Enantioselective SN1-type reaction via electrochemically generated chiral α-Imino carbocation intermediate
Qifeng Lin, Yingdong Duan, Yao Li, Ruijun Jian, Kai Yang, Zongbin Jia, Yu Xia, Long Zhang, Sanzhong Luo
Abstract
Electrochemical reactions via carbocation intermediates remain fundamental transformations that build up molecular functionality and complexity in a sustainable manner. Enantioselective control of such processes is a great challenge in a highly ionic electrolyte solution. Here, we report an anodic generation of chiral α-imino carbocation intermediates by enamine catalysis. The chiral carbocation intermediates can be intercepted by a variety of nucleophiles such as alcohols, water and thiols with high stereoselectivity. The key SN1 step proceeds via a tertiary amine-mediated proton shuttle that facilitates facial selection in reacting with carbocation. Carbocations are useful synthetic intermediates which enable direct functionalization of carbon centers, but their generation in a manner that uses mild conditions and enables stereoselective interception remains a longstanding goal of organic chemists. Here, the authors use electrochemical enamine oxidation to synthesize chiral scaffolds from racemic α-branched aldehydes.