The reaction of 4,5-dichloro-1,2,3-dithiazolium chloride with DMSO: an improved synthesis of 4-chloro-1,2,3-dithiazol-5H-one

4,5-Dichloro-1,2,3-dithiazolium chloride 2 (Appel salt) reacts with either DMSO, diphenylsulfoxide 11 or methylphenylsulfoxide 12 to give 4-chloro-5H-1,2,3-dithiazol-5-one 1 in excellent yields. The use of catalytic amounts of DMSO (1 mol %) in MeCN in the presence of water (1 equiv) transforms Appel salt 2 into dithiazolone 1 in near quantitative yields (92%). Rational mechanisms are proposed to explain the catalytic nature of these reactions.