Concise preparation of novel tricyclic chemotypes: fused hydantoin-benzodiazepines

The article describes a concise synthesis of a collection of 4,5-dihydro-1H-benzo[e][1,4]diazepines fused to a hydantoin ring, generated in a mere three steps. The protocol employs the Ugi-5-component CO2-mediated condensation, benzodiazepine formation promoted by acidic conditions and basic treatment to afford the fused hydantoin. Mechanistic caveats, dependent on the aldehydes of choice will be revealed and a facile oxidation of the final products to imidazolidenetriones is briefly discussed.