Reagent-controlled stereoselection in radical addition to α-methylenebutyrolactones

Abstract

Some β- or γ-substituted α-methylenebutyrolactones are butylated with Bul and (Me₃Si)₃SiH to give cis-α,β- or -α,γ-disubstituted lactones in high selectivites, while the same reaction with Bu₃SnH in the presence of bulky Lewis acid reverses the stereoselectivity to give a trans-disubstituted lactone as the major product.