Cross-metathesis between α-methylene-γ-butyrolactone and olefins:: A dramatic additive effect

Olefin cross-metathesis between alpha-methylene-gamma-butyrolactone and terminal olefins is described. Moderate to excellent yields of alpha-alkylidene-gamma-butyrolactones were obtained with high E-stereoselectivity in the presence of low catalyst loading in refluxing CH2Cl2. In addition, the use of various additives was found to have a dramatic effect on the efficiency of the cross-metathesis (CM) process by circumventing the formation of the isomerized byproduct.