Highly general stereo-, regio-, and chemo-selective synthesis of terminal and internal conjugated enynes by the Pd-catalysed reaction of alkynylzinc reagents with alkenyl halides

The reaction of an alkynylzinc chloride, readily obtainable from the corresponding alkynyl-lithium and anhydrous zinc chloride, with an alkenyl iodide or bromide in the presence of a catalytic amount of a Pd–phosphine complex provides the corresponding terminal or internal enyne in high yield, the stereospecificity of the reaction being 97%.