Generation of highly active manganese dioxide in situ by using catalytic amount of potassium permanganate in anhydrous ethanol system, the catalytic system promoted S-S bond construction by free radical self coupling reactions of thiophenol and mercaptan compounds at room temperature. 14 disulfides were obtained with 70%~99% yields. At the same time, it was also found that the catalytic system could also catalyze radical cross-coupling reactions between symmetric disulfides and different substituents of thiophenols, thiols, or two different symmetric disulfides, 13 asymmetric disulfides were obtained with 19%~72% yields. The protocol offered the advantages of simple and efficient, easy separation, green solvent, wide range of substrate applications, and mild conditions. All products were confirmed by ¹H NMR and ¹³C NMR spectra.

Key words: free radical coupling reaction, S-S bond, manganese dioxide