CARBOPALLADATION OF ALLENIC HYDROCARBONS. A NEW WAY TO FUNCTIONALIZED STYRENES AND 1,3-BUTADIENES.

Article abstract of DOI:10.1016/S0040-4020(01)89984-1

The palladium-catalyzed coupling reaction of allenes, vinyl or aryl halides and stabilized carbanions is described: ?-allyl palladium complexes are formed by addition of a vinyl or an aryl-palladium complex to an allenic hydrocarbon and trapped by the sodium enolate of diethyl malonate giving rise with good yields to β-butadienyl or β-styryl malonates.With monoalkyl allenes, the reaction is regiospecific with attack of the nucleophile on the unsubstituted carbon of the intermediate ?-allyl complex and in many cases highly stereoselective with the predominant formation of the E configuration for the trisubstituted double bond of the diene.This configuration was demonstrated by 1H NMR using NOE difference spectroscopy.