A novel isocyanide-based three-component synthesis of benzimidazo[1,2-a][1,4]diazepinones

3-(2-Formyl-1H-benzimidazol-1-yl)propanoic acid, as a bifunctional formyl acid was prepared in four steps. This compound underwent a one-pot reaction with amines and alkyl isocyanides via the Ugi 4-center-3-component condensation. A series of novel benzimidazole-fused 1,4-diazepine-5-ones were obtained via this method in moderate to excellent yields.