Chiral Sulfoxide Ligands Research Articles

Recent Advances for Chiral Sulfoxides in Asymmetric Catalysis

AbstractChiral sulfoxide is considered to be an ideal candidate ligand for transition-metal-catalyzed asymmetric reactions due to its ease of synthesis, stability, and exceptional S-stereological orientation control. This paper reviews the different types of asymmetrical reactions with chiral sulfoxide ligands in recent years, as well as a discussion of efficient methods for the preparation of some enantiomerically pure sulfoxides.1 Introduction2 Chiral Sulfoxides as Ligands in Metal-Catalyzed Asymmetric Catalysis3 Synthesis of Chiral Sulfoxides4 Conclusions

Thermodynamic Resolution of Pharmaceutical Precursor Modafinil Acid on the Basis of Chiral‐at‐Metal Strategy

Main observation and conclusionChiral‐at‐metal strategy was developed to resolve the essential sulfoxide pharmaceutical intermediates R‐modafinil acid and its analogues with high yields and ee values. The efficient resolution process was achieved based on the diastereoselective discrimination caused by hydrogen bond and intramolecular π‐π interaction between chiral‐at‐metal center and the coordinated chiral sulfoxide ligands. Moreover, the chiral Ir(III) receptor can be reused with complete retention of their configurations and without the loss of reaction activity and enantioselectivity. This work provides a new access to synthesize R‐modafinil acid as well as its analogues and develops the application of chiral‐at‐metal strategy in chiral resolution.

Easy Access to Polyfunctionalized Chiral Decalins.

An unexpected ring expansion that converts hydrindanes into decalins via an unprecedented dyotropic reaction involving a mesylate group has been observed, and this paved the way for easy access to polyfunctionalized chiral decalins. These polyfunctionalized chiral decalins can be very useful building blocks for the synthesis of the thia analogues of many natural compounds. They can also be used in asymmetric catalysis and also in the synthesis of the new analogues of vitamin D with a modified D ring and side chain. The use of chiral sulfoxide ligands for asymmetric catalysis or asymmetric sulfur ylide-mediated epoxidation of carbonyl compounds is a very important topic in the field of organic chemistry, hence our results could be useful to the scientific community.

Chiral Sulfoxide Ligands in Asymmetric Catalysis.

Since the original idea was explored by James in 1976, the use of chiral sulfoxides as ligands with transition metals in asymmetric catalysis has undergone a long period of development. There have been many studies into their properties, design and application in various kinds of asymmetric transformations. In this article, we document the literatures on chiral sulfoxide ligands in asymmetric catalytic reactions.

ChemInform Abstract: Development of Chiral Sulfoxide Ligands for Asymmetric Catalysis

AbstractReview: 78 refs.

Development of chiral sulfoxide ligands for asymmetric catalysis.

Nitrogen-, phosphorus-, and oxygen-based ligands with chiral backbones have been the historic workhorses of asymmetric transition-metal-catalyzed reactions. On the contrary, sulfoxides containing chirality at the sulfur atom have mainly been used as chiral auxiliaries for diastereoselective reactions. Despite several distinct advantages over traditional ligand scaffolds, such as the proximity of the chiral information to the metal center and the ability to switch between S and O coordination, these compounds have only recently emerged as a versatile class of chiral ligands. In this Review, we detail the history of the development of chiral sulfoxide ligands for asymmetric catalysis. We also provide brief descriptions of metal-sulfoxide bonding and strategies for the synthesis of enantiopure sulfoxides. Finally, insights into the future development of this underutilized ligand class are discussed.

Enantioselective syntheses of sulfoxides in octahedral ruthenium(II) complexes via a chiral-at-metal strategy.

The preparation of chiral 2-(alkylsulfinyl)phenol compounds by enantioselective coordination-oxidation of the thioether ruthenium complexes with a chiral-at-metal strategy has been developed. The enantiomerically pure sulfoxide complexes Δ-[Ru(bpy)2{(R)-LO-R}](PF6) (bpy is 2,2'-bipyridine, HLO-R is 2-(alkylsulfinyl)phenol, R = Me (Δ-1a), Et (Δ-2a), iPr (Δ-3a), Bn (Δ-4a), and Nap (Δ-5a)) and Λ-[Ru(bpy)2{(S)-LO-R}](PF6) (R = Me (Λ-1a), Et (Λ-2a), iPr (Λ-3a), Bn (Λ-4a), and Nap (Λ-5a)) have been synthesized by the reaction of Δ-[Ru(bpy)2(py)2](2+) or Λ-[Ru(bpy)2(py)2](2+) with the prochiral thioether ligands 2-(alkylthio)phenol (HL-R), followed by enantioselective oxidation with m-CPBA as oxidant. The X-ray crystallography was used to verify the stereochemistry of ruthenium complexes and sulfur atoms. The configurations of the ruthenium complexes are stable during the coordination and oxidation reactions. Moreover, the chiral sulfoxide ligands are enantioselectively generated by controlling of the configuration of ruthenium centers in the course of oxidation reaction. That is, the Λ configuration at the ruthenium center generates the S sulfoxide ligand; on the contrary, the Δ configuration of the ruthenium complex originates the R sulfoxide ligand. Acidolysis of Λ-[Ru(bpy)2{(R)-LO-R}](PF6) and Δ-[Ru(bpy)2{(S)-LO-R}](PF6) complexes in the presence of TFA-MeCN afforded the chiral ligands (R)-HLO-R and (S)-HLO-R in 96-99% ee values, respectively. Importantly, the chiral ruthenium complexes can be recycled as Δ/Λ-[Ru(bpy)2(MeCN)2](PF6)2 and reused in a next reaction cycle with complete retention of the configurations at ruthenium centers.

スルホキシド不斉配位子

Enantiopure sulfoxides are recognized as useful and versatile chiral auxiliaries in asymmetric synthesis. In contrast, much less explored is the use of chiral sulfoxide as ligands for late transition metal catalysts which favorably make sulfur coordination. This article provides a brief overview of the development of such ligands bearing chiral sulfoxide moiety. In 2008, Dorta introduced the highly efficient axially chiral bis-sulfoxide ligands (BINASO) for Rh-catalyzed enantioselective 1,4-addition of arylboronic acids to α,β-unsaturated ketones. After this seminal report, several novel chiral sulfoxide ligands appeared to work for Pd- or Rh-catalyzed asymmetric transformations.

ChemInform Abstract: New Chiral Sulfoxide Ligands in Catalytic Asymmetric Diels—Alder Reactions: Double Acceleration by the Chiralities of the Sulfoxides and Oxazolines.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

New chiral sulfoxide ligands in catalytic asymmetric Diels–Alder reactions: double acceleration by the chiralities of the sulfoxides and oxazolines

New chiral sulfoxide ligands which are useful for catalytic asymmetric Diels–Alder reactions have been developed. The new ligands involve a chiral sulfinyl function and a 1,3-oxazoline ring with an asymmetric carbon center, in which the chiral sulfinyl group has been revealed to play a crucial role in achieving high enantioselectivity in asymmetric Diels–Alder reactions. Among the Lewis acid catalysts employed, magnesium iodide provided the highest chemical and stereochemical efficiency in the cycloaddition reactions. A mechanistic pathway for the asymmetric synthesis is proposed on the basis of the stereochemical outcomes obtained.

ChemInform Abstract: Asymmetric Induction in the Inter- and Intramolecular Radical Carbon-Carbon Bond Forming Reactions of N-Arylsulfonyl-α-bromocarboxamides with Chiral Ligands: The Use of Chiral Sulfoxide Ligands in Radical Chemistry.

Abstract Inter- and intramolecular asymmetric radical carbon–carbon bond-forming reactions of sulfonamides were successfully achieved using chiral ligands in the presence of Lewis acids. The use of chiral sulfoxides as chiral ligands in the radical reactions of sulfonamides provided higher enantioselectivity, proceeding through a diastereomerically more favorable intermediate, presumably by enantiotopically selective coordination of one of the two oxygen atoms of the sulfonamides.

Asymmetric induction in the inter- and intramolecular radical carbon–carbon bond forming reactions of N-arylsulfonyl-α-bromocarboxamides with chiral ligands: the use of chiral sulfoxide ligands in radical chemistry

Inter- and intramolecular asymmetric radical carbon–carbon bond-forming reactions of sulfonamides were successfully achieved using chiral ligands in the presence of Lewis acids. The use of chiral sulfoxides as chiral ligands in the radical reactions of sulfonamides provided higher enantioselectivity, proceeding through a diastereomerically more favorable intermediate, presumably by enantiotopically selective coordination of one of the two oxygen atoms of the sulfonamides.

New Chiral Sulfoxide Ligands Possessing a Phosphano or Phosphanoamino Functionality in Palladium-Catalyzed Asymmetric Allylic Nucleophilic Substitution Reactions

New chiral sulfoxide ligands possessing a phosphano or phosphanoamino functionality as an alternative coordinating element were developed, and their usefulness was demonstrated by applying them to palladium-catalyzed asymmetric allylic nucleophilic substitution reactions. The structure of the catalyst precursor coordinated by the chiral phosphino sulfoxide was determined by X-ray crystallographic analysis. The possible mechanism for the asymmetric induction using these chiral ligands was proposed on the basis of the stereochemical outcome obtained.

ChemInform Abstract: Chiral Organosulfur Compounds. Part 7. Chiral Sulfoxide Ligands Bearing Nitrogen Atoms as Stereocontrollable Coordinating Elements in Palladium‐Catalyzed Asymmetric Allylic Alkylations.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Chiral sulfoxide ligands bearing nitrogen atoms as stereocontrollable coordinating elements in palladium-catalyzed asymmetric allylic alkylations

Palladium-catalyzed asymmetric allylic alkylations were studied by using chiral sulfoxide ligands bearing nitrogen atoms as coordinating elements, such as chiral α-sulfinylacetamides, β or γ-amino sulfoxides, and β-sulfinyl sulfonamides. The effects of the chiral sulfinyl functions on the asymmetric induction were demonstrated. Use of ( S)-2-pyrrolidinophenyl p-tolyl sulfoxide or ( S)-2-( N-butyl- N-methylaminomethyl)phenyl p-tolyl sulfoxide as chiral ligands in the palladium-catalyzed asymmetric allylic alkylations provided the highest enantioselectivity (50 or 58% e.e., respectively) among chiral sulfoxide ligands examined by us. The participation of the sulfinyl groups in these catalytic asymmetric reactions is rationalized, and the mechanism for the asymmetric induction is proposed on the basis of the stereochemical outcome obtained.

Catalytic asymmetric hydrogenation using ruthenium(II) complexes with chelating chiral sulfoxide ligands

A chelating sulfoxide ligand, (2R,3R)-2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(methyl sulfinyl)butane monohydrate, or 'dios', containing chiral carbons has been synthesized. A corresponding bis(benzyl sulfinyl) compound, 'bdios', and an acetal-cleaved derivative, 'ddios', are also reported. Ruthenium(II) neutral complexes have been made containing such ligands, which can bind via oxygen or sulphur; the complexes are active homogeneous catalysts for hydrogenation of prochiral olefinic acid substrates; optical purities of up to 25% were attained.