Photoinduced Sulfonylation Reactions through the Insertion of Sulfur Dioxide

Recent advances in the photoinduced sulfonylation reactions through the insertion of sulfur dioxide are summarized. Among the approaches developed in the sulfonylation reactions, the insertion of sulfur dioxide via radical process can be accomplished with the assistance of photoredox catalysis in the presence of visible light or under ultraviolet irradiation, depending the substrates used in the reactions. Under ultraviolet irradiation, the conversion can be completed under metal- and additive-free conditions. It is noteworthy that alkyl halides possessing eliminable beta-hydrogen atom are effective as alkyl radical precursors with the insertion of sulfur dioxide. Two parts, according to the photoinduced reaction pathways, are introduced: (a) photo-initiated formation of radical with the subsequent capture of sulfur dioxide; (b) photo-assisted single electron transfer (SET) after insertion of sulfur dioxide. During the transformation, an oxidative or reductive single electron transfer would occur under visible light photoredox catalysis.