Analysis of1H and13C NMR spectra ofcis- andtrans-10-substituted decal-2-ones by 2D NMR techniques

Abstract

The 1H and 13C NMR chemical shift assignments of 10-substituted decal-2-ones, cis (H, CH3 and CO2CH3) and trans (H, CH3, OH and CO2C2H5) were based on 2D COSY and HETCOR experiments, supported by selective spin decoupling experiments. The discrimination between the cis and the trans conformations was ruled out on the basis of the J(1a,9) magnitudes related to dihedral angles (Karplus rule) and also on the 13C shielding values of C-4 of the cis compounds, which are much more shielded than those of the trans counterparts. The best and fastest criterion of differentiation between cis and trans conformers is the constant appearance in the 13C PND spectra of the cis series of some signals of broadened linewidth and low intensity, essentially C-4, C-5 and C-7, a clue to site exchange processes; the trans counterparts showed only sharp signals because of their existence as a single conformation. Copyright © 2000 John Wiley & Sons, Ltd.