Coupling of Vinylic Tellurides with Alkynes Catalyzed by Palladium Dichloride: Evaluation of Synthetic and Mechanistic Details

Under palladium dichloride catalysis, vinylic tellurides couple efficiently with alkynes with retention of the double-bond geometry. Herein we show that the amount of the PdCl 2 catalyst can be reduced from 40 mol % to 10 mol % by using copper(II) chloride as an oxidizing agent. Under these conditions, an inert atmosphere is no longer required and the reaction occurs quite efficiently in the presence of air, leading to the enynes in 40−82% isolated yields. Mass and tandem mass spectrometric experiments using electrospray ionization were performed, and Pd−Te cationic intermediates were, for the first time, intercepted and transferred to the gas phase for structural characterization. An expanded catalytic cycle for this important method for enyne synthesis is proposed.