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Paper | Regular issue | Vol 63, No. 12, 2004, pp.2769-2783
Published online, 22nd October, 2004
DOI: 10.3987/COM-04-10215
Synthesis of 2-Arylbenzothiazoles and Imidazoles Using Scandium Triflate as a Catalyst for Both a Ring Closing and an Oxidation Steps

Takashi Itoh, Kazuhiro Nagata, Hiroyuki Ishikawa, and Akio Ohsawa*

*School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan


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.