Synthesis of indenoindene-fused α-methylene-γ-butyrolactones via a tandem intra- and intermolecular Friedel–Crafts reaction

An efficient synthesis of indenoindene-fused α-methylene-γ-butyrolactones was carried out via a tandem intra- and intermolecular Friedel–Crafts reaction from the spiro-lactone, which can be easily prepared from ninhydrin by indium-mediated Barbier reaction of cinnamyl bromide.