Palladium(II)-catalyzed carbocyclization: Vinylpalladium in 1,4-oxidation of conjugated dienes

Article abstract of DOI:10.1016/0040-4020(96)00265-7

Palladium-catalyzed 1,4-oxidation of conjugated dienes involving carbon-carbon bond formation has been realized. The reaction is performed with both acyclic and cyclic dienes with a carbon chain containing a terminal or internal triple bond. A vinylpalladium species formed by chloropalladation of the alkyne inserts one of the double bonds of the diene in a Heck-type reaction. The addition of palladium and chloride over the triple bond is non-stereoselective while the overall 1,4-addition by carbon and chloride over the diene is highly stereoselective and occurs anti. The stereoselectivity of the chloropalladation is dependent on the chloride concentration and varies with the substrate.