Radical cyclization in heterocycle synthesis. 11. A novel synthesis of alpha,beta-disubstituted gamma-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 hydroxi mate to the lactones provides a novel method for the construction of alpha, beta -disubstituted gamma -lactones. Upon treatment with thiophenol in the presence of AIBN, dienes connected-with hydroximates smoothly underwent sul fanyl radical addition-cyclization to give cyclic cis- and trans-hydroximat es. Hydrolysis of cyclic hydroximates gave the desired cis- and trans-lacto nes in high yield. This method was successfully applied to the practical sy nthesis of (+/-)-oxo-parabenzlactone.