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[摘要]：B3LYP/6-311+G(2df,p)//B3LYP/6-31+G(d) calculations convincingly show that tricyclic organic compounds 1 and 2 offer scaffolds suitable for tailoring powerful neutral organic acids Their cyanation at all C(sp(2))-H positions provide superactds as evidenced by their enthalpies of deprotonation Delta H-acid(1b(CN)) = 257 2 and Delta H-acid(2b(CN)) = 250 9 kcal mol(-1), which are close to the threshold of hyperacidity of 245 kcal mol(-1) On the other hand hexacyclic system 3 cyanated at all possible substitution sites along the perimeter except the acidic C(sp(3))-H position provides a true hyperacid with Delta H-acid(3a(CN)) = 242 8 kcal mol(-1) The reason behind the dramatic acidifying effect is a vigorous anionic resonance effect in the corresponding conjugate bases assisted by a cooperative substituent effect of the CN groups It is convincingly shown that compounds 1 and 2 represent rigid antiaromatic quasi-[12]annulene and aromatic quasi-{14]annulene par excellence, respectively, conforming to Huckel's (4n + 2)pi electron count rule in the bridged polycyclic systems Calculations of the pK(a) values in DMSO show that the polycyano derivatives are powerful superacids in solutions too |
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