A nitromethane extrusion reaction for the synthesis of polycyclic benzimidazoheterocycles

A facile base-promoted annulation of diamines with 4-chloro-3-nitrocoumarins or 4-chloro-3-nitroquinolin-2(1<i>H</i>)-ones affording 6<i>H</i>-benzimidazo[1,2-<i>c</i>][1,3]benzoxazin-6-ones or benzo[4,5]imidazo[1,2-<i>c</i>]quinazolin-6(5<i>H</i>)-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(1<i>H</i>)-ones, followed by intramolecular cyclization <i>via</i> extrusion of nitromethane and hydrogen chloride to form the target compounds.