The syn addition of alkylcopper reagents to various propargyl derivatives, i.e. HCtriple bond; length as m-dashC---C---Z (Z=X, OAc, NR2, SEt, OR, O-), has been studied. Among the various factors governing the regioselectivity, the nature of the heteroatom in the group Z and the polarity of the solvent are particularly important. The vinylcopper derivatives obtained from propargyl ethers have been carboxylated, iodinated and oxidised.