Conformational Analysis in Solution of a Chiral BisoxazolineMolecule: Vibrational Circular Dichroism Spectroscopy and DensityFunctional Theory Study

Abstract

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, C 2 symmetry; two, III and IV, have C 1 symmetry. The electronic energies of I–IV are ordered: I < II < III < IV. 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 CHCl 3 and CDCl 3 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.