INTRAMOLECULAR REACTIONS OF ALKYNES WITH ALKENES CATALYZED BY PLATINUM AND GOLD

Two major pathways are followed in the reaction of alkenes with alkynes catalyzed by electrophilic transition metals. If the metal coordinates the alkyne and the alkene, an oxidative cyclometallation can ensue to give a metallacyclopentene, which usually evolves by β-hydrogen elimination (Alder-ene cycloisomerization). Alternatively, the selective coordination of the metal to the alkyne promotes an attack of the alkene (usually anti) to give cyclopropyl metal carbenes.