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功能化介孔硅材料的合成及其在手性合成中应用的研究

作　者: Muhammad Usman Azmat
导　师: 王艳芹
学　校: 华东理工大学
专　业: 工业催化
关键词: hydrogenation SBA 介孔硅材料 reaction asymmetric catalyst Proline 手性合成功能化 aldol cinchona ethyl catalyzed catalytic supported catalysis 博士学位论文 silica Synthesis isotherms
分类号: O643.32
类　型: 博士论文
年　份: 2011年
下　载: 32次
引　用: 0次
阅　读: 论文下载

内容摘要

In serving the humanity, the role of life and material sciences is undeniable. An arousing demand of enantiomerically pure compounds in the field of pharmaceutical, agrochemicals, cosmetics, fine chemicals and material sciences has made the asymmetric synthesis as an indispensible for new era. Splendid amount of research work from all over the globe is already in place to synthesize special kinds of chiral compounds by using asymmetric catalysts. At the same time, heterogenization of such asymmetric catalysts is of crucial importance to make the processes more facile, economic and environmentally benign. Owing to high surface area, tunable pore sizes and ease of functionalization made the mesoporous silica as a prime candidate for plenty of application including the field of asymmetric heterogeneous catalysis.The present work is aimed at the development of single unit heterogeneous chiral catalyst system based on mesoporous silica for important asymmetric transformations. As cinchona alkaloids has been classified as a privileged class of chiral catalyst and known to induce chirality to plenty of achiral compounds including a-keto esters. Enantioselective hydrogenation of a-keto esters (Orito’s reaction) using Pt/cinchona chiral catalyst system is regarded as the most studied reaction system. Initially (chapter 3), the research work was focused on the grafting of cinchona alkaloid over different kinds of mesoporous silica having different morphologies and nature i.e., SBA-15, A1-SBA-15, MCM-41 and MCF. Subsequently Pt deposition over thus cinchona functionalized silica created a chiral catalyst system for the enantioselective hydrogenation of ethyl pyruvate. The catalyst was found to provide enantioselective product with an enantiomeric excess (e.e.) ranging from≈35 to 50% depending upon the nature and the morphology of the silica support. The second part of this study (chapter 4) was concerned to the one pot synthesis of cinchona functionalized mesoporous silica. In that method, the main silica precursor is co-condensed with a cinchonidine molecule linked organosilane which is renovated by triethoxy silane moiety at its C11 position to yield cinchona functionalized silica. The subsequent deposition of Pt nanoparticles over functionalized silica provides a catalytic system for the enantioselective hydrogenation of a-activated ketone (Orito’s reaction). Thus-developed catalyst system is found to be comparable in enantioselectivities with an enantiomeric excess (e.e) of 35.6% when compared to its rival synthesis route (grafting method) which resulted in e.e of 39.1%, with better cinchonidine incorporation efficiency into silica framework. While in the third part of the project (chapter 5), Cinchonidine was tethered directly without prior modification over carboxylate functionalized SBA-15 by the reaction of vinyl group in cinchonidine with -COOH group in functionalized SBA-15 through ester linkage. Then Pt nanoparticles were deposited over cinchonidine tethered SBA-15. The highest enantiomeric excess was achieved as 70.8% and the catalyst recyclability was authenticated even after 3rd reuse without significant loss in enantiomeric excess. Finally in chapter 6, trans-4-hydroxy-L-proline (another chiral organocatalyst) was grafted over acylchloride functionalized SBA-15 (SBA-R-COCl) through O-acylation reaction to yield proline grafted silica catalyst for asymmetric aldol reactions.

全文目录

Acknowledgement  6-10
Abstract  10-12
Chapter 1 Introduction  12-50
  1.1 Asymmetric Synthesis  12-15
    1.1.1 Chiral Pool Synthesis  13
    1.1.2 Asymmetric Catalysis  13-15
  1.2 Heterogeneous Asymmetric Catalysis  15-22
    1.2.1 Immobilization of Asymmetric Homogeneous Catalysts  16-17
    1.2.2 Immobilization Techniques  17-22
  1.3 Chirally Modified Metal Surfaces as Heterogeneous Catalyst  22-24
  1.4 Cinchona Alkaloids  24-26
  1.5 Enantioselective Hydrogenation of Pyruvate Ester  26-29
  1.6 Cinchona Functionalized Supports  29-36
    1.6.1 Organic Functionalized Ordered Mesoporous Silica  29-36
  1.7 Asymmetric Aldol Reaction and Supported Proline Organocatalysts  36-37
  1.8 Significance of the Project and Work outline  37-39
  References  39-50
Chapter 2 Experimental  50-54
  2.1 Reagents and Equipments  50-52
  2.2 Material Synthesis and its Catalytic Activity  52
  2.3 Characterization  52-54
Chapter 3 A Comparative Study of Cinchonidine Grafted Silica/Pt Catalyst Systemfor Enantio-selective Hydrogenation of Ethyl Pyruvate  54-75
  3.1 Introduction  54-55
  3.2 Experimental Work  55-60
    3.2.1 Synthesis of Mesoporous Silica Support  55-57
    3.2.2 Prior Modification of Cinchonidine  57-58
    3.2.3 Grafting of Modified Cinchonidine(3 or CDTESS)over Silica Supports  58-59
    3.2.4 Pt Impregnation over SiO2-CDTESS  59
    3.2.5 Asymmetric Hydrogenation of Ethyl Pyruvate  59-60
  3.3 Results and Discussion  60-71
    3.3.1 Textural Analysis  60-65
    3.3.3 XRD and TEM Analysis  65-68
    3.3.4 Thermal and FTIR Analysis  68-70
    3.3.5 Asymmetric Hydrogenation of Ethyl Pyruvate  70-71
  3.4 Conclusions  71-72
  References  72-75
Chapter 4 One Pot Synthesis of Cinchona Functionalized Mesoporous Silica and itsEnantioselectivity  75-99
  4.1 Introduction  75-76
  4.2 Experimental  76-80
    4.2.1 Synthesis Methods  76-80
  4.3 Results and Discussion  80-91
    4.3.1 Optimization of One Pot Synthesis Step and Surface Analysis  80-83
    4.3.2 Organic Functionality Determination  83-88
    4.3.3 Catalytic Activity  88-91
  4.4 Conclusions  91-92
  References  92-99
Chapter 5 An Easy and Effective Approach towards Heterogeneous Pt/SiO_(2-)Cinchonidine Catalyst System for Enantioselective Hydrogenation of Ethyl Pyruvate  99-125
  5. Introduction  99-101
  5.2 Experimental  101-104
    5.2.1 Synthesis of Carboxylate Functionalized SBA-15(CA-SBA-15)  101-102
    5.2.2 Tethering of Cinchonidine with CA-SBA-15  102-104
    5.2.3 Pt Impregnation over CA-SBA-CD  104
    5.2.4 Enantioselective Hydrogenation of Ethyl Pyruvate  104
  5.3 Results and Discussion  104-118
    5.3.1 Surface Characterization of Functionalized SBA-15  104-107
    5.3.2 Functional Group Characterization  107-112
    5.3.3 TEM Analysis  112-114
    5.3.4 Enantioselective Hydrogenation of Ethyl Pyruvate  114-118
  5.4 Conclusions  118-120
  References  120-125
Chapter 6 A New Pathway to Proline Grafted Silica for Asymmetric Aldol Reaction  125-138
  6.1 Introduction  125-126
  6.2 Experimental  126-128
    6.2.1 Synthesis of acyl chloride functionalized SBA-15(SBA-R-COCI)  126-127
    6.2.2 O-acylation of Trans-4-hydroxy-L-proline with SBA-R-COCI  127-128
    6.2.3 Asymmetric Aldol Reaction  128
  6.3 Results and Discussion  128-134
    6.3.1 Surface Analysis  128-130
    6.3.2 Functional Group Determination  130-131
    6.3.3 Catalytic Activity  131-134
  6.4 Conclusions  134-135
  References  135-138
Summary and Future Recommedations  138-139
Vitae  139-140
卷内备考表  140

功能化介孔硅材料的合成及其在手性合成中应用的研究

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