ChemInform Abstract: CHEMISTRY OF BINDING SITES. IV. UNUSUAL INCREASE IN REACTIVITY OF ARYLBORONIC ACIDS THROUGH NEIGHBORING GROUPS

Abstract

Zur späteren Verwendung als selektive Haftgruppen in Polymeren mit schneller Gleichgewichtseinstellung in nicht‐wäß‐ rigen Systemen wurden ortho‐substituierte Phenylboronsäuren des Verbindungstyps (I) und (II) untersucht, deren Darstellung überwiegend nach bekannten Methoden erfolgte.

Neighboring Group Participation and Internal Catalysis Effects on Exchangeable Covalent Bonds: Application to the Thriving Field of Vitrimer Chemistry

“…This shift of the esterification equilibrium gives a glimpse of the possible electronic and internal catalysis effects. An early study showed that arylboronic acids bearing ortho neighboring groups containing oxygen, sulfur, or fluorine do not enhance the esterification or the transesterification . Nevertheless, electron-withdrawing groups decrease the boronic acid p K a , whereas electron-donating groups increase it , and destabilize the ester bond.…”

“…An early study showed that arylboronic acids bearing ortho-neighboring groups containing oxygen, sulfur or fluorine do not enhance the esterification nor the transesterification. 234 Nevertheless, electron-withdrawing groups decrease boronic acid pKa whereas electron-donating groups increase it, 83,84 and destabilize the ester bond. For instance, the boron atom of phenylboronic acids are reported to be highly electron deficient, which reduces the pKa and facilitates ester formation.…”

“…Aminomethyl-substituted arylboronic acids were shown to be esterified several orders of magnitude faster than nonsubstituted phenylboronic acids . Their transesterification was also accelerated compared to unsubstituted boronic acids or such acids bearing substituents containing oxygen, sulfur, or fluorine. , In solution, the addition of a dimethyl­aminomethyl group on a phenylboronic ester was shown to accelerate the rate of transesterification by 5 orders of magnitude . The amino group on the ortho or para position decreases the p K a of phenylboronic acid and facilitates the formation of the ester .…”

Molecular imprinting science and technology: a survey of the literature for the years up to and including 2003

“…In the rebinding process the template reformed a covalent boronate ester bond but interacted with the amine group through ion pair formation. 151,332,333,347 The first true semi-covalent approach was reported by Sellergren and Andersson 482 for the imprinting of p-aminophenylalanine ethyl ester. A structural analogue was used which possessed two polymerizable groups attached via ester linkages.…”

“…344,345 It was also shown that an adjacent amino group increases the stability and rate of formation/hydrolysis of boronate esters, which makes them more suitable for chromatography. [346][347][348][349] The effect of binding group flexibility has also been studied. 350 Recently monosaccharides have been imprinted as boronate esters by attachment to the surface of fullerenes [297][298][299] and in Langmuir-Blodgett films.…”