Tin(IV) triflimidate-catalyzed cyclization of epoxy esters to functionalized δ-hydroxy-γ-lactones

In the presence of 5 mol % of tin(IV) triflimidate, a cyclization reaction of epoxyesters to δ-hydroxy-γ-lactones proceeding in 46-98% yields without additives, ligands, or co-catalysts was observed. The cyclization to five-membered rings is greatly favored compared to the possible six-membered rings formation and is probably under the control of a Thorpe-Ingold type effect.