Isothiazoles I: 4‐isothiazolin‐3‐ones. A general synthesis from 3,3′‐dithiodipropionamides

The syntheses of 3‐hydroxyisothiazole, 4‐methyl‐3‐hydroxyisothiazole, and a eomprehensive series of the respective 2‐substituted‐4‐isothiazoIin‐3‐ones have been achieved by the one‐step chlorination‐cyclization of the corresponding 3,3 ‐dithiodipropionamides. In several instances, 5‐chloro‐4‐isothiazolin‐3‐ones were isolated as side products; however, no 4‐chloro‐4‐isothiazo‐lin‐3‐ones were evident in the reaction mixtures. These observations, coupled with the exclusive 4‐ or 4,5‐halogenation of several preformed 4‐isothiazoIin‐3‐ones, support a proposed reaction pathway involving introduction of chlorine α to the sulfur atom in intermediate reaction products.