Synthesis and X-ray structural determination of new aniline derivatives of 2,4,6,8-tetraazabicyclo[3.3.0]octanes; anomeric effect in N-C-N moiety and implications of solvent polarity on 1H-NMR patterns

Article abstract of DOI:10.1016/S0040-4020(96)01143-X

The condensation of aniline with glyoxal and formaldehyde in stoichiometric ratio, leads to 2,4,6,8-tetraphenyl-2,4,6,8-tetraazabicyclo[3.3.0]octane (1f) with formic acid as catalyst. Nine substituted derivatives of 1f have been prepared in high yield by this synthetic method. X-ray analysis revealed the existence of an anomeric effect, n(N) → σ*(C-N) in N-C-N moieties manifested by reduction in N-pyramidality and short C-N bond lengths. Moreover, ¹H-NMR studies showed the dependency of methylenic protons splitting pattern on solvent polarity.