Photoinduced intramolecular carbosulfonylation of alkynes: access to sulfone-containing dibenzazepines from sulfur dioxide.

A photoinduced three-component reaction of N-benzyl-N-(2-ethynylaryl)amides, sulfur dioxide and aryldiazonium tetrafluoroborates is developed, providing an efficient and straightforward approach for the synthesis of diverse vinylsulfonylated dibenzazepine derivatives in moderate to good yields under mild conditions. This transformation proceeds smoothly at room temperature in the presence of visible light, which shows a wide range of substrate scope with good functional group compatibility. The synthetic utility of this methodology is further demonstrated through Suzuki coupling. Mechanistic studies show that this reaction is triggered by the addition of an arylsulfonyl radical to an alkyne from sulfur dioxide, followed by vinyl radical cyclization to afford the desired sulfonated dibenzazepines.