(+)-BINOL and Pure Shift Experiment: A Bidirectional Approach for NMR Chiral Discrimination of Overcrowded Spectra of Primary Amines

In this work, enantiopure 1,1’-bi-2-naphthol (BINOL) derivatives and carboxylic acids were evaluated as chiral solvating agents (CSAs) in the nuclear magnetic resonance (NMR) chiral discrimination of primary amines. Among the CSAs screened, the readily available (+)-BINOL revealed a simple and rapid chiral auxiliary for ¹H NMR chiral discrimination. The procedure required few minutes, assigning of the absolute configuration. The protocol was improved using the ¹H pure shift pulse sequence for overcrowded alkyl primary amines due to the absence of J_HH couplings. The ¹H pure shift NMR experiment and the readily available (+)-BINOL chiral auxiliary can be used for routine chiral discrimination analysis of complex NMR spectra.

Keywords:
NMR chiral discrimination; primary amines; pure shift experiment; chiral solvating agent