Re-examination of the Claimed Isolation of Stable Noncyclic 1,2-Disulfoxides

Re-examination of the claimed isolation and X-ray characterization of di-p-tolyl and dimesityl 1,2-disulfoxides from thermolysis of the corresponding aryl sulfinimines and thiosulfinates showed that the isolated disulfide dioxides are instead the well-known isomeric thiosulfonates, as confirmed by XAS, DART-MS, X-ray, IR and NMR methods. Concerns with the original X-ray structures are addressed. Our results agree with the DFT prediction of very weak diaryl 1,2-disulfoxide S-S bond dissociation enthalpies. For now, room-temperature-stable noncyclic 1,2-disulfoxides remain unknown.

Bifunctionalization of α-Bromophenone: An Access to Functionalized β-Keto Thiosulfones

A simple and high-yielding strategy to produce a variety of β-keto sulfides using asymmetrical and symmetrical thiosulfonates with ketones under mild conditions is reported. It was found that the various substituted compounds, with both electron-withdrawing and electron-donating substituents, afforded a wide range of β-keto thiosulfones (α-thioaryl-β-keto sulfones) in moderate to high yields. The transformations were reliable at the gram-scale, thus illustrating their efficiency and practicality. A plausible mechanism for the protocol is also proposed.

Silver-Catalyzed 1,2-Thiosulfonylation of Alkenes: Development of a Nucleophilic d3-Methylthiolating Reagent

Development of robust d3-methylthiolating reagents represents an attractive synthetic method to access deuterated molecules in the field of drug discovery. Here, we report a straightforward strategy to prepare electrophilic S-methyl-d3 arylsulfonothioates in one-step without column purification. These reagents exhibit good radical reactivity toward silver-catalyzed vicinal thiosulfonylation of alkenes or 1,6-enynes on water. As a result, simultaneous incorporation of both SCD3 and ArSO2 units into unsaturated carbon-carbon bonds with 100% atom economy has been established. Moreover, the ATRA adducts with >99% D incorporation can serve as nucleophilic d3-methylthiolating synthons via retro-Michael addition under mild basic conditions, providing a good alternative in trideuteromethylthiolating alkyl iodides to access corresponding trideuteromethyl sulfides with high efficiency.

Cross-Electrophile Couplings of Benzyl Sulfonium Salts with Thiosulfonates via C-S Bond Activation

A zinc-mediated cross-electrophile coupling of benzyl sulfonium salts with thiosulfonates via C-S bond cleavage was achieved. The reductive thiolation proceeded well under transition metal-free conditions to afford the desired benzyl sulfides in good yields, exhibiting both broad substrate scope and good functionality tolerance. In addition, the reaction could be applied to the use of selenosulfonate as an effective selenylation agent and be subjected to scale-up synthesis.

Electrochemical promoted three-component reaction to unsymmetric thiosulfonates

Compounds comprising S-S bonds serve as significant pharmacological scaffolds in medicinal chemistry and natural products. We have devised an efficient electrochemical method for the construction of asymmetric disulfide bonds, leading to the synthesis of unsymmetric thiosulfonates. Compared with existing synthesis methods, our work not only avoids the use of metals and oxidants, but also realizes the operation of a one-pot three-component method, which makes this strategy extremely attractive.

Light-Induced 1,3-Thiosulfonylation of β,γ-Unsaturated Ketones with Thiosulfonates

Sulfur-containing compounds exhibit potent significance in drug molecules. Thiosulfonates as 1,3-thiosulfonylation reactants to olefins have yet to be investigated. Herein, we report photoinduced 1,3-difunctionalization of β,γ-unsaturated ketones with thiosulfonates, which undergo a radical 1,2-acyl shift. The protocol features mild conditions, high regioselectivity, and 100% atom economy.

Oxysulfonylation of Alkynes with Sodium Sulfinates to Access β-Keto Sulfones Catalyzed by BF3·OEt2

An efficient and operationally simple method for the synthesis of β-keto sulfones through the BF3·OEt2-promoted reaction of alkynes and sodium sulfinates is developed. With its facile and selective access to the targets, it features good functional group compatibility, mild conditions, easily available starting materials, and good yields. Notably, the reaction does not require metal catalysts or chemical reagents with pungent odors.

Clickable tryptophan modification for late-stage diversification of native peptides

As the least abundant residue in proteins, tryptophan widely exists in peptide drugs and bioactive natural products and contributes to drug-target interactions in multiple ways. We report here a clickable tryptophan modification for late-stage diversification of native peptides, via catalyst-free C2-sulfenylation with 8-quinoline thiosulfonate reagents in trifluoroacetic acid (TFA). A wide range of groups including trifluoromethylthio (SCF3), difluoromethylthio (SCF2H), (ethoxycarbonyl)difluoromethylthio (SCF2CO2Et), alkylthio, and arylthio were readily incorporated. The rapid reaction kinetics of Trp modification and full tolerance with other 19 proteinogenic amino acids, as well as the super dissolving capability of TFA, render this method suitable for all kinds of Trp-containing peptides without limitations from sequences, hydrophobicity, and aggregation propensity. The late-stage modification of 15 therapeutic peptides (1.0 to 7.6 kilodaltons) and the improved bioactivity and serum stability of SCF3- and SCF2H-modified melittin analogs illustrated the effectiveness of this method and its potential in pharmacokinetic property improvement.

Visible Light-Catalyzed Reactions of Polysulfide (DBSPS) with Aryldiazonium

A visible light-catalyzed radical coupling reaction of polysulfide reagents with aryldiazonium was developed, which gave thiosulfonates under mild conditions. In this reaction, the thiosulfonates were isolated in good yields with a broad tolerance to functional groups. And the synthesis of diaryl monosulfides were achieved through a step-by-step reaction of two molecular aryldiazonium with DBSPS, where the sulfur source was provided by DBSPS. It was worth noting that the reaction of this monosulfides could also be achieved by a one pot two-step process. The described polysulfide reagents were able to produce three new radicals: sulfonyl radicals, sulfur-sulfonyl radicals and sulfur-sulfur-sulfonyl radicals.

I2-Cs2CO3 Mediated Intramolecular C2-Amination and Oxidative Rearrangement Cascade of C-3 Phenylthio Indoles: A Route to Synthesize Thiosulfonate-Embedded 2-Iminoindolin-3-ones

An efficient, transition-metal-free protocol employing I2/Cs2CO3 for the synthesis of thiosulfonate containing 2-iminoindolin-3-ones motifs has been developed from C-3 phenylthio indoles. The reaction proceeded through intramolecular cyclization involving C-N bond formation, leading to the formation of indole-fused benzothiazines as a key intermediate. Remarkably, Cs2CO3 played a crucial role in the reaction as an oxygen source, enabling oxidative rearrangement with [1,4]-sulfonyl migration to furnish the final products with the formation of multiple functional groups such as C═O, C═N, and S-SO2.

Catalyst-Free Synthesis of Thiosulfonates and 3-Sulfenylindoles from Sodium Sulfinates in Water

This paper presents a green and efficient aqueous-phase method for the synthesis of thiosulfonates, which has the benefits of no need for catalysts or redox reagents and a short reaction time, providing a method with great economic value for synthesizing thiosulfonates. Furthermore, 3-Sulfenylindoles can be easily synthesized using this method, which expands the potential applications of this reaction.

A general copper-catalysed enantioconvergent C(sp3)-S cross-coupling via biomimetic radical homolytic substitution

Although α-chiral C(sp3)-S bonds are of enormous importance in organic synthesis and related areas, the transition-metal-catalysed enantioselective C(sp3)-S bond construction still represents an underdeveloped domain probably due to the difficult heterolytic metal-sulfur bond cleavage and notorious catalyst-poisoning capability of sulfur nucleophiles. Here we demonstrate the use of chiral tridentate anionic ligands in combination with Cu(I) catalysts to enable a biomimetic enantioconvergent radical C(sp3)-S cross-coupling reaction of both racemic secondary and tertiary alkyl halides with highly transformable sulfur nucleophiles. This protocol not only exhibits a broad substrate scope with high enantioselectivity but also provides universal access to a range of useful α-chiral alkyl organosulfur compounds with different sulfur oxidation states, thus providing a complementary approach to known asymmetric C(sp3)-S bond formation methods. Mechanistic results support a biomimetic radical homolytic substitution pathway for the critical C(sp3)-S bond formation step.

Solvent-Free Reaction for Unsymmetrical Organodisulfides with High Purity and Application as Cathode-Active Materials

Unsymmetrical disulfides, in which different organic groups are bonded to disulfide bonds, have been synthesized by cross-coupling reactions using thiols as substrates. However, due to the low-binding energy of unsymmetrical disulfides, its disproportionation occurs based on the side reactions with nucleophilic thiols, resulting in the impurity of symmetric disulfides. In this study, we developed a solvent-free synthesis method for unsymmetrical disulfides using thiosulfonates, thiols, and a base. This synthetic method enabled us to obtain highly pure diaryl-substituted unsymmetrical disulfides with particularly low-binding energy without control over the nucleophilicity and elimination properties of the substrate. Furthermore, it was observed that the disproportionation of unsymmetrical disulfides occurred in the solvent. This means that solvent-free condition is one of the factors to obtain unsymmetrical disulfides. As a new application of unsymmetrical disulfides, we applied unsymmetrical disulfides to cathode active materials of lithium batteries based on the reversible multi-electron redox activity of S-S bonds. The batteries using unsymmetrical disulfide cathode-active materials with a carbon nanotube exhibited initial capacities of 127 and 158 Ah/kg, equal to 42 and 53% of their theoretical ones. We demonstrated that unsymmetrical disulfides could be used as cathode-active materials for rechargeable batteries.

Synergistic Photoredox and Iron Catalyzed 1,2-Thiosulfonylation of Alkenes with Thiophenols and Sulfonyl Chlorides

Herein, a three-component 1,2-thiosulfonylation of alkenes with thiophenols and sulfonyl chlorides via synergistic photoredox and iron catalysis is described. Compared with previous studies, this protocol avoids tedious pre-synthesis of thiosulfonates and employs more readily accessible sulfonyl chlorides as a sulfonation reagent. Moreover, the reaction exhibits high compatibility with styrenes and unactivated alkenes as well as diverse sulfonyl chlorides, especially sulfamoyl chlorides. Preliminary mechanism investigations reveal that a radical pathway is involved in the catalytic cycle.

Photocatalytic C(sp3)-H thiolation by a double SH2 strategy using thiosulfonates

Site-selective C(sp3)-H thiolation using thiosulfonates has been achieved using the decatungstate anion as a photocatalyst. Using the protocol, a variety of thiolated compounds were synthesized in good yields. The transformation consists of a cascade of double SH2 reactions, HAT and ArS group transfer, and PCET (proton-coupled electron transfer) of the leaving arylsulfonyl radical to arylsulfinic acid thus allowing the catalyst, W10O324-, to be recovered.

Isothiocyanates (in situ) and sulfonyl chlorides in water for N-functionalization of bicyclic amidines: access to N-alkylated γ-/ω-lactam derivatized thiourea and sulfonamides

Herein, we showcase the potential of isothiocyanates generated in situ and aryl sulfonyl chlorides as electrophiles in water for N-functionalization of bicyclic amidines (DBN and DBU). This strategy provides complementary access to a range of thiouredosulfides, sulfonamides, aroylthioureas and amides derivativatized with distal γ- and ω-lactams. A novel sulfonyl chloride mediated formation of β-uredo sulfides has been achieved from β-isothiocyanato sulfides, removing the requirement for the harsh synthesis of unstable isocyanates. Mechanistic studies suggest a radical mechanism for the difunctionalization of alkenes, the efficacy of H2O in the ring opening of bicyclic amidines, and an oxygen source along with sulfonyl chloride as desulfurization agents for thiourea to afford urea derivatives.

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

In the field of organosulfur chemistry, sulfenylating agents are an important key in C-S bond formation strategies. Among various organosulfur precursors, N-sulfenylsuccinimide/phthalimide derivatives have shown highly electrophilic reactivity for the asymmetric synthesis of many organic compounds. Hence, in this review article, we focus on the application of these alternative sulfenylating reagents in organic transformations.

Oxidation of Thiols with IBX or DMP: One-Pot Access to Thiosulfonates or 2-Iodobenzoates and Applications in Functional Group Transformations

o-Iodoxybenzoic acid (IBX) and Dess-Martin periodinane (DMP) are employed for thiol to thiosulfonate conversion at rt. DMP is better than IBX in terms of reaction rate, conversion, and required equivalents. IBX-mediated oxidation of benzyl thiols produced thiosulfonates, whereas DMP afforded O-benzyl esters. The one-pot conversion of a thiol to an ester is unprecedented; this atom-economic transformation has potential for functional group transformations (FGTs), e.g., an alcohol and an aldehyde are accessed from benzyl thiol.

Synthesis of 1,3-Dibenzenesulfonylpolysulfane (DBSPS) and Its Application in the Preparation of Aryl Thiosulfonates from Boronic Acids

Herein, we provide a novel method for the synthesis of 1,3-dibenzenesulfonylpolysulfane (DBSPS), which further reacts with boronic acids to afford thiosulfonates. Commercially available boron compounds greatly expanded the range of thiosulfonates. Experimental and theoretical mechanistic investigations suggested that DBSPS could provide both thiosulfone fragments and dithiosulfone fragments, but the generated aryl dithiosulfonates were unstable and decomposed into thiosulfonates.

Cu-catalysed enantioselective radical heteroatomic S-O cross-coupling

The transition-metal-catalysed cross-coupling reaction has established itself as one of the most reliable and practical synthetic tools for the efficient construction of carbon-carbon/heteroatom (p-block elements other than carbon) bonds in both racemic and enantioselective manners. In contrast, development of the corresponding heteroatom-heteroatom cross-couplings has so far remained elusive, probably due to the under-investigated and often challenging heteroatom-heteroatom reductive elimination. Here we demonstrate the use of single-electron reductive elimination as a strategy for developing enantioselective S-O coupling under Cu catalysis, based on both experimental and theoretical results. The reaction manifests its synthetic potential by the ready preparation of challenging chiral alcohols featuring congested stereocentres, the expedient valorization of the biomass-derived feedstock glycerol, and the remarkable catalytic 4,6-desymmetrization of inositol. These results demonstrate the potential of enantioselective radical heteroatomic cross-coupling as a general chiral heteroatom-heteroatom formation strategy.

Tagging Peptides with a Redox Responsive Fluorescent Probe Enabled by Photoredox Difunctionalization of Phenylacetylenes with Sulfinates and Disulfides

Herein, we describe a photoredox three-component atom-transfer radical addition (ATRA) reaction of aryl alkynes directly with dialkyl disulfides and alkylsulfinates, circumventing the utilization of chemically unstable and synthetically challenging S-alkyl alkylthiosulfonates as viable addition partners. A vast array of (E)-β-alkylsulfonylvinyl alkylsulfides was prepared with great regio- and stereoselectivity. Moreover, this powerful tactic could be employed to tag cysteine residues of complex polypeptides in solution or on resin merging with solid phase peptide synthesis (SPPS) techniques. A sulfonyl-derived redox responsive fluorescent probe could be conveniently introduced on the peptide, which displays green fluorescence in cells while showing blue fluorescence in medium. The photophysical investigations reveal that the red shift of the emission fluorescence is attested to reduction of carbonyl group to the corresponding hydroxyl moiety. Interestingly, the fluorescence change of tagged peptide could be reverted in cells by treatment of H₂O₂, arising from the reoxidation of hydroxyl group back to ketone by the elevated level of reactive oxygen species (ROS).

DBU-Catalyzed Aerobic CDC Reaction of Thiophenols

A convenient method was developed for the preparation of thiolated compounds via a DBU-catalyzed aerobic cross-dehydrogenative coupling (CDC) reaction. The established protocol is environmentally friendly and operationally simple. Substrates like (hetero)aryl acetates, (hetero)aryl ketones, and indoles could be transformed into the corresponding thiolated products in moderate to high yields and further applied in the preparation of bioactive compounds in a prefunctionalization-free manner.

Synthesis of Unsymmetric Thiosulfonates Starting from N-Substituted O-Thiocarbamates: Easy Access to the S-SO2 Bond

Using phenyliodine diacetate as an oxidant and nickel acetate as a promoter, a wide range of unsymmetric thiosulfonates could be furnished easily in moderate to excellent yields starting from N-substituted O-thiocarbamates and sodium sulfinates. This protocol features mild conditions, short reaction times, and high atomic utilization, which can provide an alternative method for the synthesis of unsymmetric thiosulfonates. In addition, the reaction could be scaled up on a gram scale, showing potential application value in industry.

Palladium-Catalyzed Desulfonative Carbonylation of Thiosulfonates: Elimination of SO2 and Insertion of CO

A palladium-catalyzed desulfonative carbonylation of thiosulfonates has been explored. Without any additive, a series of S-aryl/alkyl benzenesulfonothioates were successfully transformed to thioesters in moderate to excellent yields by SO₂ extrusion and CO insertion under the pressure of 1 bar of CO. The solvent dimethylacetamide (DMAc) facilitated this desulfonative carbonylation due to its high absorbing ability of SO₂.

PhICl2-Mediated Regioselective and Electrophilic Oxythio/Selenocyanation of o-(1-Alkynyl)benzoates: Access to Biologically Active S/SeCN-Containing Isocoumarins

The application of PhICl₂/NH₄SCN and PhICl₂/KSeCN reagent systems to the synthesis of the biologically active S/SeCN-containing isocoumarins via a process involving thio/selenocyanation, enabled by thio/selenocyanogen chloride generated in situ, followed with an intramolecular lactonization was realized. Gram-scale synthesis, further derivatization to access C4 thio/selenocyanated Xyridin A and anti-tumor activities of the obtained products highlight the potential use of this method.

Photoexcited sulfenylation of C(sp3)-H bonds in amides using thiosulfonates

A photoexcited sulfenylation of C(sp³)-H bonds in amides is developed for the synthesis of sulfenyl amides using thiosulfonates as a sulfur source. In the presence of easily available and inexpensive Na₂-eosin Y, TBHP and K₂CO₃, various sulfenyl amides can be obtained under the irradiation of blue light at room temperature.

Cyclic Thiosulfonates for Thiol-Mediated Uptake: Cascade Exchangers, Transporters, Inhibitors

Thiol-mediated uptake is emerging as a powerful method to penetrate cells. Cyclic oligochalcogenides (COCs) have been identified as privileged scaffolds to enable and inhibit thiol-mediated uptake because they can act as dynamic covalent cascade exchangers, i.e., every exchange produces a new, covalently tethered exchanger. In this study, our focus is on the essentially unexplored COCs of higher oxidation levels. Quantitative characterization of the underlying dynamic covalent exchange cascades reveals that the initial ring opening of cyclic thiosulfonates (CTOs) proceeds at a high speed even at a low pH. The released sulfinates exchange with disulfides in aprotic but much less in protic environments. Hydrophobic domains were thus introduced to direct CTOs into hydrophobic pockets to enhance their reactivity. Equipped with such directing groups, fluorescently labeled CTOs entered the cytosol of living cells more efficiently than the popular asparagusic acid. Added as competitive agents, CTOs inhibit the uptake of various COC transporters and SARS-CoV-2 lentivectors. Orthogonal trends found with different transporters support the existence of multiple cellular partners to account for the diverse expressions of thiol-mediated uptake. Dominant self-inhibition and high activity of dimers imply selective and synergistic exchange in hydrophobic pockets as distinguishing characteristics of thiol-mediated uptake with CTOs. The best CTO dimers with hydrophobic directing groups inhibit the cellular entry of SARS-CoV-2 lentivectors with an IC₅₀ significantly lower than the previous best CTO, below the 10 μM threshold and better than ebselen. Taken together, these results identify CTOs as an intriguing motif for use in cytosolic delivery, as inhibitors of lentivector entry, and for the evolution of dynamic covalent networks in the broadest sense, with reactivity-based selectivity of cascade exchange emerging as a distinguishing characteristic that deserves further attention.

Mechanism of GAPDH Redox Signaling by H2O2 Activation of a Two-Cysteine Switch

Oxidation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by reactive oxygen species such as H2O2 activate pleiotropic signaling pathways is associated with pathophysiological cell fate decisions. Oxidized GAPDH binds chaperone proteins with translocation of the complex to the nucleus and mitochondria initiating autophagy and cellular apoptosis. In this study, we establish the mechanism by which H2O2-oxidized GAPDH subunits undergo a subunit conformational rearrangement. H2O2 oxidizes both the catalytic cysteine and a vicinal cysteine (four residues downstream) to their respective sulfenic acids. A 'two-cysteine switch' is activated, whereby the sulfenic acids irreversibly condense to an intrachain thiosulfinic ester resulting in a major metastable subunit conformational rearrangement. All four subunits of the homotetramer are uniformly and independently oxidized by H2O2, and the oxidized homotetramer is stabilized at low temperatures. Over time, subunits unfold forming disulfide-linked aggregates with the catalytic cysteine oxidized to a sulfinic acid, resulting from thiosulfinic ester hydrolysis via the highly reactive thiosulfonic ester intermediate. Molecular Dynamic Simulations provide additional mechanistic insights linking GAPDH subunit oxidation with generating a putative signaling conformer. The low-temperature stability of the H2O2-oxidized subunit conformer provides an operable framework to study mechanisms associated with gain-of-function activities of oxidized GAPDH to identify novel targets for the treatment of neurodegenerative diseases.

"Green Is the Color": An Update on Ecofriendly Aspects of Organoselenium Chemistry

Organoselenium compounds have been successfully applied in biological, medicinal and material sciences, as well as a powerful tool for modern organic synthesis, attracting the attention of the scientific community. This great success is mainly due to the breaking of paradigm demonstrated by innumerous works, that the selenium compounds were toxic and would have a potential impact on the environment. In this update review, we highlight the relevance of these compounds in several fields of research as well as the possibility to synthesize them through more environmentally sustainable methodologies, involving catalytic processes, flow chemistry, electrosynthesis, as well as by the use of alternative energy sources, including mechanochemical, photochemistry, sonochemical and microwave irradiation.

Recent advances in thiolation via sulfur electrophiles

This review systematically summarizes the recent developments for constructing sulfur compounds from sulfur electrophiles, and the mechanism mainly involved thirranium ions, sulfur ylides, C–S cross coupling and electrophilic substitution.

Enantioselective [1,2]-Stevens Rearrangement of Thiosulfonates to Construct Dithio-Substituted Quaternary Carbon Centers

An enantioselective [1,2] Stevens rearrangement was realized by using chiral guanidine and copper(i) complexes. Bis-sulfuration of α-diazocarbonyl compounds was developed through using thiosulfonates as the sulfenylating agent. It was undoubtedly an atom-economic process providing an efficient route to access novel chiral dithioketal derivatives, affording the corresponding products in good yields (up to 90% yield) and enantioselectivities (up to 96 : 4 er). A novel catalytic cycle was proposed to rationalize the reaction process and enantiocontrol.

An asymmetric [1,2] Stevens rearrangement was realized via chiral guanidine and copper(i) complexes. A series of novel chiral dithioketal derivatives were obtained with good yields (up to 90% yield) and enantioselectivities (up to 96 : 4 er).

A new method for C(sp2)-H sulfonylmethylation with glyoxylic acid and sodium sulfinates

We herein describe a C4 sulfonylmethylation of pyrazol-5-amines with glyoxylic acid and sodium sulfinates. The reaction only needed to add water as the solvent, and it featured mild reaction condition,...

Synthesis of α-trifluoromethyl sulfides through fluorosulfuration of gem-difluoroalkenes

A new fluoro-sulfuration of gem-difluoroalkenes is demonstrated that occurs through a nucleophilic fluorination and subsequent interrupted electrophilic sulfuration cascade.

A Ni(ii)-catalyzed reductive cross-coupling reaction of oxalates and thiosulfonates/selenosulfonates

A Ni(ii)-catalyzed reductive cross-coupling reaction of oxalates and thiosulfonates/selenosulfonates to synthesize benzylic sulfides/selenides under mild conditions is developed.

Visible-Light-Induced Radical Cascade Reaction of 1-Allyl-2-ethynylbenzoimidazoles with Thiosulfonates to Assemble Thiosulfonylated Pyrrolo[1,2-a]benzimidazoles

A visible-light-induced radical domino reaction of 1-allyl-2-ethynylbenzoimidazoles with thiosulfonates was developed, which generated the thiosulfonylated pyrrolo[1,2-a]benzimidazoles in moderate to good yields. This reaction proceeded under transition-metal-free conditions with good functional group tolerance and high regioselectivity. The possible pathway involved thiosulfonates were activated through the energy transfer route promoted by photocatalysis.