An escapade in the world of sulfenate anions: generation, reactivity and applications in domino processes

β-Trifluorosulfinylesters: tuneable reagents for switchable trifluoromethylsulfinylation and C–H trifluoromethylthiolation

β-Trifluorosulfinylesters, a family of novel reagents from commercially available starting materials for direct trifluoromethylthiolation and trifluoromethylsulfinylation were developed.

Unusual Deoxidative Coupling Reaction of β-Sulfinyl Esters with Benzylic Trimethylammonium Salts

A KOH-promoted unusual deoxidative coupling reaction of β-sulfinyl esters with benzylic trimethylammonium salts to produce thioethers is discovered for the first time. If quaternary ammonium salts synthesized from enantiomerically enriched amines are adopted, highly enantiomerically enriched benzyl thioethers (>95-99% ee) with configurations opposite to those of the enantiomerically enriched amines are obtained.

Transition-metal-free formal cross-coupling of aryl methyl sulfoxides and alcohols via nucleophilic activation of C-S bond

Employment of sulfoxides as electrophiles in cross-coupling reactions remains underexplored. Herein we report a transition-metal-free cross-coupling strategy utilizing aryl(heteroaryl) methyl sulfoxides and alcohols to afford alkyl aryl(heteroaryl) ethers. Two drug molecules were successfully prepared using this protocol as a key step, emphasizing its potential utility in medicinal chemistry. A DFT computational study suggests that the reaction proceeds via initial addition of the alkoxide to the sulfoxide. This adduct facilitates further intramolecular addition of the alkoxide to the aromatic ring wherein charge on the aromatic system is stabilized by the nearby potassium cation. Rate-determining fragmentation then delivers methyl sulfenate and the aryl or heteroaryl ether. This study establishes the feasibility of nucleophilic addition to an appended sulfoxide as a means to form a bond to aryl(heteroaryl) systems and this modality is expected to find use with many other electrophiles and nucleophiles leading to new cross-coupling processes.

Cross-coupling processes without the use of transition metals are challenging to achieve. Here, the authors show a transition-metal-free cross-coupling utilizing aryl(heteroaryl) methyl sulfoxides and alcohols to afford alkyl aryl(heteroaryl) ethers and propose a nucleophilic addition mechanism based on experiments and theory.

Modern Stereoselective Synthesis of Chiral Sulfinyl Compounds

Chiral sulfinyl compounds, sulfoxides, sulfoximines, sulfinamides, and other derivatives, play an important role in asymmetric synthesis as versatile auxiliaries, ligands, and catalysts. They are also recognized as pharmacophores found in already marketed and well-sold drugs (e.g., esomeprazole) and used in drug design. This review is devoted to the modern methods of preparation of sulfinyl derivatives in enantiopure or enantiomerically enriched form. Selected new approaches leading to racemic products for which the asymmetric variant can be developed in the future are mentioned as well.

Palladium-Catalyzed Enantioselective Alkenylation of Sulfenate Anions

A novel approach to synthesize enantio-enriched alkenyl/aryl sulfoxides is achieved by using CsF to generate sulfenate anions and conducting the catalytic enantioselective alkenylation with [Pd(allyl)Cl]₂/(2 R)-1-[(1 R)-1-[bis(1,1-dimethylethyl)phosphino]ethyl]-2-(diphenylphosphino)ferrocene (SL-J002-1). A wide variety of sulfoxides bearing sensitive functional groups are produced with high yields (up to 94%) and enantioselectivities (up to 92%).

Transition metal-free base-promoted arylation of sulfenate anions with diaryliodonium salts

A base-promoted formal arylation of general sulfenate anions with diaryliodonium salts under transition-metal-free conditions has been described.

Nondirected Copper-Catalyzed Sulfoxidations of Benzylic C-H Bonds

A copper-catalyzed sulfoxidation of benzylic C-H bonds by nondirected oxidative C(sp³)-H activation was developed. The process proceeds via sulfenate anions, which are generated by base-triggered elimination of β-sulfinyl esters and benzyl radicals. The functional group tolerance is high, and the product yields are good.

Palladium/PC-Phos-Catalyzed Enantioselective Arylation of General Sulfenate Anions: Scope and Synthetic Applications

Herein we reported an efficient palladium-catalyzed enantioselective arylation of both alkyl and aryl sulfenate anions to deliver various chiral sulfoxides in good yields (up to 98%) with excellent enantioselectivities (up to 99% ee) by the use of our developed chiral O,P-ligands (PC-Phos). PC-Phos are easily prepared in short steps from inexpensive commercially available starting materials. The single-crystal structure of the PC4/PdCl₂ showed that a rarely observed 11-membered ring was formed via the O,P-coordination with the palladium(II) center. The salient features of this method include general substrate scope, ease of scale-up, applicable to the late-stage modification of bioactive compounds, and the synthesis of a marketed medicine Sulindac.

The use of the sterically demanding IPr* and related ligands in catalysis

This account highlights the synthesis and applications of one of the very bulky NHC ligands, IPr* (1,3-bis(2,6-bis(diphenylmethyl)-4-methylphenyl)imidazo-2-ylidene). This ligand and some of its derivatives have been found very effective in several catalytic applications and have enabled the isolation of highly reactive organometallic complexes. More specifically, applications of this ligand in Pd and Ni chemistry have permitted challenging transformations under mild reaction conditions and low catalyst loadings. We report the successes as well as the limitations encountered using transition-metal systems bearing this ligand-type. This report will hopefully serve as a guide to synthetic chemists, providing insights as to when the very sterically demanding IPr* ligand (and its congeners) and in a broader context, very bulky NHC ligands, should be used.

Whole-cell oxidation of omeprazole sulfide to enantiopure esomeprazole with Lysinibacillus sp. B71

Production of enantiopure esomeprazole by biocatalysis is of great demand by pharmaceutical industry. A Gram-positive bacterium oxidizing omeprazole sulfide 1a (5-methoxy-2-[((4-methoxy-3,5-dimethylpyridin-2-yl)methyl)thio]-1H-benzoimidazole) to (S)-sulfoxide esomeprazole 2a (S)-5-methoxy-2-[(4-methoxy-3,5-dimethylpyridin-2-yl) methylsulfinyl]-3H-benzoimidazole was isolated from soil polluted with elemental sulfur. The strain exhibited the highest identity with the genus Lysinibacillus and catalyzed oxidation of 1a into enantiopure esomeprazole with conversion of 77% in a stirred bioreactor, fed-batch culture. No consecutive oxidation of (S)-sulfoxide to sulfone was observed during whole-cell catalysis. The unique characteristics of the catalyst provide a solid basis for further improvement and development of sustainable green bioprocess.