Synthesis of polycyclic fused benzimidazole derivatives

Am easy method for the synthesis of tetraeyclie systems containing an imidazole and an iso-thiazole or an imidazole and a thiazine ring, by reacting 2H-1,3-benzothiazine-2-thion-4(3H)one with aromatic primary diarnines is reported. The structures were assigned based upon mass spectra and modes of cleavage of the compounds. The most important fragments are described.