Asymmetric Allylation by Chiral Organocatalyst‐Promoted Formal Hetero‐Ene Reactions of Alkylgold Intermediates
Guizhi Dong, Ming Bao, Xiongda Xie, Shi‐Kun Jia, Wenhao Hu, Xinfang Xu
Abstract
An unprecedented catalytic asymmetric allylation of isatins and isatin-derived ketimines is reported enabled by a gold and chiral organocatalyst cooperative catalysis strategy. This method offers expeditious access to chiral 2,5-disubsituted alkylideneoxazolines containing vicinal stereogenic centers, mainly in optically pure form, and which are otherwise impossible to access. Mechanistic evidence reveals the presence of an alkylgold intermediate, and an X-ray crystal structure of the allylgold species illuminates its unique stability and reactivity. An asymmetric formal hetero-ene reaction of this gold intermediate, involving a dearomatization process, is enabled with assistance of a quinine-derived squaramide catalyst. This novel discovery extends the synthetic applications of gold complexes and the versatility of gold catalysis.