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42 Science of Synthesis 1.1 Organometallic Complexes of Nickel 4-(2-Methylallyl)cyclohexanol (29,R 1 = 4-hydroxycyclohexyl); Typical Procedure: [8] Di-ì-bromobis[(ç 3 -2-methylallyl)nickel] (28; 0.55 g, 1.42 mmol) was weighed under N 2 or argon into a flask equipped with a three-way stopcock and rubber septum. DMF (4.0 mL, distilled at 508C/30 Torr from CaH 2 and rendered air-free by alternately evacuating and filling with inert gas several times) was added via a syringe. Then a soln of trans-4-iodocyclohexanol (0.643 g, 2.84 mmol, prepared by reaction of 1,4-epoxycyclohexane with HI, mp 60–61 8C) in DMF (2.0 mL, air-free as above) was added rapidly by syringe. After addition, the soln was allowed to warm to 23 8C during 1 h and stirred at this temperature for 22 h under a positive pressure of an inert gas. The mixture, now green, was poured into Et 2O and the Et 2O soln was washed with H 2O (4 ”), dried (MgSO 4), and concentrated at aspirator vacuum to afford 29 (R 1 = 4-hydroxycyclohexyl); yield: 388 mg (89%). Other alkyl halides used, together with products and yields, were iodobenzene fi (2methylallyl)benzene (98%), iodocyclohexane fi (2-methylallyl)cyclohexane (91%), bromoethene fi 2-methylpenta-1,4-diene (70%). 1-Substituted Acetones; General Procedure: [35] Reactions were carried out in a 100-mL one-necked flask with a side arm capped with a septum, and containing a magnetic stirring bar and fitted with a stopcock. The reaction flask was flushed with argon and placed in a N 2-filled glove bag along with a flask containing complex 30. The desired amount of 30 (1–2 mmol) was transferred into the reaction flask through the side arm (in the glove bag), the side arm was recapped with the septum, and the reaction flask was removed from the glove bag. The complex was dissolved in argon-sat. DMF (30 mL solvent/mmol complex), giving a deep red soln. Liquid reactants (1.8– 3.6 mmol) were directly added to the reaction flask, while solid reactants were dissolved in a minimum amount of DMF and added as solns. With organic halides as reactants, the soln turned emerald-green upon completion, whereas with ketones and aldehydes it turned brown-orange. Upon completion, the mixture was poured into a separatory funnel containing 3% aq HCl (50 mL) and Et 2O (50 mL), and was thoroughly shaken. The aqueous phase was washed with Et 2O (3 ” 20 mL), and the combined Et 2O extracts were washed with 3% aq HCl (3 ” 50 mL) to ensure complete hydrolysis of the enol ether and complete removal of DMF. The organic phase was dried (MgSO 4) and the solvent was removed under vacuum. The crude product, usually more than 90% pure, was purified by preparative layer chromatography (silica gel) or distillation. 1.1.2.6 Method 6: Coupling of Enal-Derived Nickel–Allyl Complexes with Alkyl Halides and Other Electrophiles Most features of the couplings described for allyl halide-derived nickel–ð-allyl complexes also hold true for the closely related enone- and enal-derived complexes. Once the enoneor enal-derived complex is generated (e.g., 27, 32), couplings with alkyl halides generally are accomplished in dimethylformamide upon photolysis of the mixture with a sunlamp, to give products such as 33 and 34 (Scheme 19). [38] Strong donor ligands are not required for coupling reactions of enals, whereas couplings involving enones require the presence of pyridine. Scheme 19 Enone or Enal Couplings with Alkyl Halides [38] TBDMSO Br Ni Ni Br 32 OTBDMS + I DMF photolysis 68% 33 OTBDMS
1.1.2 Nickel–Allyl Complexes 43 NiCl(py)2 27 OTBDMS + Br DMF photolysis 72% 34 OTBDMS (E)-1-(tert-Butyldimethylsiloxy)-4-methylpent-1-ene (33): [38] A 100-mL Schlenk tube, equipped with a magnetic stirring bar, was sequentially charged with TBDMSCl (3.56 g, 23.6 mmol, 1.30 equiv), MeCN (30 mL), (MeO)(TMSO)C=CMe 2 (3.69 mL, 18.2 mmol, 1.00 equiv; added as a proton-scavenging reagent), and propenal (2.43 mL, 36.4 mmol, 2.00 equiv). The mixture was stirred for 5 min, during which time N 2 was bubbled through the soln. The soln was then transferred via a cannula into a 100mL Schlenk tube containing [Ni(cod) 2](2; 5.00 g, 18.2 mmol, 1.00 equiv) and a spinning stirrer bar, followed by an MeCN wash (5 mL) to complete the transfer. The resulting deep burgundy-red soln was stirred for 1 h and then concentrated under reduced pressure (0.01 Torr) for 14 h to afford a dark red solid contaminated with cycloocta-1,5-diene. The solid was dissolved in MeCN (30 mL) and sequentially treated with (MeO)(TMSO)C=CMe 2 (0.10 mL, 0.49 mmol, 0.03 equiv), DMF (14 mL, 182 mmol, 10.0 equiv), and 2-iodopropane (14.1 mL, 181 mmol, 10.0 equiv). The resulting burgundy-red soln was stirred for 5 min and then irradiated with sunlight or a 275-W GE Model RSW sunlamp until the burgundy-red color of the allylnickel complex had been completely discharged (ca. 12 h), during which time a brown-green crystalline precipitate was deposited and the supernatant became light blue-green or nearly colorless (depending on the completeness of the precipitation). The supernatant was transferred via a cannula into a round-bottomed flask containing pentane, and the cloudy mixture was stirred for 30 min to complete precipitation of the nickel dihalide coproduct. The supernatant was then transferred through a filter paper tipped cannula onto a stirred aq KH 2PO 4/NaOH buffer (150 mL, pH 7) (an emulsion tended to form at this stage if most of the nickel dihalide had not been removed through the prescribed procedure). The pentane layer was separated, washed with H 2O(3”20mL), dried (MgSO 4), and concentrated under reduced pressure (15 Torr) to afford the crude product [(E/Z) 10:1] as a clear, yellow oil, contaminated by cycloocta-1,5-diene and 2-iodopropane. Column chromatography (silica gel, 343 g, hexane/EtOAc 98:2) afforded pure 33; yield: 2.64 g (68%); bp 768C/15 Torr; (E/Z) > 40:1. 1-(tert-Butyldimethylsiloxy)-3-vinylcyclopentene (34): [38] A 100-mL Schlenk tube equipped with a magnetic stirring bar and rubber septum was charged with [NiCl 2(py) 4] (10.0 g, 22.4 mmol, 1.00 equiv) and evacuated and refilled with N 2 twice to establish an inert atmosphere. THF (40 mL) was added, followed by cycloocta- 1,5-diene (8.20 mL, 67.2 mmol, 3.00 equiv), and the resulting mixture cooled to 0 8C. A second 100-mL Schlenk tube containing Na metal strips (1.03 g, 44.8mmol, 2.00 equiv; each ca. 2 cm ” 0.4 cm ” 0.1 cm) was connected to this flask with a flexible adapter (available from Aldrich) under a rapid flow of N 2 (an inert atmosphere having previously been established in the second Schlenk tube and adapter by capping the free end of the adapter and evacuating and refilling with N 2). The Na strips were then transferred to the stirred 0–58C mixture in four portions over 1.5 h to give, after an additional 40 min at 0–58C, a very dark brown (but not black) supernatant, a small amount of precipitated yellow [Ni(cod) 2], and no apparent blue [NiCl 2(py) 4]. The mixture was treated with a soln of cyclopent-2enone (1.88mL, 22.4 mmol, 1.00 equiv) and TBDMSCl (3.38g, 22.4 mmol, 1.00 equiv) in THF (15 mL) and stirred at 258C for 30 min to afford an orange mixture. A soln of bromoethene (4.74 mL, 67.2 mmol, 3.00 equiv) in THF (5 mL) was added via a cannula, and the mixture was irradiated at 10 8C with a 275-W GE Model RSW sunlamp for 12.5 h to afford an olive-green precipitate and a light brown supernatant. The mixture was poured into a 2-L separatory funnel containing pentane (400 mL) and aq KH 2PO 4/NaOH buffer (400 mL, for references see p 79
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Page 79 and 80: References 79 References [1] Chetcu
Page 81 and 82: References 81 [98] Tsuda, T.; Mizun
Page 86 and 87: 86 Biographical Sketches Rinaldo Po
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92 Science of Synthesis 2.6 Complex
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100 Science of Synthesis 2.6 Comple
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141 Science of Synthesis Houben-Wey
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4.4.27 Product Subclass 27: Æ-Halo
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4.4.27 Æ-Haloalkylsilanes 147 Sche
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4.4.27 Æ-Haloalkylsilanes 149 dros
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4.4.27 Æ-Haloalkylsilanes 151 4.4.
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4.4.27 Æ-Haloalkylsilanes 153 In g
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4.4.27 Æ-Haloalkylsilanes 155 4.4.
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4.4.27 Æ-Haloalkylsilanes 157 Æ-H
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References 159 References [1] Haman
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References 161 [93] Bruno, J. W.; S
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164
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166 Biographical Sketches Alan Spiv
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168 5.1.22 Product Subclass 22: Ary
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170 Science of Synthesis 5.1 German
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176 References [43] Eaborn, C.; Var
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178 Abbreviations Chemical (cont.)
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180 Abbreviations Ligands (cont.) 2
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182 Abbreviations General (cont.) q
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