PALLADIUM-CATALYZED COUPLING OF VINYLIC HALIDES, ALKENES, AND AMINES

The palladium-catalyzed, three component coupling of vinylic halides, alkenes, and amines has been reexamined The success of the cross-coupling of vinylic halides, alkenes and amines depends heavily on the structures of each of the three substrates, as well as the reaction conditions. The presence of water greatly improves the yield. Secondary amines give much better results than primary amines. Only unhindered monosubstituted, terminal alkenes react well. Non-conjugated 1,4- and 1,5-dienes afford good yields of a single product, apparently due to chelation during coupling. Relatively unhindered vinylic halides generally, but not always, give the best results. Mixtures of regioisomers arising from vinylic palladium addition to both ends of the alkene double bond are observed when less hindered amines and vinylic halides are employed. Mixtures of stereoisomers are also not uncommon. These reactions proceed via vinylic palladium formation and addition to the alkene, rearrangement to a pi-allylpalladium intermediate, and subsequent palladium displacement by the amine.