Formation of acyldisulfide ions from the reaction of sulfur with thiocarboxylate ions, and reactivity towards acyl chlorides in N,N-dimethylacetamide

The reactivity of sulfur towards thiocarboxylate ions RC(O)S- a (R = Ph 1, Me 2, But 3) has been studied by spectroelectrochemistry in N,N-dimethylacetamide. For 2a–3a, two parallel and partial reactions, for which equilibrium constants have been determined, led to: (i) [RC(O)]2S2- b species and S3·-/S82- polysulfide ions and (ii) RC(O)S2 ions c; only traces of 1c were detected by voltammetry. As previously observed with thiolate ions, our results are consistent with an initial monoelectronic transfer between RC(O)S- ions and S2 molecules in equilibrium with S8, followed by concurrent couplings of RC(O)S˙ and S2·- radicals. On a preparative scale, when sulfur was added to RC(O)S- ions 1a,3a the enhanced reactivity of RC(O)S2- ions towards acyl chlorides RC(O)Cl (R = C6H5 and But, respectively) only yielded diacyl disulfides 1b,3b.