Chiral Hydroxamic Acid Ligands in Asymmetric Synthesis: The Evolution of Metal‐Catalyzed Oxidation Reactions

Abstract

Asymmetric oxidation reaction is one of the significant pathways in stereoselective reactions, which is a prominent performer in academic and industrial research. However, ligands are vital for planning an ideal metal‐catalyzed asymmetric oxidation reaction as they interact with the metal to construct catalytically active metal complexes, which can catalyze numerous asymmetric reactions. Designing and synthesizing novel chiral ligands is essential for researchers in modern asymmetric synthesis. In this course, exploring the applicability and the survey of hydroxamic acid as a vital ligand has been presented, which is essential for various metal‐catalyzed transformations.

Synthesis of Novel C 2 Bishydroxamic Acid Ligands and their Application in Asymmetric Epoxidation Reactions

“…In many cases, a specific BHA ligand may demonstrate excellent enantioselectivity for one reaction but prove less effective for another. 5b This underscores the need for continuous exploration and discovery of innovative BHA ligand designs that address the challenges of different substrates, reaction conditions, and metal catalysts. Such endeavors aim to uncover new approaches in asymmetric oxidation reactions and expand the toolkit available to organic chemists to synthesize complex chiral molecules.…”

Investigation of Enantioselectivity Using TADDOL Derivatives as Chiral Ligands in Asymmetric Cyanation Reactions

“…Enantioselective transformations are cornerstone processes in modern organic synthesis, playing a crucial role in the production of chiral molecules with a high stereochemical purity. Among various strategies, asymmetric catalysis has proven exceptionally powerful, enabling the synthesis of complex bioactive compounds and pharmaceuticals . The asymmetric cyanosilylation of aldehydes, in particular, has attracted considerable attention due to its utility in constructing versatile chiral building blocks essential for the synthesis of natural products, agrochemicals, and materials with unique properties …”

Hafnium(IV)-Salen-Catalyzed Highly Reactive and Enantioselective Epoxidation Directed by Amides

“…Chiral epoxides are versatile intermediates and building blocks in organic synthesis. − Sharpless asymmetric epoxidation of allylic alcohols has been one of the most popular methods to construct chiral epoxides in high regio- and enantioselectivity . Its mechanism involves the critical OH directing group associating the chiral dititanium(IV) tartrate catalyst and the olefin (Scheme a). , Highly enantioselective epoxidation of olefins directed by more remote OH groups than allylic alcohols were achieved by metal complexes of chiral bis-hydroxamic acids as catalysts. − Nevertheless, there have been only limited types of capable directing groups for asymmetric epoxidation beyond the hydroxyl group. In particular, sulfonyl and carboxylate were reported as directing groups for metal Lewis acid-catalyzed asymmetric epoxidation (Scheme b). − It is also noteworthy that these methods typically required up to 3 days to accomplish reasonable product yield and enantioselectivity.…”