Ionic and Radical Cross-Couplings for Carbon-Silicon Bond Formation

碳-硅键形成的离子和自由基交叉偶联

基本信息

批准号：
388910461
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：
2017
资助国家：
德国
起止时间：
2016-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/388910461?language=en
关键词：
Ionic Radical Cross Couplings Carbon

项目摘要

The formation of C-Si bonds at saturated carbon atoms by bimolecular nucleophilic substitution (SN2) with silicon nucleophiles seems like a long-solved synthetic problem. Effective methods were, however, only disclosed last year. It was found that, depending on the leaving group, the displacement occurs either by an ionic mechanism or by a radical process. With triflate as leaving group, the catalytically generated copper-based silicon nucleophile reacts under SN2 whereas the same nucleophile engages in a stepwise radical mechanism with alkyl halides as electrophiles. Performing these C(sp3)-Si coupling reactions in asymmetric fashion is the next goal. With chiral alkyl triflates derived from readily available enantioenriched alcohols, the nucleophilic displacement would be enantiospecific. Conversely, the cross-coupling of alkyl halides would start from racemic material and is, as such, an enantioselective transformation. Achieving high enantioselectivity in a radical reaction is a formidable challenge. However, preliminary experiments have already shown that both ionic enantiospecific and radical enantioselective couplings with silicon nucleophiles are possible. This project aims at the systematic investigation of these new asymmetric C(sp3)-Si bond formations. Moreover, the ability of the copper-based silicon nucleophile to act as a one-electron reductant could also open a door to an unprecedented C(sp2)-Si cross-coupling reaction of diazonium ions.

通过双分子亲核取代（SN2）用硅接亲核者在饱和碳原子上形成C-SI键似乎是一个长期解决的合成问题。但是，有效方法才去年才披露。发现根据离子机制或激进过程，取决于离开组，位移发生。催化产生的基于铜的硅亲核试剂在SN2下反应，而相同的亲核试剂与烷基卤化物作为电力液作用。下一个目标是以不对称方式执行这些C（SP3）-SI耦合反应。用源自可用的对映体醇的手性烷基三烯酸酯，亲核位移将是对映体特异性的。相反，烷基卤化物的交叉耦合将从外消旋物质开始，因此是对映选择性的转化。在根本性反应中实现高对映选择性是一个巨大的挑战。然而，初步实验已经表明，与硅接亲核试剂的离子对映体和自由基对映选择性耦合都是可能的。该项目旨在系统地研究这些新的不对称C（SP3）-SI键形成。此外，基于铜的硅核定剂充当单电子还原剂的能力也可以打开通向固有的C（SP2）-si -Si交叉偶联反应的门。