Toward Antikekulene: Angular 1,2-Di-, 2,3-Di-, and 1,2,15,16-Tetrachloro[6]phenylene

The synthesis of the first ring-functionalized heliphenes is described, comprised of angular 1,2-di-, 2,3-di-, and 1,2,15,16-tetrachloro[6]phenylene, via a series of Sonogashira couplings and cobalt-catalyzed alkyne cyclotrimerization steps. These molecules are explored as potential precursors to antikekulene and their reactivity compared to that of the parent angular [6]phenylene. An X-ray structural determination of 1,2,15,16-tetrachloro[6]phenylene reveals a structure with a considerably larger helical separation than in [6]phenylene, caused by the bulk of the appended chlorine atoms.