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 C2v-substituted products 1,2,5,6,9,10,12,13-octamethoxydibenzo[fg,op]naphthacene and 1,2,5,6,9,10,12,13-octamethyldibenzo[fg,op]naphthacene. This corrects a widely propagated error in the literature in which the assignments of 1,2,5,6,9,10,12,13-octamethoxydibenzo[fg,op]naphthacene (C2v) and 1,2,5,6,8,9,12,13-octamethoxydibenzo[fg,op] naphthacene (C2h) are crossed. A mechanism involving the migration of an aryl ring on an arenium cation intermediate is proposed.