Conformational analysis. Part 17. An NMR and theoretical investigation of the conformation of bicyclo[5.2.1]decane-2,6-dione
Abstract
The conformation of bicyclo[5.2.1]decane-2,6-dione in solution has been investigated by molecular modelling and the lanthanide-induced shift (LlS) technique. Of the five possible conformers two were eliminated due to their large calculated steric energy and a third ‘twist’ conformer due to the observed symmetry in the 13C NMR and the 1H NMR spectra. The remaining exo and endo conformers were calculated as having an energy difference of 1.5 kcal mol–1. However, MNDO calculated the endo form as the more stable in contrast to MM2 and COSMIC which gave the reverse order. The LIS investigation was in agreement with a lanthanide monodentate complex bound to the exo form only confirming the MM2 and COSMIC calculations.