Regioselective Radical-Relay Sulfonylation/Cyclization Protocol to Sulfonylated Pyrrolidones under Transition-Metal-Free Conditions.

A simple and low-cost tandem sulfonylation/cyclization of 1,5-diene, aryldiazonium salt, and DABCO·(SO 2 ) 2 is disclosed. This base-promoted multicomponent reaction can provide a "green" and economic synthesis of sulfonylated pyrrolidones under transition-metal-free and moisture/oxygen-insensitive reaction conditions, thus delivering a wide range of sulfonylated pyrrolidones in moderate to high yields with excellent functional group compatibility. A plausible mechanism involving a radical process is proposed, which demonstrates highly chemoselective trapping of the aryl radical with "SO 2 " species, and a regioselective sulfonylation/cyclization protocol in this reaction.