Rearrangements in the Scholl oxidation: implications for molecular architectures

Rearrangements readily occur in Scholl oxidations and interfere with the construction of certain molecular architectures. 3,3?,4,4′,4″,4?,5′,5″-Octamethoxy-1,1′,2′,1″,2″,1?-quaterphenyl and 3,3?,4,4′,4′′,4?,5′,5′-octamethyl-1,1′,2′,1″,2″,1?-quaterphenyl, which were conceived as precursors to benzenoid strips, rearranged under Scholl conditions to the unexpected C_2v-substituted products 1,2,5,6,9,10,12,13-octamethoxydibenzofg,op]naphthacene and 1,2,5,6,9,10,12,13-octamethyldibenzofg,op]naphthacene. This corrects a widely propagated error in the literature in which the assignments of 1,2,5,6,9,10,12,13-octamethoxydibenzofg,op]naphthacene (C_2v) and 1,2,5,6,8,9,12,13-octamethoxydibenzofg,op] naphthacene (C_2h) are crossed. A mechanism involving the migration of an aryl ring on an arenium cation intermediate is proposed.