Abstract A simple and practical procedure for synthesis of 2-arylbenzimidazoles by a one- pot condensation of o-phenylenediamine with aromatic aldehydes in the presence of a catalytic amount of M (NO 3) 2· 6H 2 O (M= Mn, Fe, Co, Ni, Cu) in ethanol at room temperature is described. Major advantages of this practical procedure are use of a readily available catalyst, high yields, short reaction times, and simplicity of the reaction and ...