Preparation of diynes via selective bisalkynylation of zirconacycles

Reaction of alkynyl halides with in situ prepared zirconacyclopentanes, -pe ntenes, and -pentadienes in the presence of CuCl under mild reaction condit ions afforded alkynes or diynes. Control of the reaction conditions selecti vely afforded monoalkynylation products of zirconacycles. Reaction of zirco nacycles with 2 equiv of alkynyl halides resulted in the formation of diyne s. Selective monoalkynylation of zirconacycle with an alkynyl halide, follo wed by reaction with a different alkynyl halide, afforded unsymmetrical diy nes. Bisalkynylation product of zirconacyclopentadiene was gradually conver ted into a tricyclic compound.