Electrochemical-mediated cascading radical cyclization of activated alkynes: creation of 3-sulfonated coumarins and quinolinones

An efficient electrochemical transformation of alkynoates into 3-sulfonated coumarins under transition metal- and oxidant-free conditions at room temperature is reported. The reaction proceeded via a radical-triggered domino aryl sulfonylation/5-exo cyclization/ester migration process and allowed the synthesis of 3-sulfonylated coumarins with good functional group tolerance. The reaction can be extended to the synthesis of quinolinones by capturing the sulfonyl radical with alkyne amides in good yields.