Radical Cyclization in Heterocycle Synthesis. 11. A Novel Synthesis of α,β-Disubstituted γ-Lactones via Sulfanyl Radical Addition−Cyclization Using Hydroximates as a Tether

A combination of sulfanyl radical addition−cyclization of dienes connected with hydroximates and subsequent conversion of the resulting cyclic hydroximate to the lactones provides a novel method for the construction of α,β-disubstituted γ-lactones. Upon treatment with thiophenol in the presence of AIBN, dienes connected with hydroximates smoothly underwent sulfanyl radical addition−cyclization to give cyclic cis- and trans-hydroximates. Hydrolysis of cyclic hydroximates gave the desired cis- and trans-lactones in high yield. This method was successfully applied to the practical synthesis of (±)-oxo-parabenzlactone.