Issue 12, 2015

Multi-nuclear NMR of axially chiral biaryls in polypeptide orienting solvents: spectral discriminations and enantiorecognition mechanisms

Abstract

Due to the importance of axially chiral biaryl derivatives as chiral auxiliaries and/or ligands for asymmetric synthesis, as well as their structural role in bioactive natural products, continuous efforts have been undertaken to propose efficient methods for their atropo-selective synthesis. As a consequence, proposing robust and reliable analytical tools that are able to discriminate the spectral signal of atropisomeric enantiomers becomes crucial to evaluate the enantiomeric excesses of mixtures. In this work, we show how several multi-nuclear 1D/2D-NMR techniques using homopolypeptide chiral liquid crystals as aligning solvents can provide a panel of analytical possibilities (through differences of chemical shift anisotropies, dipolar and quadrupolar residual couplings) to spectrally discriminate enantiomers of a large collection of trisubstituted axially chiral biphenyls. Approaches involving 31P, 13C and 2H 1D- or 2D-NMR experiments at natural abundance levels are explored. Among noteworthy results, the first examples of spectral enantioseparations using 31P nuclei as nuclear probe are reported. Finally, the roles of electronic factors and shape anisotropy in the efficiency of chiral discrimination mechanisms are examined and discussed. Molecular modeling calculations were carried out to establish the electronic profile of these analytes in order to understand and rationalize the 13C–{1H} NMR results.

Graphical abstract: Multi-nuclear NMR of axially chiral biaryls in polypeptide orienting solvents: spectral discriminations and enantiorecognition mechanisms

Supplementary files

Article information

Article type
Paper
Submitted
09 Jun 2015
Accepted
09 Sep 2015
First published
11 Sep 2015
This article is Open Access
Creative Commons BY license

New J. Chem., 2015,39, 9504-9517

Author version available

Multi-nuclear NMR of axially chiral biaryls in polypeptide orienting solvents: spectral discriminations and enantiorecognition mechanisms

P. Berdagué, J. Herbert-Pucheta, V. Jha, A. Panossian, F. R. Leroux and P. Lesot, New J. Chem., 2015, 39, 9504 DOI: 10.1039/C5NJ01434D

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