Electron Donor-Acceptor Complex Enabled Cyclization/Sulfonylation Cascade of N -Heterocycles with Thianthrenium Salts.

We report a visible-light-promoted cyclization/sulfonylation cascade of N -heterocycles with thianthrenium salts using DABSO as the SO 2 surrogate. This method features excellent functional group tolerance, wide substrate scope, and late-stage elaboration of bioactive relevant molecules. Mechanistic investigations reveal that the photoactive electron donor-acceptor (EDA) complexes between thianthrenium salts and DABCO are capable of the generation of aryl radicals, which induce the following SO 2 insertion by attacking DABSO, thus triggering the key radical cyclization step.