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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.

Me2S对Me3Si+的分子间稳定作用由于产生的磺化离子[Me3SiSMe2]+的歧化而失效。因此，对硫稳定硅阳离子的化学性质所知甚少。我们的实验室最近表明，软硫给体与三配位硅阳离子的分子内配位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，可以催化特别具有挑战性的Diels-Alder反应，例如环己-1,3-二烯和α， β -不饱和酮的[4+2]-环加成。使这些对映选择性是下一个重要步骤，我们已经能够证明具有手性骨架的同源路易斯酸确实在某些情况下诱导有希望的对映选择性。从制备和测试的各种基序中，二萘衍生的矽平系统作为铅结构出现。目前项目的目标是将这一候选物精制成手性硫稳定硅阳离子，以高水平的对映体选择催化上述Diels-Alder反应。必须指出的是，到目前为止，还没有催化剂能够以不对称的方式促进这些看似简单但极其困难的环加成。它是合成化学和主基路易斯酸催化中的一个基本问题。