One-Pot Green Regioselesctive Synthesis of γ-Lactones from Epoxides and Ketene Silyl Acetals Using 1,3-Dimethylimidazolium Fluoride as a Recoverable Metal-Free Catalyst

In a straightforward and fast protocol, a mixture of 1,3-dimethylimidazolium fluoride ([DMIM] F) and 1-butylimidazolium tetrafluoroborate ([Hbim] BF4) efficiently catalyzed the reaction of epoxides with ketene silyl acetals (KSA) to give various gamma-lactones under metal-free conditions. Diverse kinds of the desired gamma-lactones were directly prepared with high regioselectivities and yields in a simple one-pot procedure using [DMIM] F as Si-O bond activator and [Hbim]B-4 as solvent and acidic ionic liquid catalyst. The ionic liquid mixture was recovered and reused three times and no loss in its activity was observed.