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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.

通过硅亲核试剂的双分子亲核取代（SN 2）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。然而，直到去年才公布了有效的方法。据发现，取决于离去基团，位移发生的离子机制或自由基的过程。用三氟甲磺酸酯作为离去基团，催化生成的铜基硅亲核试剂在SN 2下反应，而相同的亲核试剂与作为亲电试剂的烷基卤化物以逐步自由基机制进行。以不对称方式进行这些C（sp3）-Si偶联反应是下一个目标。对于衍生自容易获得的对映体富集的醇的手性烷基三氟甲磺酸酯，亲核置换将是对映体特异性的。相反，烷基卤化物的交叉偶联将从外消旋物质开始，因此是对映选择性转化。在自由基反应中实现高的对映选择性是一个艰巨的挑战。然而，初步的实验已经表明，与硅亲核试剂的离子对映体特异性和自由基对映体选择性偶联是可能的。本项目旨在系统地研究这些新的不对称C（sp3）-Si键的形成。此外，铜基硅亲核试剂作为单电子还原剂的能力也可以为前所未有的重氮离子的C（sp2）-Si交叉偶联反应打开大门。