Since the discovery of nickel-catalyzed cyclization of acetylene to benzene and cyclooctatetraene, transition-metal-activated cycloaddition of alkynes has become a powerful technique to construct ring compounds in organic synthesis. Although cyclo-trimerization and -tetramerization were discovered almost 70 years ago, direct metal-mediated acetylene oligomerization to polycyclic compounds has not been reported. Instead, cycloaddition of different alkynes, or alkynes with alkenes or arynes, has been used to synthesize polycyclic and other complex ring structures. In a recent Journal of American Chemical Society Communication, the Yang group reported the metal-activated bicycle-oligomerization of acetylene to naphthalene in a supersonic molecular beam experiment. In their work, laser-vaporized lanthanum atoms are used to activate acetylene molecules, naphthalene is detected in the form of a metal complex by laser spectroscopy, and a reaction mechanism is proposed based on the observation of three reaction intermediates.
Citation: "La-Ativated Bicyclo-Oligomerization of Acetylene to Naphthalene." D. Hewage, W. R. Silva, W. Cao, and D.-S. Yang, J. Am. Chem. Soc. 2016, 138, 2468-2471.