Facile transformation of benzocyclobutenones into 2,3-benzodiazepines via 4pi-8pi tandem electrocyclic reactions involving net insertion of diazomethylene compounds.

Efficient transformations of benzocyclobutenones into 2,3-benzodiazepines by a formal insertion of diazomethylene compounds are described. This sequential process includes nucleophilic addition of diazomethylene anion, oxy-anion accelerated o-quinodimethane formation by an electrocyclic ring-opening reaction, and 8pi-electrocyclization in one-pot under remarkably mild conditions. Intermediary oxy-anion plays an important role for the efficient transformations.