Amberlyst-15 Promoted Synthesis of Fused and Spiro γ-Butyrolactones from β-Hydroxyesters

Abstract

β-hydroxy esters have been converted into fused and spiro γ-butyrolactones in 50–90% yield by refluxing with Amberlyst-15 resin in hydrocarbon solvent. Fused-ring lactones are formed with the cis geometry at the ring junction and the regiochemistry of the closure is that expected from a process proceeding through the most stabilized carbocation. The use of an acidic resin offers several advantages over standard aqueous acid conditions: (1) easier monitoring of the reaction, (2) convenient workup, and (3) higher yields.