMR (300MHz, C 6 D 6 ) δ 7.62 (s, 1H), 7.61 (s, 1H), 7.05 (d, 3 J = 8.1 Hz, 1H), 6.96 (d, 3 J = 8.1 Hz,1H), 1.81–1.54 (m, 4H), 0.99 (s, 6H), 0.98 (s, 6H), 0.93 (d, 3 J = 6.9 Hz, 6H), 0.89 (d, 3 J =6.9 Hz, 6H), 0.87 (s, 6H), 0.84 (s, 6H), 0.80 (d, 3 J = 6.9 Hz, 6H), 0.80 (d, 3 J = 6.9 Hz,6H), 0.24 (m, 21H), 0.18 (s, 6H), 0.13 (s, 6H). 13 C NMR (125 MHz, CDCl 3 ) δ 136.26,136.18, 132.77, 131.37, 131.23, 130.71, 126.39, 125.45, 125.40, 125.03, 124.96, 107.22,107.11, 103.34, 102.98, 102.94, 102.14, 101.60, 101.14, 100.72 (2C), 100.45, 95.80,94.43, 34.59, 34.57, 34.48, 34.44, 23.66, 23.50, 23.41, 23.41, 20.91, 20.79, 20.67 (2C),18.75 (2C), 18.63, 18.59, –0.06, –2.32, –2.36, –2.41, –2.55. HR-MS Calcd for C 59 H 89 ISi 5 :1065.4964. Found: 1065.4934.Compound 188b:HexHexHexHexBrTMSHexHexHexHexA solution of 186b (0.89 g, 1.25 mmol), 187b (1.01 g, 1.21 mmol),[Pd(PPh 3 ) 2 Cl 2 ] (17.5 mg, 0.025 mmol), and CuI (5.0 mg, 0.025 mmol) in triethylamine(50 mL) was degassed thoroughly in a Schlenk tube. The tube was closed and the mixtureheated at 110 ºC for 11 h. After that time, the solids were filtered off, solvent was245

emoved in vacuo, and the resulting crude mixture purified by column chromatography(hexanes/ethyl acetate) to yield 188b as a thick brown oil (1.34 g, 78%). UV-VIS(cyclohexane): λ max (logε) = 224 (4.78), 276 (5.20), 292 (5.25), 324 (4.94), 362 (4.67),384 (4.15) nm. IR (NaCl film): ~ ν = 2930, 2857, 2230, 2157, 1578, 1458, 1249, 1113,901, 843, 759, 725 cm –1 . MS (FAB) m/z (rel intensity) 1420 (M + , 100). 1 H NMR (400MHz, C 6 D 6 ) δ 8.16 (s, 1H), 8.00 (s, 1H), 7.77 (s, 1H), 7.70 (s, 1H), 7.16 (s, 2H), 7.11 (d,3 J = 7.9 Hz, 1H), 7.08 (d, 3 J = 7.9 Hz, 1H), 2.41–2.13 (m, 16H), 1.60–1.40 (m, 16H),1.40–1.27 (m, 16H), 1.26–1.06 (m, 32H), 0.90–0.80 (m, 24H), 0.28 (s, 9H). 13 C NMR(125 MHz, CDCl 3 ) δ 136.27, 135.99, 135.29, 135.12, 131.74, 131.01, 130.95, 130.07,128.07, 127.95, 127.80, 127.74, 127.60, 126.51, 126.43, 126.36, 126.33, 126.24, 126.05,125.71, 124.61, 124.45, 124.08, 124.02, 102.74, 99.07, 97.53, 97.48, 97.37, 97.05, 96.89,96.80, 96.67, 96.64, 95.58, 95.27 (2C), 91.82, 91.75, 91.73, 79.55, 79.14, 79.08, 78.94,78.73, 78.55 (2C), 78.47, 31.45 (2C), 31.37 (3C), 31.33 (3C), 28.77 (4C), 28.69 (4C),28.64 (2C), 28.61 (3C), 28.58, 28.54 (2C), 22.66, 22.59 (2C), 22.53 (5C), 20.02, 19.88,19.84, 19.79, 19.73 (2C), 19.68, 19.66, 14.08 (6C), 14.00 (2C), –0.10. HR-MS Calcd forC 99 H 79 121 BrSi: 1416.8421. Found: 1416.8405. Anal. Calcd for C 99 H 121 BrSi: C, 83.80; H,8.59. Found: C, 84.16; H, 8.75.246

Compound 188c:DMTSDMTSDMTSDMTSBrTMSDMTSDMTSDMTSDMTSIn a 200 mL Schlenk tube, 186c (641 mg, 0.68 mmol) and 187c (721 mg, 0.68mmol) were dissolved in triethylamine (125 mL). [Pd(PPh 3 ) 2 Cl 2 ] (24 mg, 0.034 mmol)and CuI (7 mg, 0.034 mmol) were added and the mixture was degassed. The tube wasclosed and heated at 110 ºC for 17 h. Solvent was removed in vacuo and the remainingcrude material chromatographed on silica (hexanes/CH 2 Cl 2 ) to give 188c as a viscousbrown oil (1.03 g, 78%). IR (NaCl film): ~ ν = 2959, 2867, 2158, 1485, 1467, 1379, 1250,1191, 1129, 868, 841, 775 cm –1 . MS (FAB) m/z (rel intensity) 1884 (M + , 10), 1800 (13),1716 (17), 1631 (10), 895 (25), 486 (100). 1 H NMR (400 MHz, C 6 D 6 ) δ 7.95 (s, 1H),7.91 (s, 1H), 7.72 (s, 1H), 7.70 (s, 1H), 7.12 (s, 2H), 7.00 (AB q, 2H), 1.74–1.62 (m, 8H),1.02–0.84 (m, 96H), 0.35–0.25 (m, 57H). 13 C NMR (125 MHz, CDCl 3 ) δ 136.06, 135.70,135.68, 135.55, 134.76, 134.75, 132.02, 131.08, 130.20, 128.83, 128.56, 128.41, 127.32,125.98, 125.97, 125.86, 125.73, 125.51, 125.50, 125.47, 125.40, 125.06, 124.91, 124.88,103.60, 103.32, 103.29, 103.08, 102.95, 102.90, 102.22, 101.87, 101.58, 101.40, 101.05,101.03, 100.95, 100.89, 100.76, 100.44, 100.16, 99.94, 95.39, 95.06, 94.90, 91.86, 91.69,91.59, 34.52 (2C), 34.50, 34.44, 34.42, 34.40, 34.35, 34.35, 23.57, 23.41, 23.35, 23.34,247

23.28, 23.26, 23.26, 23.23, 20.83, 20.65, 20.59, 20.57, 20.56, 20.52, 20.50, 20.47, 18.69,18.65, 18.59, 18.58, 18.50 (2C), 18.48, 18.43, –0.06, –2.40, –2.46 (2C), –2.48, –2.48, –2.49, –2.53, –2.62. The high molecular mass of 188c precluded HR-MS measurements.Compound 171b:Bromine–iodine exchange: A solution of 188b (1.10 g, 0.77 mmol) in ether (40mL) was cooled to –45 ºC, and BuLi (0.6 mL of 2.5 M solution in hexane, 1.50 mmol)was added via syringe. The dark brown solution was stirred at –45 ºC for 30 min.Subsequently, an ethereal solution (20 mL) of iodine (762 mg, 3.00 mmol) was addeddropwise via syringe. The mixture was stirred at –45 ºC for 10 min, left to warm to 23 °Cover 90 min, extracted with ether (2 x 100 mL), and washed with aq. Na 2 S 2 O 3 and thenbrine. Drying over MgSO 4 , followed by removal of solvent in vacuo, gave theintermediate iodide as a thick brown oil (1.11 g, 98%). The compound was partlycharacterized and used without purification in the following step. MS (FAB) m/z (rel248

intensity) 1466 (M + , 100). 1 H NMR (400 MHz, C 6 D 6 ) δ 8.16 (s, 1H), 7.98 (s, 1H), 7.76(s, 1H), 7.69 (s, 1H), 7.16 (s, 2H), 7.14 (d, 3 J = 8.0 Hz, 1H), 7.04 (d, 3 J = 8.0 Hz, 1H),2.41–2.12 (m, 16H), 1.83–0.98 (m, 64H), 0.91–0.79 (m, 24H), 0.28 (s, 9H). HR-MSCalcd for C 99 H 121 SiI: 1464.8282. Found: 1464.8253.Cleavage of the TMS group: A solution of the iodide (973 mg, 0.66 mmol) inTHF (100 mL) was treated with Bu 4 N + F – (2.00 mL of 1.0 M solution in THF, 2.00 mmol)and stirred at 23 °C for 40 min. Ethanol (30 mL) was added via syringe and the resultingbrown solution stirred for an additional 2 h; subsequently, the mixture was filteredthrough short plug of silica (ethyl acetate). Removal of solvent in vacuo gave thedeprotected material as a dark brown oil (876 mg, 95%), which was used immediately inthe next step.Macrocyclization: A thoroughly degassed solution of the terminal alkyne (563mg, 0.40 mmol) in triethylamine (50 mL) was injected slowly (syringe pump, 36 h) into arefluxing solution of PdCl 2 (PPh 3 ) 2 (14.0 mg, 0.02 mmol) and CuI (4.0 mg, 0.02 mmol) intriethylamine (100 mL). After the addition was complete, the mixture was left at refluxfor an additional 10 h. The solvent was removed in vacuo and the resulting crude productpurified by column chromatography (hexanes/ethyl acetate = 95/5) to yield 171b as darkred waxy solid (344 mg, 67%).Performing this reaction on a larger scale (0.63 mmol) and without the slowaddition of the alkyne gave 171b in somewhat lower yield (53%). UV-VIS(cyclohexane): λ max (logε) = 229 (4.73), 271 (5.00), 286 (4.98), 307 (4.92), 351 (4.56),370 (4.33) nm. IR (NaCl film): ~ ν = 2929, 2857, 2228, 1646, 1541, 1466, 1378, 1117,901, 829 cm –1 . MS (FAB) m/z (rel intensity) 1266 (M + , 100). 1 H NMR (400 MHz,249

CD 2 Cl 2 ) δ 7.81 (s, 2H), 7.43 (s, 2H), 7.32 (s, 4H), 2.42 (t, 3 J = 7.0 Hz, 8H), 2.35 (t, 3 J =7.0 Hz, 8H), 1.60 (t, 3 J = 7.6 Hz, 8H), 1.56 (t, 3 J = 7.6 Hz, 8H), 1.46–1.36 (m, 8H), 1.36–1.28 (m, 8H), 1.25–1.19 (m, 16H) 1.16–1.12 (m, 16H), 0.92–0.85 (m, 24H). 1 H NMR(500 MHz, C 6 D 6 ) δ 7.88 (s, 2H), 7.66 (s, 2H), 7.18 (s, 4H), 2.40 (t, 3 J = 7.0 Hz, 8H), 2.34(t, 3 J = 7.0 Hz, 8H), 1.61 (t, 3 J = 7.6 Hz, 8H), 1.54 (t, 3 J = 7.6 Hz, 8H), 1.46–1.38 (m,8H), 1.38–1.29 (m, 8H), 1.23–1.17 (m, 16H) 1.17–1.11 (m, 16H), 0.90–0.82 (m, 24H).13 C NMR (125 MHz, CDCl 3 ) δ 137.03, 135.02, 130.93, 128.60, 126.01, 125.47, 124.49,96.86, 96.55, 95.29, 91.43, 79.00, 78.70, 31.39 (2C), 28.72 (2C), 28.60, 28.58, 22.49,22.45, 19.90 (2C), 14.01, 14.00. HR-MS Calcd for C 96 H 112 : 1264.8764. Found:1264.8762.Compound 171c:DMTS DMTSDMTS DMTSDMTSDMTSDMTSDMTSBromine–iodine exchange: A solution of 188c (1.00 g, 0.512 mmol) in ether (100mL) was cooled to –50 ºC, and BuLi (0.44 mL of 2.34 M solution in hexane, 1.03 mmol)was added via syringe. The dark brown solution was stirred at –50 ºC for 45 min.Subsequently, an ethereal solution (100 mL) of iodine (523 g, 2.06 mmol) was addeddropwise via syringe. The mixture was left to warm to 23 °C overnight, extracted withether (2 x 100 mL), and washed with aq. Na 2 S 2 O 3 and then brine. Drying over MgSO 4 ,250

followed by removal of solvent in vacuo gave the desired iodide as a dark brown oil (875mg, 85%). IR (NaCl film): ~ ν = 2983, 2956, 2914, 2866, 2157, 1485, 1463, 1378, 1253,1190, 1090, 997, 930, 871, 844, 770, 675 cm –1 . MS (FAB) m/z (rel intensity) 1932 (M + ,22), 1846 (26), 1762 (30), 1678 (29), 1595 (24), matrix peak (100). 1 H NMR (500 MHz,C 6 D 6 ) δ 7.84 (s, 1H), 7.79 (s, 1H), 7.65 (s, 1H), 7.59 (s, 1H), 7.08 (br s, 2H), 7.03 (d, 3 J =8.1 Hz, 1H), 6.94 (d, 3 J = 8.1 Hz, 1H), 1.74–1.52 (m, 8H), 1.02–0.76 (m, 96H), 0.27–0.15(m, 57H). The crude material was used in the next step without further purification.Cleavage of the TMS group: A solution of the above iodide (765 mg, 0.040mmol) in a mixture of ether (50 mL) and ethanol (50 mL) was treated with solid K 2 CO 3(110 mg, 0.80 mmol). After stirring for 2 h at 23 °C, the solvents were removed in vacuo,and the resulting oil was redissolved in a small amount of CH 2 Cl 2 and filtered through ashort plug of silica to give (729 mg, 99%) of the deprotected material as a brown oil. Thismaterial was used in the subsequent steps without further purification.Macrocyclization: To a thoroughly degassed solution of the alkyne from theprevious step (631 mg, 0.34 mmol) in triethylamine (250 mL) were added [Pd(PPh 3 ) 2 Cl 2 ](12.0 mg, 0.017 mmol) and CuI (3.3 mg, 0.017 mmol). The mixture was brought to refluxand stirred for 16 h, after which the solvent was removed in vacuo and the resulting crudeproduct purified by column chromatography (hexanes/CH 2 Cl 2 ) to yield 171c as yellowflaky crystals, m.p. 144–145 ºC (311 mg, 53%). UV-VIS (CH 2 Cl 2 ): λ max (logε) = 249(4.68), 274 (4.88), 305 (4.90), 330 (4.58), 377 (3.77) nm. IR (NaCl film): ~ ν = 2959,2928, 2867, 2156, 1486, 1463, 1378, 1250, 1192, 997, 929, 836, 775, 675 cm –1 . MS(FAB) m/z (rel intensity) 1732 (M + , 13), 1564 (10), 1396 (7), 503 (92), 488 (100). 1 HNMR (500 MHz, C 6 D 6 ) δ 7.63 (s, 2H), 7.24 (s, 2H), 7.09 (s, 4H), 1.84 (sept, 3 J = 6.9 Hz,251

4H), 1.77 (sept, 3 J = 6.9 Hz, 4H), 1.10 (s, 12H), 1.07 (s, 12H), 1.05 (s, 12H), 1.03 (s,12H), 1.01 (d, 3 J = 6.6 Hz, 12H), 0.99 (d, 3 J = 6.6 Hz, 12H), 0.97 (d, 3 J = 7.1 Hz, 12H),0.95 (d, 3 J = 7.1 Hz, 12H), 0.40 (s, 12H), 0.38 (s, 12H), 0.36 (s, 12H), 0.32 (s, 12H). 13 CNMR (100 MHz, CDCl 3 ) δ 137.76, 135.88, 131.27, 129.39, 125.23, 125.05, 124.93,103.37, 103.06, 101.24, 101.06, 95.76, 91.54, 34.68, 34.56 (2C), 34.48, 23.68 (2C), 23.53(2C), 21.06, 20.85, 20.65, 20.60, 18.75, 18.68, 18.61, 18.55, –2.35, –2.38 (3C).Compound 156:A solution of 171c (17 mg, 0.01 mmol) in THF–d 8 (0.5 mL) was treated withTBAF (0.1 mL of 1.0 M solution in THF, 0.1 mmol). The mixture turned brownimmediately. After 2 h, water (0.5 mL) was added, along with diethyl ether (5 mL). Thelayers were separated and the organic layer, containing 156, was analyzed by 1 H NMR:1 H NMR (400 MHz, THF–d 8 /ether) δ 7.93 (s, 2H), 7.62 (s, 2H), 7.44 (s, 4H), 3.97 (s,4H), 3.95 (s, 4H). UV-VIS (THF) λ max (rel. absorbance) = 235 (0.63), 271 (0.40), 288(0.40), 306 (0.79), 340 (0.25), 373 (0.08), 401 (0.06) nm. Removal of solvent at highvacuum gave an insoluble yellow-white powder, which darkened in less than 1 min.252

Compounds 189 and 190 (CpCo-mediated cycloisomerization of 171b):To 171b (46 mg, 0.036 mmol) in degassed toluene (10 mL) was added[CpCo(CO) 2 ] (26 mg, 0.144 mmol, 4 equiv). The resulting solution was added over 25min to boiling, degassed toluene (100 mL), and irradiated with a slide projector lamp.After 1 h, heating and irradiation were discontinued and the solvents removed underreduced pressure. The residue was dissolved in CH 2 Cl 2 , preadsorbed on silica, and driedovernight under high vacuum. Column chromatography (hexanes/ethyl acetate) gave adeep red band that contained 189 and 190 in a ~ 1:1 ratio (by 1 H NMR). The total yieldwas 9.1 mg (19%).In a separate attempt, treating 171b (140 mg, 0.11 mmol) with six equiv of[CpCo(CO) 2 ] (116 mg, 0.66 mmol) gave 15.5 mg (11%) of 189 only, as an orange oil.Both pure 189 and the 189/190 mixture decomposed within several hours, whenleft exposed to air.189: UV-VIS (dichloromethane) λ max (logε) = 235 (4.50), 273 (4.81), 311 (4.90),350sh (4.44), 369sh (4.40), 420sh (4.20), 444 (4.31), 508 (3.80), 544 (3.68) nm. IR(KBr): ~ ν = 2958, 2930, 2858, 2227, 2170, 1451, 1329, 1249, 1111, 1031, 844 cm –1 . MS253

(FAB) m/z (rel intensity) 1266 (M + , 5), 501 (100), 486 (91). 1 H NMR (400 MHz, CD 2 Cl 2 )δ 7.69 (s, 1H), 7.49 (s, 1H), 7.06 (d, 3 J = 7.3 Hz, 2H), 6.72 (d, 3 J = 7.3 Hz, 2H), 6.67 (d,3 J = 1.5 Hz), 6.47 (d, 3 J = 1.5 Hz, 1H), 2.50–2.42 (m, 8H), 2.32–2.26 (m, 8H), 1.60–1.10(m, 64H), 0.89–0.80 (m, 24H). HR-MS Calcd for C 96 H 112 : 1264.8764. Found: 1264.8774.190 (based on the difference between 189/190 mixture and pure 189): 1 H NMR(400 MHz, CD 2 Cl 2 ) δ 7.12 (s, 2H), 7.08 (d, 3 J = 7.5 Hz, 2H), 6.87 (s, 2H), 6.72 (d, 3 J =6.6 Hz, 2H), 2.49–2.42 (m, 8H), 2.31–2.26 (m, 8H), 1.57–1.10 (m, 64H), 0.89–0.81 (m,24H).6.4.1 Calculated Structures of 121, 156, and 191–195Calculated positional parameters for the planar structure of 121:Atom x y zC1 0.0000000000 5.7631791204 –1.3735933016C2 0.0000000000 5.7631791204 1.3735933016C3 0.0000000000 4.4946408315 –0.6793841882C4 0.0000000000 6.9747603226 –0.7189211185C5 0.0000000000 6.9747603226 0.7189211185C6 0.0000000000 4.4946408315 0.6793841882C7 0.0000000000 1.1473170575 2.7304484215C8 0.0000000000 –1.1662414596 4.1554084185C9 0.0000000000 0.0000000000 1.9560033812C10 0.0000000000 1.1662414596 4.1554084185C11 0.0000000000 0.0000000000 4.9318418836C12 0.0000000000 –1.1473170575 2.7304484215C13 0.0000000000 1.1473170575 –2.7304484215C14 0.0000000000 –1.1662414596 –4.1554084185C15 0.0000000000 1.1662414596 –4.1554084185C16 0.0000000000 0.0000000000 –1.9560033812C17 0.0000000000 –1.1473170575 –2.7304484215C18 0.0000000000 0.0000000000 –4.9318418836C19 0.0000000000 –4.4946408315 –0.6793841882C20 0.0000000000 –6.9747603226 0.7189211185254

C21 0.0000000000 –5.7631791204 –1.3735933016C22 0.0000000000 –4.4946408315 0.6793841882C23 0.0000000000 –5.7631791204 1.3735933016C24 0.0000000000 –6.9747603226 –0.7189211185C25 0.0000000000 5.0327142569 –2.6914196499C26 0.0000000000 2.6830646757 –4.1249724903C27 0.0000000000 5.1032287174 –4.0597570334C28 0.0000000000 3.7710865561 –1.9681491057C29 0.0000000000 2.6218474041 –2.6769955711C30 0.0000000000 3.8649095917 –4.8161927194C31 0.0000000000 –5.0327142569 2.6914196499C32 0.0000000000 –2.6830646757 4.1249724903C33 0.0000000000 –3.7710865561 1.9681491057C34 0.0000000000 –5.1032287174 4.0597570334C35 0.0000000000 –3.8649095917 4.8161927194C36 0.0000000000 –2.6218474041 2.6769955711C37 0.0000000000 –5.0327142569 –2.6914196499C38 0.0000000000 –2.6830646757 –4.1249724903C39 0.0000000000 –5.1032287174 –4.0597570334C40 0.0000000000 –3.7710865561 –1.9681491057C41 0.0000000000 –2.6218474041 –2.6769955711C42 0.0000000000 –3.8649095917 –4.8161927194C43 0.0000000000 2.6830646757 4.1249724903C44 0.0000000000 5.0327142569 2.6914196499C45 0.0000000000 2.6218474041 2.6769955711C46 0.0000000000 3.8649095917 4.8161927194C47 0.0000000000 5.1032287174 4.0597570334C48 0.0000000000 3.7710865561 1.9681491057H1 0.0000000000 7.9210776320 –1.2521911470H2 0.0000000000 7.9210776320 1.2521911470H3 0.0000000000 0.0000000000 0.8765635444H4 0.0000000000 0.0000000000 6.0173474308H5 0.0000000000 0.0000000000 –0.8765635444H6 0.0000000000 0.0000000000 –6.0173474308H7 0.0000000000 –7.9210776320 –1.2521911470H8 0.0000000000 –7.9210776320 1.2521911470H9 0.0000000000 6.0486558343 –4.5945629231H10 0.0000000000 3.9075229634 –5.9015550425H11 0.0000000000 –6.0486558343 4.5945629231H12 0.0000000000 –3.9075229634 5.9015550425H13 0.0000000000 –6.0486558343 –4.5945629231H14 0.0000000000 –3.9075229634 –5.9015550425H15 0.0000000000 3.9075229634 5.9015550425H16 0.0000000000 6.0486558343 4.5945629231255

Calculated positional parameters for the non planar structure of 121:Atom x y zC1 0.3239589662 –1.3350403605 5.7634717974C2 –0.2883571257 1.3431261500 5.7643409283C3 0.1244584234 –0.6679597477 4.4961852979C4 0.2144374930 –0.6888421466 6.9746169901C5 –0.1112219204 0.7116884265 6.9752291492C6 –0.1597478968 0.6603684734 4.4965134250C7 –1.0591502381 4.6956487788 3.8623328013C8 –0.5681840298 2.6117412907 2.6218298696C9 –0.5614226753 2.6658413340 1.1471936071C10 –0.9022677227 4.0497654530 –1.1655458638C11 –0.3595386931 1.9167098573 0.0000000000C12 –0.9022677227 4.0497654530 1.1655458638C13 –1.0848808022 4.8045332386 0.0000000000C14 –0.5614226753 2.6658413340 –1.1471936071C15 0.4729899003 –2.6881028313 1.1474625074C16 0.8709495014 –4.0567686652 –1.1654654053C17 0.8709495014 –4.0567686652 1.1654654053C18 0.2378284529 –1.9488012127 0.0000000000C19 0.4729899003 –2.6881028313 –1.1474625074C20 1.0851294696 –4.8031131590 0.0000000000C21 0.5064448825 –2.6263929469 –2.6221106834C22 1.1167454627 –4.6809489502 –3.8600717640C23 0.1244584234 –0.6679597477 –4.4961852979C24 –0.1112219204 0.7116884265 –6.9752291492C25 0.3239589662 –1.3350403605 –5.7634717974C26 –0.1597478968 0.6603684734 –4.4965134250C27 –0.2883571257 1.3431261500 –5.7643409283C28 0.2144374930 –0.6888421466 –6.9746169901C29 0.6137600983 –2.6196304918 5.0314520596C30 0.8923997571 –4.0219409465 2.6809962303C31 0.9633023631 –3.9426125657 5.0995819333C32 0.3900835416 –1.9279787191 3.7719496907C33 0.5064448825 –2.6263929469 2.6221106834C34 1.1167454627 –4.6809489502 3.8600717640C35 –0.5865894898 2.6263400001 –5.0330060226C36 –0.8988197454 4.0211936160 –2.6816556380C37 –0.4329438967 1.9182843357 –3.7722321561C38 –0.8886994002 3.9608927649 –5.1018804137C39 –1.0591502381 4.6956487788 –3.8623328013C40 –0.5681840298 2.6117412907 –2.6218298696C41 0.6137600983 –2.6196304918 –5.0314520596C42 0.8923997571 –4.0219409465 –2.6809962303256

C43 0.9633023631 –3.9426125657 –5.0995819333C44 0.3900835416 –1.9279787191 –3.7719496907C45 –0.8886994002 3.9608927649 5.1018804137C46 –0.8988197454 4.0211936160 2.6816556380C47 –0.4329438967 1.9182843357 3.7722321561C48 –0.5865894898 2.6263400001 5.0330060226H1 0.3674451868 –1.2009964371 7.9201722769H2 –0.2042926656 1.2366614074 7.9215787610H3 1.4071574788 –5.7268842984 –3.8988609688H4 1.1351891004 –4.4523438701 –6.0432049281H5 –1.0046945462 4.4845621520 6.0463955788H6 –0.0631166648 0.8778911324 0.0000000000H7 –1.3416664479 5.8592396283 0.0000000000H8 –0.0973380193 –0.9217258854 0.0000000000H9 1.3921141350 –5.8443389906 0.0000000000H10 –1.3052117282 5.7528079016 3.9031149259H11 0.3674451868 –1.2009964371 –7.9201722769H12 –0.2042926656 1.2366614074 –7.9215787610H13 1.1351891004 –4.4523438701 6.0432049281H14 1.4071574788 –5.7268842984 3.8988609688H15 –1.0046945462 4.4845621520 –6.0463955788H16 –1.3052117282 5.7528079016 –3.9031149259Calculated positional parameters for the planar structure of 156:Atom x y zC1 0.0000000000 5.9449587962 –1.4100330467C2 0.0000000000 5.9449587962 1.4100330467C3 0.0000000000 4.7064763409 –0.7135992462C4 0.0000000000 7.1519697690 –0.6913791040C5 0.0000000000 7.1519697690 0.6913791040C6 0.0000000000 4.7064763409 0.7135992462C7 0.0000000000 3.4842966984 –1.4361053498C8 0.0000000000 3.4842966984 1.4361053498C9 0.0000000000 2.4482656017 2.0753950775C10 0.0000000000 2.4482656017 –2.0753950775C11 0.0000000000 6.0243504772 –2.8316035951C12 0.0000000000 6.2157424677 –4.0258340773C13 0.0000000000 6.0243504772 2.8316035951C14 0.0000000000 6.2157424677 4.0258340773C15 0.0000000000 1.2308200723 2.8084212247C16 0.0000000000 –1.2244438342 4.2327300655C17 0.0000000000 0.0000000000 2.1334826427C18 0.0000000000 1.2244438342 4.2327300655257

C19 0.0000000000 0.0000000000 4.9071111447C20 0.0000000000 –1.2308200723 2.8084212247C21 0.0000000000 1.2308200723 –2.8084212247C22 0.0000000000 –1.2244438342 –4.2327300655C23 0.0000000000 1.2244438342 –4.2327300655C24 0.0000000000 0.0000000000 –2.1334826427C25 0.0000000000 –1.2308200723 –2.8084212247C26 0.0000000000 0.0000000000 –4.9071111447C27 0.0000000000 –2.4482656017 2.0753950775C28 0.0000000000 –3.4842966984 1.4361053498C29 0.0000000000 2.4134336114 5.0151903592C30 0.0000000000 3.3555751919 5.7735963669C31 0.0000000000 –2.4134336114 5.0151903592C32 0.0000000000 –3.3555751919 5.7735963669C33 0.0000000000 2.4134336114 –5.0151903592C34 0.0000000000 3.3555751919 –5.7735963669C35 0.0000000000 –4.7064763409 –0.7135992462C36 0.0000000000 –7.1519697690 0.6913791040C37 0.0000000000 –5.9449587962 –1.4100330467C38 0.0000000000 –4.7064763409 0.7135992462C39 0.0000000000 –5.9449587962 1.4100330467C40 0.0000000000 –7.1519697690 –0.6913791040C41 0.0000000000 –6.0243504772 2.8316035951C42 0.0000000000 –6.2157424677 4.0258340773C43 0.0000000000 –2.4482656017 –2.0753950775C44 0.0000000000 –3.4842966984 –1.4361053498C45 0.0000000000 –2.4134336114 –5.0151903592C46 0.0000000000 –3.3555751919 –5.7735963669C47 0.0000000000 –6.0243504772 –2.8316035951C48 0.0000000000 –6.2157424677 –4.0258340773H1 0.0000000000 8.0856984692 –1.2429588285H2 0.0000000000 8.0856984692 1.2429588285H3 0.0000000000 6.3701544067 –5.0789644667H4 0.0000000000 6.3701544067 5.0789644667H5 0.0000000000 0.0000000000 1.0506309370H6 0.0000000000 0.0000000000 5.9908294781H7 0.0000000000 0.0000000000 –1.0506309370H8 0.0000000000 0.0000000000 –5.9908294781H9 0.0000000000 4.1886234325 6.4364573440H10 0.0000000000 –4.1886234325 6.4364573440H11 0.0000000000 4.1886234325 –6.4364573440H12 0.0000000000 –8.0856984692 –1.2429588285H13 0.0000000000 –8.0856984692 1.2429588285H14 0.0000000000 –6.3701544067 5.0789644667H15 0.0000000000 –4.1886234325 –6.4364573440H16 0.0000000000 –6.3701544067 –5.0789644667258

Calculated positional parameters for the non planar structure of 156:Atom x y zC1 –0.3245961271 –1.3747351375 –5.9585905776C2 0.3245961271 1.3747351375 –5.9585905776C3 –0.1816701840 –0.6880128539 –4.7233364017C4 –0.1518228387 –0.6760334977 –7.1644860953C5 0.1518228387 0.6760334977 –7.1644860953C6 0.1816701840 0.6880128539 –4.7233364017C7 –0.4291223859 –1.3559235193 –3.4959061152C8 0.4291223859 1.3559235193 –3.4959061152C9 0.7199694284 1.8993690062 –2.4475610330C10 –0.7199694284 –1.8993690062 –2.4475610330C11 –0.6184234277 –2.7679550069 –6.0023004320C12 –0.8379804395 –3.9542356902 –6.0928628756C13 0.6184234277 2.7679550069 –6.0023004320C14 0.8379804395 3.9542356902 –6.0928628756C15 1.1307556647 2.4981333285 –1.2268261067C16 2.0486715103 3.5879044924 1.2228804457C17 0.6836641529 1.9854963044 0.0000000000C18 2.0486715103 3.5879044924 –1.2228804457C19 2.4800781466 4.1116337867 0.0000000000C20 1.1307556647 2.4981333285 1.2268261067C21 –1.1307556647 –2.4981333285 –1.2268261067C22 –2.0486715103 –3.5879044924 1.2228804457C23 –2.0486715103 –3.5879044924 –1.2228804457C24 –0.6836641529 –1.9854963044 0.0000000000C25 –1.1307556647 –2.4981333285 1.2268261067C26 –2.4800781466 –4.1116337867 0.0000000000C27 0.7199694284 1.8993690062 2.4475610330C28 0.4291223859 1.3559235193 3.4959061152C29 2.5687806488 4.1324647137 –2.4315966586C30 3.0511777113 4.6097324853 –3.4330383622C31 2.5687806488 4.1324647137 2.4315966586C32 3.0511777113 4.6097324853 3.4330383622C33 –2.5687806488 –4.1324647137 –2.4315966586C34 –3.0511777113 –4.6097324853 –3.4330383622C35 –0.1816701840 –0.6880128539 4.7233364017C36 0.1518228387 0.6760334977 7.1644860953C37 –0.3245961271 –1.3747351375 5.9585905776C38 0.1816701840 0.6880128539 4.7233364017C39 0.3245961271 1.3747351375 5.9585905776C40 –0.1518228387 –0.6760334977 7.1644860953259

C41 0.6184234277 2.7679550069 6.0023004320C42 0.8379804395 3.9542356902 6.0928628756C43 –0.7199694284 –1.8993690062 2.4475610330C44 –0.4291223859 –1.3559235193 3.4959061152C45 –2.5687806488 –4.1324647137 2.4315966586C46 –3.0511777113 –4.6097324853 3.4330383622C47 –0.6184234277 –2.7679550069 6.0023004320C48 –0.8379804395 –3.9542356902 6.0928628756H1 –0.2653900212 –1.2133065580 –8.0998068395H2 0.2653900212 1.2133065580 –8.0998068395H3 –1.0226098201 –5.0023276796 –6.1437670822H4 1.0226098201 5.0023276796 –6.1437670822H5 –0.0187688578 1.1601031974 0.0000000000H6 3.1861670320 4.9339098514 0.0000000000H7 0.0187688578 –1.1601031974 0.0000000000H8 –3.1861670320 –4.9339098514 0.0000000000H9 3.4735006073 5.0077995198 –4.3262399399H10 3.4735006073 5.0077995198 4.3262399399H11 –3.4735006073 –5.0077995198 –4.3262399399H12 –0.2653900212 –1.2133065580 8.0998068395H13 0.2653900212 1.2133065580 8.0998068395H14 1.0226098201 5.0023276796 6.1437670822H15 –3.4735006073 –5.0077995198 4.3262399399H16 –1.0226098201 –5.0023276796 6.1437670822Calculated positional parameters for the planar structure of 191:Atom x y zC1 2.8711963134 5.3815371523 0.0000000000C2 0.1439896360 6.0974099118 0.0000000000C3 1.8831513144 4.3593797614 0.0000000000C4 2.4831389471 6.7311388050 0.0000000000C5 1.1454132895 7.0824683101 0.0000000000C6 0.5020892745 4.7220803233 0.0000000000C7 2.2783022617 2.9972071455 0.0000000000C8 –0.5119250690 3.7274249856 0.0000000000C9 –1.4066823140 2.9011504132 0.0000000000C10 2.6572918029 1.8392794183 0.0000000000C11 4.2649359078 5.0904641976 0.0000000000C12 5.4666432998 4.9524513937 0.0000000000C13 –1.2113145603 6.5343918890 0.0000000000C14 –2.3193846322 7.0194146117 0.0000000000C15 –2.4249882171 1.9090721031 0.0000000000260

C16 –4.4116404484 –0.1210896353 0.0000000000C17 –2.0765539612 0.5494075624 0.0000000000C18 –3.8070874408 2.2533045944 0.0000000000C19 –4.7632031427 1.2319697624 0.0000000000C20 –3.0325787140 –0.4768450424 0.0000000000C21 3.0077346712 0.4639737052 0.0000000000C22 3.6836116788 –2.2331963786 0.0000000000C23 4.3681046180 0.0473573191 0.0000000000C24 1.9542278745 –0.5015561928 0.0000000000C25 2.3175118866 –1.8212987434 0.0000000000C26 4.7170190315 –1.3332671209 0.0000000000C27 –2.6205132837 –1.8371520554 0.0000000000C28 –2.2607858967 –3.0001420461 0.0000000000C29 –4.2710484523 3.5991841646 0.0000000000C30 –4.7700513450 4.7010685247 0.0000000000C31 –5.4527097569 –1.0918637292 0.0000000000C32 –6.3932087652 –1.8523225246 0.0000000000C33 5.4383920854 0.9858245765 0.0000000000C34 6.4186685454 1.6954685247 0.0000000000C35 –0.4790406512 –4.7060500739 0.0000000000C36 –2.2709890818 –6.7900739497 0.0000000000C37 –0.0312860877 –6.0557714646 0.0000000000C38 –1.8194556794 –4.3491705840 0.0000000000C39 –2.7375707951 –5.4667597644 0.0000000000C40 –0.9021157709 –7.1219729783 0.0000000000C41 –4.1470907629 –5.2610973953 0.0000000000C42 –5.3531675713 –5.1634839961 0.0000000000C43 3.2761158501 –3.6665123213 0.0000000000C44 1.3919019855 –5.6063608531 0.0000000000C45 1.8807590806 –3.2521347584 0.0000000000C46 3.7058713861 –4.9640048219 0.0000000000C47 2.7008969929 –5.9979020668 0.0000000000C48 0.9361318104 –4.2246280967 0.0000000000H1 3.2536054766 7.4944750580 0.0000000000H2 0.8491833296 8.1257256127 0.0000000000H3 6.5221940021 4.8149802720 0.0000000000H4 –3.3008641232 7.4312776504 0.0000000000H5 –1.0277010448 0.2831554941 0.0000000000H6 –5.8134269533 1.4997265382 0.0000000000H7 0.9268818217 –0.1605788481 0.0000000000H8 5.7640567418 –1.6156886388 0.0000000000H9 –5.2028887619 5.6737849818 0.0000000000H10 –7.2160147298 –2.5280935644 0.0000000000H11 7.2750350430 2.3279788140 0.0000000000H12 –0.5807676796 –8.1585869141 0.0000000000H13 –3.0134505171 –7.5813951224 0.0000000000261

H14 –6.4137229715 –5.0702556913 0.0000000000H15 4.7588420538 –5.2290576756 0.0000000000H16 2.9962955503 –7.0427896743 0.0000000000Calculated positional parameters for the non planar structure of 191:Atom x y zC1 3.0438399320 5.3172268616 0.5038322060C2 0.3580148273 6.0060401215 –0.0359774031C3 2.1214748683 4.2990076432 0.1388525005C4 2.6122968090 6.6515649874 0.5811379659C5 1.2952963590 6.9909603578 0.3144607597C6 0.7665499679 4.6486876677 –0.1267212412C7 2.5394413416 2.9461194125 0.0487169561C8 –0.1757115457 3.6469614396 –0.4764251487C9 –0.9980761403 2.8045443687 –0.7800483665C10 2.8983540211 1.7845931381 –0.0204495599C11 4.4004905270 5.0143218228 0.8151364588C12 5.5570458941 4.8151610182 1.1091756565C13 –0.9938186340 6.3859435208 –0.2789514027C14 –2.1337012436 6.7460464718 –0.4657352039C15 –1.9194198181 1.7852352220 –1.1383905484C16 –3.6795506715 –0.3105865323 –1.8784010917C17 –1.7252478800 0.4800393534 –0.6669700901C18 –3.0270691318 2.0465600078 –1.9942834842C19 –3.8855583888 0.9955093327 –2.3369818819C20 –2.5681491842 –0.5786125140 –1.0289336858C21 3.2418405294 0.4074083637 –0.0488396759C22 3.9199632175 –2.2871221514 0.0428834942C23 4.6030569334 –0.0077965414 –0.0480039463C24 2.1882558202 –0.5567686263 –0.0462859849C25 2.5544912703 –1.8757197814 –0.0044272652C26 4.9537956838 –1.3865788935 0.0069852575C27 –2.2723624665 –1.8985154910 –0.5951923469C28 –1.9765037997 –3.0355229078 –0.2806528122C29 –3.2641932347 3.3462319517 –2.5270649051C30 –3.4803473783 4.4361968563 –3.0056283955C31 –4.5657012341 –1.3480723028 –2.2875391904C32 –5.3245079633 –2.2165112810 –2.6534917931C33 5.6581321864 0.9464450749 –0.1154214637C34 6.5971658377 1.7055115845 –0.2005432561C35 –0.2505361073 –4.7352405447 0.1330418550C36 –2.0824715944 –6.7749803809 0.3031962600262

C37 0.1753868100 –6.0804206944 0.3076182653C38 –1.5789570165 –4.3681794726 –0.0004003920C39 –2.5221805185 –5.4574473169 0.1072858866C40 –0.7189021721 –7.1241262048 0.3984279162C41 –3.9213807132 –5.2010841624 0.0206835520C42 –5.1129360680 –4.9963132778 –0.0388592665C43 3.5075829840 –3.7187404462 0.1384247514C44 1.6071447210 –5.6460189569 0.2896241173C45 2.1152817664 –3.3028939079 0.0733841225C46 3.9259915475 –5.0134672479 0.2724429752C47 2.9144370689 –6.0386906491 0.3561116270C48 1.1663129157 –4.2688814564 0.1300872110H1 3.3299302278 7.4156274626 0.8599672233H2 0.9694188101 8.0234040491 0.3805422086H3 6.5685085359 4.6138219094 1.3752477745H4 –3.1460342054 7.0364619992 –0.6270031553H5 –0.8928537237 0.2833079978 –0.0026247514H6 –4.7262243507 1.1959542631 –2.9914801289H7 1.1598364599 –0.2188382182 –0.0683807212H8 6.0011054583 –1.6680881957 0.0239061989H9 –3.6493718884 5.4000565363 –3.4270283714H10 –5.9782167558 –2.9947389725 –2.9733673921H11 7.4084939593 2.3898799054 –0.2890768666H12 –0.4203325756 –8.1590450665 0.5316837423H13 –2.8380558432 –7.5505566606 0.3757255898H14 –6.1588929400 –4.7985552367 –0.0848746411H15 4.9764449905 –5.2834722647 0.3238187583H16 3.2054533978 –7.0784161743 0.4713502702Calculated positional parameters for the planar structure of 192:Atom x y zC1 –0.8136479177 5.9906811026 0.0000000000C2 –3.4226643095 5.0649522227 0.0000000000C3 –1.0842381701 4.5942989444 0.0000000000C4 –1.8123679356 6.9384785426 0.0000000000C5 –3.1285257033 6.4366406201 0.0000000000C6 –2.3709316796 4.0711676539 0.0000000000C7 –2.6481092760 2.6799063827 0.0000000000C8 –2.8806713238 1.4840520964 0.0000000000C9 –4.7929590803 4.6753311957 0.0000000000C10 –5.9720241706 4.4031055281 0.0000000000C11 –3.0549184727 0.0751533737 0.0000000000C12 –3.3732699383 –2.6873666128 0.0000000000263

C13 –1.8866055576 –0.7456062659 0.0000000000C14 –4.3494825920 –0.5135874079 0.0000000000C15 –4.5152159072 –1.9281128434 0.0000000000C16 –2.0727741130 –2.1013922308 0.0000000000C17 2.0727741130 2.1013922308 0.0000000000C18 4.3494825920 0.5135874079 0.0000000000C19 3.3732699383 2.6873666128 0.0000000000C20 1.8866055576 0.7456062659 0.0000000000C21 3.0549184727 –0.0751533737 0.0000000000C22 4.5152159072 1.9281128434 0.0000000000C23 2.8806713238 –1.4840520964 0.0000000000C24 2.6481092760 –2.6799063827 0.0000000000C25 –5.5245147005 0.2898252024 0.0000000000C26 –6.5646268783 0.9082607044 0.0000000000C27 5.5245147005 –0.2898252024 0.0000000000C28 6.5646268783 –0.9082607044 0.0000000000C29 2.3709316796 –4.0711676539 0.0000000000C30 1.8123679356 –6.9384785426 0.0000000000C31 3.4226643095 –5.0649522227 0.0000000000C32 1.0842381701 –4.5942989444 0.0000000000C33 0.8136479177 –5.9906811026 0.0000000000C34 3.1285257033 –6.4366406201 0.0000000000C35 4.7929590803 –4.6753311957 0.0000000000C36 5.9720241706 –4.4031055281 0.0000000000C37 0.6554712990 5.7299240157 0.0000000000C38 2.7800211778 4.0555200394 0.0000000000C39 1.9017392742 6.2899482176 0.0000000000C40 0.3838520968 4.3002826465 0.0000000000C41 1.4503232806 3.4616941766 0.0000000000C42 3.0347521443 5.3981938333 0.0000000000C43 –0.6554712990 –5.7299240157 0.0000000000C44 –2.7800211778 –4.0555200394 0.0000000000C45 –0.3838520968 –4.3002826465 0.0000000000C46 –1.9017392742 –6.2899482176 0.0000000000C47 –3.0347521443 –5.3981938333 0.0000000000C48 –1.4503232806 –3.4616941766 0.0000000000H1 –1.6239400570 8.0073058974 0.0000000000H2 –3.9651843819 7.1277266413 0.0000000000H3 –7.0080026891 4.1574556985 0.0000000000H4 –0.9134758470 –0.2739515473 0.0000000000H5 –5.5165967921 –2.3446938745 0.0000000000H6 0.9134758470 0.2739515473 0.0000000000H7 5.5165967921 2.3446938745 0.0000000000H8 –7.4758573519 1.4593392966 0.0000000000H9 7.4758573519 –1.4593392966 0.0000000000H10 3.9651843819 –7.1277266413 0.0000000000264

H11 1.6239400570 –8.0073058974 0.0000000000H12 7.0080026891 –4.1574556985 0.0000000000H13 2.0565252047 7.3647717636 0.0000000000H14 4.0435012685 5.8001155537 0.0000000000H15 –2.0565252047 –7.3647717636 0.0000000000H16 –4.0435012685 –5.8001155537 0.0000000000Calculated positional parameters for the non planar structure of 192:Atom x y zC1 0.0888459014 6.1284891366 0.6897145792C2 –2.3274962291 5.4293222368 1.8485452784C3 –0.2986336905 4.7635855986 0.7866286668C4 –0.6989114519 7.1551985747 1.1599180766C5 –1.9188902772 6.7678065621 1.7488610480C6 –1.5037513466 4.3539465592 1.3405428477C7 –1.9160114319 2.9980398054 1.3961431100C8 –2.2784519102 1.8352255720 1.4150048368C9 –3.5750453290 5.1521773424 2.4784774395C10 –4.6335529568 4.9683551222 3.0359557840C11 –2.6161369239 0.4562132299 1.4007473387C12 –3.2537370596 –2.2514342311 1.3741775255C13 –1.6219691948 –0.4736507985 0.9713781613C14 –3.9055627304 0.0025317226 1.7943967609C15 –4.2329653048 –1.3838751609 1.7867757769C16 –1.9651700589 –1.7982659308 0.9624113592C17 2.2728247892 2.0051361919 –0.5974835778C18 4.1425534837 0.2146452741 –1.5968909523C19 3.4850054475 2.4692695891 –1.1893107217C20 1.9829742444 0.6729955500 –0.4808461843C21 2.9426143970 –0.2518427182 –0.9917769378C22 4.4251758915 1.6074742218 –1.6944998470C23 2.6573536308 –1.6383476507 –0.8821926922C24 2.3393753588 –2.8075029453 –0.7562929545C25 –4.9149135341 0.9222621843 2.1971108812C26 –5.8214635081 1.6493860363 2.5353319172C27 5.0944020456 –0.6968386320 –2.1355968293C28 5.9366570514 –1.4149171039 –2.6255021891C29 1.9527797883 –4.1671554073 –0.6408814936C30 1.1394394073 –6.9672420528 –0.4824066330C31 2.8436591258 –5.2519311932 –0.9904490731C32 0.6978965280 –4.5697648441 –0.2050754913C33 0.2988165449 –5.9330736397 –0.1365885369265

C34 2.4287236108 –6.5895173664 –0.9070186687C35 4.1772496108 –4.9865196603 –1.4158817544C36 5.3231218509 –4.8148677721 –1.7658702483C37 1.3668789686 5.7413568030 0.0223433366C38 3.0903176764 3.8857019494 –0.9335105477C39 2.5334819831 6.1871298057 –0.5316818725C40 0.9785034776 4.3435233495 0.1306157226C41 1.8480191616 3.4145387696 –0.3379147818C42 3.4511436389 5.1992701303 –1.0434652097C43 –1.0530017546 –5.5356532049 0.3568237676C44 –2.8573550277 –3.6682640629 1.1226716089C45 –0.6438363096 –4.1407665606 0.2983905957C46 –2.2821243147 –5.9724266852 0.7632224477C47 –3.2449175266 –4.9781244841 1.1687920729C48 –1.5446721577 –3.2071816995 0.6930731500H1 –0.4201658238 8.2021394350 1.0956940721H2 –2.5846305198 7.5257707739 2.1487815094H3 –5.5589903091 4.7938863242 3.5328574867H4 –0.6496146782 –0.1045024379 0.6751682573H5 –5.2236162837 –1.6963311969 2.0987531189H6 1.0776145549 0.2942075573 –0.0265995460H7 5.3523850258 1.9291321246 –2.1561859347H8 –6.6134530398 2.3010282505 2.8217753091H9 6.6654704449 –2.0577188562 –3.0609594699H10 3.1462396579 –7.3546488828 –1.1851830784H11 0.8531122446 –8.0130925106 –0.4365479674H12 6.3325375094 –4.6520710676 –2.0631782499H13 2.7830998153 7.2421729639 –0.5925019794H14 4.3899715041 5.5105293601 –1.4915612089H15 –2.5458017265 –7.0254323554 0.7905941505H16 –4.2336827092 –5.2823659526 1.4987729371Calculated positional parameters for the planar structure of 193:Atom x y zC1 0.0000000000 5.8430029800 –1.5252391965C2 0.0000000000 5.9759994888 1.2443807100C3 0.0000000000 4.6557024572 –0.7398399064C4 0.0000000000 7.0987879797 –0.9586608113C5 0.0000000000 7.1332274077 0.4490942109C6 0.0000000000 4.6587122259 0.6489946065C7 0.0000000000 3.4705769611 1.4284677156C8 0.0000000000 2.4452697948 2.0860869823266

C9 0.0000000000 6.1435246687 2.6591621138C10 0.0000000000 6.3574564345 3.8502459933C11 0.0000000000 1.2324668305 2.8301734790C12 0.0000000000 –1.2261842897 4.2545381712C13 0.0000000000 0.0000000000 2.1600834089C14 0.0000000000 1.2261842897 4.2545381712C15 0.0000000000 0.0000000000 4.9287041858C16 0.0000000000 –1.2324668305 2.8301734790C17 0.0000000000 1.1516057756 –2.6502915473C18 0.0000000000 –1.1570894335 –4.0770411097C19 0.0000000000 1.1570894335 –4.0770411097C20 0.0000000000 0.0000000000 –1.8731594791C21 0.0000000000 –1.1516057756 –2.6502915473C22 0.0000000000 0.0000000000 –4.8561614675C23 0.0000000000 –2.4452697948 2.0860869823C24 0.0000000000 –3.4705769611 1.4284677156C25 0.0000000000 2.4249361447 5.0224306384C26 0.0000000000 3.4000909275 5.7378993808C27 0.0000000000 –2.4249361447 5.0224306384C28 0.0000000000 –3.4000909275 5.7378993808C29 0.0000000000 –4.6557024572 –0.7398399064C30 0.0000000000 –7.1332274077 0.4490942109C31 0.0000000000 –5.8430029800 –1.5252391965C32 0.0000000000 –4.6587122259 0.6489946065C33 0.0000000000 –5.9759994888 1.2443807100C34 0.0000000000 –7.0987879797 –0.9586608113C35 0.0000000000 –6.1435246687 2.6591621138C36 0.0000000000 –6.3574564345 3.8502459933C37 0.0000000000 5.0388773588 –2.7828503425C38 0.0000000000 2.6543382062 –4.0839518892C39 0.0000000000 5.0608594092 –4.1469534028C40 0.0000000000 3.8234827848 –1.9764628450C41 0.0000000000 2.6382204133 –2.6273448866C42 0.0000000000 3.7898795510 –4.8412073638C43 0.0000000000 –5.0388773588 –2.7828503425C44 0.0000000000 –2.6543382062 –4.0839518892C45 0.0000000000 –5.0608594092 –4.1469534028C46 0.0000000000 –3.8234827848 –1.9764628450C47 0.0000000000 –2.6382204133 –2.6273448866C48 0.0000000000 –3.7898795510 –4.8412073638H1 0.0000000000 8.0171925630 –1.5370160825H2 0.0000000000 8.0902654477 0.9605934245H3 0.0000000000 6.5389428787 4.8993268569H4 0.0000000000 0.0000000000 1.0794435370H5 0.0000000000 0.0000000000 6.0126249960H6 0.0000000000 0.0000000000 –0.7919042756267

H7 0.0000000000 0.0000000000 –5.9414399327H8 0.0000000000 4.2624351160 6.3626187568H9 0.0000000000 –4.2624351160 6.3626187568H10 0.0000000000 –8.0171925630 –1.5370160825H11 0.0000000000 –8.0902654477 0.9605934245H12 0.0000000000 –6.5389428787 4.8993268569H13 0.0000000000 5.9857583821 –4.7160490687H14 0.0000000000 3.7686486876 –5.9269406817H15 0.0000000000 –5.9857583821 –4.7160490687H16 0.0000000000 –3.7686486876 –5.9269406817Calculated positional parameters for the non planar structure of 193:Atom x y zC1 0.5356749502 –1.4133961270 5.8440951182C2 0.2289541362 1.3441561500 5.9655574382C3 0.3393615094 –0.6480696593 4.6609955776C4 0.5802343260 –0.8293566712 7.0916776250C5 0.4241579105 0.5715077268 7.1208074585C6 0.1729727183 0.7278706347 4.6606551997C7 –0.0581065196 1.4687114412 3.4724037429C8 –0.2948140789 2.0684824998 2.4406698054C9 0.1021851513 2.7575108478 6.0969910739C10 0.0124175493 3.9574044243 6.2290518994C11 –0.6317062317 2.7283469190 1.2280916937C12 –1.4097474369 3.9215183484 –1.2246142586C13 –0.2436173357 2.1752345060 0.0000000000C14 –1.4097474369 3.9215183484 1.2246142586C15 –1.7707556208 4.4950336619 0.0000000000C16 –0.6317062317 2.7283469190 –1.2280916937C17 0.3583384360 –2.5531847313 1.1528782401C18 0.5762112903 –3.9636204741 –1.1564709547C19 0.5762112903 –3.9636204741 1.1564709547C20 0.2297806617 –1.7847960764 0.0000000000C21 0.3583384360 –2.5531847313 –1.1528782401C22 0.6929240090 –4.7336319822 0.0000000000C23 –0.2948140789 2.0684824998 –2.4406698054C24 –0.0581065196 1.4687114412 –3.4724037429C25 –1.8490037617 4.5246651211 2.4378695440C26 –2.2460731417 5.0491480116 3.4532545810C27 –1.8490037617 4.5246651211 –2.4378695440C28 –2.2460731417 5.0491480116 –3.4532545810C29 0.3393615094 –0.6480696593 –4.6609955776C30 0.4241579105 0.5715077268 –7.1208074585268

C31 0.5356749502 –1.4133961270 –5.8440951182C32 0.1729727183 0.7278706347 –4.6606551997C33 0.2289541362 1.3441561500 –5.9655574382C34 0.5802343260 –0.8293566712 –7.0916776250C35 0.1021851513 2.7575108478 –6.0969910739C36 0.0124175493 3.9574044243 –6.2290518994C37 0.6199632293 –2.6701984715 5.0388871366C38 0.6320660449 –3.9678706364 2.6515478029C39 0.8100112704 –4.0211687636 5.0529644371C40 0.4173497800 –1.8799910477 3.8291227174C41 0.4180829695 –2.5278242997 2.6416026538C42 0.8190079680 –4.7122951867 3.7806099368C43 0.6199632293 –2.6701984715 –5.0388871366C44 0.6320660449 –3.9678706364 –2.6515478029C45 0.8100112704 –4.0211687636 –5.0529644371C46 0.4173497800 –1.8799910477 –3.8291227174C47 0.4180829695 –2.5278242997 –2.6416026538C48 0.8190079680 –4.7122951867 –3.7806099368H1 0.7279187536 –1.3890130054 8.0098201873H2 0.4568273013 1.0923567394 8.0722726456H3 –0.0580860336 5.0158742273 6.3271902489H4 0.3713288356 1.2840014063 0.0000000000H5 –2.3673051051 5.4002134479 0.0000000000H6 0.0523966689 –0.7168329193 0.0000000000H7 0.8695605413 –5.8044132381 0.0000000000H8 –2.5952606019 5.4921416604 4.3570482049H9 –2.5952606019 5.4921416604 –4.3570482049H10 0.7279187536 –1.3890130054 –8.0098201873H11 0.4568273013 1.0923567394 –8.0722726456H12 –0.0580860336 5.0158742273 –6.3271902489H13 0.9626373030 –4.5803247606 5.9712371339H14 0.9823557410 –5.7854410927 3.7518467551H15 0.9626373030 –4.5803247606 –5.9712371339H16 0.9823557410 –5.7854410927 –3.7518467551Calculated positional parameters for the planar structure of 194:Atom x y zC1 0.0000000000 –1.3696624865 5.8159966245C2 0.0000000000 1.3696624865 5.8159966245C3 0.0000000000 –0.6769273629 4.5463695612C4 0.0000000000 –0.7197169631 7.0276400390C5 0.0000000000 0.7197169631 7.0276400390C6 0.0000000000 0.6769273629 4.5463695612269

C7 0.0000000000 2.7603818264 1.1847902765C8 0.0000000000 4.2806285674 –1.1257214087C9 0.0000000000 2.0812298642 –0.0012063555C10 0.0000000000 4.1857322714 1.2602277519C11 0.0000000000 4.9614187870 0.1297172874C12 0.0000000000 2.8599837212 –1.1987847791C13 0.0000000000 –2.7603818264 1.1847902765C14 0.0000000000 –4.2806285674 –1.1257214087C15 0.0000000000 –4.1857322714 1.2602277519C16 0.0000000000 –2.0812298642 –0.0012063555C17 0.0000000000 –2.8599837212 –1.1987847791C18 0.0000000000 –4.9614187870 0.1297172874C19 0.0000000000 –2.1613276724 –2.4353313922C20 0.0000000000 2.1613276724 –2.4353313922C21 0.0000000000 1.4575651756 –3.4311698232C22 0.0000000000 –1.4575651756 –3.4311698232C23 0.0000000000 5.0878849051 –2.2983657957C24 0.0000000000 5.8606943976 –3.2298682592C25 0.0000000000 –5.0878849051 –2.2983657957C26 0.0000000000 –5.8606943976 –3.2298682592C27 0.0000000000 –0.7144955156 –4.6404635726C28 0.0000000000 0.6918280290 –7.0893945830C29 0.0000000000 –1.4089466154 –5.8824550538C30 0.0000000000 0.7144955156 –4.6404635726C31 0.0000000000 1.4089466154 –5.8824550538C32 0.0000000000 –0.6918280290 –7.0893945830C33 0.0000000000 2.8312058597 –5.9536040122C34 0.0000000000 4.0295493097 –6.1183560570C35 0.0000000000 –2.8312058597 –5.9536040122C36 0.0000000000 –4.0295493097 –6.1183560570C37 0.0000000000 –2.6836024062 5.0841446331C38 0.0000000000 –4.1198727887 2.7600356499C39 0.0000000000 –4.0527178788 5.1719158503C40 0.0000000000 –1.9650624431 3.8228573458C41 0.0000000000 –2.6752984414 2.6711046425C42 0.0000000000 –4.8106187844 3.9447229481C43 0.0000000000 2.6836024062 5.0841446331C44 0.0000000000 4.1198727887 2.7600356499C45 0.0000000000 4.0527178788 5.1719158503C46 0.0000000000 1.9650624431 3.8228573458C47 0.0000000000 2.6752984414 2.6711046425C48 0.0000000000 4.8106187844 3.9447229481H1 0.0000000000 –1.2545347832 7.9729898032H2 0.0000000000 1.2545347832 7.9729898032H3 0.0000000000 1.0012480122 –0.0750644879H4 0.0000000000 6.0459559064 0.1397923398270

H5 0.0000000000 –1.0012480122 –0.0750644879H6 0.0000000000 –6.0459559064 0.1397923398H7 0.0000000000 6.5339533895 –4.0547805157H8 0.0000000000 –6.5339533895 –4.0547805157H9 0.0000000000 –1.2434871437 –8.0232070412H10 0.0000000000 1.2434871437 –8.0232070412H11 0.0000000000 5.0864427774 –6.2446191172H12 0.0000000000 –5.0864427774 –6.2446191172H13 0.0000000000 –4.5753455106 6.1239414018H14 0.0000000000 –5.8959382425 3.9847084762H15 0.0000000000 4.5753455106 6.1239414018H16 0.0000000000 5.8959382425 3.9847084762Calculated positional parameters for the non planar structure of 194:Atom x y zC1 0.5932254918 5.7775545854 –1.3698624762C2 0.5932254918 5.7775545854 1.3698624762C3 0.4112288747 4.5207626356 –0.6772536870C4 0.7552704555 6.9782056486 –0.7195154095C5 0.7552704555 6.9782056486 0.7195154095C6 0.4112288747 4.5207626356 0.6772536870C7 0.1729429935 1.1656478665 2.7550096293C8 0.1638252780 –1.1593498588 4.2518660498C9 –0.0036338284 –0.0058773651 2.0739845042C10 0.3206443229 1.2221160023 4.1733953118C11 0.3287236484 0.0824627611 4.9368673535C12 –0.0186788452 –1.2090265563 2.8419476243C13 0.1729429935 1.1656478665 –2.7550096293C14 0.1638252780 –1.1593498588 –4.2518660498C15 0.3206443229 1.2221160023 –4.1733953118C16 –0.0036338284 –0.0058773651 –2.0739845042C17 –0.0186788452 –1.2090265563 –2.8419476243C18 0.3287236484 0.0824627611 –4.9368673535C19 –0.2336468289 –2.4283308346 –2.1465326241C20 –0.2336468289 –2.4283308346 2.1465326241C21 –0.4579835413 –3.4039625846 1.4511355470C22 –0.4579835413 –3.4039625846 –1.4511355470C23 0.2161879220 –2.3520134853 5.0277923203C24 0.3040765135 –3.3215305338 5.7472723521C25 0.2161879220 –2.3520134853 –5.0277923203C26 0.3040765135 –3.3215305338 –5.7472723521C27 –0.7514407799 –4.5806983881 –0.7138011322271

C28 –1.3715975253 –6.9478101712 0.6923369219C29 –1.0736138040 –5.7790541278 –1.4099823023C30 –0.7514407799 –4.5806983881 0.7138011322C31 –1.0736138040 –5.7790541278 1.4099823023C32 –1.3715975253 –6.9478101712 –0.6923369219C33 –1.1307834069 –5.8254256449 2.8324402008C34 –1.2224989391 –5.9358525522 4.0336804208C35 –1.1307834069 –5.8254256449 –2.8324402008C36 –1.2224989391 –5.9358525522 –4.0336804208C37 0.5644790473 5.0439832274 –2.6825071416C38 0.4378340888 2.7185637547 –4.1134017017C39 0.6811544141 5.1183015446 –4.0474886205C40 0.3756271202 3.7961526093 –1.9654482719C41 0.3018818192 2.6457639137 –2.6741988848C42 0.6163093227 3.8906791980 –4.8022086014C43 0.5644790473 5.0439832274 2.6825071416C44 0.4378340888 2.7185637547 4.1134017017C45 0.6811544141 5.1183015446 4.0474886205C46 0.3756271202 3.7961526093 1.9654482719C47 0.3018818192 2.6457639137 2.6741988848C48 0.6163093227 3.8906791980 4.8022086014H1 0.8981984369 7.9127345481 –1.2540241720H2 0.8981984369 7.9127345481 1.2540241720H3 –0.1332141653 –0.0631884533 1.0008267059H4 0.4576441173 0.0767096113 6.0137075167H5 –0.1332141653 –0.0631884533 –1.0008267059H6 0.4576441173 0.0767096113 –6.0137075167H7 0.3923739987 –4.1860391603 6.3630014646H8 0.3923739987 –4.1860391603 –6.3630014646H9 –1.6127361907 –7.8506348361 –1.2427926472H10 –1.6127361907 –7.8506348361 1.2427926472H11 –1.3072415065 –6.0030176207 5.0929371862H12 –1.3072415065 –6.0030176207 –5.0929371862H13 0.8302442505 6.0592692739 –4.5686682993H14 0.7184184366 3.9200761632 –5.8829462072H15 0.8302442505 6.0592692739 4.5686682993H16 0.7184184366 3.9200761632 5.8829462072Calculated positional parameters for the planar structure of 195:Atom x y zC1 0.8836671466 5.9290591622 0.0000000000C2 3.4774461520 4.9589371166 0.0000000000C3 1.1305946529 4.5256716396 0.0000000000272

C4 1.8996756690 6.8593324486 0.0000000000C5 3.2064450430 6.3356803144 0.0000000000C6 2.4112565450 3.9809331424 0.0000000000C7 2.6845395830 2.5869633996 0.0000000000C8 2.9457490159 1.3957926327 0.0000000000C9 4.8409564734 4.5460555593 0.0000000000C10 6.0133123058 4.2462055748 0.0000000000C11 3.1059162873 –0.0171614826 0.0000000000C12 3.3505792884 –2.8026495017 0.0000000000C13 1.9202907069 –0.8121516851 0.0000000000C14 4.3820473958 –0.6451824038 0.0000000000C15 4.5100700968 –2.0682631042 0.0000000000C16 2.0716448866 –2.1703072321 0.0000000000C17 –2.0350276033 2.0941973689 0.0000000000C18 –4.2661667412 0.5324102284 0.0000000000C19 –3.3422671061 2.6628333253 0.0000000000C20 –1.7788960732 0.7306582931 0.0000000000C21 –2.9481263978 –0.0138360315 0.0000000000C22 –4.5188683362 1.9059852584 0.0000000000C23 5.5790223311 0.1258060620 0.0000000000C24 6.6320230468 0.7226114794 0.0000000000C25 –2.4249295048 –3.8978746973 0.0000000000C26 –2.1246915950 –6.7254817413 0.0000000000C27 –3.5671602097 –4.7861544546 0.0000000000C28 –1.1797408100 –4.4326663056 0.0000000000C29 –1.0460570147 –5.8707607999 0.0000000000C30 –3.4467996167 –6.1571919417 0.0000000000C31 –0.5900729379 5.6977887221 0.0000000000C32 –2.7470493142 4.0412584721 0.0000000000C33 –1.8301972820 6.2670996708 0.0000000000C34 –0.3402542349 4.2607484084 0.0000000000C35 –1.4178553645 3.4427766086 0.0000000000C36 –2.9805675349 5.3858195106 0.0000000000C37 0.4515115098 –5.7189226539 0.0000000000C38 2.6941788838 –4.1546103317 0.0000000000C39 0.2915338394 –4.2756565974 0.0000000000C40 1.6739521905 –6.3417343961 0.0000000000C41 2.8574295423 –5.5160497194 0.0000000000C42 1.4019500959 –3.5006442237 0.0000000000C43 –4.4825139138 –3.5888612466 0.0000000000C44 –4.8446153753 –0.8647020855 0.0000000000C45 –5.7641187041 –3.1040012011 0.0000000000C46 –3.3140106457 –2.7235556983 0.0000000000C47 –3.4944364702 –1.3868969011 0.0000000000C48 –5.9549424628 –1.6665810716 0.0000000000H1 1.7292912200 7.9312432041 0.0000000000273

H2 4.0548517825 7.0123137479 0.0000000000H3 7.0430486157 3.9752320391 0.0000000000H4 0.9591533221 –0.3180604104 0.0000000000H5 5.5024077269 –2.5063264223 0.0000000000H6 –0.7876046024 0.2994260875 0.0000000000H7 –5.5140442905 2.3393800978 0.0000000000H8 7.5563458217 1.2517289270 0.0000000000H9 –4.3106537558 –6.8158075194 0.0000000000H10 –2.0082894872 –7.8055068472 0.0000000000H11 –1.9770615809 7.3431930637 0.0000000000H12 –3.9817235893 5.8066350190 0.0000000000H13 1.7764610098 –7.4230442560 0.0000000000H14 3.8374826076 –5.9842505851 0.0000000000H15 –6.6344941026 –3.7538881683 0.0000000000H16 –6.9644962531 –1.2656683060 0.0000000000Calculated positional parameters for the non planar structure of 195:Atom x y zC1 0.9170846128 5.9025314297 –0.3107939631C2 3.4713977072 4.9373058949 0.1554948180C3 1.1448308933 4.5059197285 –0.1480452280C4 1.9334793752 6.8292633612 –0.2399313303C5 3.2200255118 6.3083464545 –0.0040657750C6 2.4027027212 3.9647339136 0.0937354551C7 2.6489483986 2.5775562696 0.2712792217C8 2.8828225611 1.3931328526 0.4429701096C9 4.8180667784 4.5190991233 0.3592923282C10 5.9774009118 4.2055830372 0.5099727436C11 3.0214433331 –0.0109628907 0.6213051390C12 3.2225031706 –2.7737599938 0.9987371970C13 1.8903935759 –0.8288682515 0.3221685596C14 4.2213692282 –0.6041928887 1.1038889522C15 4.3302862133 –2.0166271075 1.2883168899C16 2.0134229452 –2.1733779849 0.5362218327C17 –1.9860749262 2.0614992830 –0.5106663851C18 –4.1737729933 0.4826541338 –0.8796981561C19 –3.2645603352 2.6178796069 –0.8101447035C20 –1.7397760793 0.7023339525 –0.3748876800C21 –2.8843594149 –0.0523264240 –0.5831581724C22 –4.4184747746 1.8517320859 –1.0049509747C23 5.3480792818 0.2003670857 1.4387430689C24 6.3296786049 0.8336569578 1.7566880283C25 –2.3902701393 –3.9306127735 –0.2735728445274

C26 –2.1434894254 –6.7392409418 0.0951607242C27 –3.5223617406 –4.8203517141 –0.4127060584C28 –1.1769168606 –4.4570760655 0.0213823007C29 –1.0726843689 –5.8839076374 0.2196170923C30 –3.4268468996 –6.1825594700 –0.2415060499C31 –0.5397971982 5.6658458071 –0.5303435666C32 –2.6742677485 3.9984124057 –0.7875237790C33 –1.7542607434 6.2238245560 –0.8042022066C34 –0.3078129886 4.2359345516 –0.3625848082C35 –1.3736695740 3.4124969946 –0.4876536449C36 –2.8918862586 5.3368018848 –0.9424364364C37 0.3849794477 –5.7174152305 0.5570270802C38 2.5761608860 –4.1303695044 0.9596578527C39 0.2589468009 –4.2882460990 0.3337333614C40 1.5502303371 –6.3151926829 0.9652397924C41 2.7045892060 –5.4768733790 1.1833053767C42 1.3490798305 –3.5053014322 0.5115447765C43 –4.4067070480 –3.6322072793 –0.6880413463C44 –4.7454441369 –0.9157902612 –0.9190852416C45 –5.6628047800 –3.1552313882 –0.9553299769C46 –3.2516577090 –2.7631187797 –0.5291765588C47 –3.4231130484 –1.4287318520 –0.6284061332C48 –5.8404256977 –1.7219826830 –1.0822210828H1 1.7794001321 7.8966683864 –0.3610863309H2 4.0681727978 6.9827091963 0.0544115336H3 6.9940758581 3.9136794603 0.6332017526H4 0.9919962265 –0.3635748392 –0.0596701337H5 5.2645482198 –2.4280556989 1.6549264816H6 –0.7741419601 0.2827077354 –0.1279228411H7 –5.3917676548 2.2753209102 –1.2314733681H8 7.1818617574 1.4049969580 2.0417644237H9 –4.2847166707 –6.8413416212 –0.3399255702H10 –2.0511455246 –7.8100926596 0.2511695818H11 –1.8896357313 7.2942205787 –0.9276922596H12 –3.8707523308 5.7486902800 –1.1693285910H13 1.6262318284 –7.3844057545 1.1395927393H14 3.6341358485 –5.9239638697 1.5231756968H15 –6.5234258543 –3.8077895990 –1.0697562150H16 –6.8295511739 –1.3268599363 –1.2948424372275

6.5 Experiments Related to Chapter 51,1'-(1,2-Ethynediyl)bis[2-bromo-6-iodo]benzene (210):IBrBrIA solution of 2,2’,6,6’-tetrabromotolane (209) 202 (100 mg, 0.20 mmol) in ether(60 mL) was cooled to –45 °C, and BuLi (0.28 mL of 1.6 M solution in hexane, 0.45mmol) was added via syringe. The dark brown solution was stirred at –45 °C for 1 h.After that time, an ethereal solution (10 mL) of iodine (178 mg, 0.70 mmol) was addeddropwise via syringe. The color of the solution lightened gradually with addition ofiodine. The mixture was left to warm to 23 °C overnight, and was then extracted withether (2 x 50 mL) and washed with aq. Na 2 S 2 O 3 and brine. Drying over MgSO 4 , followedby removal of solvent in vacuo, gave the crude 210 as yellow solid. Afterrecrystallization (CHCl 3 /MeOH), the product was obtained as off-white needles, mp 187–190 °C (90 mg, 75%). MS (EI, 70 eV) m/z (rel intensity) 588 (M + , 72), 382 (18), 380(18), 334 (15), 174 (100), 74 (14). 1 H NMR (400 MHz, CDCl 3 ) δ 7.85 (dd, 3 J 1 = 7.9 Hz,4 J 2 = 0.9 Hz, 2H), 7.62 (dd, 3 J 1 = 8.0 Hz, 4 J 2 = 0.9 Hz, 2H), 6.87 (t, 3 J = 8.0 Hz, 2H). 13 CNMR (125 MHz, CDCl 3 ) δ 138.10, 132.43, 130.59, 130.56, 125.94, 101.22, 97.12. HR-MS Calcd for C 14 H 6 Br 2 I 2 : 587.6905. Found: 587.6892. Anal. Calcd for C 14 H 6 Br 2 I 2 : C,28.61; H, 1.03. Found: C, 28.90; H, 0.97.276

1,1'-(1,2-Ethynediyl)bis[2-bromo-6-({dimethylthexylsilyl}ethynyl)]benzene (211):DMTSBrBrDMTSA solution of 210 (114 mg, 0.19 mmol), [Pd(PPh 3 ) 2 Cl 2 ] (10.0 mg, 0.015 mmol),and CuI (3.0 mg, 0.015 mmol) in triethylamine (25 mL) was degassed thoroughly.DMTSA 209 (372 mg, 2.21 mmol) was injected through a septum and the mixture stirred at23 °C for 20 h. Solvent was removed in vacuo and the resulting crude product subjectedto sublimation (200 °C, 0.5 Torr), which removed DMTS–≡–≡–DMTS side product andyielded pure 211 as a yellow oil (69 mg, 52%). IR (NaCl film): ~ ν = 2959, 2865, 2164,1544, 1459, 1442, 1249, 1130, 880, 838, 815, 731, 681 cm –1 . MS (EI, 70 eV) m/z (relintensity) 668 (M + , 1.5), 584 (2), 531 (1), 499 (60), 73 (100). 1 H NMR (300 MHz,CDCl 3 ) δ 7.56 (dd, 3 J 1 = 8.1 Hz, 4 J 2 = 1.1 Hz, 2H), 7.44 (dd, 3 J 1 = 7.8 Hz, 4 J 2 = 1.1 Hz,2H), 7.11 (t, 3 J = 7.9 Hz, 2H), 1.62 (sept, 3 J = 6.9 Hz, 2H), 0.80 (s, 12H), 0.77 (d, 3 J = 6.9Hz, 12H), 0.14 (s, 12H). 13 C NMR (100 MHz, CDCl 3 ) δ 131.98, 130.85, 128.70, 128.20,127.63, 125.60, 103.19, 99.97, 94.72, 34.41, 23.27, 20.51, 18.51, –2.52. HR-MS Calcdfor C 34 H 44 Br 2 Si 2 : 668.1328. Found: 668.1311.277

1,1'-(1,2-Ethynediyl)bis[2-({dimethylthexylsilyl}ethynyl)-6-iodo]benzene (212):DMTSIIDMTSA solution of 211 (50 mg, 0.07 mmol) in ether (20 mL) was cooled to –45 °C, andBuLi (0.18 mL of 1.6 M solution in hexane, 0.29 mmol) was added via syringe. Thebrownish solution was stirred at –45 °C for 1 h. After that time, an ethereal solution (10mL) of iodine (101 mg, 0.40 mmol) was added dropwise via syringe. The color of thesolution lightened gradually with addition of iodine. The mixture was left to warm to 23°C overnight, then extracted with ether (2 x 50 mL), and washed with aq. Na 2 S 2 O 3 andbrine. Drying over MgSO 4 , followed by removal of solvent in vacuo gave a brown oil,which was purified by filtration through a short plug of silica (eluting with CHCl 3 ), toyield 212 as a yellow oil (51 mg, 92%). IR (NaCl film): ~ ν = 2958, 2925, 2865, 2161,1540, 1452, 1391, 1378, 1250, 1037, 875, 837, 814, 779, 679 cm –1 . MS (EI, 70 eV) m/z(rel intensity) 762 (M + , 0.2), 592 (44), 467 (36), 341 (19), 73 (100). 1 H NMR (500 MHz,CDCl 3 ) δ 7.83 (dd, 3 J 1 = 8.1 Hz, 4 J 2 = 1.1 Hz, 2H), 7.48 (dd, 3 J 1 = 7.9 Hz, 4 J 2 = 1.1 Hz,2H), 6.95 (t, 3 J = 7.9 Hz, 2H), 1.64 (sept, 3 J = 6.9 Hz, 2H), 0.80 (s, 12H), 0.77 (d, 3 J = 6.9Hz, 12H), 0.14 (s, 12H). 13 C NMR (125 MHz, CDCl 3 ) δ 138.28, 131.85, 131.53, 128.74,127.41, 103.46, 100.63, 99.73, 97.26, 34.36, 23.27, 20.51, 18.50, –2.49. HR-MS Calcdfor C 34 H 44 I 2 Si 2 : 762.1071. Found: 762.1057.278

1,1'-(1,2-Ethynediyl)bis[2-({dimethylthexylsilyl}ethynyl)-6-({trimethylsilyl}ethynyl)]benzene (205b):DMTSTMSTMSDMTSA solution of 212 (22 mg, 0.03 mmol), [Pd(PPh 3 ) 2 Cl 2 ] (2.1 mg, 0.003 mmol), andCuI (0.6 mg, 0.003 mmol) in triethylamine (15 mL) was degassed in a 50 mL Schlenktube. TMSA (420 µL, 294 mg, 3.00 mmol) was added via syringe and the tube closed.The mixture was heated at 100 °C for 72 h. The crude material was purified repeatedly bycolumn chromatography (petroleum ether/CH 2 Cl 2 ) and then subjected to Kugelrohrdistillation (225 °C, 0.8 Torr), giving 205b as colorless oil (3.0 mg, 15%). IR (NaClfilm): ~ ν = 2960, 2927, 2156, 1455, 1250, 979, 842, 797, 761, 740 cm –1 . MS (EI, 70 eV)m/z (rel intensity) 702 (M + , 0.5), 617 (2), 533 (8), 445 (28), 371 (18), 73 (100). 1 H NMR(500 MHz, CDCl 3 ) δ 7.40 (t, 3 J = 8.0 Hz, 4H), 7.17 (t, 3 J = 7.9 Hz, 2H), 1.63 (sept, 3 J =6.8 Hz, 2H), 0.79 (s, 6H), 0.79 (s, 6H), 0.74 (d, 3 J = 6.9 Hz, 6H), 0.73 (d, 3 J = 6.9 Hz,6H), 0.14 (s, 6H), 0.13 (s, 6H), 0.10 (s, 9H). 13 C NMR (125 MHz, CDCl 3 ) δ 131.31,130.71, 129.72, 127.15, 126.20, 126.12, 103.60, 103.21, 99.43, 98.73, 96.08, 34.35 (2C),23.24 (2C), 20.43, 20.41, 18.50, 18.47, –0.33, –2.43 (2C). HR-MS Calcd for C 44 H 62 Si 4 :702.3929. Found: 702.3926.279

6.5.1 Calculated Structures of Transition States for the Inversion of 171c and 213-216Calculated positional parameters of the transition state for the inversion of 213:Atom x y zSi1 -0.02330 5.18210 -2.55140Si2 1.62310 5.14290 2.28510C1 -1.24410 0.32050 -1.04270C2 -1.99320 1.50230 -1.19840C3 -3.36990 1.44670 -1.45770C4 -4.01690 0.21890 -1.56010C5 -3.28540 -0.95820 -1.42150C6 -1.90800 -0.91680 -1.15410C7 1.19950 0.40980 -0.03710C8 0.10260 0.38210 -0.53020C9 -0.71670 -3.24220 -0.80430C10 -1.23710 -2.17200 -0.96960C11 1.11090 -6.97520 -0.04650C12 -0.27800 -6.89230 -0.16800C13 -0.88550 -5.66100 -0.42710C14 -0.10360 -4.51340 -0.57580C15 1.28440 -4.60180 -0.47370C16 1.89140 -5.82800 -0.19550C17 5.35230 0.19710 0.71730C18 4.58850 -0.96530 0.61170C19 3.20080 -0.87420 0.46150C20 2.56320 0.37590 0.41550C21 3.33940 1.53970 0.53070C22 4.72870 1.44520 0.68940C23 5.81900 -3.29330 0.61010C24 5.23830 -2.24080 0.62000C25 4.49930 -5.85340 0.13080C26 3.30980 -5.88150 -0.03340C27 -0.80350 3.78420 -1.71680C28 -1.34300 2.77320 -1.35770C29 2.25120 3.82090 1.22710C30 2.72770 2.81800 0.76790C31 8.04980 -6.89650 0.54230C32 6.67090 -6.94140 0.32890C33 5.91300 -5.76380 0.34910C34 6.54520 -4.53230 0.58510280

C35 7.92950 -4.49720 0.79820C36 8.67850 -5.67550 0.77710C37 -0.45070 4.90780 -4.65530C38 -0.81330 6.81530 -2.06800C39 1.71650 6.83290 1.49160C40 2.59140 5.17080 3.90660C41 -0.42380 4.72650 2.78860C42 1.82340 5.23950 -2.31310C43 -0.66170 5.23870 4.22820C44 -1.28230 5.57710 1.81690C45 -0.70580 3.18270 2.61430C46 -0.01410 2.29100 3.65630C47 -2.20450 2.83940 2.62580C48 0.15910 6.11180 -5.40760C49 -2.00040 4.97820 -4.75600C50 0.11590 3.50870 -5.12310C51 1.61990 3.50770 -5.43370C52 -0.60590 2.95810 -6.36470H1 -3.93350 2.36390 -1.61580H2 -5.08320 0.17890 -1.76680H3 -3.79780 -1.91470 -1.50630H4 1.57620 -7.93350 0.17140H5 -0.88770 -7.78440 -0.04970H6 -1.96860 -5.60250 -0.50490H7 1.89580 -3.71340 -0.60040H8 6.43170 0.13970 0.83650H9 2.61310 -1.77920 0.33940H10 5.32640 2.34420 0.82290H11 8.63200 -7.81450 0.52530H12 6.19000 -7.90000 0.14710H13 8.43200 -3.55000 0.98140H14 9.75240 -5.63940 0.94340H15 -1.89760 6.78720 -2.20650H16 -0.61860 7.04190 -1.01660H17 -0.40990 7.63530 -2.66870H18 1.13700 6.87250 0.56730H19 1.33110 7.60100 2.16880H20 2.75290 7.08750 1.24970H21 3.65370 5.34150 3.70750H22 2.23430 5.97580 4.55540H23 2.49220 4.22280 4.44180H24 2.30160 5.88510 -3.05490H25 2.07370 5.63650 -1.32630H26 2.26590 4.24200 -2.38480H27 -1.70380 5.08930 4.52950H28 -0.02820 4.72900 4.96030281

H29 -0.45010 6.31150 4.30790H30 -2.34820 5.50100 2.05610H31 -1.03120 6.64160 1.87600H32 -1.14390 5.25570 0.78200H33 -0.33520 2.87720 1.62870H34 1.06590 2.44710 3.68640H35 -0.41420 2.45850 4.66130H36 -0.17340 1.23340 3.41560H37 -2.68610 3.16360 3.55330H38 -2.72870 3.29980 1.78310H39 -2.35410 1.75760 2.53270H40 -0.00520 6.01600 -6.48630H41 -0.29910 7.05550 -5.09130H42 1.23610 6.20480 -5.23730H43 -2.32810 4.95490 -5.80100H44 -2.47590 4.14180 -4.23240H45 -2.39560 5.90640 -4.33030H46 -0.05030 2.77690 -4.32300H47 2.21730 3.88800 -4.60600H48 1.96590 2.48700 -5.63410H49 1.84840 4.10710 -6.32140H50 -0.56300 3.66560 -7.19910H51 -0.14810 2.01950 -6.69730H52 -1.65570 2.73490 -6.15100Calculated positional parameters of the transition state for the inversion of 214:Atom x y zSi1 1.09000 4.65790 -2.70140Si2 0.48650 5.20590 2.48980Si3 9.04620 1.15870 3.54370Si4 10.91290 -0.93300 -0.55990C1 -1.35760 0.53680 -0.50690C2 -1.81300 1.69340 -1.16380C3 -3.15840 1.80090 -1.53740C4 -4.04730 0.75590 -1.28250C5 -3.58930 -0.41710 -0.68280C6 -2.24740 -0.53500 -0.30520C7 1.12110 0.46110 0.40150C8 -0.00140 0.45890 -0.02800C9 -1.22390 -2.81000 0.51380C10 -1.77320 -1.78970 0.19960C11 1.28520 -6.09280 1.34790C12 -0.03880 -6.10590 1.79690282

C13 -0.88210 -5.02720 1.52290C14 -0.40050 -3.94330 0.79030C15 0.91840 -3.93950 0.32430C16 1.76710 -5.00590 0.61370C17 5.21390 0.74610 1.42530C18 4.66140 -0.50890 1.13540C19 3.29430 -0.57970 0.81790C20 2.47640 0.55850 0.86030C21 3.01540 1.78180 1.27700C22 4.38540 1.87310 1.53880C23 6.01890 -2.64690 0.41100C24 5.46060 -1.65890 0.81050C25 4.31090 -4.94680 -0.05380C26 3.13670 -4.96320 0.20200C27 -0.12790 3.55980 -1.94860C28 -0.91190 2.74440 -1.54510C29 1.50440 3.86630 1.83600C30 2.19320 2.93360 1.52140C31 7.65830 -6.49160 -0.40930C32 6.28140 -6.29420 -0.43880C33 5.73740 -5.01910 -0.21320C34 6.58230 -3.90550 -0.01340C35 7.96910 -4.13300 0.06910C36 8.49880 -5.41480 -0.14720C37 1.69660 3.69570 -4.53460C38 0.31300 6.30120 -3.18500C39 0.43810 6.68880 1.34530C40 1.11180 5.73920 4.18410C41 -1.52650 4.49690 2.74740C42 2.59160 4.95730 -1.63990C43 -2.12560 5.23860 3.96480C44 -2.29550 4.93730 1.47360C45 -1.51750 2.92680 2.90690C46 -0.89540 2.42580 4.21870C47 -2.91690 2.30130 2.78520C48 2.76920 4.59170 -5.19300C49 0.42130 3.69500 -5.42330C50 2.19810 2.23050 -4.21600C51 3.62960 2.15530 -3.66540C52 2.12970 1.29870 -5.43780C53 7.62330 0.99950 2.43950C54 6.57110 0.87860 1.87340C55 9.71570 -2.17400 -0.02530C56 8.90570 -3.04610 0.13430C57 8.27690 2.02990 5.36770C58 7.64280 3.38880 4.99050283

C59 7.15340 1.05900 5.82870C60 10.35460 2.28240 2.83930C61 11.95270 -1.71980 -2.23600C62 13.19590 -0.81620 -2.45740C63 12.46150 -3.12890 -1.81440C64 11.09050 -1.83100 -3.55310C65 10.83090 -0.50900 -4.28830C66 9.76990 -2.59820 -3.41670C67 12.21800 -0.63400 0.75990C68 10.07830 0.66340 -1.04190C69 9.73320 -0.51980 4.01520C70 9.44320 2.14240 6.42620C71 8.93200 2.16840 7.87680C72 10.34750 3.37020 6.24260H1 -3.51480 2.69530 -2.04410H2 -5.08930 0.84410 -1.57990H3 -4.27850 -1.24430 -0.52780H4 1.93920 -6.92900 1.58440H5 -0.40860 -6.95180 2.37110H6 -1.90620 -5.03560 1.88720H7 1.28390 -3.09450 -0.25390H8 2.87620 -1.52480 0.48050H9 4.80800 2.82070 1.86860H10 8.07370 -7.48150 -0.57830H11 5.62630 -7.14880 -0.59760H12 9.57620 -5.56850 -0.13820H13 -0.59390 6.15100 -3.77730H14 0.04040 6.86900 -2.29020H15 1.01310 6.90480 -3.76930H16 0.05850 6.41350 0.35770H17 -0.20570 7.47310 1.75450H18 1.44070 7.10810 1.21790H19 2.15000 6.07830 4.11470H20 0.51220 6.56630 4.57520H21 1.07090 4.91400 4.89990H22 3.40560 5.40290 -2.21840H23 2.35390 5.64690 -0.82510H24 2.95750 4.03210 -1.18940H25 -3.17010 4.95080 4.12350H26 -1.57870 5.02840 4.88890H27 -2.10610 6.32480 3.81710H28 -3.35840 4.68340 1.54090H29 -2.25110 6.02190 1.32690H30 -1.88770 4.46160 0.57810H31 -0.92600 2.50540 2.08600H32 0.12540 2.78640 4.35900284

H33 -1.48920 2.72420 5.08850H34 -0.84510 1.33070 4.22040H35 -3.60530 2.70230 3.53530H36 -3.34820 2.46880 1.79430H37 -2.86820 1.21530 2.92440H38 3.12410 4.14620 -6.12860H39 2.36910 5.58280 -5.43510H40 3.63650 4.74530 -4.54370H41 0.64050 3.31590 -6.42740H42 -0.36960 3.07290 -4.99000H43 0.01710 4.70390 -5.55780H44 1.53710 1.79040 -3.45910H45 3.77270 2.78510 -2.78870H46 3.86630 1.12910 -3.36100H47 4.36770 2.44790 -4.41970H48 2.69830 1.70220 -6.28180H49 2.54090 0.31140 -5.19830H50 1.09650 1.13660 -5.75990H51 8.35930 4.06010 4.50680H52 6.80360 3.26140 4.29720H53 7.25470 3.89390 5.88160H54 6.40900 0.88940 5.04350H55 7.55970 0.08400 6.11820H56 6.60930 1.46740 6.68740H57 10.01650 3.32210 2.81140H58 11.27520 2.23230 3.42740H59 10.61110 1.99230 1.81750H60 13.89100 -0.86950 -1.61180H61 13.74960 -1.13400 -3.34830H62 12.92210 0.23650 -2.58350H63 13.12350 -3.07550 -0.94260H64 11.64370 -3.80860 -1.55750H65 13.03360 -3.59030 -2.62750H66 11.70090 -2.42250 -4.25240H67 10.21640 0.17850 -3.70730H68 11.76300 -0.00140 -4.55250H69 10.30170 -0.69670 -5.23000H70 9.01980 -2.02530 -2.86450H71 9.34750 -2.79950 -4.40820H72 9.90550 -3.56730 -2.93010H73 12.76570 -1.55360 0.98440H74 12.93550 0.12350 0.43170H75 11.76030 -0.27970 1.68570H76 10.78130 1.34890 -1.52340H77 9.24340 0.48290 -1.72470H78 9.66830 1.16690 -0.16280285

H79 10.62100 -0.41650 4.64550H80 8.99190 -1.10970 4.56160H81 10.01550 -1.08690 3.12420H82 10.07960 1.25310 6.34090H83 8.21860 2.98380 8.03490H84 8.44790 1.22510 8.14780H85 9.76130 2.30770 8.57960H86 9.81330 4.30030 6.46480H87 11.20340 3.31720 6.92530H88 10.75030 3.44580 5.23340Calculated positional parameters of the transition state for the inversion of 215:Atom x y zSi1 -1.01990 4.30190 -2.52440Si2 2.27490 5.86940 1.14630Si3 -5.28850 -4.26640 3.58540Si4 -4.47560 -4.66550 -1.49000C1 -1.46570 0.50850 0.94790C2 -2.25310 1.65170 0.72670C3 -3.60150 1.66920 1.10060C4 -4.18030 0.54560 1.68910C5 -3.42820 -0.61960 1.86220C6 -2.07290 -0.64790 1.47970C7 1.17090 0.62860 0.90630C8 -0.02920 0.58140 0.83990C9 -0.74950 -2.92550 1.55260C10 -1.32950 -1.87450 1.58070C11 1.38570 -6.53790 1.01690C12 0.10720 -6.40860 0.46700C13 -0.61940 -5.22410 0.64010C14 -0.07300 -4.17860 1.40170C15 1.19820 -4.32020 1.96420C16 1.93500 -5.48690 1.75120C17 5.39830 0.33430 0.95740C18 4.60770 -0.74040 1.36340C19 3.21510 -0.61480 1.36410C20 2.60440 0.59720 1.00120C21 3.40500 1.68540 0.62360C22 4.79990 1.54240 0.59340C23 5.78550 -2.93710 2.21390C24 5.23230 -1.95080 1.80550C25 4.43300 -5.49270 2.55700C26 3.28160 -5.55080 2.22140286

C27 -1.43120 3.45530 -0.98790C28 -1.76940 2.71810 -0.10270C29 2.55390 4.16560 0.61570C30 2.87760 3.01490 0.49460C31 7.86510 -6.29200 3.76020C32 6.51760 -6.42030 3.41890C33 5.81290 -5.32560 2.90400C34 6.46510 -4.09350 2.73030C35 7.81730 -3.97470 3.07580C36 8.51440 -5.07070 3.58860C37 -2.11120 3.28470 -4.08850C38 -1.60170 6.08580 -2.51860C39 2.05320 7.05820 -0.27920C40 3.72420 6.44330 2.21240C41 0.52190 5.94060 2.38780C42 0.79700 4.21320 -2.96110C43 0.77700 6.99040 3.49430C44 -0.62280 6.45640 1.47760C45 0.21630 4.49650 2.94870C46 1.22620 3.99910 3.99420C47 -1.18900 4.37280 3.56010C48 -1.40680 3.62560 -5.42130C49 -3.52720 3.92370 -4.08390C50 -2.18880 1.73610 -3.78240C51 -0.83820 1.00650 -3.78110C52 -3.12050 0.98600 -4.75050C53 -4.58170 -2.75330 2.89350C54 -4.07280 -1.77090 2.42720C55 -2.93560 -4.94740 -0.58570C56 -1.89160 -5.09430 -0.01060C57 -4.00040 -4.69920 -3.58710C58 -5.70450 -6.03950 -1.17170C59 -5.17860 -2.98060 -1.07640C60 -2.88750 -5.77310 -3.74480C61 -3.41460 -3.31140 -3.93670C62 -4.17080 -5.74120 3.29270C63 -6.99800 -4.56640 2.89940C64 -5.38920 -3.96750 5.71130C65 -3.92080 -3.68820 6.14040C66 -6.23430 -2.69600 5.95630C67 -5.97680 -5.26040 6.40150C68 -5.56150 -5.39130 7.87690C69 -7.50860 -5.36310 6.35040C70 -5.28050 -5.08440 -4.42820C71 -6.40450 -4.03940 -4.40930C72 -4.95470 -5.38680 -5.90150287

H1 -4.21340 2.54710 0.90490H2 -5.22940 0.57000 1.97540H3 1.95590 -7.44730 0.84340H4 -0.30620 -7.22270 -0.12410H5 1.63200 -3.50370 2.53690H6 6.48260 0.25090 0.95180H7 2.59770 -1.46300 1.64830H8 5.43010 2.38970 0.33100H9 8.40760 -7.14530 4.15990H10 6.02050 -7.37800 3.55610H11 8.33460 -3.02630 2.94840H12 9.56380 -4.97030 3.85490H13 -2.65650 6.15520 -2.23700H14 -1.02600 6.67820 -1.80240H15 -1.47720 6.53660 -3.50750H16 1.19490 6.78530 -0.89640H17 1.90000 8.07810 0.08620H18 2.94060 7.06060 -0.91960H19 4.65580 6.39150 1.64090H20 3.58060 7.47880 2.53410H21 3.83240 5.81460 3.10030H22 0.99110 4.70760 -3.91750H23 1.39980 4.71750 -2.20260H24 1.15230 3.18290 -3.03410H25 -0.10060 7.09920 4.14020H26 1.62650 6.72510 4.13070H27 0.98940 7.97650 3.06470H28 -1.54610 6.60940 2.04610H29 -0.37890 7.42350 1.02490H30 -0.83470 5.75170 0.67040H31 0.24220 3.79050 2.10990H32 2.25480 4.03310 3.62970H33 1.17060 4.58240 4.91900H34 1.01720 2.95520 4.25580H35 -1.33900 5.08710 4.37550H36 -1.96890 4.53360 2.81010H37 -1.34730 3.36660 3.96470H38 -1.94590 3.19670 -6.27210H39 -1.36070 4.70920 -5.58070H40 -0.37980 3.25010 -5.45340H41 -4.14230 3.53460 -4.90170H42 -4.04990 3.72740 -3.14120H43 -3.48500 5.00850 -4.22680H44 -2.62450 1.60630 -2.78360H45 -0.17320 1.37710 -2.99940H46 -0.98090 -0.06160 -3.57830288

H47 -0.32770 1.08810 -4.74510H48 -2.78960 1.08370 -5.78880H49 -3.14580 -0.08320 -4.51120H50 -4.15130 1.34380 -4.67840H51 -5.31610 -6.99960 -1.52440H52 -5.91130 -6.13080 -0.10110H53 -6.65310 -5.84590 -1.68060H54 -6.01750 -2.71380 -1.72200H55 -5.54100 -2.96410 -0.04520H56 -4.41460 -2.20380 -1.17790H57 -2.01900 -5.55960 -3.11290H58 -3.25710 -6.77090 -3.48380H59 -2.51070 -5.80690 -4.77230H60 -2.52800 -3.08950 -3.33100H61 -3.10890 -3.26660 -4.98690H62 -4.13270 -2.50440 -3.76260H63 -3.16200 -5.55270 3.67130H64 -4.56130 -6.63510 3.78690H65 -4.09590 -5.95770 2.22340H66 -6.98640 -4.50960 1.80640H67 -7.36320 -5.56120 3.16940H68 -7.71110 -3.82170 3.26410H69 -3.47640 -2.86510 5.56990H70 -3.86710 -3.39860 7.19560H71 -3.28760 -4.57080 5.99800H72 -5.76310 -1.80980 5.51580H73 -7.23610 -2.77540 5.52210H74 -6.34450 -2.50570 7.02930H75 -5.57440 -6.14330 5.89010H76 -4.48100 -5.53190 7.97780H77 -5.85290 -4.50810 8.45460H78 -6.03520 -6.26500 8.33870H79 -7.98450 -4.59680 6.97160H80 -7.90020 -5.26770 5.33830H81 -7.83690 -6.33760 6.72980H82 -5.69610 -6.01130 -4.01200H83 -6.80030 -3.88370 -3.40500H84 -6.07600 -3.07670 -4.81190H85 -7.24950 -4.37540 -5.02160H86 -4.48020 -4.53300 -6.39460H87 -4.29670 -6.25500 -5.99890H88 -5.86750 -5.62630 -6.45900289

Calculated positional parameters of the transition state for the inversion of 216:Atom x y zSi1 -1.09520 4.66370 -2.29760Si2 1.20130 5.91170 2.17110Si3 -6.08470 -3.88240 3.10780Si4 -4.83470 -4.97000 -1.71650Si5 10.53410 -1.57390 0.32170Si6 8.91460 2.21320 2.73850C1 -1.87990 0.80070 0.87880C2 -2.58560 2.01760 0.80650C3 -3.94110 2.08240 1.14550C4 -4.60790 0.93640 1.57370C5 -3.93630 -0.28910 1.62250C6 -2.57530 -0.36490 1.26510C7 0.75160 0.86500 1.08960C8 -0.43590 0.81420 0.90260C9 -1.30730 -2.67560 1.29640C10 -1.89350 -1.62830 1.31140C11 1.10470 -6.13070 0.99370C12 -0.16350 -6.13240 0.40620C13 -0.98720 -5.00410 0.50070C14 -0.54550 -3.88400 1.22040C15 0.71640 -3.89500 1.82280C16 1.54820 -5.00500 1.68910C17 4.98950 0.99580 1.26590C18 4.31360 -0.18300 1.61160C19 2.90760 -0.19870 1.58630C20 2.17570 0.95840 1.27130C21 2.86420 2.12660 0.91220C22 4.26240 2.13900 0.90890C23 5.58650 -2.45160 2.08230C24 5.01940 -1.41160 1.86720C25 4.02920 -4.86540 2.53760C26 2.88090 -4.94700 2.19710C27 -1.60050 3.88190 -0.74830C28 -2.01450 3.12650 0.08930C29 1.72520 4.45700 1.24170C30 2.19840 3.40110 0.91830C31 7.36870 -5.93590 3.75110C32 6.00620 -5.91380 3.46910C33 5.42760 -4.79910 2.84400C34 6.21580 -3.68370 2.49490C35 7.59970 -3.74030 2.74020C36 8.16510 -4.85950 3.37150290

C37 -0.27070 3.07260 -3.50890C38 -2.60050 5.30820 -3.23230C39 0.00460 7.03210 1.27620C40 2.69070 6.92570 2.72360C41 0.20950 5.20950 3.95530C42 0.16440 6.01910 -2.13440C43 0.34250 6.32720 5.01470C44 -1.28590 5.05820 3.56510C45 0.81850 3.82440 4.40810C46 2.28100 3.88400 4.86950C47 0.00390 3.15300 5.52720C48 0.06660 3.67390 -4.89140C49 -1.43170 2.05180 -3.67040C50 0.97490 2.45310 -2.75970C51 2.28120 3.23760 -2.95170C52 1.25350 0.99500 -3.15960C53 -5.24960 -2.41060 2.47240C54 -4.66350 -1.44230 2.07190C55 -3.29150 -5.01360 -0.77630C56 -2.25030 -5.01790 -0.17820C57 -4.31230 -5.44670 -3.74920C58 -6.02190 -6.29880 -1.13450C59 -5.61670 -3.27880 -1.64560C60 -3.61890 -6.83600 -3.66490C61 -3.27650 -4.39630 -4.21320C62 -4.96240 -5.38110 3.06390C63 -7.67340 -4.18990 2.17790C64 -6.51390 -3.48380 5.17760C65 -5.12920 -3.18050 5.81720C66 -7.38100 -2.20450 5.22770C67 -7.20670 -4.74480 5.82790C68 -7.03400 -4.79950 7.35550C69 -8.71040 -4.86030 5.53660C70 -5.61840 -5.48390 -4.63570C71 -6.10950 -4.10300 -5.09520C72 -5.46080 -6.35240 -5.89550C73 7.47700 1.50760 1.90580C74 6.39060 1.17940 1.51380C75 9.32060 -2.19430 1.50500C76 8.50970 -2.79400 2.15750C77 8.17000 3.95200 3.79480C78 9.67410 1.03610 3.96760C79 9.75030 -0.37720 -0.88960C80 10.19510 2.85720 1.52900C81 11.21090 -3.26410 -0.84660C82 7.03370 3.50600 4.79830291

C83 7.63430 4.89230 2.67860C84 9.38140 4.62200 4.48140C85 6.05490 4.64390 5.13420C86 7.55260 2.94560 6.13070C87 12.06090 -0.85940 1.12710C88 12.25850 -4.10380 -0.01620C89 11.86200 -2.64720 -2.11500C90 9.95180 -4.06070 -1.26000C91 12.97920 -5.16100 -0.87060C92 11.68300 -4.81710 1.21550H1 -4.48870 3.01680 1.04460H2 -5.66020 0.99700 1.84280H3 1.74950 -6.99900 0.88090H4 -0.49400 -7.00610 -0.15100H5 1.06430 -3.01940 2.36540H6 2.37960 -1.12570 1.79400H7 4.78870 3.07540 0.72860H8 7.81420 -6.80240 4.23290H9 5.39270 -6.77150 3.73800H10 9.23950 -4.90770 3.53740H11 -3.35710 4.52750 -3.34890H12 -3.05420 6.14090 -2.68630H13 -2.31540 5.66780 -4.22490H14 -0.84680 6.47430 0.87820H15 -0.38020 7.80380 1.95000H16 0.50350 7.53970 0.44620H17 3.24850 7.27960 1.85110H18 2.36980 7.80110 3.29580H19 3.37140 6.33940 3.34490H20 0.60480 6.27120 -3.10330H21 -0.30310 6.92850 -1.74560H22 0.97330 5.74210 -1.45500H23 -0.19140 6.06350 5.93340H24 1.38570 6.52290 5.28000H25 -0.08230 7.27060 4.65250H26 -1.89940 4.79750 4.43370H27 -1.70220 5.98980 3.16800H28 -1.42000 4.27880 2.80900H29 0.77640 3.13750 3.55400H30 2.94710 4.23510 4.08010H31 2.40720 4.52780 5.74510H32 2.63490 2.88430 5.14770H33 -0.05700 3.78450 6.41870H34 -1.01190 2.91500 5.19910H35 0.46470 2.20390 5.82420H36 0.51970 2.91670 -5.54050292

H37 -0.83270 4.04100 -5.39860H38 0.76100 4.51660 -4.81940H39 -1.15480 1.24880 -4.36230H40 -1.70300 1.59430 -2.71300H41 -2.33170 2.51940 -4.08320H42 0.76060 2.43800 -1.68530H43 2.17900 4.28860 -2.68280H44 3.07320 2.82080 -2.31930H45 2.63430 3.18400 -3.98710H46 1.40220 0.89860 -4.24000H47 2.15490 0.62020 -2.66140H48 0.43410 0.33440 -2.86010H49 -5.57850 -7.29370 -1.23330H50 -6.28050 -6.14900 -0.08240H51 -6.94890 -6.27730 -1.71450H52 -6.62780 -3.29240 -2.06180H53 -5.69850 -2.93780 -0.60980H54 -5.02400 -2.54010 -2.19260H55 -2.78530 -6.83600 -2.95410H56 -4.32180 -7.61600 -3.35300H57 -3.19910 -7.12580 -4.63450H58 -2.36170 -4.44160 -3.61120H59 -2.98880 -4.57160 -5.25540H60 -3.66060 -3.37420 -4.13570H61 -4.04050 -5.19990 3.62400H62 -5.45820 -6.25620 3.49320H63 -4.68790 -5.62500 2.03400H64 -7.49750 -4.15930 1.09830H65 -8.08430 -5.17570 2.41290H66 -8.42680 -3.43270 2.41270H67 -4.59740 -2.38370 5.28560H68 -5.23970 -2.84150 6.85300H69 -4.48570 -4.06700 5.81720H70 -6.84400 -1.33950 4.82170H71 -8.30490 -2.30820 4.65000H72 -7.65340 -1.96220 6.26060H73 -6.72820 -5.64900 5.43250H74 -5.98400 -4.92790 7.63550H75 -7.41300 -3.89060 7.83410H76 -7.57710 -5.65220 7.77850H77 -9.27870 -4.06490 6.03050H78 -8.93340 -4.82300 4.47100H79 -9.09750 -5.81510 5.91070H80 -6.42610 -5.93810 -4.04880H81 -6.23830 -3.40800 -4.26630H82 -5.41900 -3.64880 -5.81400293

H83 -7.08230 -4.19180 -5.59240H84 -4.61640 -6.01960 -6.50790H85 -5.31090 -7.40570 -5.63960H86 -6.36310 -6.30620 -6.51570H87 8.90740 0.54020 4.56940H88 10.23760 0.25160 3.45630H89 10.36410 1.55280 4.64060H90 9.25440 0.44150 -0.36330H91 10.50370 0.05960 -1.55150H92 9.00040 -0.88120 -1.50630H93 10.99750 3.38250 2.05470H94 10.64610 2.03670 0.96620H95 9.74760 3.54660 0.80760H96 6.43560 2.71760 4.32510H97 6.77340 4.45410 2.16230H98 7.32570 5.85840 3.09270H99 8.39910 5.11030 1.92600H100 9.06230 5.49590 5.05960H101 9.90270 3.93960 5.15990H102 10.11670 4.96930 3.74700H103 5.49000 4.95850 4.25150H104 5.31920 4.31810 5.87810H105 6.57850 5.51520 5.54090H106 8.03060 3.72350 6.73560H107 6.72290 2.54000 6.72100H108 8.27000 2.13740 5.99290H109 12.82700 -0.63750 0.37830H110 11.83210 0.06910 1.65510H111 12.48700 -1.55820 1.85300H112 13.03770 -3.41950 0.34340H113 12.15920 -3.42470 -2.82650H114 11.16830 -1.99240 -2.65260H115 12.75120 -2.05970 -1.86160H116 10.21790 -4.91120 -1.89590H117 9.40320 -4.44870 -0.39690H118 9.25490 -3.43600 -1.83050H119 12.27460 -5.86810 -1.31860H120 13.56600 -4.70080 -1.67070H121 13.68430 -5.73710 -0.26050H122 10.89710 -5.52920 0.94680H123 12.46840 -5.38130 1.73190H124 11.28360 -4.11290 1.94670294

Calculated positional parameters of the transition state for the inversion of 171c:Atom x y zSi1 0.76540 5.44570 -2.26930Si2 -0.07220 5.09600 2.94440Si3 -5.32060 -4.39200 -2.23910Si4 -5.02010 -3.46240 2.82910Si5 9.99460 0.18180 0.43490Si6 7.97580 -0.22410 5.22750Si7 3.64680 -8.05770 5.00320Si8 4.56820 -10.00580 -0.11420C1 -1.19790 0.71410 -1.02960C2 -1.75100 1.88450 -1.57950C3 -2.98850 1.83290 -2.23140C4 -3.67850 0.62460 -2.34180C5 -3.13600 -0.54820 -1.80760C6 -1.89890 -0.50850 -1.13990C7 1.01040 0.77990 0.41890C8 0.01780 0.77360 -0.25860C9 -0.85090 -2.66140 -0.02790C10 -1.34970 -1.70700 -0.56050C11 1.25350 -5.57890 2.20790C12 -0.10290 -5.35240 2.47340C13 -0.82610 -4.41420 1.72590C14 -0.19370 -3.71590 0.68680C15 1.15040 -3.97350 0.39450C16 1.88150 -4.88760 1.16140C17 4.77380 0.64890 2.36080C18 4.27430 -0.47460 1.68700C19 3.01400 -0.41480 1.08250C20 2.23430 0.74470 1.16610C21 2.73110 1.86440 1.84880C22 3.99640 1.81000 2.45030C23 5.78000 -2.56790 1.15070C24 5.09110 -1.62340 1.42680C25 4.47740 -5.05110 0.76440C26 3.28420 -5.02280 0.90050C27 -0.33980 4.09460 -1.80520C28 -1.01390 3.11620 -1.62910C29 1.15610 3.90810 2.36300C30 1.90970 3.01870 2.07530C31 8.07110 -6.10490 0.68240C32 6.67600 -6.16620 0.60720C33 5.91550 -4.98960 0.72330C34 6.56500 -3.74540 0.88670295

C35 7.96770 -3.70020 0.97720C36 8.71350 -4.87880 0.86780C37 2.62660 4.52440 -2.85250C38 0.11780 6.34720 -3.78830C39 -1.56190 5.17970 1.80420C40 0.64870 6.79780 3.19760C41 -0.79430 4.32660 4.82600C42 1.08010 6.65560 -0.89170C43 -1.86940 5.30840 5.34350C44 -1.47340 2.97500 4.46510C45 0.42280 4.13680 5.81560C46 0.87720 5.42810 6.51170C47 0.14100 3.10000 6.91610C48 3.51940 5.63210 -3.45550C49 2.23930 3.52120 -3.97450C50 3.25710 3.81160 -1.59100C51 4.09460 4.74000 -0.69780C52 4.14250 2.60980 -1.95590C53 -4.47010 -2.80520 -2.07540C54 -3.87360 -1.77010 -1.95590C55 -3.32730 -3.90700 2.37900C56 -2.19210 -4.15820 2.07960C57 -4.96820 -2.93010 4.91230C58 -5.60130 -1.94570 1.89530C59 -6.17320 -4.90620 2.56890C60 -3.94190 -1.76450 4.99710C61 -4.40880 -4.14850 5.68280C62 -7.07350 -4.29140 -1.58300C63 -4.35610 -5.74880 -1.39700C64 -5.45980 -4.78970 -4.34660C65 -6.20640 -3.55890 -4.93480C66 -4.01770 -4.81490 -4.90430C67 -6.25300 -6.13490 -4.58070C68 -6.89470 -6.21490 -5.97640C69 -5.41060 -7.40570 -4.39480C70 -6.40990 -2.49050 5.38280C71 -7.35190 -3.65920 5.70860C72 -6.38140 -1.57200 6.61640C73 6.86160 0.31540 3.91720C74 5.97330 0.54630 3.14260C75 9.22990 -1.39230 0.87850C76 8.67130 -2.44770 1.01160C77 6.76240 -1.31940 6.64020C78 9.35180 -1.35900 4.66590C79 9.80280 1.48470 1.76540C80 8.71200 1.24370 6.14260296

C81 8.97730 0.91950 -1.31580C82 5.68190 -2.18410 5.87530C83 6.08670 -0.23520 7.52420C84 7.72760 -2.15410 7.51190C85 4.63590 -2.79990 6.82100C86 6.25140 -3.32050 5.01480C87 11.79840 -0.02250 -0.03070C88 9.48910 0.15310 -2.59780C89 9.32270 2.43210 -1.38720C90 7.46130 0.76100 -1.05570C91 9.01980 0.81030 -3.90750C92 9.10070 -1.33130 -2.66000C93 2.62910 -7.13130 3.83140C94 1.98600 -6.45590 3.07510C95 5.49470 -8.48800 0.21240C96 6.05380 -7.44320 0.40610C97 2.43350 -9.68420 5.71100C98 4.14970 -6.96670 6.43390C99 5.39860 -11.49440 0.66330C100 5.14720 -8.81080 4.17520C101 4.61560 -10.29750 -2.24300C102 2.80290 -9.83130 0.46410C103 6.12750 -10.34560 -2.60340C104 3.87300 -11.64170 -2.61060C105 4.32600 -12.22450 -3.96020C106 2.34220 -11.52580 -2.65690C107 3.98500 -9.04310 -2.89140C108 1.18240 -9.06660 6.37750C109 1.99610 -10.44310 4.42620C110 3.28310 -10.59620 6.68030C111 3.40230 -10.05580 8.11300C112 2.74020 -12.03200 6.77920H1 -3.40960 2.73090 -2.67890H2 -4.63540 0.60030 -2.85890H3 -0.58720 -5.87690 3.29500H4 1.64440 -3.42220 -0.40350H5 2.65260 -1.26530 0.50900H6 4.35730 2.65850 3.02800H7 8.66530 -7.01160 0.58940H8 9.80040 -4.84440 0.90170H9 -0.04510 5.65520 -4.61910H10 -0.83530 6.83470 -3.56150H11 0.82310 7.11760 -4.11260H12 -1.95120 4.18090 1.58750H13 -2.36350 5.77280 2.25310H14 -1.29120 5.64890 0.85480297

H15 0.79400 7.29900 2.23570H16 -0.01360 7.42540 3.80030H17 1.62420 6.74890 3.68930H18 1.85410 7.37760 -1.16760H19 0.17120 7.21780 -0.65580H20 1.39800 6.14380 0.01880H21 -2.25550 4.98160 6.31510H22 -1.48070 6.32490 5.45930H23 -2.72240 5.36640 4.65820H24 -1.97390 2.54030 5.33720H25 -2.24440 3.09780 3.69700H26 -0.74520 2.24600 4.09280H27 1.28050 3.75510 5.24780H28 1.09570 6.22800 5.80520H29 0.12210 5.79340 7.21590H30 1.79440 5.24850 7.08450H31 -0.75600 3.35750 7.48860H32 0.01070 2.09740 6.49740H33 0.98050 3.03920 7.61800H34 4.50070 5.22910 -3.72900H35 3.07620 6.05280 -4.36520H36 3.67460 6.46350 -2.76050H37 3.13150 3.07070 -4.42320H38 1.60760 2.71200 -3.59220H39 1.69450 4.01090 -4.78880H40 2.44230 3.41410 -0.97490H41 3.54890 5.63450 -0.39730H42 4.39290 4.22140 0.21990H43 5.01430 5.05800 -1.20070H44 4.94760 2.90020 -2.63880H45 4.60150 2.18000 -1.05870H46 3.56030 1.80950 -2.42270H47 -4.92760 -1.09970 2.05900H48 -5.63460 -2.14660 0.82120H49 -6.60580 -1.65060 2.21110H50 -7.21870 -4.59760 2.65590H51 -6.04030 -5.32690 1.56740H52 -5.98360 -5.70430 3.29220H53 -2.97590 -2.03580 4.55700H54 -4.30560 -0.87220 4.47610H55 -3.74180 -1.49110 6.03890H56 -3.38500 -4.38510 5.37090H57 -4.38200 -3.94640 6.75900H58 -5.00890 -5.04990 5.52280H59 -7.65070 -3.53100 -2.11660H60 -7.58770 -5.25060 -1.69050298

H61 -7.07140 -4.02880 -0.52110H62 -4.08950 -5.45250 -0.37810H63 -4.94560 -6.66680 -1.32350H64 -3.42830 -5.97140 -1.93150H65 -5.71710 -2.61600 -4.66700H66 -6.22700 -3.59710 -6.02940H67 -7.24080 -3.51000 -4.57770H68 -3.52060 -3.84670 -4.77470H69 -3.39450 -5.56420 -4.40600H70 -4.02160 -5.03740 -5.97670H71 -7.07860 -6.18330 -3.86020H72 -7.66790 -5.45150 -6.10610H73 -6.14820 -6.09210 -6.76790H74 -7.38410 -7.18420 -6.12500H75 -4.65220 -7.50440 -5.17890H76 -4.90480 -7.43430 -3.43050H77 -6.04860 -8.29550 -4.44750H78 -6.87800 -1.90980 4.57860H79 -7.42870 -4.37450 4.89050H80 -7.02710 -4.20080 6.60350H81 -8.36440 -3.28780 5.90440H82 -5.85480 -2.04200 7.45330H83 -5.89680 -0.61660 6.39310H84 -7.39830 -1.33660 6.95020H85 8.97480 -2.24370 4.14970H86 10.02850 -0.83780 3.98430H87 9.94760 -1.69570 5.51960H88 10.23590 1.14410 2.70920H89 10.31900 2.40730 1.48400H90 8.74950 1.72290 1.93380H91 9.25510 0.91210 7.03240H92 9.41280 1.78090 5.49630H93 7.93300 1.94620 6.45270H94 5.12580 -1.51990 5.20210H95 5.40800 0.39250 6.93620H96 5.51220 -0.68780 8.33890H97 6.82390 0.41970 8.00040H98 7.18360 -2.69310 8.29430H99 8.28270 -2.89090 6.92370H100 8.46570 -1.51570 8.01120H101 4.06340 -2.03020 7.34610H102 3.90930 -3.39640 6.25730H103 5.09840 -3.45740 7.56330H104 6.81290 -4.04500 5.61210H105 5.44110 -3.86790 4.51860H106 6.89690 -2.94620 4.22010299

H107 12.20630 0.91390 -0.42240H108 12.38930 -0.31080 0.84390H109 11.92370 -0.79730 -0.79260H110 10.58570 0.19980 -2.60930H111 8.77690 2.92630 -2.19770H112 9.04230 2.95820 -0.46870H113 10.39430 2.58930 -1.55200H114 6.87970 1.14570 -1.89910H115 7.17260 -0.28260 -0.90160H116 7.14920 1.31730 -0.16430H117 7.92830 0.86090 -3.96660H118 9.42120 1.82190 -4.01700H119 9.37280 0.24100 -4.77500H120 8.01550 -1.47080 -2.66300H121 9.48840 -1.78920 -3.57760H122 9.52510 -1.90160 -1.83270H123 3.29320 -6.71250 7.06440H124 4.90890 -7.45130 7.05370H125 4.58210 -6.03180 6.06380H126 6.42130 -11.61240 0.29400H127 5.44320 -11.38510 1.75110H128 4.84610 -12.41180 0.44160H129 5.76960 -9.34310 4.90010H130 4.85120 -9.51750 3.39660H131 5.76200 -8.03240 3.71320H132 2.28540 -10.79450 0.45640H133 2.77620 -9.45600 1.49100H134 2.24390 -9.12870 -0.16030H135 6.66420 -9.46280 -2.23890H136 6.61280 -11.22980 -2.17590H137 6.27300 -10.37020 -3.68890H138 4.11970 -12.39530 -1.85280H139 4.19240 -11.50320 -4.77290H140 5.37720 -12.52720 -3.93320H141 3.74840 -13.12170 -4.21040H142 2.01060 -10.90050 -3.49270H143 1.89030 -12.51510 -2.79330H144 1.92680 -11.11100 -1.73930H145 3.95930 -9.14290 -3.98180H146 2.96190 -8.86790 -2.54390H147 4.56120 -8.13960 -2.66090H148 1.44200 -8.39100 7.19860H149 0.59070 -8.48660 5.65990H150 0.53080 -9.85060 6.77810H151 1.50320 -9.77940 3.70750H152 2.85220 -10.90430 3.92170300

H153 1.27460 -11.23310 4.66120H154 4.30020 -10.68040 6.27830H155 3.77240 -9.03170 8.14350H156 2.44020 -10.08480 8.63570H157 4.10410 -10.66680 8.69240H158 1.69230 -12.04290 7.09650H159 2.81940 -12.55680 5.82220H160 3.31600 -12.61700 7.50540301

References[1] This chapter constitutes a book chapter in press: Miljanić, O. Š.; Vollhardt, K. P. C.,[N]Phenylenes: a Novel Class of Cyclohexatrienoid Hydrocarbons, in Carbon RichCompounds: From Molecules to Materials (Eds.: Haley, M. M.; Tykwinski, R. R.),Wiley-VCH, Weinheim, 2005, in press. The large majority of the presented material is areview of the field; my original work is limited to Section 1.2.2.3 (synthesis of syndoublebent[5]phenylene 60) and other minor results, properly acknowledged by thegiven references.[2] (a) Minkin, V. I.; Glukhovtsev, M. N.; Simkin, B. Ya. Aromaticity andAntiaromaticity: Electronic and Structural Aspects, Wiley, New York, 1994; (b) Garratt,P. J. Aromaticity, Wiley, New York, 1986; (c) Chem. Rev. 2001, 101, 1115, SpecialIssue: Aromaticity (some of the reviews from this issue are also cited separately).[3] Krygowski, T. M.; Cyrański, M. K. Chem. Rev. 2001, 101, 1385 and the referencescited therein.[4] (a) Schaad, L. J.; Hess, B. A. Jr. Chem. Rev. 2001, 101, 1465 and the references citedtherein; (b) Slayden, S. W.; Liebman, J. F. Chem. Rev. 2001, 101, 1541 and thereferences cited therein.[5] (a) Mitchell, R. H. Chem. Rev. 2001, 101, 1301 and the references cited therein; (b)Gomes, J. A. N. F.; Mallion, R. B. Chem. Rev. 2001, 101, 1349 and the references citedtherein.302

[6] (a) Armit, J. W.; Robinson, R. J. Chem. Soc. 1925, 127, 1604; (b) Kruszewski, J.;Krygowski, T. M. Tetrahedron Lett. 1970, 11, 319; (c) Krygowski, T. M. TetrahedronLett. 1970, 11, 1311; (d) Dixon, W. T. J. Chem. Soc. B 1970, 612.[7] Cyrañski, M. K.; Krygowski, T. M.; Katrizky, A. R.; Schleyer, P. v. R. J. Org. Chem.2002, 67, 1333.[8] (a) Jug, K.; Köster, A. M. J. Phys. Org. Chem. 1991, 4, 163; (b) Katrizky, A. R.;Barczynski, P.; Masummarra, G.; Pisano, D.; Szafan, M. J. Am. Chem. Soc. 1989, 111, 7.[9] Jeffrey, G. A.; Ruble, J. R.; McMullan, R. K.; Pople, J. A. Proc. R. Soc. London 1987,A414, 47.[10] (a) Irngartinger, H.; Nixford, M. Angew. Chem., Int. Ed. Engl. 1983, 22, 403; (b)Sekiguchi, A.; Tanaka, M.; Matsuo, T.; Watanabe, H. Angew. Chem., Int. Ed. 2001, 40,1675.[11] Deniz, A. A.; Peters, K. S.; Snyder, G. J. Science 1999, 286, 1119.[12] Faraday, M. Phil. Trans. R. Soc. London 1825, 115, 440.[13] (a) Chapman, O. L.; McIntosh, C. L.; Pacansky, J. J. Am. Chem. Soc. 1973, 95, 614;(b) Krantz, A.; Lin, C. Y.; Newton, M. D. J. Am. Chem. Soc. 1973, 95, 2744.[14] Kennedy, R. D.; Lloyd, D.; McNab, H. J. Chem. Soc., Perkin Trans 1 2002, 1600and the references cited therein.[15] (a) Hückel, E. Grundzüge der Theorie ungesättigter und aromatischerVerbindungen, Verlag Berlin, 1938; (b) Hückel, E. Z. Phys. 1931, 70, 204.[16] Lothrop, W. C. J. Am. Chem. Soc. 1941, 63, 1187.303

[17] (a) Shepherd, M. K. Cyclobutarenes: The Chemistry of Benzocyclobutene,Biphenylene, and Related Compounds, Elsevier, New York, 1991; (b) Toda, F.; Garratt,P. J. Chem. Rev. 1992, 92, 1685.[18] Sigma-Aldrich Fine Chemicals Catalog, 2003–2004.[19] Iyoda, M.; Kabir, S. M. H.; Vorasingha, A.; Kuwatani, Y.; Yoshida, M. TetrahedronLett. 1998, 39, 5393.[20] (a) Kanoktanapora, S.; MacBride, J. A. H. J. Chem. Res. (S) 1980, 203; (b)MacBride, J. A. J. Chem. Soc., Chem. Commun. 1972, 1219.[21] (a) Droske, J. P.; Stille, J. K. Macromolecules 1984, 17, 1; (b) Friedman, L.;Lindow, D. F. J. Am. Chem. Soc. 1968, 90, 2324; (c) Lindow, D. F.; Friedman, L. J. Am.Chem. Soc. 1967, 89, 1271.[22] Perthuisot, C.; Edelbach, B. L.; Zubris, D. L.; Simhai, N.; Iverson, C. N.; Müller, C.;Satoh, T.; Jones, W. D. J. Mol. Catal. A 2002, 189, 157 and the references cited therein.[23] Jeany, H.; Mason, K. G.; Sketchley, J. M. Tetrahedron Lett. 1970, 11, 485.[24] Heaney, H.; Lees, P. Tetrahedron Lett. 1964, 5, 3049.[25] (a) Yokozeki, A.; Wilcox, C. F.; Bauer, S. H. J. Am. Chem. Soc. 1974, 96, 1026; (b)Fawcett, J. K.; Trotter, J. Acta Crystallogr. 1966, 20, 87; (c) Mak, T. C. W.; Trotter, J. J.Chem. Soc. 1962, 1.[26] Yamaguchi, H.; Masafumi, A.; McOmie, J. F. W.; Barton, J. W.; Baumann, H. J.Chem. Soc., Faraday Trans. 2 1983, 79, 599.[27] Figeys, H. P.; Defay, N.; Martin, R. H.; McOmie, J. F. W.; Ayers, B. E.; Chadwick,J. B. Tetrahedron 1976, 32, 2571.304

[28] Jones, A. P.; Garratt, P. J.; Vollhardt, K. P. C. Angew. Chem., Int. Ed. Engl. 1973,12, 241.[29] (a) Maksić, Z. B.; Eckert-Maksić, M.; Mó, O.; Yáñez, M. in Pauling’s Legacy:Modern Modelling of the Chemical Bond (Eds.: Maksić, Z. B., Orville-Thomas, W. J.),Elsevier, Amsterdam, 1999, 47 and the references cited therein; (b) Stanger, A.; Ben-Mergui, N.; Perl, S. Eur. J. Org. Chem. 2003, 2709; (c) Stanger, A.; Tkachenko, E. J.Comp. Chem. 2001, 22 1377; (d) Stanger, A. J. Am. Chem. Soc. 1998, 120, 12034; (e)Frank, N. L.; Siegel, J. S. in Advances in Theoretically Interesting Molecules, Vol. 3 (Ed.:Thummel, R. P.), JAI, London, 1995, 209; (f) Siegel, J. S. Angew. Chem., Int. Ed. Engl.1994, 33, 1721 and the references cited therein; (g) Jug, K.; Hiberty, P. C.; Shaik, S.Chem. Rev. 2001, 101, 1477 and the references cited therein.[30] (a) Shaik, S.; Shurki, A.; Danovich, D.; Hiberty, P. C. Chem. Rev. 2001, 101, 1501and the references cited therein; (b) Hiberty, P. C.; Danovich, D.; Shurki, A.; Shaik, S. J.Am. Chem. Soc. 1995, 117, 7760 and the references cited therein. For a popular account:(c) Narahari Sastry, G. Curr. Sci. 2001, 81, 1288.[31] Wannere, C. S.; Sattelmeyer, K. W.; Schaefer, H. F. III; Schleyer, P. v. R. Angew.Chem., Int. Ed. 2004, 43, 4200.[32] Randić, M. Chem. Rev. 2003, 103, 3449 and the numerous references cited therein.[33] Gutman, I.; Cyvin, S. J.; Brunvoll, J. Monatsh. Chem. 1994, 125, 887. Forillustration, there are 12 [5]phenylenes, 122 [7]phenylenes and 6387 [10]phenylenes.[34] Trinajstić, N.; Schmalz, T. G.; Živković, T. P.; Nikolić, S.; Hite, G. E.; Klein, D. J.;Seitz, W. A. New J. Chem. 1991, 15, 27.305

[35] Beckhaus, H.-D.; Faust, R.; Matzger, A. J.; Mohler, D. L.; Rogers, D. W.; Rüchardt,C.; Sawhey, A. K.; Verevkin, S. P.; Vollhardt, K. P. C.; Wolff, S. J. Am. Chem. Soc.2000, 122, 7819.[36] (a) Watson, M. D.; Fechtenkötter, A.; Müllen, K. Chem. Rev. 2001, 101, 1267 andthe references cited therein; (b) Harvey, R. G. Polycyclic Aromatic Hydrocarbons,Wiley-VCH, New York, 1995; c) Clar, E. The Aromatic Sextet, Wiley, London, 1972.[37] Recent examples: (a) Debije, M. G.; Piris, J.; de Haas, M. P.; Warman, J. M.;Tomović, Ž.; Simpson, C. D.; Watson, M. D.; Müllen, K.; J. Am. Chem. Soc. 2004, 126,4641; (b) Wu, J. S.; Gherghel, L.; Watson, M. D.; Li, J. X.; Wang, Z. H.; Simpson, C. D.;Kolb, U.; Müllen, K. Macromolecules 2003, 36, 7082; (c) Meng, H.; Bendikov, M.;Mitchell, G.; Helgeson, R.; Wudl, F.; Bao, Z.; Siegrist, T.; Kloc, C.; Chem, C.-H. Adv.Mater. 2003, 15, 1090; (d) Zhang, Y.; Petta, J. R.; Ambily, S.; Shen, Y.; Ralph, D. C.;Malliaras, G. C. Adv. Mater. 2003, 15, 1632; (e) Dimitrakopoulos, C. D.; Kymissis, I.;Purushothaman, S.; Neumayer, D. A.; Duncombe, P. R.; Laibowitz. R. B. Adv. Mater.1999, 11, 1372.[38] Gutman, I. J. Chem. Soc., Faraday Trans. 1993, 89, 2413.[39] Alternatively, phenylenes can be treated as PAHs in which neighboring benzenerings are separated by a two-bond spacer.[40] Bühl, M.; Hirsch, A. Chem. Rev. 2001, 101, 1153 and the references cited therein.[41] Tomović, Ž.; Gutman, I. Hemijski Pregled, 2001, 42, 29 and the references citedtherein.306

[42] (a) Wilcox, C. F. Tetrahedron Lett. 1968, 9, 795; (b) Wilcox, C. F. J. Am. Chem.Soc. 1969, 91, 2732.[43] (a) Gutman, I.; Trinajstić, N.; Wilcox, C. F. Tetrahedron 1975, 31, 143; (b) Wilcox,C. F.; Gutman, I.; Trinajstić, N. Tetrahedron 1975, 31, 147.[44] (a) Nikolić, S.; Trinajstić, N.; Mihalić, Z. Croat. Chem. Acta. 1995, 68, 105; (b)Gutman, I.; Yeh, Y. N.; Lee, S. L.; Luo, Y. L. Indian J. Chem. 1993, 32A, 651; (c)Wiener, H. J. Am. Chem. Soc. 1947, 69, 17.[45] Pavlović, Lj.; Gutman, I. J. Chem. Inf. Comput. Sci. 1997, 37, 355.[46] Gutman, I.; Ivanov-Petrović, V. J. Mol. Struct. (THEOCHEM) 1997, 389, 227.[47] For the two earlier summaries, see: (a) Vollhardt, K. P. C.; Mohler, D. L. inAdvances in Strain in Organic Chemistry, Vol. 5 (Ed.: Halton, B.), JAI, London, 1996,121; (b) Vollhardt, K. P. C. Pure. Appl. Chem. 1993, 65, 153.[48] Losey, E. N.; LeGoff, E. J. Org. Chem. 1973, 38, 3812.[49] (a) Barton, J. W.; Walker, R. B. Tetrahedron Lett. 1978, 19, 1005; (b) Jamieson, N.C.; Lewis, G. E. Aust. J. Chem. 1967, 20, 321.[50] Barton, J. W.; Shepard, M. K. Tetrahedron Lett. 1984, 25, 4967.[51] (a) Saito, S.; Yamamoto, Y. Chem. Rev. 2000, 100, 2901; (b) Aubert, C.; Buisine,O.; Petit, M.; Slowinski, F.; Malacria, M. Pure. Appl. Chem. 1999, 71, 1463; (c)Grotjahn, D. B. in Comprehensive Organometallic Chemistry II, Vol. 12 (Eds.: Abel, E.W.; Stone, F. G. A.; Wilkinson, G.; Vol. Ed.: Hegedus, L. S.), Pergamon, Oxford, 1995,741; (d) Vollhardt, K. P. C. Angew. Chem., Int. Ed. Engl. 1984, 23, 539; (e) Schore, N.Chem. Rev. 1988, 88, 1081.307

[52] Berris, B. C.; Lai, Y.-H.; Vollhardt, K. P. C. J. Chem. Soc., Chem. Commun. 1982,953.[53] Berris, B. C.; Hovakeemian, G. H.; Lai, Y.-H., Mestdagh, H.; Vollhardt, K. P. C. J.Am. Chem. Soc. 1985, 107, 5670.[54] Hirthammer, M.; Vollhardt, K. P. C. J. Am. Chem. Soc. 1986, 108, 2481.[55] Schulman, J. M.; Disch, R. L. J. Am. Chem. Soc. 1996, 118, 8470 and the referencescited therein.[56] Berris, B. C.; Hovakeemian, G. H.; Vollhardt, K. P. C. J. Chem. Soc., Chem.Commun. 1983, 502.[57] Blanco, L.; Helson, H. E.; Hirthammer, M.; Mestdagh, H.; Spyroudis, S.; Vollhardt,K. P. C. Angew. Chem., Int. Ed. Engl. 1987, 26, 1246.[58] Holmes, D.; Kumaraswamy, S.; Matzger, A. J.; Vollhardt, K. P. C. Chem. Eur. J.1999, 5, 3399 and unpublished results.[59] Diercks, R.; Vollhardt, K. P. C. Angew. Chem., Int. Ed. Engl. 1986, 25, 266.[60] Schmidt-Radde, R. H.; Vollhardt, K. P. C. J. Am. Chem. Soc. 1992, 114, 9713.[61] Diercks, R.; Eaton, B. E.; Gürtzgen, S.; Jalisatgi, S.; Matzger, A. J.; Radde, R. H.;Vollhardt, K. P. C. J. Am. Chem. Soc. 1998, 120, 8247.[62] Dosa, P. I.; Whitener, G. D.; Vollhardt, K. P. C.; Bond, A. D.; Teat, S. J. Org. Lett.2002, 4, 2075.[63] Jonas, K.; Deffense, E.; Habermann, D. Angew. Chem., Int. Ed. Engl. 1983, 22, 716.[64] Diercks, R.; Armstrong, J. C.; Boese, R.; Vollhardt, K. P. C. Angew. Chem., Int. Ed.Engl. 1986, 25, 268.308

[65] Diercks, R.; Vollhardt, K. P. C. J. Am. Chem. Soc. 1986, 108, 3150.[66] Han, S.; Bond, A. D.; Disch, R. L.; Holmes, D.; Schulman, J. M.; Teat, S. J.;Vollhardt, K. P. C.; Whitener, G. D. Angew. Chem., Int. Ed. 2002, 41, 3223.[67] Schulman, J. M.; Disch, R. L. J. Phys. Chem. A 1997, 101, 5596.[68] (a) Hopf, H. Classics in Hydrocarbon Chemistry, Wiley-VCH, Weinheim, 2000,321; (b) Vögtle, F. Fascinating Molecules in Organic Chemistry, Wiley, New York,1992, 156; (c) Meurer, K. P.; Vögtle, F. Top. Curr. Chem. 1985, 127, 1; (d) Laarhoven,W. H.; Prinsen, W. J. C. Top. Curr. Chem. 1984, 125, 63.[69] Eickmeier, C.; Junga, H.; Matzger, A. J.; Scherhag, F.; Shim, M.; Vollhardt, K. P. C.Angew. Chem., Int. Ed. Engl. 1997, 36, 2103.[70] Han, S.; Anderson, D. R.; Bond, A. D.; Chu, H. V.; Disch, R. L.; Holmes, D.;Schulman, J. M.; Teat, S. J.; Vollhardt, K. P. C.; Whitener, G. D. Angew. Chem., Int. Ed.2002, 41, 3227.[71] Schulman, J. M.; Disch, R. L. J. Phys. Chem. A 2003, 107, 5223.[72] (a) Schulman, J. M.; Disch, R. L. Chem. Phys. Lett. 1996, 262, 813; (b) Haymet, A.D. J. Chem. Phys. Lett. 1985, 122, 421.[73] Dunlap, B. T.; Taylor, R. J. Phys. Chem. 1994, 98, 11018.[74] Eickmeier, C.; Holmes, D.; Junga, H.; Matzger, A. J.; Scherhag, F.; Shim, M.;Vollhardt, K. P. C. Angew. Chem., Int. Ed. Engl. 1999, 38, 800.[75] Bong, D. T.-Y.; Gentric, L.; Holmes, D.; Matzger, A. J.; Scherhag, F.; Vollhardt, K.P. C. Chem. Commun. 2002, 278.309

[76] Bong, D. T.-Y.; Chan, E. W. L.; Diercks, R.; Dosa, P. I.; Haley, M. M.; Matzger, A.J.; Miljanić, O. Š.; Vollhardt, K. P. C.; Bond, A. D.; Teat, S. J.; Stanger, A. Org. Lett.2004, 6, 2249.[77] Hart, H.; Katsumasa, K.; Du, C.-J. F. J. Org. Chem. 1985, 50, 3104.[78] Goldfinger, M. B.; Crawford, K. B.; Swager, T. M. J. Am. Chem. Soc. 1997, 119,4578.[79] Boese, R.; Matzger, A. J.; Mohler, D. L.; Vollhardt, K. P. C. Angew. Chem., Int. Ed.Engl. 1995, 34, 1478.[80] Anthony, J. E.; Khan, S. I.; Rubin, Y. Tetrahedron Lett. 1997, 38, 3499.[81] Baxter, P. N. J. Org. Chem. 2001, 66, 4170.[82] Bruns, D.; Miura, H.; Vollhardt, K. P. C.; Stanger, A. Org. Lett. 2003, 5, 549.[83] (a) Schleyer, P. v. R.; Jiao, H. Angew. Chem., Int. Ed. Engl. 1996, 35, 2383; (b)Aihara, J. J. Chem. Soc., Faraday Trans. 1995, 91, 237; (c) Babić, D.; Trinajstić, N. J.Mol. Struct. (THEOCHEM) 1994, 120, 321; (d) Gutman, I.; Cyvin, S. J. J. Mol. Struct.(THEOCHEM) 1993, 107, 85; (e) Aihara, J. Bull. Chem. Soc. Jpn. 1993, 66, 57; (f)Aihara, J. J. Am. Chem. Soc. 1992, 114, 865; (g) Cioslowski, J.; O’Connor, P. B.;Fleischmann, E. D. J. Am. Chem. Soc. 1991, 113, 1086.[84] (a) Matzger, A. J.; Shim, M.; Vollhardt, K. P. C. Chem. Commun. 1999, 1871; (b)Miljanić, O. Š.; Vollhardt, K. P. C.; Whitener, G. D. Synlett 2003, 29.[85] (a) Staab, H. A.; Diederich, F. Chem. Ber. 1983, 116, 3487; (b) Staab, H. A.;Diederich, F.; Krieger, C.; Schweitzer, D. Chem. Ber. 1983, 116, 3504.310

[86] (a) Campbell, I. D.; Eglinton, G.; Henderson, W.; Raphael, R. A. Chem. Commun.1966, 87; (b) Solooki, D.; Ferrara, J. D.; Malaba, D.; Bradshaw, J. D.; Tessier, C. A.;Youngs, W. J. Inorg. Synth. 1997, 31, 122; (c) Huynh, C.; Linstrumelle, G. Tetrahedron1988, 44, 6337; (d) Iyoda, M.; Vorasingha, A.; Kuwatani, Y.; Yoshida, M. TetrahedronLett. 1988, 39, 4701.[87] (a) Staab, H. A.; Graf, F. Tetrahedron Lett. 1966, 7, 751; (b) Staab, H. A.; Graf, F.Chem. Ber. 1970, 103, 1107.[88] (a) Bunz, U. H. F.; Rubin, Y.; Tobe, Y. Chem. Soc. Rev. 1999, 28, 107; (b)Diederich, F. Nature 1994, 369, 199.[89] (a) Coluci, V. R.; Galvão, D. S.; Baughman, R. H. J. Chem. Phys. 2004, 121, 3228;(b) Narita, N.; Nagai, S.; Suzuki, S. Phys. Rev. B 2001, 64, 245408/1; (c) Narita, N.;Nagai, S.; Suzuki, S.; Nakao, K. Phys. Rev. B 2000, 62, 11146; (d) Narita, N.; Nagai, S.;Suzuki, S.; Nakao, K. Phys. Rev. B 1998, 58, 11009; (e) Haley, M. M. Synlett 1998, 557.[90] Hovakeemian, G. H.; Vollhardt, K. P. C. Angew. Chem., Int. Ed. Engl. 1983, 22,994.[91] Mohler, D. L.; Vollhardt, K. P. C.; Wolff, S. Angew. Chem., Int. Ed. Engl. 1990, 29,1151.[92] Augustine, R. L. Heterogeneous Catalysis for the Synthetic Chemist, Marcel Dekker,New York/Basel/Hong Kong, 1996.[93] (a) Soncini, A.; Havenith, R. W. A.; Fowler, P. W.; Jenneskens, L. W.; Steiner, E. J.Org. Chem. 2002, 67, 4753; (b) Fowler, P. F.; Havenith, R. W. A.; Jenneskens, L. W.;Soncini, A.; Steiner, E. Chem. Commun. 2001, 2386.311

[94] Miljanić, O. Š.; Vollhardt, K. P. C. unpublished results.[95] (a) Jeyaraman, R.; Murray, R. W. J. Am. Chem. Soc. 1984, 106, 2462; (b) Murray,R. W.; Jeyaraman, R. J. Org. Chem. 1985, 50, 2847; (c) Adam, W.; Chan, Y.-Y.; Cremer,D.; Gauss, J.; Scheutzow, D.; Schindler, M. J. Org. Chem. 1987, 52, 2800; (d) Adam, W.;Curci, R.; Edwards, J. O. Acc. Chem. Res. 1989, 22, 205.[96] Adam, W.; Balci, M.; Kiliç, H. J. Org. Chem. 1998, 63, 8544.[97] Kumaraswamy, S.; Jalisatgi, S. S.; Matzger, A. J.; Miljanić, O. Š.; Vollhardt, K. P.C. Angew. Chem., Int. Ed. 2004, 43, 3771.[98] Kende, A. S.; MacGregor, P. T. J. Am. Chem. Soc. 1964, 86, 2088.[99] Furukawa, J.; Kawabata, N.; Nishimura, J. Tetrahedron 1968, 24, 53.[100] Sevin, F.; McKee, M. L. J. Am. Chem. Soc. 2001, 123, 4591 and the referencescited therein.[101] Mestdagh, H.; Vollhardt, K. P. C. J. Chem. Soc., Chem. Commun. 1986, 281.[102] (a) Gajewski, J. J. Hydrocarbon Thermal Isomerizations, Academic Press, NewYork/London/Toronto/Syndey/San Francisco, 1981; (b) Harvey, R. G. Curr. Org. Chem.2004, 8, 303; (c) Scott, L. T. Angew. Chem., Int. Ed. 2004, 43, 4994.[103] Wiersum, U.; Jenneskens, L. W. Tetrahedron Lett. 1993, 34, 6615.[104] For recent mechanistic reviews, see: (a) Necula, A.; Scott, L. T. J. Anal. Appl.Pyrol. 2000, 54, 65; (b) Brown, R. F. C. Eur. J. Org. Chem. 1999, 3211.[105] Dosa, P. I.; Schleifenbaum, A. S.; Vollhardt, K. P. C. Org. Lett. 2001, 3, 1017.[106] Matzger, A. J.; Vollhardt, K. P. C. Chem. Commun. 1997, 1415.[107] Preda, D. V.; Scott, L. T. Org. Lett. 2000, 2, 1489.312

[108] (a) Oh, M.; Yu, K.; Li, H.; Watson, E. J.; Carpenter, G. B.; Sweigart, D. A. Adv.Synth. Catal. 2003, 345, 1053 and the references cited therein; (b) Perthuisot, C.;Edelbach, B. L.; Zubris, D. L.; Jones, W. D. Organometallics 1997, 16, 2016.[109] (a) Oprunenko, Y.; Gloriozov, I.; Lyssenko, K.; Malyugina, S.; Mityk, D.;Mstislavsky, V.; Günther, H.; von Firks, G.; Ebener, M. J. Organomet. Chem. 2002, 656,27; (b) Dullaghan, C. A.; Carpenter, G. B.; Sweigart, D. A. Chem. Eur. J. 1997, 3, 75; (c)Eischenbroich, C.; Schneider, J.; Massa, W.; Baum, G.; Mellinghoff, H. J. Organomet.Chem. 1988, 355, 163.[110] Ceccon, A.; Gambaro, A.; Romanin, A. M.; Venzo, A. J. Organomet. Chem. 1982,239, 345.[111] Nambu, M.; Siegel, J. S. J. Am. Chem. Soc. 1988, 110, 3675.[112] Nambu, M.; Hardcastle, K.; Baldridge, K. K.; Siegel, J. S. J. Am. Chem. Soc. 1992,114, 369.[113] Nambu, M.; Mohler, D. L.; Hardcastle, K.; Baldridge, K. K.; Siegel, J. S. J. Am.Chem. Soc. 1993, 115, 6138.[114] Brown, R. D.; Godfrey, P. D.; Hart, B. T.; Ottrey, A. L.; Onda, M.; Woodruff, M.Aust. J. Chem. 1983, 36, 639.[115] Schleifenbaum, A.; Feeder, N.; Vollhardt, K. P. C. Tetrahedron Lett. 2001, 42,7329.[116] (a) Volland, W. V.; Davidson, E. R.; Borden, W. T. J. Am. Chem. Soc. 1979, 101,533; (b) Allinger, N. L. J. Am. Chem. Soc. 1958, 80, 1953; (c) Allinger, N. L.; Sprague, J.T. J. Am. Chem. Soc. 1972, 94, 5734; (d) Rogers, D. W.; Voitkenberg, H.; Allinger, N. L.313

J. Org. Chem. 1978, 43, 360; (e) Mock, W. L. Tetrahedron Lett. 1972, 475; (f) Pople, J.A.; Mock, W. L. Tetrahedron Lett. 1972, 479.[117] (a) Petersson, E. J.; Fanuele, J. C.; Nimlos, M. R.; Lemal, D. M.; Ellison, G. B.;Radziszewski, J. G. J. Am. Chem. Soc. 1997, 119, 11122; (b) Bremer, M.; Schleyer, P. v.R.; Fleischer, U. J. Am. Chem. Soc. 1989, 111, 1147.[118] De Rango, C.; Tsoucaris, G.; Declerq, J. P.; Germain, G.; Putzeys, J. P. ActaCrystallogr. Sect. C 1973, 2, 189.[119] (a) van den Hark, T. E. M.; Beurskens, P. T. Acta Crystallogr. Sect. C 1976, 5, 247;(b) Beurskens, P. T.; Beurskens, G.; van den Hark, T. E. M. Acta Crystallogr. Sect. C1976, 5, 241.[120] Grimme, S.; Harren, J.; Sobanski, A.; Vögtle, F. Eur. J. Org. Chem. 1998, 1491.[121] Schleyer, P. v. R.; Maerker, C.; Dransfeld, A.; Jiao, H.; van Eikema Hommes, N. J.R. J. Am. Chem. Soc. 1996, 118, 6317.[122] Schleyer, P. v. R.; Manoharan, M.; Wang, Z.-X.; Kiran, B.; Jiao, H.; Puchta, R.;van Eikema Hommes, N. J. R. Org. Lett. 2001, 3, 2465.[123] Schulman, J. M.; Disch, R. L.; Jiao, H.; Schleyer, P. v. R. J. Phys. Chem. A 1998,102, 8051.[124] Adcock, W.; Gupta, B. D.; Khor, T. C.; Doddrell, D.; Kitching, W. J. Org. Chem.1976, 41, 751.[125] Thummel, R. P.; Nutakul, W. J. Org. Chem. 1978, 43, 3170.[126] Fukui, K. Orientation and Stereoselection, Springer, Berlin, 1970.[127] Heeger, A. J. Angew. Chem., Int. Ed. 2001, 40, 2591 (Nobel lecture).314

[128] NIST Chemistry WebBook, NIST Standard Reference Database Number 69,November 1998, National Institute of Standards and Technology, Gaithersburg, MD20899 (http://webbook.nist.gov).[129] Maksić, Z. B.; Kovaček, D.; Maksić-Eckert, M.; Böckmann, M.; Klessinger, M. J.Phys. Chem. 1995, 99, 6410.[130] (a) Wenz, G.; Müller, M. A.; Schmidt, M.; Wegner, G. Macromolecules 1984, 17,837; (b) Martin, R. E.; Diederich, F. Angew. Chem., Int. Ed. 1999, 38, 1350; (c) Geerts,Y.; Klärner, G.; Müllen, K. in Electronic Materials: The Oligomer Approach, Wiley-VCH, Weinheim, 1998.[131] Dosche, C.; Löhmannsröben, H.-G.; Bieser, A.; Dosa, P. I.; Han, S.; Iwamoto, M.;Schleifenbaum, A.; Vollhardt, K. P. C. Phys. Chem. Chem. Phys. 2002, 4, 2156.[132] Shpol’skii, E. V.; Il’ina, A. A.; Klimova, L. A. Dokl. Akad. Nauk SSSR 1952, 87,935.[133] Dosche, C.; Kumke, M. U.; Ariese, F.; Bader, A. N.; Gooijer, C.; Dosa, P. I.; Han,S.; Miljanić, O. Š.; Vollhardt, K. P. C.; Puchta, R.; van Eikema Hommes, N. J. R. Phys.Chem. Chem. Phys. 2003, 5, 4563.[134] Dosche, C.; Kumke, M. U.; Löhmannsröben, H.-G.; Ariese, F.; Bader, A. N.;Gooijer, C.; Miljanić, O. Š.; Iwamoto, M.; Vollhardt, K. P. C.; Puchta, R.; van EikemaHommes, N. J. R. Phys. Chem. Chem. Phys. 2004, 6, 5476.[135] Haley, M. M. Postdoctoral Report, University of California, Berkeley, 1993.[136] Westmoreland, I.; Que, E.; Miyagi, L. Acta Crystallogr. Sect. E 2005, manuscriptin preparation.315

[137] Hillard III, R. L.; Vollhardt, K. P. C. J. Am. Chem. Soc. 1977, 99, 4058.[138] Review: (a) Beller, M.; Seayad, J.; Tillack, A.; Jiao, H. Angew. Chem., Int. Ed.2004, 43, 3368. Examples: (b) Alper, H.; Saldana–Maldonado, M.; Lin, L. J. B. J. Mol.Catal. 1988, 49, L27; (c) El Ali, B.; Alper, H. J. Mol. Catal. A 1995, 96, 197.[139] Camacho, D. H.; Saito, S.; Yamamoto, Y. Tetrahedron Lett. 2002, 43, 1085.[140] Selected examples: (a) Ogo, S.; Uehara, K.; Abura, T.; Watanabe, Y.; Fukuzumi, S.J. Am. Chem. Soc. 2004, 126, 16520; (b) Grotjahn, D. B.; Incarvito, C. D.; Rheingold, A.L. Angew. Chem., Int. Ed. 2001, 40, 3884.[141] Selected recent examples: (a) Liang, B.; Dai, M.; Chen, J.; Yang, Z. J. Org. Chem.2005, 70, 391; (b) Wolf, C.; Lerebours, R. Org. Biomol. Chem. 2004, 2, 2161; (c)Bhattacharya, S.; Sengupta, S. Tetrahedron Lett. 2004, 45, 8733.[142] Nicolaou, K. C.; Dai, W. M.; Hong, Y. P.; Baldridge, K. K.; Siegel, J. S.; Tsay, S.C. J. Am. Chem. Soc. 1993, 115, 7944.[143] Moran, D.; Stahl, F.; Bettinger, H. F.; Schaefer, H. F. III, Schleyer, P. v. R. J. Am.Chem. Soc. 2003, 125, 6746.[144] Reviews: (a) Fürstner, A.; Davies, P. W. Chem. Commun. 2005, 2307; (b) Fürstner,A. in Handbook of Metathesis, Vol. 2 (Ed.: Grubbs, R. H.), Wiley-VCH, Weinheim,2005, 432; (c) Bunz, U. H. F. Science 2005, 308, 216.[145] Selected references: (a) Mortreux, A.; Petit, F.; Blanchard, M. Tetrahedron Lett.1978, 49, 4967; (b) Mortreux, A.; Dy, N.; Blanchard, M. J. Mol. Catal. 1976, 1, 101; (c)Mortreux, A.; Blanchard, M. J. Chem. Soc, Chem. Commun. 1974, 786.[146] Summary of the reactivity of [Mo(CO) 6 ]: Marradi, M. Synlett 2005, 1196.316

[147] Selected references: (a) Sashuk, V.; Ignatowska, J.; Grela, K. J. Org. Chem. 2004,69, 7748; (b) Grela, K.; Ignatowska, J. Org. Lett. 2002, 4, 3747; (c) Brizius, G.; Bunz, U.H. F. Org. Lett. 2002, 4, 2829; (d) Villemin, D.; Héroux, M.; Blot, V. Tetrahedron 2001,42, 3701; (e) Pschirer, N. G.; Bunz, U. H. F. Tetrahedron Lett. 1999, 40, 2481; (f) duPlessis, J. A. K.; Vosloo, H. C. M. J. Mol. Catal. A: Chem. 1998, 133, 305.[148] Selected references: (a) Hellbach, B.; Gleiter, R.; Rominger, F. Synthesis 2003,2535; (b) Brizius, G.; Billingsley, K.; Smith, M. D.; Bunz, U. H. F. Org. Lett. 2003, 5,3951; (c) Brizius, G.; Kroth, S.; Bunz, U. H. F. Macromolecules 2002, 35, 5317; (d)Pschirer, N. G.; Fu, W.; Adams, R. D.; Bunz, U. H. F. Chem. Commun. 2000, 87; (e) Ge,P.-H.; Fu, W.; Herrmann, W. A.; Herdtweck, E.; Campana, C.; Adams, R. A.; Bunz, U.H. F. Angew. Chem., Int. Ed. 2000, 39, 3607. Reviews: (f) Bunz, U. H. F. Acc. Chem.Res. 2001, 34, 998; (g) Bunz, U. H. F.; Kloppenburg, L. Angew. Chem., Int. Ed. 1999, 38,478.[149] (a) Schrock, R. R. Acc. Chem. Res. 1986, 19, 342; (b) Schrock R. R.; Clark, D. N.;Sancho, J.; Wengrovius, J. H.; Rocklage, S. M.; Pedersen, S. F.Organometallics 1982, 1, 1645; (c) Wengrovius, J. H.; Sancho, J.; Schrock, R. R. J. Am.Chem. Soc. 1981, 103, 3932.[150] Selected references: (a) Fürstner, A.; Castanet, A.-S.; Radkowski, K.; Lehmann, C.W. J. Org. Chem. 2003, 68, 1521; (b) Song, D.; Blond, G.; Fürstner, A. Tetrahedron2003, 59, 6899; (c) Fürstner, A.; Dierkes, T. Org. Lett. 2000, 2, 2463; (d) Fürstner, A.;Seidel, G. J. Organomet. Chem. 2000, 606, 75; (e) Fürstner, A.; Guth, O.; Rumbo, A.;317

Seidel, G. J. Am. Chem. Soc. 1999, 121, 11108; (f) Fürstner, A.; Seidel, G. Angew.Chem., Int. Ed. 1998, 37, 1734.[151] (a) Bauer, E. B.; Hampel, F.; Gladysz, J. A. Adv. Synth. Cat. 2004, 346, 812; (b)Bauer, E. B.; Szafert, S.; Hampel, F.; Gladysz, J. A. Organometallics 2003, 22, 2184; (c)Ijsselstijn, M.; Aguilera, B.; van der Marel, G. A.; van Boom, J. H.; van Delft, F. L.;Schoemaker, H. E.; Overkleeft, H. S.; Rutjes, F. P. J. T.; Overhand, M. Tetrahedron Lett.2004, 45, 4379.[152] Strem Chemicals, catalog number 74-1800, $295.00/500 mg (May 2005).[153] (a) Fürstner, A.; Mathes, C.; Lehmann, C. W. Chem. Eur. J. 2001, 7, 5299; (b)Fürstner, A.; Grela, K.; Mathes, C.; Lehmann, C. W. J. Am. Chem. Soc. 2000, 122,11799; (c) Fürstner, A.; Mathes, C.; Lehmann, C. W. J. Am. Chem. Soc. 1999, 121, 9453.[154] Selected references: (a) Zhang, W.; Moore, J. S. J. Am. Chem. Soc. 2004, 126,12796 and the references cited therein; (b) Fürstner, A.; Mathes, C. Org. Lett. 2001, 3,221.[155] Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. in Principles andApplications of Organotransition Metal Chemistry, University Science Books, MillValley, 1987, Chapter 9.[156] Bino, A.; Ardon, M.; Shirman, E. Science 2005, 308, 324.[157] For a highlight, see: (a) Höger, S. Angew. Chem., Int. Ed. 2005, 44, 3806. Reviews:(b) Tobe, Y.; Sonoda, M. in Modern Cyclophane Chemistry (Eds.: Gleiter, R.; Hopf, H.),Wiley-VCH, Weinheim, 2004, 1; (c) Marsden, J. A.; Palmer, G. J.; Haley, M. M. Eur. J.Org. Chem. 2003, 2355; (d) Haley, M. M. Synlett 1998, 557; (e) Haley, M. M.; Pak, J. J.;318

Brand, S. C. Top. Curr. Chem. 1999, 202, 81; (f) Haley, M. M.; Wan, W. B. in Advancesin Strained and Interesting Organic Molecules, Vol. 8 (Ed.: Halton, B.), JAI Press, NewYork, 2000, 1; (g) Kennedy, R. D.; Lloyd, D.; McNab, H. J. Chem. Soc., Perkin Trans. 12002, 1601; (h) Balaban, A.T.; Banciu, M.; Ciorba, V. Annulenes, Benzo-, Hetero-,Homo-Derivatives and Their Valence Isomers, Vol. 2, CRC Press, Boca Raton, 1987,146. For very recent work, see, inter alia: (i) Marsden, J. A.; Miller, J. J.; Shirtcliff, L. D.;Haley, M. M. J. Am. Chem. Soc. 2005, 127, 2464; (j) Johnson, C. A.; Haley, M. M.;Rather, E.; Han, F.; Weakley, T. J. R. Organometallics 2005, 24, 1161; (k) Baxter, P. N.W.; Dali-Youcef, R. J. Org. Chem. 2005, 70, 4935; (l) Hisaki, I.; Eda, T.; Sonoda, M.;Niino, H.; Sato, T.; Wakabayashi, T.; Tobe, Y. J. Org. Chem. 2005, 70, 1853.[158] Review: (a) Youngs, W. J.; Tessier, C. A.; Bradshaw, J. D. Chem. Rev. 1999, 99,3153. Selected references: (b) Iyoda, M.; Sirinintasak, S.; Nishiyama, Y.; Vorasingha, A.;Sultana, F.; Nakao, K.; Kuwatani, Y.; Matsuyama, H.; Yoshida, M.; Miyake, Y. Synthesis2004, 1527; (c) Nishinaga, T.; Kawamura, T.; Komatsu, K. Chem. Commun. 1998, 2263;(d) Youngs, W. J.; Kinder, J. D.; Bradshaw, J. D.; Tessier, C. A. Organometallics 1993,12, 2406; (e) Djebli, A.; Ferrara, J. D.; Tessier-Youngs, C.; Youngs, W. J. J. Chem. Soc.,Chem. Commun. 1988, 548; (f) Ferrara, J. D.; Tessier-Youngs, C.; Youngs, W. J. J. Am.Chem. Soc. 1988, 110, 3326.[159] (a) Iyer, V. S.; Vollhardt, K. P. C.; Wilhelm, R. Angew. Chem., Int. Ed. 2003, 42,4379; (b) Dosa, P. I.; Erben, C.; Iyer, V. S.; Vollhardt, K. P. C.; Wasser, I. M. J. Am.Chem. Soc. 1999, 121, 10430; (c) Boese, R.; Matzger, A. J.; Vollhardt, K. P. C. J. Am.Chem. Soc. 1997, 119, 2052.319

[160] Selected references: (a) Pak, J. J.; Weakley, T. J. R.; Haley, M. M.; Lau, D. Y. K.;Stoddart, J. F. Synthesis 2002, 1256; (b) Tobe, Y.; Utsumi, N.; Kawabata, K.; Nagano,A.; Adachi, K.; Araki, S.; Sonoda, M.; Hirose, K.; Naemura, K. J. Am. Chem. Soc. 2002,124, 5350; (c) Hosokawa, Y.; Kawase, T.; Oda, M. Chem. Commun. 2001, 1948; (d)Nakamura, K.; Okubo, H.; Yamaguchi, M. Org. Lett. 2001, 3, 1097; (e) Höger, S.;Enkelmann, V.; Bonrad, K.; Tschierske, C. Angew. Chem., Int. Ed. 2000, 39, 2268. Seealso: (f) Moore, J. S. Acc. Chem. Res. 1997, 30, 402; (g) Zhang, J.; Pesak, D. J.; Ludwick,J. L.; Moore, J. S. J. Am. Chem. Soc. 1994, 116, 4227; (h) Pickholz, M.; Stafström, S.Chem. Phys. 2001, 270, 245.[161] Selected references: (a) Sarkar, A.; Pak, J. J.; Rayfield, G. W.; Haley, M. M. J.Mater. Chem. 2001, 11, 2943. (b) Wan, W. B.; Haley, M. M. J. Org. Chem. 2001, 66,3893.[162] Holmes, D. Ph. D. Dissertation, University of California, Berkeley, 1999.[163] Kehoe, J. M.; Kiley, J. H.; English, J. J.; Johnson, C. A.; Petersen, R. C.; Haley, M.M. Org. Lett. 2000, 2, 969.[164] For 155b and 155d: (a) Kryska, A.; Skulski, L. J. Chem. Res.(S) 1999, 590. For155c: (b) Lacour, J.; Monchaud, D.; Bernardinelli, G.; Favarger, F. Org. Lett. 2001, 3,1407. For 161b: (c) Mattern, D. L. J. Org. Chem. 1983, 48, 4772. For 57, ref. 78.[165] Nakayama, J.; Sakai, A.; Hoshino, M. J. Org. Chem. 1984, 49, 5084.[166] Professor John Anthony, personal communication.[167] Garden, S. J.; Torres, J. C.; Ferreira, A. A.; Silva, R. B.; Pinto, A. C. TetrahedronLett. 1997, 38, 1501.320

[168] Lisowski, V.; Robba, M.; Rault, S. J. Org. Chem. 2000, 65, 4193.[169] Wan, W. B.; Haley, M. M. J. Org. Chem. 2001, 66, 3893.[170] Recent reports opened the possibility of using chloroiodoarenes for the samepurpose: (a) Gelman, D.; Buchwald, S. L. Angew. Chem., Int. Ed. 2003, 42, 5993; (b)Köllhofer, A.; Pullmann, T.; Plenio, H. Angew. Chem., Int. Ed. 2003, 42, 1056. Due tothe huge difference in Sonogashira reactivity between chlorides and iodides,distinguishing these two groups was trivial in our propynylation experiments.[171] (a) Sonogashira, K. in Handbook of Organopalladium Chemistry for OrganicSynthesis, Vol. 1 (Ed.: Negishi, E.-i.), Wiley, New York, 2002, 493 and the referencescited therein; (b) Sonogashira, K. in Metal-Catalyzed Cross-Coupling Reactions (Eds.:Diederich, F., Stang, P. J.), Wiley-VCH, New York, 1998, Chapter 5; (c) Sonogashira, K.in Comprehensive Organic Synthesis, Vol. 3 (Ed.: Trost, B. M.), Pergamon, New York,1991, Chapter 2.4.[172] Related applications of microwaves in Sonogashira reactions: (a) Petricci, E.; Radi,M.; Corelli, F.; Botta, M. Tetrahedron Lett. 2003, 44, 9181; (b) Erdelyi, M.; Gogoll, A. J.Org. Chem. 2001, 66, 4165. General reviews of microwave-assisted reactivity: (c) Kappe,C. O. Angew. Chem., Int. Ed. 2004, 43, 6250; (d) Lidström, P.; Tierney, J.; Wathey, B.;Westman, J. Tetrahedron 2001, 57, 9225.[173] We are indebted to Personal Chemistry, Inc. (now Biotage, Inc.) for the loan of aSmith Synthesizer TM .321

[174] We would like to thank Prof. Alois Fürstner and Mr. Günter Seidel (Max-Planck-Institut für Kohlenforschung, Mülheim/Ruhr, Germany) for catalyzing the initiation ofthis effort with generous samples of [(Me 3 CO) 3 W≡CCMe 3 ].[175] Li, Y.; Zhang, J.; Wang, W.; Miao, Q.; She, X.; Pan, X. J. Org. Chem. 2005, 70,3285.[176] The spectral data are in good agreement with those in ref. 87b.[177] The spectral data are in good agreement with those in ref. 86d.[178] Srinivasan, M.; Sankararaman, S.; Dix, I.; Jones, P. G. Org. Lett. 2000, 2, 3849.[179] See Experimental Section for complete details. Details of the crystal structuredetermination (deposition number CCDC 192630) may also be obtained free of charge onapplication to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: (+44) 1223–336–033; E-mail: deposit@ccdc.cam.ac.uk).[180] (a) Alkorta, I.; Rozas, I.; Elguero, J. Tetrahedron 2001, 57, 6043; (b) Jusélius, J.;Sundholm, D. Phys.Chem. Chem.Phys. 2001, 3, 2433; (c) Godard, C.; Lepetit, C.;Chauvin, R. Chem. Commun. 2000, 1833; (d) Wan, W. B.; Kimball, D. B.; Haley, M. M.Tetrahedron Lett. 1998, 39, 6795; (e) Matzger, A. J.; Vollhardt, K. P. C. TetrahedronLett. 1998, 39, 6791.[181] Miljanić, O. Š.; Holmes, D.; Vollhardt, K. P. C. Org. Lett. 2005, 7, in press.[182] Gilles, J.-M.; Oth, J. F. M.; Sondheimer, F.; Woo, E. P. J. Chem. Soc. (B) 1971,2177.[183] For triple cyclizations of this type, see ref. 82 and references therein.322

[184] For an isomeric dehydrotetrabenz[32]annulene, see: Haley, M. M.; Bell, M. L.;Brand, S. C.; Kimball, D. B.; Pak, J. J.; Wan, W. B. Tetrahedron Lett. 1997, 43, 7483.[185] While 184b and 176b were not known prior to this work, they were readilyprepared using the procedure described for 184c and 146 (see Section 6.4).[186] Strained ring fusion increases J para in arenes. For a review, see: Frank, N. L.; Siegel,J. S. in Advances in Theoretically Interesting Molecules, Vol. 3 (Ed.: Thummel R. P.),JAI, London, 1995, 209.[187] Miljanić, O. Š.; Han, S.; Holmes, D.; Schaller, G. R.; Vollhardt, K. P. C. Chem.Commun. 2005, 2606.[188] Eliel, E. L.; Wilen, S. H.; Mander, L. N. Stereochemistry of Organic Compounds,Wiley, New York, 1994, 1142.[189] Yamamoto, G.; Ōki, M. Chem. Lett. 1972, 45.[190] Nakamura, M.; Ōki, M. Tetrahedron Lett. 1974, 15, 505.[191] Mew, P. K. T.; Vögtle, F. Angew. Chem., Int. Ed. Engl. 1979, 18, 159.[192] Meyer, W. L.; Meyer, R. B. J. Am. Chem. Soc. 1963, 85, 2170.[193] Toyota, S.; Makino, T. Tetrahedron Lett. 2003, 44, 7775.[194] First observation: Christie, G. H.; Kenner, J. H. J. Chem. Soc. 1922, 121, 614.[195] (a) Seminario, J. M.; Zacarias, A. G.; Tour, J. M. J. Am. Chem. Soc. 1998, 120,3970; (b) Stølevic, R.; Bakken, P. J. Mol. Struct. 1990, 239, 205; (c) Grumadas, A.;Poskus, D. Zh. Fiz. Khim. 1987, 61, 2838; (d) Okuyama, K.; Hasegawa, T.; Ito, M.;Mikami, N. J. Phys. Chem. 1984, 88, 1711.323

[196] Toyota, S.; Yamamori, T.; Makino, T. Tetrahedron 2001, 57, 3521 and referencescited therein.[197] Dominguez, Z.; Dang, H.; Strouse, M. J.; Garcia-Garibay, M. A. J. Am. Chem. Soc.2002, 124, 2398.[198] Bedard, T. C.; J. S. Moore J. Am. Chem. Soc. 1995, 117, 10662.[199] Toyota, S.; Iida, T.; Kunizane, C.; Tanifuji, N.; Yoshida, Y. Org. Biomol. Chem.2003, 1, 2298.[200] (a) Raker, J.; Glass, T. E. J. Org. Chem. 2001, 66, 6505; (b) Glass, T. E. J. Am.Chem. Soc. 2000, 122, 4522; (c) Yagi, S.; Kitayama, H.; Takagishi, T. J. Chem. Soc.,Perkin Trans. 1 2000, 925; (d) Godinez, C. E.; Zepeda, G.; Mortko, C. J.; Dang, H.;Garcia-Garibay, M. A. J. Org. Chem. 2004, 69, 1652; (e) Dominguez, Z.; Dang, H.;Strouse, M. J.; Garcia-Garibay, M. A. J. Am. Chem. Soc. 2002, 124, 7719; (f) Joachim,C.; Tang, H.; Moresco, F.; Rapenne, G.; Meyer, G. Nanotechnology 2002, 13, 330.[201] Examples: (a) Toyota, S.; Goichi, M.; Kotani, M. Angew. Chem., Int. Ed. 2004, 43,2248; (b) Brizius, G.; Billingsley, K.; Smith, M. D.; Bunz, U. H. F. Org. Lett. 2003, 5,3951; (c) Levitus, M.; Schmieder, K.; Ricks, H.; Shimizu, K. D.; Bunz, U. H. F.; Garcia-Garibay, M. A. J. Am. Chem. Soc. 2001, 123, 4259; (d) Miteva, T.; Palmer, L.;Kloppenburg, L.; Neher, D.; Bunz, U. H. F. Macromolecules 2000, 33, 652.[202] The parent 2,2’,6,6’-tetrakisethynyldiphenylacetylene (205a, R = R’ = H) isknown: Bradshaw, J. D.; Guo, L.; Tessier, C. A.; Youngs, W. J. Organometallics 1996,15, 2582.324

[203] Houk, K. N.; Scott, L. T.; Rondan, N. G.; Spellmeyer, D. C.; Reinhardt, G.; Hyun,J. L.; DeCicco, G. J.; Weiss, R.; Chen, M. H. M.; Bass, L. S.; Clardy, J.; Jørgensen, F. S.;Eaton, T. A.; Sarkozi, V.; Petit, C. M.; Ng, L.; Jordan, K. D. J. Am. Chem. Soc. 1985,107, 6556.[204] (a) Marsden, J. A.; O’Connor, M. J.; Haley, M. M. Org. Lett. 2004, 6, 2385; (b)Sonoda, M.; Sakai, Y.; Yoshimura, T.; Tobe, Y.; Kamada, K. Chem. Lett. 2004, 33, 972.[205] Reviews: (a) Tang, W.; Zhang, X. Chem. Rev. 2003, 103, 3029; (b) Mikami, K.;Aikawa, K.; Yusa, Y.; Jodry, J. J.; Yamanaka, M. Synlett 2002, 1561; (c) McCarthy, M.;Guiry, P. J. Tetrahedron 2001, 57, 3809.[206] For previous examples of conformationally locked dehydrobenzannulenes (andanalogs) in which this phenomenon is skeleton-induced, see: (a) Heuft, M. A.; Collins, S.K.; Fallis, A. G. Org. Lett. 2003, 5, 1911; (b) Heuft, M. A.; Fallis, A. G. Angew. Chem.,Int. Ed. 2002, 41, 4520; (c) Marsella, M.; Kim, I. T.; Tham, F. J. Am. Chem. Soc. 2000,122, 974; (d) Boese, R.; Matzger, A. J.; Vollhardt, K. P. C. J. Am. Chem. Soc. 1997, 119,2052.[207] (a) Ōki, M. Applications of Dynamic NMR Spectroscopy to Organic Chemistry,VCH, Weinheim, 1985; (b) Gasparro, F. P.; Kolodny, N. H. J. Chem. Ed. 1977, 54, 258.[208] (a) Tobe, Y.; Ohki, I.; Sonoda, M.; Niino, H.; Sato, T.; Wakabayashi, T. J. Am.Chem. Soc. 2003, 125, 5614; (b) Kowalik, J.; Tolbert, L. M. J. Org. Chem. 2001, 66,3229.[209] Müller, M.; Förster, W.-R.; Holst, A.; Kingma, A. J.; Schaumann, E.; Adiwidjaja,G. Chem. Eur. J. 1996, 2, 949.325

[210] Hisaki, I.; Vollhardt, K. P. C., unpublished results.[211] We are grateful to Prof. Odile Eisenstein (University of Montpellier, France) for aninsightful discussion.[212] The limitations of this approach are clear: two independent variables define a twodimensionalconformation space, within which we meant to explore only a singletrajectory. While the software used had an option of a 2D conformational search, wefound the results much less accurate than those obtained by a sequence of single pointoptimizations. As a compromise, we went ahead with our “single-trajectory” strategy,and confirmed the reasonableness of the selected trajectory by the comparison with thelowest-energy interconversion pathway suggested by the crude 2D conformationalsearch.[213] Heck, R. F. Palladium Reagents in Organic Syntheses, Academic Press,London/Orlando, 1985, 18.[214] Still, W. C.; Kahn, M.; Mitra, S. J. Org. Chem. 1978, 43, 2923.[215] Jaguar 5.5, Schrödinger, L.L.C., Portland, OR, 1991–2003; Macromodel 8.1,Schrödinger, L.L.C., Portland, OR, 1991–2003; Maestro 6.5, Schrödinger, L.L.C.,Portland, OR, 1991–2004.[216] (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648; (b) Lee, C.; Yang, W.; Parr, R. G.Phys. Rev. B 1988, 37, 785.[217] Suzuki, H.; Maruyama, K.; Goto, R. Bull. Chem. Soc. Jpn. 1965, 38, 1590.326

[218] (a) Bleckmann, W.; Hanack, M. Chem. Ber. 1984, 117, 3021; (b) Müller, E.;Sauerbier, M.; Streichfuss, D.; Thomas, R.; Winter, W.; Zountsas, G.; Heiss, J. JustusLiebigs Ann. Chem. 1971, 750, 63.[219] Tanaka, Y.; Yamashita, H.; Tanaka, M. Organometallics 1995, 14, 530.[220] Kinder, J. D.; Tessier, C. A.; Youngs, W. J. Synlett 1993, 149.[221] Collins, I.; Suschitzky, H. J. Chem. Soc. C 1969, 17, 2337.327