A Rapid ¹H NMR Assay for Enantiomeric Excess of α-Substituted Aldehydes

Abstract

In situ derivatization of a variety of alpha-substituted aldehydes via reaction with chiral amines allows convenient and efficient determination of enantiomeric excess. (1)H NMR analysis of the imine diastereomer ratio can be conducted immediately after the aldehyde and amine have been mixed. The results correlate well with ee values determined by more traditional (and slower) methods. This approach may be broadly applicable to alpha-substituted aldehydes. [reaction: see text]

A modular family of phosphine-phosphoramidite ligands and their hydroformylation catalysts: steric tuning impacts upon the coordination geometry of trigonal bipyramidal complexes of type [Rh(H)(CO)2(P^P*)]

“…al. 6 0.1 ml reaction mixture was added to an NMR tube with ~0.5 mL CDCl 3 . To this was added (R)-1-phenylpropan-1-amine (40 µL) to make the imine as diastereomers.…”

NMR Studies of Optically Active Schiff Bases

“…Chi et al 3 have examined a series of chiral primary amines as a derivatizing agent in determination of the enantiomeric purity of the a-substituted d-keto-aldehydes obtained from catalysed Michael additions. The imine proton signals were well resolved even if the reaction was not completed.…”

“…The largest differences in chemical shifts of the imine signal 9.9 Hz (at 500 MHz) were observed when the ratio of sulfinimines to (S)-BINOL was 1:2.2 in C 6 D 6 . Lower values were measured in CDCl 3 . Usually the use of benzene instead of CDCl 3 has twice increased separation of the signals.…”

“…Derivatives of (R)-BINOL and amino acids formed Schiff bases containing the OHÁ Á Á N intramolecular hydrogen bond [3]. 5 The splitting of the signal assigned to the proton engaged in the intramolecular hydrogen bond permitted determination of the R:S ratio.…”

Enantiomeric excess detection with (S)-3-Phenyl-2-(selenophenyl)propan-1-ol derivatizing agent via mix and shake 77Se NMR

“…A wide variety of optically pure discriminating agents have been developed to facilitate the determination of ee. 4,5 One of the main procedures is based on the covalent attachment of an enantiopure chiral derivatizing agent (CDA) to the chiral substrate to be analyzed. Therefore, a pair of enantiomers attached to a CDA, yields diastereomers, which are expected to have different chemical shifts in the NMR spectrum.…”