A Simple Protocol for NMR Analysis of the Enantiomeric Purity of Chiral Hydroxylamines

Abstract

A practically simple three-component chiral derivatization protocol for determining the enantiopurity of chiral hydroxylamines by (1)H NMR spectroscopic analysis is described, involving their treatment with 2-formylphenylboronic acid and enantiopure BINOL to afford a mixture of diastereomeric nitrono-boronate esters whose ratio is an accurate reflection of the enantiopurity of the parent hydroxylamine.

Boronic acids for sensing and other applications - a mini-review of papers published in 2013

“…The resulting mixture of diastereomeric nitrono-boronate esters reflects the enantiopurity of the parent hydroxylamine [97]. Finally, a sensor for cationic surfactants based on polydiacetylene oxyphenylboronic acids was developed and tested [98].…”

A simple and rapid approach for testing enantiopurity of hydroxy acids and their derivatives using 1H NMR spectroscopy

“…As a consequence continuous research is being carried out to discover reliable and efficient chiral reagents for the accurate determination of the enantiopurity of chiral molecules of diverse functionality. The simple threecomponent derivatization protocols for the accurate assessment of enantiopurity, using 2-formylphenylboronic acid and (S)-BINOL, have been reported for chiral primary amines 32,33 , diamines 34 , amino alcohols 35 and hydroxy amines 36 . For discrimination of different diols the mixture of enantiopure αmethylbenzylamine and 2-formylphenylboronic acid has been reported as a CDA [37][38][39] .…”

Complex Functional Systems with Three Different Types of Dynamic Covalent Bonds

“…was general and occurred in quantitative yield ( Figure S1). Among other boronic acids tested, the ones in the ortho position to aldehydes [7,8] did not perform as well, presumably because of unfavorable topology and direct dependence of boronic ester exchange on hydrazone exchange. Among other boronic acids tested, the ones in the ortho position to aldehydes [7,8] did not perform as well, presumably because of unfavorable topology and direct dependence of boronic ester exchange on hydrazone exchange.…”

“…[1] In sharp contrast, only af ew pioneering examples exist for two types of dynamic covalent bonds that work together. [2][3][4][5][6] Additional promising alternatives include boronic ester, [7][8][9][10] thioester, [11] amide, [11,12] imine [8,[13][14][15] and hemiaminal exchange, [16] Michael adducts, [17] olefin metathesis, [15] and Cope rearrangements. [2][3][4][5][6] Additional promising alternatives include boronic ester, [7][8][9][10] thioester, [11] amide, [11,12] imine [8,[13][14][15] and hemiaminal exchange, [16] Michael adducts, [17] olefin metathesis, [15] and Cope rearrangements.…”