Synthesis of α-methylene-β,γ-diphenyl-γ-butyrolactone using cobaloxime-catalysed radical cyclisation

α-Methylene-β,γ-diphenyl-γ-butyrolactone was synthesised by the bromoprop-2-yn-1-yloxylation of stilbene 1. Cobaloxime-catalysed radical cyclisation of the resulting 1-bromo-1,2-diphenylethylprop-2-yn-1-yl ether 2 gave 2,3-diphenyl-4-methylene-tetrahydrofuran 3; oxidation of the latter with chromium trioxide in the presence of pyridine afforded target product 4 in a total yield of 25%.