A simple protocol for determination of enantiopurity of amines using BINOL derivatives as chiral solvating agents via1H- and 19F-NMR spectroscopic analysis

Abstract

A rapid and simple protocol for the determination of enantiopurity of primary and secondary amines was developed by using (S)-BINOL/(S)-BINOL derivatives/(R)-1,1′-binaphthyl-2,2′-diyl hydrogenphosphate as chiral solvating agents via ¹H- and ¹⁹F-NMR spectroscopic analysis. In this protocol, the analyte and chiral solvating agent were directly mixed in an NMR tube in chloroform-d and after shaking for 30 seconds the ¹H- and ¹⁹F-NMR spectra were recorded, which affords well-resolved resonance peaks for both the enantiomers present in an analyte. The enantiomeric excess of 1,2-diphenylethylenediamine was determined and linear relationship with coefficient of R² = 0.9995 was observed. The binding constant and associated ΔG values were also calculated for diastereomeric complexes formed between both the enantiomers of analyte 5 with CSA (S)-3a by using UV-visible spectroscopy.