Rhodium(III)-Catalyzed [4+3] Annulation of N-Aryl-pyrazolidinones and Propargylic Acetates: Access to Benzo[c][1,2]diazepines.

The generation of 2,3-dihydro-benzo[c][1,2]diazepine derivatives via rhodium(III)-catalyzed [4+3] annulation of pyrazolidinones and propargylic acetates is disclosed. The reaction proceeds smoothly under relatively mild conditions from propargylic acetates as novel C3 synthons. A range of dinitrogen-fused heterocyclic compounds are readily accessed by this approach.