Free radical macrocyclisation via propiolate esters.

Intramolecular free-radical addition to propiolate esters has provided a new and a stereoselective route to 14–16 membered trans-α,β-unsaturated macrocylic lactones from their corresponding ω-iodoalkyl-propionate esters under triphenyltin hydride/AIBN mediated conditions. Attemps to synthesise analogous 10–13 membered lactones proved unsuccessful, resulting in acyclic products derived from direct reduction at the radical centre.