Rhodium(iii)-catalyzed intramolecular annulations involving amide-directed C–H activations: synthetic scope and mechanistic studies

Abstract

Alkyne tethered benzamides undergo rhodium(III)-catalyzed intramolecular annulations to give tricyclic isoquinoline derivatives in good yields. DFT calculations suggest that the reaction mechanism involves a migratory insertion of the alkyne into the rhodium–nitrogen bond of the rhodacycle intermediate that results from the initial C–H activation. This contrasts with the pathway proposed for intermolecular cases, which considers an insertion into the rhodium–carbon instead of the rhodium–nitrogen bond. The annulation is also effective with acrylamides; and, while anilides fail to participate in the process, naphthylamides do undergo the intramolecular annulation, albeit the chemoselectivity is different than for the intermolecular reactions.