1 Citation (SciVal)

Abstract

1H NMR spectroscopic studies using BINOL as a chiral solvating agent (CSA) for a scalemic sulfiniminoboronic acid (SIBA) have revealed concentration- and enantiopurity-dependent variations in the chemical shifts of diagnostic imine protons used to determine enantiopurity levels. 11B/15N NMR spectroscopic studies and X-ray structural investigations revealed that unlike other iminoboronate species, BINOL–SIBA assemblies do not contain N–B coordination bonds, with 1H NMR NOESY experiments indicating that intermolecular H-bonding networks between BINOL and the SIBA analyte are responsible for these variations. These effects can lead to diastereomeric signal overlap at certain er values that could potentially lead to enantiopurity/configuration misassignments. Consequently, it is recommended that hydrogen-bonding-CSA-based 1H NMR protocols should be repeated using both CSA enantiomers to ensure that any concentration- and/or er-dependent variations in diagnostic chemical shifts are accounted for when determining the enantiopurity of a scalemic analyte.
Original languageEnglish
Pages (from-to)16801-16809
Number of pages9
JournalAnalytical Chemistry
Volume95
Issue number46
Early online date6 Nov 2023
DOIs
Publication statusPublished - 21 Nov 2023

Bibliographical note

The authors would like to dedicate this work to John S. Fossey (April 29, 1977 – April 15, 2022), a close friend and colleague who will be sorely missed. This work was funded by the EPSRC through a studentship in the Centre for Doctoral Training in Catalysis (EP/L016443/1) and by the Leverhulme Trust via a Leverhulme Trust Research Project Grant (ORPG-9125). T.D.J. wishes to thank the Royal Society for a Wolfson Research Merit Award and the Open Research Fund of the School of Chemistry and Chemical Engineering, Henan Normal University for support (2020ZD01). Characterization facilities were provided by the Material and Chemical Characterisation Facility (MC2) at the University of Bath (10.15125/mx6j-3r54).

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