Haloacid/dimethyl sulfoxide-catalyzed synthesis of symmetrical disulfides by oxidation of thiols

A novel method is developed for the oxidation of thiols to the corresponding disulfides using 20 mol % haloacid (HBr or HI) in combination with dimethyl sulfoxide. A tentative mechanism is proposed for the oxidation. In addition to the advantages of cost-effectiveness, simple processes, and broad functional group tolerance, the exclusive formation of disulfides is the principle reward of this methodology while compared to known methods that further oxidize disulfides to S-oxides and other byproducts.