Cobalt-Catalyzed Cross Addition of Silylacetylenes to Internal Alkynes

A CoCl₂·6H₂O/Zn reagent using 2-(2,6-diisopropylphenyl)­iminomethylpyridine (dipimp), 1,2-bis­(diphenylphosphino)­ethane (dppe), or 1,2-bis­(diphenylphosphino)­benzene (dppPh) as a ligand effectively catalyzed the cross-addition reaction of silylacetylene to internal alkynes. The reaction of some unsymmetrical internal alkynes, such as 3-arylpropargyl alcohols, proceeded in a highly regioselective manner in the presence of dppe or dppPh but gave a nearly 1:1 mixture of regioisomers in the presence of dipimp. The results of reactions using 1-deuterated 2-silylacetylene revealed that the reaction involves a direct oxidative addition of the silylacetylenic C–H bond to cobalt.