Cascade Cyclization/Annulation\nof β‑Enamino\nDiketones and <i>o</i>‑Phenylenediamine: A Strategy\nto Access Pyrrole-fused 1,5-Benzodiazepines

Herein, we introduce an unprecedented cascade reaction\nfor the\nassembly of pyrrole-fused 1,5-benzodiazepine frameworks. These diverse\nprivileged scaffolds were controllably constructed by intramolecular\ncyclization of β-enamino diketone, followed by annulation with <i>o</i>-phenylenediamine. The protocol features efficient one-pot\ncascade cyclization/annulation, performed under simple and mild reaction\nconditions. The products are obtained in a metal-free manner, in good\nto excellent yields (65–91%), and represent a fused heterocyclic\nscaffold that is not yet found in nature.