Dicyclopentaheptalene (Azupyrene) Chemistry. Electrophilic Monosubstitution. Theory and Experiment

Article abstract of DOI:10.1021/ja00293a016

MNDO calculations were used to estimate the ground-state geometry, atom electron densities, heat of formation, ionization potential, gas-phase ΔH values for protonation, and ΔH and E_a values for electrophilic trifluoroacetylation and nitration with protonated trifluoroacetc anhydride and trifluoroacetyl nitrate, respectively, of azupyrene (1).The electron density at C-4 was greater than that at C-1, and C-3 was electron-deficient.Relative ΔH values predicted C-1 to be more reactive than C-4 in each case.Relative E_a values predicted C-1 to be more reactive to protonated trifluoroacetic amhydride but C-4 to be more reactive to protonated trifluoroacetyl nitrate.Experimentally, protonation of solid 1 with DClO4 showed a C-1:C-4 D incorporation ratio of ca. 2:1, and trifluoroacetylation gave mostly 1-substitution with trifluoroacetic achydride or trifluoroacetylpyridinium chloride.In contrast, nitration with trifluoroacetyl nitrate, 1-nitropyridinium fluoroborate, or nitronium fluoroborate gave very predominantly 4-substitution.