T. Polonski et al., MOLECULAR-GEOMETRY AND CIRCULAR-DICHROISM SPECTRA OF BICYCLO[2.2.1]HEPTANE-2,3-DICARBOXYLIC ANHYDRIDES AND IMIDES, Journal of organic chemistry, 58(11), 1993, pp. 3134-3139
Several tricyclic anhydrides and imides derived from optically active
bicyclo[2.2.1]heptane-2,3-dicarboxylic acids were synthesized, and the
ir circular dichroism spectra are reported. On the basis of MNDO calcu
lations it was estalished that despite rigidity of the norbornane syst
em the five-membered rings of succinic anhydride and imide moieties ar
e slightly twisted. The chromophores are flexible and can be more or l
ess skewed depending on solvent polarity. The chromophore nonplanarity
significantly influences magnitude and sign of the first Cotton effec
t associated with the lowest energy n-pi electronic transition. The s
ign of the second n-pi Cotton effect is governed by vicinal effect of
substituents. The crystal structures of three N-(S)-1-phenylethylimid
es were solved to establish the configuration at C-2 of the imide moie
ties.