Facile synthesis of γ-alkylidenebutenolides from Morita–Baylis–Hillman adducts

An expedient synthetic procedure of γ-alkylidenebutenolides was developed via a sequential indium-mediated Barbier-type reaction of Morita–Baylis–Hillman bromide with aldehyde, lactonization, and double-bond isomerization. Various γ-alkylidenebutenolides including bovolide and its derivatives were synthesized in good overall yields.