Pure shift NMR and DFT methods for revealing long-range heteronuclear couplings

Abstract

Determination of dihedral angles from heteronuclear nJHX couplings (where n is 2, 3 or 4 and X stands for 31P, 19F, etc.) is very useful in structure elucidation. It is a challenging task to extract these couplings from 1D 1H NMR spectra due to the presence of a large number of nJHH and nJHX. Herein, we demonstrate the utility of two different pure shift NMR methods wherein 1H–1H multiplets are collapsed into singlets, revealing only nJHX in the spectrum. The benefit of DFT calculations for prediction of these couplings and congruence with their experimental counterparts is also demonstrated.