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-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 (C-2v) and 1,2,5,6,8,9,12,13-octamethoxydibenzo[fg,op]naphthacene (C-2h) are crossed. A mechanism involving the migration of an aryl ring on a it arenium cation intermediate is proposed. (C) 2008 Elsevier Ltd. All rights reserved.