A readily accessible and modular carbohydrate-derived thioether/selenoether-phosphite ligand library for Pd-catalyzed asymmetric allylic substitutions

Abstract

A series of modular carbohydrate-derived P,S/Se-ligands have been successfully applied to Pd-AAS of a range of hindered and unhindered substrates.

Recent Advances in Enantioselective Pd-Catalyzed Allylic Substitution: From Design to Applications

“…Research on P,S-ligands was inspired by the remarkable enantioselectivities achieved with Evans’ phosphinite-thioether ligands . This work encouraged the development of many P-thioether ligand libraries, although only a few of them provided high enantioselectivities and were applicable to diverse substrates. − The unsatisfactory results were mainly explained by the fact that the sulfur thioether group becomes a stereogenic center upon coordination, which may lead to diastereomeric mixtures of active species resulting in low enantiocontrol. However, configuration at the coordinating sulfur atom can be controlled with the chirality at the ligand backbone as demonstrated by the development of ligands L92 – L97 (Figure ).…”

“…Efficient control of the configuration of the S-atom was also achieved by combining an appropriate ligand scaffold with a chiral biaryl phosphite ,− or phosphoramidite , group as illustrated by three of these families of ligands L98 , L99 , and L100 (Figure ).…”

“…Subsequently, a large variety of heterodonor biaryl phosphite-containing ligands, mainly belonging to the P,N (N = oxazoline, pyridine, oxazole, thiazole, etc. ) ,,,,,, and P,thioether ,− types, have been developed. Mechanistic studies of allylic substitutions with all these ligands show an early TS, in which the stereochemistry of the reaction is governed by the relative populations of the exo and endo Pd-η 3 -allyl complexes and the electrophilicity of the allylic terminal carbon atoms.…”

Development of a novel phosphoramidite-selenide ligand for Pd-catalyzed asymmetric allylic substitution

“…9 Recently, an elegant work on the carbohydrate-derived selenoether-phosphite ligand has also been reported by Pàmies and Diéguez. 10 Despite these significant achievements, the application of these selenide ligands is mainly limited to the palladium-catalyzed allylic alkylation of methyl malonate, the 1,4-addition of organic zinc to unsaturated ketones and asymmetric hydrogenation. 11 Therefore, the development of new chiral selenide-containing ligands for variable asymmetric reactions as well as broad substrate scope is still in great need.…”

Carbohydrate-based N-heterocyclic carbene-metal complexes: a new avenue for sustainable catalysts in organic transformations

“…[20][21][22][23][24][25] Pioneering work involving carbohydrate incorporation into phosphine and phosphate ligands has been well established. [26][27][28][29][30][31] Furthermore, carbohydrates incorporated with NHC ligands have been recently developed. The incorporation of these physiologically active residues into the skeleton of NHC-metal complexes may reduce toxicity while increasing biocompatibility and solubility.…”