Metal-Free Regioselective Radical Cyclization of 1,6-Enynes with Carbonyl Compounds

A regioselective cyclization of 1,6-enynes is reported by a tert-butyl hydroperoxide (TBHP)-mediated, one-pot, cascade reaction with commercially available carbonyl compounds under metal- and additive-free conditions. The reaction scope includes both 1,6-enynes and carbonyl compounds. A possible cascade reaction mechanism, consisting of acyl radical addition, intramolecular cyclization, and hydrogen abstraction, is proposed.