Polyvalent Catalysts Operating on Polyvalent Substrates: A Model for Surface‐Controlled Reactivity

Abstract

Unusually fast rates of nucleophilic catalysis of hydrazone ligation were observed when polyvalent anthranilic acid catalysts operating on polyvalent aldehyde substrates were used with PAMAM dendrimers as the common platform. When presented in this way, the catalyst has a strong accelerating effect at concentrations 40-400 times lower than those required for similar monovalent catalysts and displays unique kinetic parameters. We attribute these properties to polyvalent engagement between the dendrimer surface groups, and a potential "rolling" effect leading to fast interparticle kinetic turnover. The phenomenon is sensitive to the density of functional groups on each dendrimer, and insensitive to factors that promote or inhibit nonspecific particle aggregation. These findings constitute a rare experimental example of an underappreciated phenomenon in biological and chemical systems that are organized on interacting surfaces.

Oximes and Hydrazones in Bioconjugation: Mechanism and Catalysis

“…McKay and Finn described the testing of polyvalent and dendrimer-based anthranilic acid catalysts, confirming superior activity over anilines in dendrimer labeling. 163 Langenhan and co-workers used mono- and bifunctional aniline derivatives for fluorescent conjugation of aldose sugars, and confirmed 5MA as the most effective catalyst among 10 tested. 164 …”

“…McKay and Finn described the testing of polyvalent and dendrimer-based anthranilic acid catalysts, confirming superior activity over anilines in dendrimer labeling. 163 Langenhan and co-workers used mono-and bifunctional aniline derivatives for fluorescent conjugation of aldose sugars, and confirmed 5MA as the most effective catalyst among 10 tested. 164 Crisalli and Kool followed up on their earlier work to investigate the mechanism of bifunctional catalysis in hydrazone and oxime formation, resulting in the design of further improved catalysts.…”

Multivalency as a Design Criterion in Catalyst Development

“…Yet, related to catalysis it is an argument that has received relatively little attention [37,38]. Recently, a first attempt was made by McKay and Finn [39] to qualitatively describe what happens when both the catalyst and substrate are attached to a multivalent dendritic support.…”

Hydrophobic pockets built in polymer micelles enhance the reactivity of Cu2+ions

“…Despite being catalytically inactive, previous literature has suggested that polymer frameworks could show a positive impact on chemical reactions. [47][48][49][50][51][52] The reactivity enhancement has been attributed to three functionalities from the hydrophobic domain in catalysis; (i) the presence of the hydrophobic pocket that can provide the shield for the unstable metals, e.g., Pd NP-catalyzed Suzuki coupling reaction; [53][54][55][56] (ii) the hydrophobic domain that increases the affinity between nonpolar substrates and the catalyst via hydrophobic association; 57,58 (iii) incorporating the hydrophobic domain near the active sites can screen the size and polarity of the substrate thus improving the reaction selectivity. 59,60 Since the design of the micellar catalysts is mainly focused on the high reaction efficiency with multiple anchoring groups and recyclability.…”