Chromium(VI) oxide catalyzed oxidation of sulfides to sulfones with periodic acid

Selective Oxidation of Benzo[d]isothiazol-3(2H)-Ones Enabled by Selectfluor

A metal-free and Selectfluor-mediated selective oxidation reaction of benzo[d]isothiazol-3(2H)-ones in aqueous media is presented. This novel strategy provides a facile, green, and efficient approach to access important benzo[d]isothiazol-3(2H)-one-1-oxides with excellent yields and high tolerance to various functional groups. Furthermore, the purification of benzoisothiazol-3-one-1-oxides does not rely on column chromatography. Moreover, the preparation of saccharine derivatives has been achieved through sequential, double oxidation reactions in a one-pot aqueous media.

Mimicking Ozonolysis via Mechanochemistry: Internal Alkynes to 1,2-Diketones using H5IO6

Utilizing periodic acid as an environmentally benign oxidizing agent, this study introduces a novel mechanochemical method that mimics ozonolysis to convert internal alkynes into 1,2-diketones, showcasing effective emulation of ozone's reactivity. Notably, this oxidation occurs at room temperature in aerobic conditions, eliminating the need for toxic transition metals, hazardous oxidants, or expensive solvents. Through control experiments validating the mechanism, substantial evidence supports a concerted reaction pathway. This progress marks a significant stride toward cleaner and more efficient chemical synthesis, mitigating the environmental impact of conventional processes. Assessing the green chemistry metrics in both solvent-free and previously reported solvent-based methods, our eco-friendly protocol demonstrates an E-factor of 7.40, a 51.7 % atom economy, a 45.5 % atom efficiency, 100 % carbon efficiency, and 11.9 % reaction mass efficiency when solvents are not used.

Enantioselective sulfonylation to construct 3-sulfonylated oxindoles

Asymmetric synthesis of 3-sulfonylated 3-substituted oxindoles through the addition of sodium sulfinate salts to 3-bromo-3-substituted oxindoles has been achieved using chiral nickel complexes of N,N'-dioxides. This method facilitates the creation of diverse chiral sulfonyl oxindoles, several of which display promising anticancer properties. Notably, the catalyst demonstrates remarkable tolerance to water, crucial for maintaining enantioselectivity. Furthermore, the utilization of topographic steric maps of the catalysts offers valuable insights into the mechanism underlying enantioselection reversal.

Bypassing Sulfonyl Halides: Synthesis of Sulfonamides from Other Sulfur-Containing Building Blocks

This review disclosed synthetic approaches to sulfonyl amides from non-sulfonyl halogenated precursors. Known methods were systematized into groups and subgroups according to the type of starting organosulfur compound. Thiols, disulfides, and sulfonamides form a group of S(II)-containing precursors, which are used in oxidative amination reactions. An important and versatile group for oxidative amination is represented with S(IV)-containing compounds, i. e., sufinates, sulfinamides, DMSO, N-sulfinyl-O-(tert-butyl)hydroxylamine, etc. A series of S(VI)-containing precursors for amination reactions (except sulfonyl halides) include sulfonic acids, sulfonyl azides, thiosulfonates, and sulfones. All approaches are represented with the most prominent examples of the resulting sulfonamides, which could be obtained in high yields mostly via short reaction sequences. Promising electrochemical methods for the preparation of sulfonamides from thiols, disulfides, sulfonamides, sulfinic acid derivatives, and dimethyl sulfoxide under mild and green conditions are also highlighted.

The Properties, Synthesis, and Materials Applications of 1,4-Dithiins and Thianthrenes

1,4-Dithiin and its dibenzo-analogue, thianthrene, represent a class of non-aromatic, sulfur-rich heterocycles. Their unique properties, stemming from both their non-planar structures and reversible one- and two-electron oxidations, serve as primary motivators for their use in the development of new materials. The applications of 1,4-dithiins and thianthrenes are rich and diverse, having been used for energy storage and harvesting, and the synthesis of phosphorescent compounds and porous polymers, among other uses. This review offers first an overview of the properties of 1,4-dithiin and thianthrene. Next, we describe enabling synthetic methodology to access 1,4-dithiins and thianthrenes with various substitution patterns. Lastly, the utility of 1,4-dithiin and thianthrene in the construction and design of new materials is detailed using select literature examples.

1 Introduction

2 Properties of 1,4-Dithiins and Thianthrenes

3 Synthesis of 1,4-Dithiins and Thianthrenes

3.1 Synthesis of 1,4-Dithiins

3.2 Synthesis of Thianthrenes

4 Application of 1,4-Dithiins and Thianthrenes in Materials

4.1 Thianthrene-Containing Polymers

4.2 Thianthrene in Redox-Active Materials

4.3 Thianthrenes and 1,4-Dithiins in Supramolecular Chemistry and Self-Assembly

4.4 Thianthrenes in Phosphorescent Materials

4.5 Thianthrenes with Other Interesting Photophysical Properties

4.6 Thianthrenes in the Synthesis of Non-natural Products

5 Conclusion

Copper-assisted trifluoromethylthiolation/radical cascade cyclization of alkynes to construct SCF3-containing dioxodibenzothiazepines

A mild and efficient Cu-assisted trifluoromethylthiolation/radical cascade cyclization of alkynes with readily available and stable AgSCF₃ as the trifluoromethylthiolating reagent has been disclosed. This transformation provides an opportunity to construct a series of potential medicinally valuable trifluoromethylthio-substituted dioxodibenzothiazepines with wide functional group compatibility. This protocol opens up a new avenue for the construction of useful trifluoromethylthiolated seven-membered N-heterocycles.

Co(NO3)2/covalent organic framework nanoparticles for high-efficiency photocatalytic oxidation of thioanisole

Herein, we demonstrated a highly efficient photocatalytic sulfide oxidation reaction at ambient conditions without a sacrificial reagent or redox mediator, by using Co(NO₃)₂/covalent organic framework nanoparticles as a photocatalyst.

Recent trends in dehydroxylative trifluoro-methylation, -methoxylation, -methylthiolation, and -methylselenylation of alcohols

This review studies on the direct dehydroxylative trifluoromethylation, trifluoromethoxylation, trifluoromethylthiolation, and trifluoromethylselenylation of alcohols.

Electrophilic Chlorine from Chlorosulfonium Salts: A Highly Chemoselective Reduction of Sulfoxides

Herein, we describe a selective late-stage deoxygenation of sulfoxides based on a novel application of chlorosulfonium salts and demonstrate a new process using these species generated in situ from sulfoxides as the source of electrophilic chlorine. The use of highly nucleophilic 1,3,5-trimethoxybenzene (TMB) as the reducing agent is described for the first time and applied in the deoxygenation of simple and functionalized sulfoxides. The method is easy to handle, economic, suitable for gram-scale operations, and readily applied for poly-functionalized molecules, as demonstrated with more than 45 examples, including commercial medicines and analogues. We also report the results of competition experiments that define the more reactive sulfoxide and we present a mechanistic proposal based on substrate and product observations.

Formal α-trifluoromethylthiolation of carboxylic acid derivatives via N-acyl pyrazoles

A direct and general one-pot approach to α-trifluoromethylthiolated amides, esters and carboxylic acids has been successfully developed under mild, catalytic and metal-free conditions.

Nickel(ii)-catalyzed C(sp2)-H sulfuration/annulation with elemental sulfur: selective access to benzoisothiazolones

The first nickel(ii)-catalyzed direct sulfuration/annulation of C(sp²)-H bonds with elemental sulfur has been achieved by using 2-amino alkylbenzimidazole (MBIP-amine) as a N,N-bidentate directing group. This strategy tolerates a wide range of functional groups, furnishing structurally diverse benzoisothiazolone derivatives with benzimidazole skeletons in moderate to excellent yields in a simple and efficient way.

Synthesis and nano-Pd catalyzed chemoselective oxidation of symmetrical and unsymmetrical sulfides

A highly chemoselective, efficient and nano-Pd catalyzed protocol for the rapid construction of sulfoxides and sulfones via the oxidation of symmetrical and unsymmetrical sulfides using H2O2 as an oxidant has been developed, respectively. The ready availability of starting materials, easy recovery and reutilization of the catalyst, wide substrate scope, and high yields make this protocol an attractive alternative. The process also involves the metal-free and microwave-promoted synthesis of symmetrical diarylsulfides, and FeCl3-mediated preparation of symmetrical diaryldisulfides through the reaction of arenediazonium tetrafluoroborates with Na2S·9H2O as a sulfur source. In addition, unsymmetrical sulfides were generated via the K2CO3-mediated reaction of arenediazonium tetrafluoroborates with symmetrical disulfides.

Catalytic Hydrothiolation: Counterion-Controlled Regioselectivity

In this Article, we expand upon the catalytic hydrothiolation of 1,3-dienes to afford either allylic or homoallylic sulfides with high regiocontrol. Mechanistic studies support a pathway in which regioselectivity is dictated by the choice of counterion associated with the Rh center. Non-coordinating counterions, such as SbF6-, allow for η4-diene coordination to Rh complexes and result in allylic sulfides. In contrast, coordinating counterions, such as Cl-, favor neutral Rh complexes in which the diene binds η2 to afford homoallylic sulfides. We propose mechanisms that rationalize a fractional dependence on thiol for the 1,2-Markovnikov hydrothiolation while accounting for an inverse dependence on thiol in the 3,4- anti-Markovnikov pathway. Through the hydrothiolation of an essential oil (β-farnesene), we achieve the first enantioselective synthesis of (-)-agelasidine A.

Novel Sulfones with Antifungal Properties: Antifungal Activities and Interactions with Candida spp. Virulence Factors

Since candidiasis is so difficult to eradicate with an antifungal treatment and the existing antimycotics display many limitations, hopefully new sulfone derivatives may overcome these deficiencies. It is pertinent to study new strategies such as sulfone derivatives targeting the virulence attributes of C. albicans that differentiate them from the host. During infections, the pathogenic potential of C. albicans relies on the virulence factors as follows: hydrolytic enzymes, transcriptional factors, adhesion, and development of biofilms. In the article we explored how the above-presented C. albicans fitness and virulence attributes provided a robust response to the environmental stress exerted by sulfones upon C. albicans; C. albicans fitness and virulence attributes are fungal properties whose inactivation attenuates virulence. Our understanding of how these mechanisms and factors are inhibited by sulfones has increased over the last years. As lack of toxicity is a prerequisite for medical approaches, sulfones (non-toxic as assessed in vitro and in vivo) may prove to be useful for reducing C. albicans pathogenesis in humans. The antifungal activity of sulfones dealing with these multiple virulence factors and fitness attributes is discussed.

One-pot sequential synthesis and antifungal activity of 2-(benzylsulfonyl)benzothiazole derivatives

New antifungal agrochemicals, derived from 2-(benzylsulfonyl)benzothiazole were synthesized by an environmentally friendly method, using water as reaction medium.

Visible-light-induced cascade sulfonylation/cyclization of N-propargylindoles with aryldiazonium tetrafluoroborates via the insertion of sulfur dioxide

A simple and efficient visible-light-catalyzed cascade sulfonylation/cyclization of N-propargylindoles with K₂S₂O₅ and aryldiazonium tetrafluoroborates for the construction of 2-sulfonyl-substituted 9H-pyrrolo[1,2-a]indoles is developed.

Metal- and Additive-Free Oxidation of Sulfides into Sulfoxides by Fullerene-Modified Carbon Nitride with Visible-Light Illumination

Photocatalytic selective oxidation has attracted considerable attention as an environmentally friendly strategy for organic transformations. Some methods have been reported for the photocatalytic oxidation of sulfides into sulfoxides in recent years. However, the practical application of these processes is undermined by several challenges, such as low selectivity, sluggish reaction rates, the requirement of UV-light irradiation, the use of additives, and the instability of the photocatalyst. Herein, a metal-free C₆₀ /graphitic carbon nitride (g-C₃ N₄ ) composite photocatalyst was fabricated by a facile method, and well characterized by TEM, SEM, FTIR spectroscopy, XRD, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The C₆₀ /g-C₃ N₄ catalyst exhibited a high photocatalytic activity at room temperature for the selective oxidation of sulfides into the corresponding sulfoxides in the presence of other functional groups, due to the synergetic roles of C₆₀ and g-C₃ N₄ . Several important parameters have been screened, and this method afforded good to excellent yields of sulfoxides under optimal conditions. The superoxide radical (^. O₂^- ) and singlet oxygen (¹ O₂ ) were identified as the oxidative species for the oxidation of sulfides into sulfoxides by exploring EPR experiments, and hence, a plausible mechanism for this oxidation was proposed. Moreover, the C₆₀ /g-C₃ N₄ catalyst can be easily recovered by filtration and then reused at least four times without loss in activity.

Synthesis of Aryl Triflones through the Trifluoromethanesulfonylation of Benzynes

The direct synthesis of aryl triflones, that is, trifluoromethanesulfonyl arenes, was achieved through the trifluoromethanesulfonylation of benzynes. The trifluoromethanesulfonyl group, one of the fluorinated functional groups, is a highly electron-negative and mild lipophilic substituent. Aryl triflones have high potential in the synthesis of bioactive compounds and specialty materials. The treatment of 2-(trimethylsilyl)aryl trifluoromethanesulfonates with cesium fluoride in the presence of 15-crown-5 generated benzynes, which reacted with sodium trifluoromethanesulfinate followed by protonation with tBuOH under heating conditions, provided aryl triflones in moderated to good yields. Both symmetrical and unsymmetrical triflones were nicely accessed under the same reaction conditions. Interestingly, the trifluoromethanesulfonylation of unsymmetrical benzyne precursors proceeded smoothly to furnish corresponding aryl triflones in good yields with good to high regioselectivities. The balance of polarization of electric charge as well as steric hindrance of the benzyne intermediates are central factors to control the outcome of regioselectivity.

Irreversible Cysteine-Selective Protein Labeling Employing Modular Electrophilic Tetrafluoroethylation Reagents

Fluoroalkylation reagents based on hypervalent iodine are widely used to transfer fluoroalkyl moieties to various nucleophiles. However, the transferred groups have so far been limited to simple structural motifs. We herein report a reagent featuring a secondary amine that can be converted to amide, sulfonamide, and tertiary amine derivatives in one step. The resulting reagents bear manifold functional groups, many of which would not be compatible with the original synthetic pathway. Exploiting this structural versatility and the known high reactivity toward thiols, the new-generation reagents were used in bioconjugation with an artificial retro-aldolase, containing an exposed cysteine and a reactive catalytic lysine. Whereas commercial reagents based on maleimide and iodoacetamide labeled both sites, the iodanes exclusively modified the cysteine residue. The study thus demonstrates that modular fluoroalkylation reagents can be used as tools for cysteine-selective bioconjugation.

Synthesis of aryl triflones by insertion of arynes into C–SO2CF3 bonds

A new approach toward the synthesis of aryl triflones was achieved by the formal insertion of arynes into C–SO₂CF₃ bonds.

Highly selective oxidation of sulfides on a CdS/C3N4 catalyst with dioxygen under visible-light irradiation

A CdS/C₃N₄ visible-light catalyst exhibits high product selectivity towards photocatalytic oxidation of sulfides into corresponding sulfoxides with dioxygen in methanol.

Ti(Phen)(OC2H5)2Cl2: a highly efficient pre-catalyst for selective oxidation of organic sulfides to sulfoxides by hydrogen peroxide

A structurally characterized titanium complex [Ti(Phen)(OC₂H₅)₂Cl₂] (Phen = 1,10-phenanthroline) is reported as a homogeneous pre-catalyst for the selective oxidation of organic sulfides to sulfoxides with a stoichiometric amount H₂O₂ in CH₃OH at room temperature.

Cobalt(ii)-catalyzed remote C5-selective C–H sulfonylation of quinolines via insertion of sulfur dioxide

A cobalt(ii)-catalyzed reaction for highly selective C5-sulfonylation of quinolines via insertion of sulfur dioxide is developed, leading to diverse sulfonated quinolines in moderate to good yields.

Engineering an Affinity-Enhanced Peptide through Optimization of Cyclization Chemistry

Peptide cyclization is a strategy used to improve stability and activity of peptides. The most commonly used cyclization method is disulfide bridge formation of cysteine-containing peptides, as is typically found in nature. Over the years, an increasing number of alternative chemistries for peptide cyclization with improved efficiency, kinetics, orthogonality, and stability have been reported. However, there has been less appreciation for the opportunity to fine-tune peptide activity via the diverse chemical entities introduced at the site of linkage by different cyclization strategies. Here, we demonstrate how cyclization optimization of an M2 "anti-inflammatory" macrophage-binding peptide (M2pep) resulted in a significant increase in binding affinity of the optimized analog to M2 macrophages while maintaining binding selectivity compared to M1 "pro-inflammatory" macrophages. In this study, we report synthesis and evaluation of four cyclic M2pep(RY) analogs with diverse cyclization strategies: (1) Asp-[amide]-Lys, (2) azido-Lys-[triazole(copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC))]-propargyl-Gly, (3) Cys-[decafluorobiphenyl (DFBP)]-Cys, and (4) Cys-[decafluorobiphenyl sulfone (DFS)]-Cys, whereby the chemical entity or linker at the linkage site is shown in the square bracket and is between the residues involved in cyclization. These peptides are compared to a disulfide-cyclized M2pep(RY) that we previously reported as a serum-stable, affinity-enhanced analog to the original linear M2pep. DFBP-cyclized M2pep(RY) exhibits the highest binding activity to M2 macrophages with apparent dissociation constant (K_D) about 2.03 μM compared to 36.3 μM for the original disulfide-cyclized M2pep(RY) and 220 μM for the original linear peptide. DFS-cyclized M2pep(RY) also binds more strongly than the original cyclized analog, whereas amide- and triazole-cyclized M2pep(RY) analogs bind less strongly. We verified that DFBP alone has negligible binding to M2 macrophages and the incorporation of diphenylalanine to the original sequence improves binding activity at the expense of solubility and increased toxicity. In conclusion, we report development of cyclic M2pep(RY) analogs with diverse cyclization strategies leading to the discovery of DFBP-cyclized M2pep(RY) with enhanced M2 macrophage-binding activity.

Palladium Catalyzed Monoselective α-Arylation of Sulfones and Sulfonamides with 2,2,6,6-Tetramethylpiperidine·ZnCl·LiCl Base and Aryl Bromides

A palladium catalyzed Negishi-type α-arylation of sulfones and sulfonamides with a broad range of aryl bromides has been developed. The substrates are selectively metalated in situ with tmp·ZnCl·LiCl base (tmp: 2,2,6,6-tetramethylpiperidine) and cross-coupled in the presence of a catalyst system that is generated from Pd(dba)2 and XPhos. Electron-deficient, electron-rich, and heterocyclic aryl bromides have been successfully cross-coupled, and sensitive functional groups are well tolerated. Simple aryl bromides are converted overnight at 60 °C in THF while heteroaryl bromides are efficiently coupled within 2 h at 130 °C in a microwave reactor. The desired monoarylated α-branched benzyl sulfones and sulfonamides were obtained in good yields, and overarylation was not detected. The procedure is ideal for late stage functionalization in parallel medicinal chemistry.