Palladium-Catalyzed Regioselective Coupling of Propargylic Substrates with Terminal Alkynes. Application to the Synthesis of 1,2-Dien-4-ynes

The palladium-catalyzed reaction of propargyl halides, tosylates and acetates with terminal alkynes is reported. The best yields are obtained from propargyl chlorides and l-alkynes (i) in the presence of 2 equiv. of amine (triethylamine, diisopropylamine) in benzene, toluene or ethylacetate (ii) or in pure diisopropylamine. Propargyl acetates undergo the cross coupling reaction with moderate to high yields after modification of the general procedure.