A palladium-catalyzed sequence of allylic alkylation and Hiyama cross-coupling:: Convenient synthesis of 4-(α-styryl) γ-lactones

Unsaturated malonyl esters underwent Pd-catalyzed intramolecular allylic alkylation to give 4-vinyl -substituted gamma-lactones. In contrast to the previously studied cyclization of malonamides, this reaction could only be achieved with a substrate incorporating ajudiciously positioned silicon moiety, which directs the ionization toward the desired eta(3)-allyl-palladium complex. The resulting 4-[dimethyl(2-thienyl)silylvinyl]lactone could be subsequently engaged into Hiyama couplings to give the corresponding 4-(alpha-styryl) gamma-lactones.