Palladium-catalyzed carbonylation of yne esters leading to gamma-alkylidene alpha,beta-unsaturated gamma-lactones.

[reaction: see text] The reaction of yne esters with carbon monoxide (1 atm) in the presence of palladium complexes gives bicyclic unsaturated lactone derivatives in good to high yields. The 2-pyridinyloxy group is a good leaving group among leaving groups examined.