Palladium-Catalyzed Alkynylative Lactonization of Unsaturated Bicyclic Carboxylic Acids: Synthesis of Fused Polycyclic γ-Lactone Compounds

Unsaturated bicyclic carboxylic acids undergo palladium-catalyzed coupling with bromoalkynes to produce -alkynyl lactones in moderate to good yields with excellent chemo- and regioselectivity. The reaction conditions were extremely mild, and functional groups such as methyl, methoxy, chloro, and bromo were tolerated under the optimized reaction conditions. Moreover, -chloroalkenyl lactones were facilely synthesized through chloropalladation/carboesterification of electron-deficient CC bonds by using molecular oxygen as the sole oxidant.