Conformational Analysis in Solution of a Chiral Bisoxazoline Molecule : Vibrational Circular Dichroism Spectroscopy and Density Functional Theory Study

Abstract EN

The conformations of the chiral bisoxazoline: 2,2′-methylenebis[3a,8a-dihydro-8H-indeno[1,2-d]oxazole] (also named IndaBOX), have been studied.

Density functional theory (DFT) calculations identify four inequivalent stable conformations.

Two, I and II have, C2 symmetry; two, III and IV, have C1 symmetry.

The electronic energies of I–IV are ordered: I

The span in energy is <1.0 kcal/mole.

Vibrational unpolarised absorption and circular dichroism spectra have been predicted for the four conformations using DFT.

Comparison of population-weighted spectra to experimental spectra of CHCl3 and CDCl3 solutions in mid-IR region strongly supports the DFT predictions of the number, structures, and relative energies of the conformations of IndaBOX.

This shows that DFT predicts spectra with a high degree of reliability.

We will undoubtedly illustrate the advantage added by vibrational circular dichroism spectroscopy in conformational analysis and in the absolute configuration determination.