权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Catalytic Enantioselective Reaction

催化对映选择性反应

基本信息

批准号：
01470137
负责人：
KOBAYASHI Susumu
金额：
$ 4.35万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1991
项目状态：
已结题

项目摘要

An enantioselective rraction ffimugh a catalytic process is now recognized as one of the most important and challenging problems in organic synthesis. There have been reported a number of chiml Lewis acids modified by a variety of chiral ligands such as chiml alcohols or amities. However, such an electron-donating ligand decreases the acidity of the Lewis acid. In order to realize efficient catalytic process, we reasoned that the rate accelomting effect or attractive effect of the catalyst seemed to be important in addition to the sterwwntrol and the facile exchange of the product with the substrate on the catalyst. Based on this consideration we became interested in modifying a Lewis acid by electron-withdrawing chiral ligands rather than chiral alcohols or amities. In such a modified Lewis acid, the chiral ligand will not only provide a chiral environment but also increase the acidity of the Lewis acid. Among various acidic compounds we selected C_2-symmetric sulfonamide as a chiral ligand. We have developed two types of catalytic enantioselective reactions. (1) Alkylation of an aldehyde with dialkylzinc, Ti(O-i-Pr)_4 and disulfonamide, and (2) Cyclopropanation of an allylic alcohol using CH_2I_2, Et_2Zn and disulfonamide. Significant features of alkylation are unprecedent high catalytic turnover (up to 2, 000 times) as well as excellent enantioselectivity. The present cyclopropanation is the first example of a catalytic and enantioselective cyclopropanation. And these results will strongly demonstrate that the concept of modifying a Lewis acid with chiral sulfonmft ligand is promising in developing other types of catalytic enantioselective reactions.

催化过程中的不对称反应是有机合成中最重要和最具挑战性的问题之一。已经报道了许多由各种手性配体如手性醇或酰胺修饰的手性刘易斯酸。然而，这种给电子配体降低了刘易斯酸的酸性。为了实现高效的催化过程，我们认为，催化剂的速率加速效应或吸引效应似乎是重要的，除了sterwntrol和产物与底物在催化剂上的容易交换。基于这种考虑，我们开始对通过吸电子手性配体而不是手性醇或酰胺来修饰刘易斯酸感兴趣。在这种改性的刘易斯酸中，手性配体不仅提供手性环境，而且增加了刘易斯酸的酸性。在各种酸性化合物中，我们选择了C_2-对称磺酰胺作为手性配体。我们已经开发了两种类型的催化对映选择性反应。(1)醛与二烷基锌、Ti（O-i-Pr）_4和二磺酰胺的烷基化反应;（2）烯丙醇与CH_2I_2、Et_2Zn和二磺酰胺的环丙烷化反应。烷基化反应的显著特点是前所未有的高催化转化率（高达2000倍）以及优异的对映选择性。本发明的环丙烷化是催化和对映选择性环丙烷化的第一个实例。这些结果将有力地表明，用手性磺酰基配体修饰刘易斯酸的概念在发展其他类型的催化不对称反应中是有希望的。