Synthesis of 2-Arylbenzothiazoles and Imidazoles Using Scandium Triflate as a Catalyst for Both a Ring Closing and an Oxidation Steps

Abstract

2-Aminobenzenethiol and an aryl aldehyde were allowed to react to give a 2-arylbenzothiazole in good yield in the presence of a catalytic amount of scandium triflate Sc(OTf) 3 . The detailed study showed that Sc(OTf) 3 catalyzed two steps, that is, the formation of a thiazoline ring and the oxidation of the thiazoline to a thiazole ring. This is the first example that scandium(III) ion catalyzed oxidation of an organic compound using molecular oxygen as an oxidant. The reaction was applied to o-phenylenediamine and an aryl aldehyde to give corresponding 2-arylbenzimidazole in moderate to good yields depending upon the structure of aldehyde.