Electrochemical Sulfenylation of Indoles with Disulfides Mediated by Potassium Iodide

A novel electrochemical system for sulfenylation of indoles with disulfides to generate 3-sulfenylindoles via C-S bond formation mediated by potassium iodide at a low potential was developed. Iodine was electrogenerated from iodide ions at a graphite anode and showed a high catalytic activity for the electrochemical sulfenylation reactions. A variety of aromatic, heteroaromatic and aliphatic disulfides could react with 2-methlyindole to synthesize the corresponding 3-sulfenylindoles in good to excellent yields. In addition, protected and unprotected indoles with various groups, especially electron-donating groups, also performed well in the sulfenylation reactions. The transformation, which proceeded through the redox of iodine and the generation of intermediate 3-iodoindole, provided an efficient and environmentally benign protocol for the synthesis of 3-sulfenylindoles under mild conditions.