Copper-Catalyzed Allylations of Zirconocene Intermediates Generated from o-Alkenyl or o-Alkynylbenzyl Ether Derivatives and Zirconocene−Butene Complex

o-Alkenyl or alkynyl benzylzirconocene intermediate, which was readily generated by the reaction of 2-alkoxymethylstyrene or 2-alkoxymethyl-1-(trimethylsilylethynyl)-benzene derivative with zirconocene−butene complex (Negishi reagent, “Cp2Zr”), reacted with allyl or propargyl halides in the presence of a catalytic amount of CuCl to give allylation or allenylation products. Conversion to Dane's diene, which is a key intermediate for estrone synthesis, was efficiently carried out by enyne olefin metathesis of the allylation products.