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

A novel annelation procedure has been developed for the conversion of gamma-hydoxy enones into alpha-alkylidene-gamma-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 alpha-alkylidene-gamma-butyrolactones including alpha-methylene-gamma-butyrolactone examples, which can be particularly base-sensitive.