Synthesis and spectroscopy of nitroaceanthrylenes and nitroaceanthrenes

Article abstract of DOI:10.1002/recl.19931120504

The syntheses of nine mononitro derivatives of aceanthrylene (1) and nine mononitro derivatives of aceanthrene (2) are described.In addition to 1 and 2, 1,2,6,10b-tetrahydroaceanthrylene (3), 6,10b-dihydro-2(1H)-aceanthrylenone (5), 1(2H)-aceanthrylenone (4) and 2(1H)-aceanthrylenone (8) were also used as starting materials.The resulting nitroaceanthrylenes and nitroaceanthrenes were characterized by their 1H-NMR, 13C-NMR, UV-VIS, IR and mass spectra.The conformation of the nitro group and the interaction between the nitro group and the aromatic system are discussed.In 2-nitroaceanthrylene (1b), the nitro group interacts exceptionally well with the aromatic nucleus.The 3-, 4-, 8- and 9-nitro derivatives of 1 and 2 display all the characteristics of normally conjugated planar nitroaromatic compounds.In the remaining nitro derivatives of 1 and 2, conjugation is diminished owing to steric interactions with nearby protons.The order of decreasing conjugation and increasing twist angle is 5-nitro > 7-nitro > 6-nitro > 10-nitro.The twist angle of the nitro group was calculated using semi-empirical SCF methods PM3 and AM1.Although the values obtained by these methods deviate substantially, they both give the same order of increasing twist angles as the spectroscopically derived order.