A One-Pot, Base-Free Annelation Approach to α-Alkylidene-γ-butyrolactones

A novel annelation procedure has been developed for the conversion of γ-hydoxy enones into α-alkylidene-γ-butyrolactones. This one-pot method utilizes the Bestmann ylide (triphenylphosphoranylideneketene) and proceeds by way of acylation followed by an intramolecular conjugate addition/proton transfer/Wittig olefination sequence. The procedure is “base-free” and is useful for the preparation of a range of α-alkylidene-γ-butyrolactones including α-methylene-γ-butyrolactone examples, which can be particularly base-sensitive.