Tandem Sulfonylation/Cyclization of Vinyl Azides with Aryldiazonium Tetrafluoroborates and SO2

An efficient and facile strategy for the synthesis of 6‐(sulfonylmethyl)phenanthridines and its derivatives has been developed via tandem sulfonylation cyclization of vinyl azides under mild conditions in the absence of any catalysts and additives. The reaction simply utilizes easily accessible and cheap K 2 S 2 O 5 as the sulfur dioxide source, delivering functionalized phenanthridines in moderate to excellent yields with operational simplicity and gram‐scale synthesis, as well as good functional‐group tolerance.