DOI•
Anion‐Binding Catalysis with Other Anions
14 Feb 2022-pp 161-199
About: The article was published on 2022-02-14 and is currently open access. It has received None citations till now. The article focuses on the topics: Anion binding.
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4,107 citations
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TL;DR: This review documents the structural and mechanistic features that contribute to high enantioselectivity in hydrogen-bond-mediated catalytic processes in small-molecule, synthetic catalyst systems.
Abstract: Hydrogen bonding is responsible for the structure of much of the world around us. The unusual and complex properties of bulk water, the ability of proteins to fold into stable three-dimensional structures, the fidelity of DNA base pairing, and the binding of ligands to receptors are among the manifestations of this ubiquitous noncovalent interaction. In addition to its primacy as a structural determinant, hydrogen bonding plays a crucial functional role in catalysis. Hydrogen bonding to an electrophile serves to decrease the electron density of this species, activating it toward nucleophilic attack. This principle is employed frequently by Nature's catalysts, enzymes, for the acceleration of a wide range of chemical processes. Recently, organic chemists have begun to appreciate the tremendous potential offered by hydrogen bonding as a mechanism for electrophile activation in small-molecule, synthetic catalyst systems. In particular, chiral hydrogen-bond donors have emerged as a broadly applicable class of catalysts for enantioselective synthesis. This review documents these advances, emphasizing the structural and mechanistic features that contribute to high enantioselectivity in hydrogen-bond-mediated catalytic processes.
1,580 citations
TL;DR: This field is briefly reviewed here, along with some rough guidelines and concepts for further catalyst development, which offers attractive alternatives to metal (ion)-catalyzed reactions by combining supramolecular recognition with chemical transformations in an environmentally benign fashion.
Abstract: The metal (ion)-free catalysis of organic reactions is a contemporary challenge that is just being taken up by chemists. Hence, this field is in its infancy and is briefly reviewed here, along with some rough guidelines and concepts for further catalyst development. Catalysis through explicit hydrogen bonding interactions offers attractive alternatives to metal (ion)-catalyzed reactions by combining supramolecular recognition with chemical transformations in an environmentally benign fashion. Although the catalytic rate accelerations relative to uncatalyzed reactions are often considerably less than for the metal (ion)-catalyzed variants, this need not be a disadvantage. Also, owing to weaker enthalpic binding interactions, product inhibition is rarely a problem and hydrogen bond additives are truly catalytic, even in water.
1,050 citations
TL;DR: The present critical review outlines the close relationship and mutual interplay between molecular recognition, active site considerations in enzyme catalysis involving anions, and organocatalysis utilizing explicit hydrogen bonding.
Abstract: The present critical review outlines the close relationship and mutual interplay between molecular recognition, active site considerations in enzyme catalysis involving anions, and organocatalysis utilizing explicit hydrogen bonding. These interconnections are generally not made although, as we demonstrate, they are quite apparent as exemplified with pertinent examples in the field of (thio)urea organocatalysis. Indeed, the concepts of anion binding or binding with negatively (partially) charged heteroatoms is key for designing new organocatalytic transformations. Utilizing anions through recognition with hydrogen-bonding organocatalysts is still in its infancy but bears great potential. In turn, the discovery and mechanistic elucidation of such reactions is likely to improve the understanding of enzyme active sites (108 references).
889 citations