Facile Access to 1,5-Benzodiazepines Via Amine-Promoted (4+3) Annulations of Delta-Acetoxy Allenoates with O-Diaminobenzenes under Mild Conditions

An amine-promoted (4+3) annulation of delta-acetoxy allenoate with o-diaminobenzene is reported, providing a facile access to 1,5-benzodiazepine. This method features wide reaction scope, mild conditions, and readily available starting materials. The cascade reaction involves aza-Michael addition of o-diaminobenzene to allenoate, elimination of acetate group, and subsequent 1,6-aza-Michael addition.