Electrochemical Sulfenylation of 4-Hydroxycoumarins with Aryl Thiols Catalyzed by Potassium Iodide

A KI-catalyzed indirect electrochemical oxidative method for the synthesis of sulfenylated 4-hydroxycoumarins via cross-coupling of 4-hydroxycoumarins and aryl thiols at a low potential has been reported. The electrocatalytic activity of KI for sulfenylation of 4-hydroxycoumarin was investigated by cyclic voltammetry. In situ FTIR data reflected the structural change of functional groups during the reaction process. The mechanism of electrochemical sulfenylation involved the generation of intermediate 1,2-bis(4-chlorophenyl)disulfane has been revealed by control experiments. Various sulfenylated 4-hydroxycoumarins were obtained under the optimum reaction conditions in moderate to excellent yields with good functional group tolerance.