chapter 2 palladium catalysts in suzuki cross- coupling reaction

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L nM m X + XY L nM m+2 Figure 2.5. Oxidative Addition In Suzuki reactions, oxidative addition involves the insertion of palladium metal into an aryl halide. The empty ligand field orbital (LFO) of metal interacts with the carbon halogen bonding orbital, while a second orbital overlap occurs between the nonbonding t2g orbital containing an electron pair and the carbon-halogen antibonding orbital. This destabilizes the carbon-halogen bond leading to cleavage and eventually oxidative addition to the palladium. The palladium catalyst in the reaction must be ‘0’ oxidation state as an 18 electron system and after oxidative addition, it would be oxidation state of II as a 16 electron system (Figure 2.6). X X Pd Pd C L Figure 2.6. The Carbon- halogen bond cleavage in oxidative addition This step is often the rate-determining step in a catalytic cycle. The relative reactivity of aryl halides decreases in the order of C- I > C-OTf > C-Br >> C-C1>>> C- F. Aryl and 1-alkenyl halides bearing electron-withdrawing groups are more reactive to the oxidative addition than those with donating groups (Miyaura and Suzuki 1995). 2.2.1.2. Transmetallation Ar-Pd-X complexes formed by oxidative addition react with organic compounds (M-R) and hydrides (M-H) of main group metals such as Mg, Zn, B, Al, Sn, Si, and Hg. Y L C 10
As a result, organic group or hydride is transferred to Pd (Figure 2.7.). A driving force for the reaction called transmetallation, is due to the difference in the electro negativities of two metals (Tsuji 1995). L R X Pd L M - R' L R L R' Pd M X Figure 2.7. Transmetallation (Source: Tsuji 1995) L R R' Pd L + MX M: main group metal In Suzuki reactions, transmetallation between organopalladium (II) halides and organoboron compounds does not occur readily due to the low nucleophilicity of organic group on boron atom. However, the nucleophilicity of organic group on boron atom can be enhanced with base giving the corresponding “ate” complexes (Miyaura and Suzuki 1995). 2.2.1.3. Reductive Elimination Reductive elimination is simply the reverse reaction of oxidative addition. In this step, two carbon metal bonds are broken (Tsuji 1995). The catalytic cycle is completed by reduction of the Pd II species into a Pd 0 species and finally coupling product forms (Figure 2.8.). L L Pd II R R' 2L L L Pd 0 Figure 2.8. Reductive Elimination (Source: Tsuji 1995) L L + R R' 11
Page 1 and 2: SHORT-TIME SUZUKI REACTIONS OF ARYL
Page 3 and 4: ACKNOWLEDGEMENTS Firstly, I’d lik
Page 5 and 6: ÖZET ARİL HALOJENÜRLERİN HAVA A
Page 7 and 8: 3.2.2. Catalysts Anchored to Inorga
Page 9 and 10: LIST OF FIGURES Figure Page Figure
Page 11 and 12: Figure A.27. 13 C NMR of 4-cyanobip
Page 13 and 14: CHAPTER 1 INTRODUCTION The palladiu
Page 15 and 16: CHAPTER 2 PALLADIUM CATALYSTS IN SU
Page 17 and 18: 2.1.2. The Coordination Geometry of
Page 19 and 20: R 1 R 1 4. Sonogashira Reaction: H
Page 21: 2.2.1. Mechanism of Suzuki Coupling
Page 25 and 26: 2.2.2.2. Halogen Effect Nearly all
Page 27 and 28: found to be excellent complexes for
Page 29 and 30: R Table 2.2. Examples from literatu
Page 31 and 32: L R Pd X R Pd L OR'' X L L + OR' R'
Page 33 and 34: omides and iodides is performed eff
Page 35 and 36: times for the transformation of a l
Page 37 and 38: R Br + (HO) 2B R' 5% Pd(OAc) 2 15%
Page 39 and 40: of insoluble solids are among the m
Page 41 and 42: could be reused multiple times. The
Page 43 and 44: 3.2.2. Catalysts Anchored to Inorga
Page 45 and 46: SO 2NH N Pd SO 2 N SO 2 NH NH H O1.
Page 47 and 48: utilized them in Heck and Suzuki co
Page 49 and 50: Smith et al introduced the use of P
Page 51 and 52: • Complexes immobilized in zeolit
Page 53 and 54: 3.3.3. Preparation of Zeolite-Suppo
Page 55 and 56: CHAPTER 4 EXPERIMENTAL STUDY 4.1. P
Page 57 and 58: temperature, the catalyst was recov
Page 59 and 60: amount of both reactant and product
Page 61 and 62: 4-Methoxybiphenyl: 1 H NMR (400 MHz
Page 63 and 64: 51 Table 4.1. Purification of coupl
Page 65 and 66: CHAPTER 5 RESULTS AND DISCUSSIONS I
Page 67 and 68: Table 5.2. The effect of base on Pd
Page 69 and 70: Table 5.4. The Optimization of Pd-N
Page 71 and 72: H 3COC Table 5.5. Effect of zeolite
Page 73 and 74:
Table 5.6. Pd(NH3)4 2+ -loaded NaY
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The type of other organic co-solven
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yield was very low (Table 5.8, entr
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evealed excellent reactivity toward
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CHAPTER 6 CONCLUSIONS In this thesi
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REFERENCES Albisson, D.A., Bedford,
Page 85 and 86:
Choudary, B.M., Madhi, S., Chowdari
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Heiden, M. Plenio, H. 2004. ‘‘H
Page 89 and 90:
Coupling Reactions of Aryl Chloride
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Phan, N.T.S., Brown, D.H., Styring,
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Wolfe, J.P., Singer, R.A., Yang, B.
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Figure A.1. 13 C NMR of 1-phenylnap
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Figure A.3. 13 C NMR of 2-acetylbip
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Figure A.5 . 13 C NMR of 2-methoxyb
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Figure A.7. 13 C NMR of 2-methylbip
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Figure A.9. 13 C NMR of 2-phenylnap
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Figure A.11. 13 C NMR of 3-acetylbi
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Figure A.13. 13 C NMR of 3-methoxyb
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Figure A.15. 13 C NMR of 3-phenylpy
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Figure A.17. 13 C NMR of 4-acetyl-4
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Figure A.19. 13 C NMR of 4-methoxyb
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Figure A.21. 13 C NMR of 4-methylbi
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Figure A.23. 13 C NMR of 4-phenylbe
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Figure A.25. 13 C NMR of 4-acetylbi
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Figure A.27. 13 C NMR of 4-cyanobip
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Figure A.29. 13 C NMR of 4-nitrobip
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Figure A.31. 13 C NMR of 4-phenylan
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APPENDIX B MASS SPECTRUMS OF SUZUKI
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Figure B.2. Mass spectrum of 2-acet
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Figure B.4. Mass spectrum of 2-meth
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Figure B.6. Mass spectrum of 3-acet
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Figure B.8. Mass spectrum of 3-phen
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Figure B.10. Mass spectrum of 4-phe
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Figure B.12. Mass spectrum of 4-met
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Figure B.14. Mass spectrum of 4-cya
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Figure B.16. Mass spectrum of 4-met
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