MOLECULAR-OXYGEN PROMOTED OXIDATIVE CLEAVAGE OF CARBON-PALLADIUM BONDS - CATALYTIC CYCLIZATION OF ALLYLIC 2-ALKYNOATES TO ALPHA-ALKYLIDENE-GAMMA-BUTYROLACTONES BY A PD-II COMPLEX

Molecular oxygen was used as the oxidant to promote the Pd-II and Cu-I I catalyzed cyclization of acyclic allylic 2-alkynoates, yielding alph a-haloalkylidene-gamma-butyrolactones with high stereoselectivity. The stereochemistry of halopalladation of the carbon-carbon triple bond, 1,2-induction in the intramolecular carbon-carbon double insertion and oxidative cleavage of carbon-palladium bonds in the cyclization react ion were studied in detail.