N-Arylimino-1,2,3-dithiazole derivatives 2 of 2-bromoanilines are converted in high yield into 2-cyanobenzothiazoles 3 by heating or, more rapidly, by focused microwave irradiation at atmospheric pressure, in pyridine containing cuprous iodide.5-(N-Arylimino)-4-chloro-5H-1,2,3-dithiazoles 2 are stable crystalline solids readily prepared in high yield from anilines and 4,5-dichloro-1,2,3-dithiazolium chloride 1, itself easily available from chloroacetonitrile and disulfur dichloride. 1 These iminodithiazoles 2 have proved to be highly versatile intermediates in heterocyclic synthesis. 2 Previous work showed that imino compounds 2 cyclised on vigorous heating to give sulfur, hydrogen chloride and 2-cyanobenzothiazoles 3 (Scheme 1). 3 An electron releasing group (R = m-OMe) favoured formation of the benzothiazole 3 whilst a strongly electron withdrawing group (R = m-or p-NO 2 ) reduced the yield of 3 dramatically, in favour of the cyanoimidoyl chloride 4 which became the major product (e.g. 9% of 3 and 54% of 4 with R = m-NO 2 ). 3
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