Isomerization and Dimerization of 1-Phenylpropyne upon Metalation with Alkyl Lithium Bases and Lewis Basic Polyamine Donors

Since the isomerization of C–C multiple bonds is a powerful strategy in organic synthesis, in this study we have investigated the isomerization upon metalation of 1-phenylpropyne with alkyllithium bases in the presence of polydentate amine donors. Combining NMR monitoring and X-ray crystallographic studies, we have found that the terminal alkynylide is formed as the major product, can be isolated, and undergoes dimerization upon heating to selectively form an enyne in high yields.