Nitromethane Extrusion Reaction for Synthesis of Polycyclic Benzimidazoheterocycles

A facile base-promoted annulation of diamines with 4-chloro-3-nitrocoumarins or 4-chloro-3-nitroquinolin-2(1H)-ones affording 6H-benzimidazo[1,2-c][1,3]benzoxazin-6-ones or benzo[4,5]imidazo[1,2-c]quinazolin-6(5H)-ones in moderate to good yields is reported. These metal- and triphosgene-free reactions presumably proceed by the conjugate addition of diamines to 4-chloro-3-nitrocoumarins/4-chloro-3-nitroquinolin-2(1H)-ones, followed by intramolecular cyclization via extrusion of nitromethane and hydrogen chloride to form the target compounds.