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Chiral Sulfur-Stabilized Silicon Cations as Lewis Acids for Enantioselective Diels-Alder Reactions

手性硫稳定硅阳离子作为路易斯酸用于对映选择性狄尔斯-阿尔德反应

基本信息

批准号：
287280002
负责人：
Professor Dr. Martin Oestreich
金额：
--
依托单位：
Institut für Chemie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/287280002?language=en
关键词：
Chiral Sulfur Stabilized Silicon Cations

项目摘要

The intermolecular stabilization of Me3Si+ by Me2S fails due to disproportionation of the resulting sulfonium ion [Me3SiSMe2]+. Hence, little is known about the chemistry of sulfur-stabilized silicon cations. Our laboratory recently showed that intramolecular coordination of soft sulfur donors to tricoordinate silicon cations leads to chemically stable adducts. These "tamed" cations are sufficiently Lewis acidic to catalyze particularly challenging Diels-Alder reactions, e.g., [4+2]-cycloadditions of cyclohexa-1,3-diene and alpha,beta-unsaturated ketones. Rendering these enantioselective is the next big step, and we have already been able to demonstrate that cognate Lewis acids with chiral backbones do indeed induce promising enantioselectivities in selected cases. From the various motifs prepared and tested, a binaphthalene-derived silepine system emerged as a lead structure. The goal of the present project is now to elaborate this candidate into a chiral sulfur-stabilized silicon cation that will catalyze the aforementioned Diels-Alder reactions with high levels of enantioselection. It must be noted here that, to date, there are no catalysts exist to promote these simple looking but exceedingly difficult cycloadditions in asymmetric fashion. It is a fundamental problem in both synthetic chemistry and catalysis with main-group Lewis acids.

Me 2S对Me 3Si+的分子间稳定作用由于所产生的锍离子[Me 3SiSMe 2]+的反离子化而失败。因此，对硫稳定的硅阳离子的化学性质知之甚少。我们的实验室最近表明，软硫供体的分子内协调三配位硅阳离子导致化学稳定的加合物。这些“驯服的”阳离子具有足够的刘易斯酸性以催化特别具有挑战性的狄尔斯-阿尔德反应，例如，环己-1，3-二烯与α，β-不饱和酮的[4+2]-环加成反应。使这些对映选择性是下一个重要步骤，我们已经能够证明，同源刘易斯酸与手性骨干确实诱导有前途的对映选择性在选定的情况下。从各种图案的制备和测试，联萘衍生的silepine系统出现作为一个铅结构。本项目的目标是将这一候选化合物合成为手性硫稳定的硅阳离子，以高水平的对映选择性催化上述Diels-Alder反应。这里必须指出的是，迄今为止，还没有催化剂存在，以促进这些简单的外观，但非常困难的环加成在不对称的方式。它是合成化学和主族刘易斯酸催化中的一个基本问题。