Visible-Light-Induced Radical Cascade Sulfonylation/Cyclization to Access Sulfonylated Benzazepines and Benzoxepines by EDA Complexes

A visible light-mediated sulfonylation of 1-(2-(allyloxy)aryl)-3,3-bis(methylthio)prop-2-en-1-ones and N-allyl-N-(2-(3,3-bis(methylthio) acryloyl)aryl)-4-methylbenzenesulfonamides for the synthesis of a wide range of sulfonylated benzazepines and benzoxepines is developed. This protocol features simple operation, photocatalyst- and additive-free, good regioselectivity, and the use of K2S2O5 as a sulfur dioxide substitute, providing a novel environmentally friendly strategy to access the seven-membered heterocycles. The mechanistic studies revealed that aryldiazonium tetrafluoroborates served as electron acceptors, enabling the formation of EDA complexes with α-oxoketene dithioacetal substrates.