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Catalytic Asymmetric Formation and Reactions of Lithium Enolates and Elucidation of their Mechanisms

烯醇锂的催化不对称形成和反应及其机理的阐明

基本信息

批准号：
09470482
负责人：
KOGA Kenji
金额：
$ 8.38万
依托单位：
Research and Education Center for Materials Science, Nara Institute of Science and Technology (1998)The University of Tokyo (1997)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

Formation and reactions of lithium enolates constitute the most fundamental processes frequently employed in synthetic organic chemistry. We have previously reported novel enantioselective asymmetric deprotonation, alkylation, and protonation reactions. The purpose of the present research is to make these enantioselective asymmetric reactions catalytically asymmetric reactions as to the chiral amines used as chiral auxiliaries.To make these reactions catalytically asymmetric, it is necessary to find out conditions in which the reactions influenced by chiral auxiliaries proceed reasonably faster than those not influenced by chiral auxiliaries. Based on the studies on the mechanisms of these reactions, we examined various possibilities that satisfy such conditions.In enantioselective asymmetric deprotonation reactions of prochiral carbonyl compounds. we have found that the rates of deprotonation by bidentate chiral lithium amides proceed faster than those by tridentate lithium amides. We … More have also found that in situ lithium-hydrogen interchange reactions between chiral bidentate amine and achiral tridentate lithium amides occur rapidly favoring the formation of either sides, depending on the structures of these two species. Thus, using a combination of less than a stoichiometric amount of chiral bidentate amines and more than a stoichiometric amount of achiral tridentate lithium amides having appropriate structures, catalytic asymmetric deprotonation reactions as to the chiral bidentate amines were realized for the first time.In the enantioselective asymmetric alkylation reactions of prochiral lithium enolates, we have found that the rates of alkylation in the presence of bidentate amines are not enhanced, while those in the presence of tetradentate amines are reasonably enhanced. Thus, expecting fast ligand exchange reactions to the lithium between tetradentate chiral amines and bidentate achiral amines, catalytic asymmetric alkylation reactions were realized for the first time using a combination of less than a stoichiometric amount of chiral tetradentate amines and more than a stoichiometric amount of achiral bidentate amines. The same strategy was successfully applied to catalytic asymmetric protonation reactions. Less

烯醇化锂的形成和反应是有机合成中最基本的反应过程。我们以前已经报道了新的对映选择性不对称去质子化，烷基化和质子化反应。本研究的目的是使这些对映选择性的不对称反应成为手性胺作为手性助剂的催化不对称反应，为了使这些反应成为催化不对称反应，有必要找出在哪些条件下，受手性助剂影响的反应比不受手性助剂影响的反应进行得快。在对这些反应机理研究的基础上，我们考察了满足这些条件的各种可能性。在前手性羰基化合物的不对称去质子化反应中。我们已经发现，通过二齿手性氨基化锂的去质子化速率比通过三齿氨基化锂的去质子化速率进行得更快。我们 ...更多信息还发现，在手性二齿胺和非手性三齿氨基锂之间的原位锂-氢交换反应快速发生，有利于形成任一侧，这取决于这两种物质的结构。因此，使用小于化学计量量的手性二齿胺和大于化学计量量的具有适当结构的非手性三齿氨基锂的组合，首次实现了手性二齿胺的催化不对称去质子化反应。我们已经发现，在二齿胺存在下烷基化的速率没有提高，而在四齿胺存在下烷基化的速率被合理地提高。因此，预期快速配体交换反应的锂之间的四齿手性胺和双齿非手性胺，催化不对称烷基化反应首次实现使用小于化学计量量的手性四齿胺和大于化学计量量的非手性双齿胺的组合。同样的策略被成功地应用于催化不对称质子化反应。少