Transmetalation of Palladium Enolate and Its Application in Palladium-Catalyzed Homocoupling of Alkynes: A Room-Temperature, Highly Efficient Route To Make Diynes

A novel pathway for the homocoupling reaction has been achieved using a similar protocol as the cross-coupling reaction. Ethyl bromoacetate is chosen to initiate the coupling reaction through oxidative addition to a Pd(0) species, and an PdBr(enolate) intermediate is formed. This intermediate can undergo double transmetalation with an alkynyl copper reagent, and reductive elimination produces a variety of diynes in high yields.