Expansion of diazepine heterocyclic chemical space via sequential Knoevenagel condensation-intramolecular aza-Wittig reaction: 2-acyl-4-aryl-5H-pyrrolo[1,2-d][1,4]diazepines.

A highly efficient synthetic route to a new 1,4-diazepene skeleton, 2-acyl-4-aryl-5H-pyrrolo[1,2-d][1,4]diazepine, was established where Knoevenagel condensation of readily available two fragments, N-substituted pyrrole-2-carboxaldehyde and α-azidoketone, followed by intramolecular aza-Wittig reaction under Staudinger azide reduction conditions permitted facile access to a poly-substituted 1,4-diazepine ring system for the first time. Successful application of this protocol to construct new 1-alkoxy-3-acylisoquinolines and 1-alkoxy-3-acyl-β-carbolines is also demonstrated.