Molecular Geometry and Circular Dichroism Spectra of Bicyclo[2.2.1]heptane-2,3-dicarboxylic Anhydrides and Imides

Authors:

• Tadeusz Połoński,
• Maria J. Milewska,
• Maria Gdaniec,
• Mirosław Gilski

Abstract

Several tricyclic anhydrides and imides derived from optically active bicyclo[2.2.1]heptane-2,3-dicarboxylic acids Were synthesized, and their circular dichroism spectra are reported. On the basis of MNDO calculations it was estalished that despite rigidity of the norbornane system the five-membered rings of succinic anhydride and imide moieties are slightly twisted. The chromophores are flexible and can be more or less skewed depending on solvent polarity. The chromophore nonplanarity significantly influences magnitude and sign of the first Cotton effect associated with the lowest energy n-π* electronic transition. The sign of the second n-π* Cotton effect is governed by vicinal effect of substituents. The crystal structures of three N-(S)-1-phenylethylimides were solved to establish the configuration at C-2 of the imide moieties. © 1993, American Chemical Society. All rights reserved.