Cobalt-Catalyzed ortho-C−H functionalization/alkyne annulation of benzylamine derivatives: Access to dihydroisoquinolines

Abstract

A practical picolinamide-directed C−H functionalization/alkyne annulation of benzylamine derivatives enabling access to the previously elusive 1,4-dihydroisoquinoline skeleton was developed using molecular O2as the sole oxidant and Co(OAc)2as precatalyst. The method is compatible with both internal and terminal alkynes and shows high versatility and functional-group tolerance. Furthermore, full preservation of enantiopurity is observed when using non-racemic α-substituted benzylamine derivatives. Kinetic analysis of the reagents and catalyst, labeling experiments, and the isolation and identification of catalytically competent Co-complexes revealed important insights about the mechanism