Facile Synthesis of Benzimidazole and Benzothiazole Compounds Mediated by a Zinc Precatalyst Supported by an Iminopyrrole-Morpholine Ligand

Three zinc complexes, with the general formula {kappa(2)-C4H3NH[2-CH=NCH2CH2N(CH2CH2)(2)O]ZnX2} [X=Cl (2 a), Br (2 b), I (2 c)], supported by a neutral iminopyrrole-morpholine ligand, were synthesized by the reaction between {C4H3NH-2-[CH=NCH2CH2N (CH2CH2)(2)O]} (1) and anhydrous zinc dihalides (ZnCl2, ZnBr2, ZnI2) at ambient temperature in dry methanol. The zinc complexes were fully characterized using multinuclear NMR spectroscopic techniques and the molecular structures of complexes 2 a and 2 c in their solid states were determined by single-crystal X-ray diffraction analysis. The zinc diiodo complex (2 c) proved to be a competent precatalyst in the formation of a wide range of benzimidazole and benzothiazole compounds, via aerobic oxidative condensation of several benzylamines with o-phenylenediamine, N-phenyl-o-phenylene-diamine, and o-mercaptoaniline. The benzimidazole and benzothiazole derivatives were successfully characterized using H-1 and C-13{H-1} NMR spectroscopy.