Effect of Substituents at 1,4-Positions of Polycyclic Aromatic Compounds and Preparation of 2,3-Difunctionalized Pentacenes and Naphthacenes

Effects of substituents at 1,4-positions of polycyclic aromatic compounds were investigated in the case of reduction of 2,3-bis(alkoxycarbonyl)arenes with the LiAIH(4)/AlCl3 system. 2,3-Bis(alkoxycarbonyl)dihydronaphthacenes and dihydropentacenes 1 were treated with a mixture of LiAlH4 and AlCl3. The products were dependent on the substituents at 1,4-positions. Similar type of influence of the substituents at 1,4-positions was observed in the oxidation of diols 2 to dialdehydes 4. Without substituents at 1,4-positions, dialdehydes 4 were conveniently obtained. However, with substituents at 1,4-positions, dialdehydes 4 were not obtained. Instead, 1,3-dihydroisobenzofuran-1,3-diol or 1,3-dihydroisobenzofuran-1-ol derivatives 5, 6 were obtained in good yields. Preparation of pentacene imides and pentacene carboxylic acid anhydride was also reported.