Superacid-promoted synthesis of aza-polycyclic aromatic compounds and polycyclic aromatic compounds

The concept of superelectrophile activation was first proposed by Olah and co-workers in the 1970's. Recent work has shown that superelectrophiles and related dicationic electrophiles can be exceedingly reactive and useful in synthetic chemistry.;Aza-polycyclic aromatic compounds and their substituted derivatives exhibit a variety of biological activities. Aza-policyclic aromatic compounds also have been shown in recent applications to have useful optical properties. Because of these unique features, aza-polycyclic aromatic compounds have drawn a lot of attention and they have become important synthetic targets. In this research, we synthesized a series of alcohols and reacted them with the Bronsted superacid, trifluoromethansulfonic acid (CF3SO3H). The cyclization products were obtained in good yield. Charge migration is driven by the increased separation of the charge centers and formation of the benzylic type of cation. Using isotopic labeling, we observed that the charge migration can occur through deprotonation-reprotonation steps. Elimination of benzene via ipso-protonation provides a new synthetic pathway for benzo[c]phenathridine derivatives.;It has also been observed that appropriately designed olefinic systems give dicationic electrophiles that yield aza-polycyclic aromatic compounds from cyclization and benzene elimination steps. The results show that olefin precursors are superior to alcohol precursors. The olefin system not only improves product yields but also enables the reactions to occur in mild conditions. Theoretical calculations suggest a preference for charge-separated intermediates with typical values being 10-15 kcal/mol for a 1,5 versus 1,4 dication.;Polycyclic aromatic hydrocarbons are widely used as intermediates in pharmaceuticals, agricultural products, lubricating materials. Also, due to extended delocalized pi-bonds, they can exhibit semiconductor and optical properities. Therefore, developing new synthetic routes to polycyclic aromatic hydrocabons and their derivatives is desirable. In this research, a number of styryl-substituted arenes were prepared and reacted with CF3SO 3H. The polycyclic aromatic compounds were obtained through cyclization and benzene elimination steps. Substituted olefin groups are shown to impart some regioselectivity of the protonation and cyclization to the phenathrene system. It is also apparent that the electron donating ability of aromatic ring in the substrate enhances cyclization reaction. The conversions with superacid are superior to the metal-catalyzed and other acid-catalyzed reactions under similar conditions. Elimination of benzene in the final step leads to formation of the phenanthrenes.