chapter 2 palladium catalysts in suzuki cross- coupling reaction

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clay materials was found to be an effective method for preparing active catalysts in Suzuki cross coupling reactions. They also tested the reusability of the catalyst. It was observed that after three catalytic cycles the catalyst lost some activity after each reuse (Ruiz et al. 2006). Corma et al. tested bifunctional (palladium and basic sites) sepiolites clay for their catalytic activities for the Heck and Suzuki reactions in the absence of any extrinsic base at 145 °C. However, irreversible depletion of the basic sites of the sepiolite was considered to be responsible for the deactivation of the catalyst (Corma et al. 2004). Shimizu et al. reported that [Pd(NH3)4] +2 -exchanged sepiolite clay was highly active for Suzuki reactions of 4-bromophenol with phenylboronic acid or sodium tetraphenylborate in water (Shimizu et al. 2004). The recyclable nanopalladium particles supported on layered double hydroxide (LDH) were designed and developed by a simple ion-exchange technique following reduction processes. This heterogeneous palladium catalyst showed high activity for Heck-, Suzuki-, Sonogashira-, and Stille-type coupling reactions of chloroarenes to afford good to excellent yields of coupling products (Choudary et al. 2002). Researchers synthesized palladium hollow spheres showing good catalytic activities in Suzuki cross coupling reactions of iodothiophene and phenylboronic acid and can be reused at least for 7 cycles at 78 °C with no apparent leaching (Kim et al. 2002). They reported that Pd shell is not active enough to catalyze the reaction of aryl chloride (Figure 3.12). Silica sphere HF, Etching palladium hollow spheres Figure 3.12. Preparation of palladium hollow spheres (Source: Kim et al. 2002) 36
Smith et al introduced the use of Pd(II)-exchanged perovskites (LaFe0.57Co0.38 Pd0.05O3) as a new class of catalysts in the Suzuki coupling of 2-bromoanisole, 2-bromo pyridine and arylboronic acids with low levels of Pd leaching at 80 °C (Smith et al. 2003). Zeolites, which have specific properties because of their well-defined structure and pores with molecular dimensions, have been also used as a support material (Smith and Nothesisz 1995). 3.3. Zeolite supported palladium catalysts in the Suzuki Reactions 3.3.1. Structural Features of Zeolite Zeolites are three-dimensional, microporous, crystalline solids with well-defined structures that contain aluminum, silicon, and oxygen in their regular framework; cations and water are located in the pores. Zeolites have a uniform pore structure (Weitkamp and Puppe 1999). The formula of zeolite is written as M2/n. Al2O3. xSiO2. yH2O where n is the cation valence; M is the cation which balances the negative charge. The framework of zeolites consists of (SiO4) 4− and (AlO4) 5− , combined with each other at the corners by sharing their oxygen, resulting in the general formula of (AlO2)x. (SiO2)(n-x), Where n is the number of tetrahedra per unit cell, and x≤ n/2 (Weitkamp and Puppe 1999). - O O - Si O- O- - O O - Al +3 O- O- Silica Tetrahedron Alumina Tetrahedron Figure 3.13. Silica and alumina tetrahedron structures -1 37
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 and 22: 2.2.1. Mechanism of Suzuki Coupling
Page 23 and 24: As a result, organic group or hydri
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: utilized them in Heck and Suzuki co
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
Page 75 and 76: The type of other organic co-solven
Page 77 and 78: yield was very low (Table 5.8, entr
Page 79 and 80: evealed excellent reactivity toward
Page 81 and 82: CHAPTER 6 CONCLUSIONS In this thesi
Page 83 and 84: REFERENCES Albisson, D.A., Bedford,
Page 85 and 86: Choudary, B.M., Madhi, S., Chowdari
Page 87 and 88: Heiden, M. Plenio, H. 2004. ‘‘H
Page 89 and 90: Coupling Reactions of Aryl Chloride
Page 91 and 92: Phan, N.T.S., Brown, D.H., Styring,
Page 93 and 94: Wolfe, J.P., Singer, R.A., Yang, B.
Page 95 and 96: Figure A.1. 13 C NMR of 1-phenylnap
Page 97 and 98: Figure A.3. 13 C NMR of 2-acetylbip
Page 99 and 100:
Figure A.5 . 13 C NMR of 2-methoxyb
Page 101 and 102:
Figure A.7. 13 C NMR of 2-methylbip
Page 103 and 104:
Figure A.9. 13 C NMR of 2-phenylnap
Page 105 and 106:
Figure A.11. 13 C NMR of 3-acetylbi
Page 107 and 108:
Figure A.13. 13 C NMR of 3-methoxyb
Page 109 and 110:
Figure A.15. 13 C NMR of 3-phenylpy
Page 111 and 112:
Figure A.17. 13 C NMR of 4-acetyl-4
Page 113 and 114:
Figure A.19. 13 C NMR of 4-methoxyb
Page 115 and 116:
Figure A.21. 13 C NMR of 4-methylbi
Page 117 and 118:
Figure A.23. 13 C NMR of 4-phenylbe
Page 119 and 120:
Figure A.25. 13 C NMR of 4-acetylbi
Page 121 and 122:
Figure A.27. 13 C NMR of 4-cyanobip
Page 123 and 124:
Figure A.29. 13 C NMR of 4-nitrobip
Page 125 and 126:
Figure A.31. 13 C NMR of 4-phenylan
Page 127 and 128:
APPENDIX B MASS SPECTRUMS OF SUZUKI
Page 129 and 130:
Figure B.2. Mass spectrum of 2-acet
Page 131 and 132:
Figure B.4. Mass spectrum of 2-meth
Page 133 and 134:
Figure B.6. Mass spectrum of 3-acet
Page 135 and 136:
Figure B.8. Mass spectrum of 3-phen
Page 137 and 138:
Figure B.10. Mass spectrum of 4-phe
Page 139 and 140:
Figure B.12. Mass spectrum of 4-met
Page 141 and 142:
Figure B.14. Mass spectrum of 4-cya
Page 143:
Figure B.16. Mass spectrum of 4-met
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