Diastereoselectivity‐Switchable Gold‐Catalyzed Formal [3+2]‐Cycloadditions of N‐2,2,2‐Trifluoroethylisatin Ketimines with Yne−Enones

The unexpected gold‐catalyzed formal [3+2]‐cycloaddition of N‐2,2,2‐trifluoroethylisatin ketimines with 2‐(1‐Alkynyl)‐2‐alken‐1‐ones is reported. Both diastereomers of the corresponding cycloadducts were formed in moderate to excellent yields with excellent diastereoselectivities by switching the catalytic system from mono‐gold to gold/silver bimetallic catalytic system. The practicality of this protocol is demonstrated by scale‐up reaction and the transformations of the cycloadduct. An unexpected formal [3+2]‐cycloaddition of ketimines with yne−enones enabled by gold catalysis has been developed, affording both diastereomers in excellent diastereoselectivities and moderate to excellent yields.