An (NH4)2S2O8-promoted cross-coupling of thiols/diselenides and sulfoxides to construct unsymmetrical disulfides/selenosulfides is disclosed. Control experiments demonstrate that (NH4)2S2O8 acts as an acid and an oxidant, while both ionic and radical routes are involved in the reaction. The KIE experiments reveal that C-H bond cleavage of sulfoxides was involved in the turnover-limiting step.