Stereoselective Sequential Spirocyclopropanation/Cloke-Wilson Rearrangement Reactions for Synthesis of trans-β,γ-Disubstituted γ-Butyrolactones Using Alkylidene Meldrum's Acid and Benzyl Halides

The stereoselective sequential spirocyclopropanation/Cloke-Wilson rearrangement reactions have been developed to synthesize gamma-butyrolactones using alkylidene Meldrum's acids and benzyl halides. The DBU-promoted spirocyclopropanation was carried out efficiently at room temperature to generate trans-isomeric spirocyclopropyl Meldrum's acid, and the following stereospecific thermal decarboxylative Cloke-Wilson rearrangement afforded trans-gamma-butyrolactones. A variety of aromatic and aliphatic Meldrum's acid derived olefins and benzyl halides were tolerated. Various trans-beta,gamma-disubstituted gamma-butyrolactones were produced with moderate to good overall yields from 46 to 96% and excellent diastereoselectivities.