Gas-phase Diels-Alder cycloaddition of benzyne to an aromatic hydrocarbon bay region: Groundwork for the selective solvent-free growth of armchair carbon nanotubes

Benzyne, generated in the gas phase by pyrolysis of phthalic anhydride, has been shown to undergo Diels-Alder cycloaddition to the bay region of perylene, a typical polycyclic aromatic hydrocarbon, under solvent-free conditions in a high temperature flow system. The initial cycloadduct spontaneously loses two hydrogen atoms, thereby rearomatizing to give naphtho[1,2,3,4-ghi]perylene. Analogous Diels-Alder cycloadditions of benzyne to bay regions on the rims of suitable cylindrical hydrocarbon templates, when followed by rearomatizations and thermal cyclodehydrogenations to join adjacent benzo groups, are proposed as key steps for a directed chemical synthesis of uniform diameter armchair carbon nanotubes.