Cascade Cyclization/Annulation of β-Enamino Diketones and o-Phenylenediamine: A Strategy to Access Pyrrole-fused 1,5-Benzodiazepines.

Herein, we introduce an unprecedented cascade reaction for the assembly of pyrrole-fused 1,5-benzodiazepine frameworks. These diverse privileged scaffolds were controllably constructed by intramolecular cyclization of β-enamino diketone, followed by annulation with o-phenylenediamine. The protocol features efficient one-pot cascade cyclization/annulation, performed under simple and mild reaction conditions. The products are obtained in a metal-free manner, in good to excellent yields (65-91%), and represent a fused heterocyclic scaffold that is not yet found in nature.