Pd‐Catalyzed Asymmetric Allylic Substitution Annulation Using Enolizable Ketimines as Nucleophiles: An Alternative Approach to Chiral Tetrahydroindoles

A synthesis of chiral tetrahydroindoles has been developed via a Pd‐catalyzed asymmetric allylic substitution annulation using unstable enolizable ketimines as nucleophiles and our previously developed t Bu‐RuPHOX as a chiral ligand. The reaction proceeds via an asymmetric desymmetrization of the meso ‐diacetatecycloalkenes, providing the desired chiral tetrahydroindoles in moderate to good yields and with up to 96% ee. The annulation reaction could be performed on a gram‐scale in high yields and the resulting products can be transformed to several types of N ‐hetereobicyclic derivatives. In addition, a chiral cis ‐perhydroindolic acid derivative was also readily synthesized starting from a prepared chiral tetrahydroindole.