Asymmetric Allylation by Chiral Organocatalyst-Promoted Formal Hetero-Ene Reactions of Alkylgold Intermediates.

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.