Stereoselective Synthesis of (E)- or (Z)-α-Alkylidene-γ-butyrolactone from γ-Butyrolactone and Bis Disulfide and Mechanistic Studies of the Effect of Metal Complexes on the Stereoselection

Article abstract of DOI:10.1246/bcsj.60.1853

Treatment of γ-butyrolactone with bis disulfide in presence of 2.2. equiv of lithium diisopropylamide (LDA) produced lithium enolate of O-ethyl S-(tetrahydro-2-oxo-3-furanyl) dithiocarbonate, which reacted with an aldehyde to afford exclusively (E)-α-alkylidene-γ-butyrolactone.Interestingly, when the reaction was quenched below -20 deg C or when it was carried out in the presence of metal complex such as zinc chloride, copper(I) iodide, or tributyltin chloride, (Z)-α-alkylidene-γ-butyrolactone was obtained as the major product.The stereoselectivity of this reaction was sensitive to the reaction temperature and the metal cation employed.