A new visible-light-mediated protocol has been proposed for the synthesis of thiosulfonates via metal-free sulfonylation of thiols with aryldiazonium and sodium metabisulphite at room temperature. This mild three-component reaction simply utilizes readily available rhodamine 6G as the photocatalyst and cheap inorganic sulfite of sodium metabisulfite as a SO2 surrogate and provides an attractive strategy to access various unsymmetrical thiosulfonates in moderate to good yields under oxidant- or strong acid-free conditions. Preliminary mechanistic studies indicated that a radical pathway was involved in the present transformation.
