Synthesis of 3‑(Methylsulfonyl)­benzo[b]thiophenes from Methyl(2-alkynyl­phenyl)­sulfanes and Sodium Metabisulfite via a Radical Relay Strategy

A radical relay strategy for the generation of 3-(methyl­sulfonyl)­benzo­[b]­thiophenes through a reaction of methyl­(2-alkynyl­phenyl)­sulfanes with sodium metabisulfite in the presence of a photocatalyst under visible light irradiation is developed. This photoinduced sulfonylation proceeds efficiently under mild conditions by using a catalytic amount of sodium methylsulfinate as an initiator. During the reaction process, the methyl radical generated in situ is the key intermediate, which undergoes a radical relay with the combination of sulfur dioxide to afford methyl­sulfonyl-containing compounds.