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Development of New Catalytic Asymmetric Reactions Based on the Synthesis of Optically Active Phosphine Ligands

基于光学活性膦配体合成的新型催化不对称反应的发展

基本信息

批准号：
16350020
负责人：
IMAMOTO Tsuneo
金额：
$ 8.7万
依托单位：
Chiba University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

项目摘要

This study is directed toward the development of new catalytic asymmetric reactions based on the design and synthesis of novel chiral phosphine ligands. A new tetraphosphine ligand bearing their four chiral centers at phosphorus atoms has been synthesized via phosphine-boranes as the intermediates and the molecular structure of its dirhodium complex was determined by the single crystal X-ray analysis. The tetraphosphine lidand itself is C_2 symmetric, but each Rh-diphosphine sphere forms a C_1 symmetric three-hindered quadrant. This dirhodium complex exhibited excellent enantioinduction ability in Rh-catalyzed asymmetric hydrogenation of dehydroamino acids. Low temperature hydrogenation of the complex afforded a tetrahydrorhodium complex quantitatively, and the reactions of the tetrahydride complex with alkene substrates were studied in order to elucidate the detailed enantioselection mechanism. The results including the stereochemical outcome are reasonably interpreted by assuming tha … More t the enantioselection would be determined at the migratory insertion step.A new P-chiral phosphinophenol was prepared and employed in copper-catalyzed asymmetric conjugate addition to α,β-unsaturated carbonyl compounds. The reactions proceeded smoothly under mild conditions to afford the corresponding products with high enantiomeric excesses of up to 96%.Asymmetric hydrosilylation of simple ketones was tested by the use of several P-chiral phosphine ligands prepared in our laboratory. Very high enantioselectivity of up to 99% was observed when a bulky silylation reagent such as α-naphtyldiphenylsilane was used. The sense of the stereoselection has been rationalized by considering that the enantioselection occurs at the migratory insertion step.A new P-chiral diphosphine ligand, (R,R)-2,3-bis(tert-butylmethylphosphino)quinoxaline (QuinoxP^*)) was designed and synthesized by reacting enantiomerically pure (R)-tert-butyl(hydroxymethyl)methylphosphine-borane with 2,3-dichloroquinoxaline. This ligand, in contrast to most of the previously reported P-chiral ligands, is an air-stable solid and exhibits excellent enantioselectivities in both Rh-catalyzed asymmetric hydrogenations and Rh- or Pd-catalyzed carbon-carbon bond-forming reactions. Less

本研究的目的是在设计和合成新型手性膦配体的基础上，发展新的催化不对称反应。以磷硼烷为中间体合成了一种具有磷原子4个手性中心的四膦配体，并通过单晶x射线分析确定了其配合物的分子结构。四膦球本身是C_2对称的，但是每个铑二膦球形成一个C_1对称的三阻碍象限。该配合物在铑催化脱氢氨基酸的不对称加氢反应中表现出优异的对映诱导能力。低温加氢生成四氢化物配合物，并对四氢化物配合物与烯烃底物的反应进行了研究，以阐明其对映体选择机理。结果包括立体化学结果可以合理地解释为假设…更多的对映体选择将在迁移插入步骤决定。制备了一种新的p手性膦酚，并将其用于铜催化的α，β-不饱和羰基化合物的不对称共轭加成。反应在温和条件下进行顺利，产物的对映体含量高达96%。本实验室制备了几种p -手性膦配体，对单酮的不对称硅氢化反应进行了研究。当使用体积较大的硅基化试剂（如α-萘基二苯硅烷）时，观察到高达99%的对映选择性。考虑到对映体选择发生在迁移插入步骤，立体选择的意义被合理化了。通过对映体纯的(R)-叔丁基（羟甲基）甲基膦-硼烷与2,3-二氯喹啉反应，设计并合成了一种新的p -手性二膦配体（R，R）-2,3-双（叔丁基甲基膦）喹啉（QuinoxP^*）。与之前报道的大多数p手性配体不同，该配体是一种空气稳定的固体，在Rh催化的不对称氢化反应和Rh或pd催化的碳-碳成键反应中都表现出优异的对映选择性。少