Analysis of US FDA-Approved Drugs Containing Sulfur Atoms

Light-induced β-hydroxy sulfone synthesis in DNA-encoded libraries

We here describe a visible-light photooxidation of sulfinate salts with common alkenes to yield β-hydroxy sulfones on DNA. This process demonstrates a broad substrate compatibility and achieves conversion rates ranging from moderate to excellent. Most importantly, it presents a straightforward, efficient, and metal-free approach for synthesizing Csp3-rich DNA-encoded libraries.

Fluoride-Mediated Aryne 1,2-Difunctionalization Involving C═S Bond Heterolysis

We have successfully synthesized a series of bidentate ligands by utilizing 2-(trimethylsilyl)phenyl trifluorosulfonate as a precursor for the benzyl group. This method proceeded by inserting a polythiourea into the C═S π-bond, intramolecular ring proton migration, and ring opening. Salient features of this strategy are mild reaction conditions, a novel product structure, excellent stereochemistry, and a good functional group tolerance. Furthermore, a series of density functional theory calculations were performed to gain insights into the transfer mechanism.

Enantioselective Synthesis of Allylic Sulfones via Rhodium-Catalyzed Direct Hydrosulfonylation of Allenes and Alkynes

A highly regio- and enantioselective hydrosulfonylation using commercially available sodium sulfinates is reported, providing the first direct asymmetric rhodium-catalyzed hydrosulfonylation of allenes/alkynes to synthesize chiral allylic sulfones. Ligand screening studies demonstrated the indispensable role of the C1-symmetric P,N-ligand (Rax,S,S)-StackPhim for achieving both high regioselecitivity (>20:1) and enantioselectivity (up to 97% ee). Notably, the operationally simple method and mild conditions allow for the rapid preparation of chiral allylic sulfones with a wide scope of functional groups. Moreover, the use of sodium tert-butyldimethylsilyloxymethanesulfinate enables the collective synthesis of various chiral sulfone derivatives after simple transformations of the protected hydroxymethyl product.

Catalytic Asymmetric Synthesis of Sulfinamides via Cu-Catalyzed Asymmetric Addition of Aryl Boroxines to Sulfinylamines

The application of sulfinamides has been witnessed in medicinal and agrochemistry with employment in asymmetric transformations. However, methods for their asymmetric catalytic synthesis have rarely been explored. Herein, the catalytic enantioselective addition of aryl boroxines to sulfinylamines via Cu catalyst and the newly developed Xuphos ligand were reported. A series of chiral aryl sulfinamides can be readily accessed in one step. This protocol enables the stereospecific transformation of sulfinamides to sulfonimidoyl fluorides, sulfonimidamides, and sulfonimidate esters. DFT calculations have revealed the reaction pathway, and the migratory insertion is the enantio-determining step. The noncovalent interaction between the oxygen atom of sulfinylamines and the C-H bonds in the ligand is crucial for enantioselectivity control.

C(sp3)-H sulfinylation of light hydrocarbons with sulfur dioxide via hydrogen atom transfer photocatalysis in flow

Sulfur-containing scaffolds originating from small alkyl fragments play a crucial role in various pharmaceuticals, agrochemicals, and materials. Nonetheless, their synthesis using conventional methods presents significant challenges. In this study, we introduce a practical and efficient approach that harnesses hydrogen atom transfer photocatalysis to activate volatile alkanes, such as isobutane, butane, propane, ethane, and methane. Subsequently, these nucleophilic radicals react with SO2 to yield the corresponding sulfinates. These sulfinates then serve as versatile building blocks for the synthesis of diverse sulfur-containing organic compounds, including sulfones, sulfonamides, and sulfonate esters. Our use of flow technology offers a robust, safe and scalable platform for effectively activating these challenging gaseous alkanes, facilitating their transformation into valuable sulfinates.

Synthesis, Structural Characterization, and Biological Activities of 1,3,4- Thiadiazole Derivatives Containing Sulfonylpiperazine Structures

To develop novel bacterial biofilm inhibiting agents, a series of 1,3,4-thiadiazole derivatives containing sulfonylpiperazine structures were designed, synthesized, and characterized using 1H nuclear magnetic resonance (1H NMR), 13C nuclear magnetic resonance (13C NMR), and high-resolution mass spectrometry. Meanwhile, their biological activities were evaluated, and the ensuing structure-activity relationships were discussed. The bioassay results showed the substantial antimicrobial efficacy exhibited by most of the compounds. Among them, compound A24 demonstrated a strong efficacy with an EC50 value of 7.8 μg/mL in vitro against the Xanthomonas oryzae pv. oryzicola (Xoc) pathogen, surpassing commercial agents thiodiazole copper (31.8 μg/mL) and bismerthiazol (43.3 μg/mL). Mechanistic investigations into its anti-Xoc properties revealed that compound A24 operates by increasing the permeability of bacterial cell membranes, inhibiting biofilm formation and cell motility, and inducing morphological changes in bacterial cells. Importantly, in vivo tests showed its excellent protective and curative effects on rice bacterial leaf streak. Besides, molecular docking showed that the hydrophobic effect and hydrogen-bond interactions are key factors between the binding of A24 and AvrRxo1-ORF1. Therefore, these results suggest the utilization of 1,3,4-thiadiazole derivatives containing sulfonylpiperazine structures as a bacterial biofilm inhibiting agent, warranting further exploration in the realm of agrochemical development.

Catalytic Enantioselective Electrophilic Difunctionalization of Unsaturated Sulfones

An efficient protocol of enantioselective thiolative azidation of sulfone-tethered alkenes via a chiral chalcogenide catalyzed electrophilic reaction is disclosed. A series of enantioenriched sulfones bearing remote stereogenic centers was achieved with good yields and high enantioselectivities with linear unsaturated sulfones and cyclic unsaturated sulfones. Mechanistic studies revealed the importance of the sulfone group in the improvement of the reactivity and enantioselectivity of the reaction.

Unveiling the Use of 1,1-Bis(triflyl)ethylene as CF3SO2CH═CH2 Source with the Assistance of (n-Bu)4NF: Synthesis of 3-[(Trifluoromethyl)sulfonyl]cyclobut-1-enes

Allylic sulfone-embedded cyclobutenes have been prepared in one pot from alkynes. The carbocycle and the alkenyl sulfone moieties were installed through consecutive bis(triflyl)cyclobutenylation of a triple bond and tetra-n-butylammonium fluoride (TBAF)-assisted hydrodesulfonylation of an allylic bis(sulfone). It is noteworthy that 1,1-bis(triflyl)ethylene acts as a CF3SO2CH═CH2 source for the first time.

Iron-catalyzed benzylic C-H thiolation via photoinduced ligand-to-metal charge-transfer

Here, we describe an iron-catalyzed benzylic C-H thiolation of alkylarenes via photoinduced ligand-to-metal charge-transfer. The protocol features operational simplicity, mild reaction conditions, and the use of FeCl3 as catalyst and thiols/disulfides as sulfur sources, which enables the transformation of diverse benzylic C-H bonds into C-S bonds with a high efficiency.

Aminosulfonylation of Alkenes for the Synthesis of β-Amino Sulfone Derivatives

β-amino sulfones are important motifs found in natural products and active pharmaceutical compounds. Herein, we report a general and highly regioselective intermolecular aminosulfonylation of alkenes via the homolysis of sulfinyl oximes from ketoximes and sulfinyl chloride. This method features catalyst-free, step-efficient functionalization and prominent functional group tolerance, providing a straightforward, green, and widely applicable approach to accessing β-amino sulfone derivatives.

Organocatalytic skeletal reorganization for enantioselective synthesis of S-stereogenic sulfinamides

The enantioselective synthesis of S-stereogenic sulfinamides has garnered considerable attention due to their structural and physicochemical properties. However, catalytic asymmetric synthesis of sulfinamides still remains daunting challenges, impeding their broad application in drug discovery and development. Here, we present an approach for the synthesis of S-stereogenic sulfinamides through peptide-mimic phosphonium salt-catalyzed asymmetric skeletal reorganization of simple prochiral and/or racemic sulfoximines. This methodology allows for the facile access to a diverse array of substituted sulfinamides with excellent enantioselectivities, accommodating various substituent patterns through desymmetrization or parallel kinetic resolution process. Mechanistic experiments, coupled with density functional theory calculations, clarify a stepwise pathway involving ring-opening and ring-closing processes, with the ring-opening step identified as crucial for achieving stereoselective control. Given the prevalence of S-stereogenic centers in pharmaceuticals, we anticipate that this protocol will enhance the efficient and precise synthesis of relevant chiral molecules and their analogs, thereby contributing to advancements in drug discovery.

Lewis Acid-Catalyzed Formal [4 + 2] Reaction of Alkynyl Sulfides and 2-Pyrones To Access Polysubstituted Aryl Sulfides

A practical and efficient method to access polysubstituted aryl sulfides has been discovered via a Lewis acid-catalyzed reaction between alkynyl sulfide and 2-pyrone, involving a Diels-Alder/retro-Diels-Alder pathway. Alkynyl sulfide as an electron-rich dienophile and 2-pyrones as electron-poor dienes are conjunctively transformed into a series of polysubstituted aryl sulfides with broad functional group compatibility in good to excellent yields (40 examples, 43-88% yield). The robustness and practicality of the protocol has been demonstrated through gram-scale synthesis and the ease of transformation of the resulting products.

Innovative On-DNA Synthesis of Sulfides and Sulfoximines: Enriching the DEL Synthesis Toolbox

DNA-encoded library (DEL) technologies enable the fast exploration of gigantic chemical space to identify ligands for the target protein of interest and have become a powerful hit finding tool for drug discovery projects. However, amenable DEL chemistry is restricted to a handful of reactions, limiting the creativity of drug hunters. Here, we describe a new on-DNA synthetic pathway to access sulfides and sulfoximines. These moieties, usually contemplated as challenging to achieve through alkylation and oxidation, can now be leveraged in routine DEL selection campaigns.

Synthesis of Benzo[e][1,4,3]oxathiazin-3-one 1-Oxides from NH-S-(2-Hydroxyaryl)sulfoximines

Cyclizations of NH-S-(2-hydroxyaryl)sulfoximines with 1,1'-carbonyldiimidazol (CDI) give unprecedented benzo[e][1,4,3]oxathiazin-3-one 1-oxides in good yields. The standard synthetic protocol involves the use of DCE at an increased temperature for 16 h. Under mechanochemical conditions, a representative product was obtained without a solvent at ambient temperature in only 60 min. X-ray single-crystal structure analysis confirmed the molecular scaffold representing a three-dimensional heterocycle.

Navigating Antibacterial Frontiers: A Panoramic Exploration of Antibacterial Landscapes, Resistance Mechanisms, and Emerging Therapeutic Strategies

The development of effective antibacterial solutions has become paramount in maintaining global health in this era of increasing bacterial threats and rampant antibiotic resistance. Traditional antibiotics have played a significant role in combating bacterial infections throughout history. However, the emergence of novel resistant strains necessitates constant innovation in antibacterial research. We have analyzed the data on antibacterials from the CAS Content Collection, the largest human-curated collection of published scientific knowledge, which has proven valuable for quantitative analysis of global scientific knowledge. Our analysis focuses on mining the CAS Content Collection data for recent publications (since 2012). This article aims to explore the intricate landscape of antibacterial research while reviewing the advancement from traditional antibiotics to novel and emerging antibacterial strategies. By delving into the resistance mechanisms, this paper highlights the need to find alternate strategies to address the growing concern.

Copper-Catalyzed Sulfur Alkylation of Sulfenamides with N-Sulfonylhydrazones

Sulfilimines are valuable compounds in both organic synthesis and pharmaceuticals. In this study, we present a copper-catalyzed sulfur alkylation of sulfenamides with N-sulfonylhydrazones. In contrast to prior findings, hydrazones derived from aldehydes act as donor-type carbene precursors, effectively engaging in coupling with sulfenamides via a copper catalyst, demonstrating exclusive S selectivity. The utility of the protocol was highlighted in the rapid access to a wide range of sulfoximine derivatives.

Photocatalytic Thio/Selenosulfonylation-Bicyclization of Indole-Tethered 1,6-Enynes Leading to Substituted Benzo[c]pyrrolo[1,2,3-lm]carbazoles

The photocatalyzed radical-triggered thio/selenosulfonylation-bicyclization of indole-tethered 1,6-enynes has been established for the first time, enabling the synthesis of various previously unreported thio/selenosulfonylated benzo[c]pyrrolo[1,2,3-lm]carbazoles with moderate to good yields under mild conditions. The reaction pathway was proposed, consisting of energy transfer, homolytic cleavage, radical addition, 5-exo-dig, radical coupling, and a Mallory reaction cascade. This approach exhibits a wide substrate compatibility and excellent tolerability toward various functional groups and is characterized by its remarkable efficiency in both bond formation and annulation.

In-vitro and in-silico investigations of SLC-0111 hydrazinyl analogs as human carbonic anhydrase I, II, IX, and XII inhibitors

Two novel series of hydrazinyl-based benzenesulfonamides 9a-j and 10a-j were designed and synthesized using SLC-0111 as the lead molecule. The newly synthesized compounds were evaluated for their inhibitory activity against four different human carbonic anhydrase (hCA) isoforms I, II, IX, and XII. Both the series reported here were practically inactive against the off-target isozyme hCA I. Notably, derivative 10a exhibited superior potency (Ki of 10.2 nM) than acetazolamide (AAZ) against the cytosolic isoform hCA II. The hCA IX and XII isoforms implicated in tumor progression were effectively inhibited with Kis in the low nanomolar range of 20.5-176.6 nM and 6.0-127.5 nM, respectively. Compound 9g emerged as the most potent and selective hCA IX and XII inhibitor with Ki of 20.5 nM and SI of 200.1, and Ki of 6.0 nM and SI of 683.7, respectively, over hCA I. Furthermore, six compounds (9a, 9h, 10a, 10g, 10i, and 10j) exhibited significant inhibition toward hCA IX (Kis = 27.0, 41.1, 27.4, 25.9, 40.7, and 30.8 nM) relative to AAZ and SLC-0111 (Kis = 25.0 and 45.0 nM, respectively). These findings underscore the potential of these derivatives as potent and selective inhibitors of hCA IX and XII over the off-target hCA I and II.

Multimodal Acridine Photocatalysis Enables Direct Access to Thiols from Carboxylic Acids and Elemental Sulfur

Development of photocatalytic systems that facilitate mechanistically divergent steps in complex catalytic manifolds by distinct activation modes can enable previously inaccessible synthetic transformations. However, multimodal photocatalytic systems remain understudied, impeding their implementation in catalytic methodology. We report herein a photocatalytic access to thiols that directly merges the structural diversity of carboxylic acids with the ready availability of elemental sulfur without substrate preactivation. The photocatalytic transformation provides a direct radical-mediated segue to one of the most biologically important and synthetically versatile organosulfur functionalities, whose synthetic accessibility remains largely dominated by two-electron-mediated processes based on toxic and uneconomical reagents and precursors. The two-phase radical process is facilitated by a multimodal catalytic reactivity of acridine photocatalysis that enables both the singlet excited state PCET-mediated decarboxylative carbon-sulfur bond formation and the previously unknown radical reductive disulfur bond cleavage by a photoinduced HAT process in the silane-triplet acridine system. The study points to a significant potential of multimodal photocatalytic systems in providing unexplored directions to previously inaccessible transformations.

Unraveling the Potential of Vinyl Ether as an Ethylene Surrogate in Heteroarene C─H Functionalization via the Spin-Center Shift

Despite the simplicity and abundance of ethylene, its practical application presents significant hurdles due to its nature as a highly flammable gas. Herein, a strategic use of easily handled vinyl ether is reported as a latent ethylene surrogate achieved via a spin-center shift (SCS) pathway, enabling the successful three-component reaction that bridges heteroarenes and various coupling partners, including sulfinates, thiols, and phosphine oxides. Through a photoredox catalytic process, α-oxy radicals are generated by combining various radicals with phenyl vinyl ether, which are subsequently added to N-heteroarenes. Subsequently, the radical-mediated SCS pathway serves as the driving force for C─O bond cleavage, effectively engaging the phenoxy group as a leaving group. In addition, by broadening the utility of the method, a valuable synthon is provided for efficient C─H vinylation of N-heteroarenes following sulfonyl group elimination. This approach not only enriches the toolbox of synthetic methodology but also provides a more streamlined alternative, circumventing the challenges associated with direct ethylene gas usage. The versatility of the method, particularly evident in late-stage functionalizations of medicinally relevant molecules and peptides, underscores its capability to produce invaluable three-component compounds and vinylated N-heteroarene derivatives.

Photoinduced decatungstate-catalyzed C(sp3)-H thioetherification by sulfinate salts

Thiols and thioesters play crucial roles in pharmaceuticals, biology, and material science as essential organosulfur compounds. Leveraging readily available and cost-effective inert alkanes through direct thioetherification holds promise for yielding high-value-added products. Herein, we present a photoinduced strategy for sulfur-containing modification of inert alkanes utilizing decatungstate as hydrogen atom transfer reagent, offering a straightforward and practical approach for synthesizing thioethers and thioesters.

De novo development of small cyclic peptides that are orally bioavailable

Cyclic peptides can bind challenging disease targets with high affinity and specificity, offering enormous opportunities for addressing unmet medical needs. However, as with biological drugs, most cyclic peptides cannot be applied orally because they are rapidly digested and/or display low absorption in the gastrointestinal tract, hampering their development as therapeutics. In this study, we developed a combinatorial synthesis and screening approach based on sequential cyclization and one-pot peptide acylation and screening, with the possibility of simultaneously interrogating activity and permeability. In a proof of concept, we synthesized a library of 8,448 cyclic peptides and screened them against the disease target thrombin. Our workflow allowed multiple iterative cycles of library synthesis and yielded cyclic peptides with nanomolar affinities, high stabilities and an oral bioavailability (%F) as high as 18% in rats. This method for generating orally available peptides is general and provides a promising push toward unlocking the full potential of peptides as therapeutics.

NBS-Promoted Synthesis of Thiocyanated Aminomaleimides and Site-Selective Intramolecular Cyclization Access to 1,4-Benzothiazepines via S-CN Bond Cleavage

A transition metal-free concise and efficient protocol for the synthesis of thiocyanated aminomaleimides and benzo[e][1,4]thiazepine derivatives has been developed. The method involves an initial α-C-H thiocyanation of aminomaleimides with KSCN and TEMPO-mediated tandem S-CN bond cleavage/intramolecular cyclization substitution processes, which enables the formation of seven-membered S/N-heterocycles. This synthetic strategy provides a reliable method for the synthesis of biologically interesting benzo[e][1,4]thiazepine derivatives by using KSCN as sulfur sources as well as expands the application of enaminones thiocyanation reactions in heterocycles synthesis.

Iodine-Promoted Reductive Sulfenylation Using Ketones as Hydride Donors

Herein, an iodine-promoted reductive sulfenylation reaction of ketones with disulfides has been developed. This method provides an approach for synthesizing unsymmetrical alkyl-alkyl and alkyl-aryl sulfides in a single step. Investigation of the reaction mechanism revealed that ketones play a dual role in this process. They react with disulfides to produce vinyl thioethers and act as effective organic hydride donors, reducing the number of vinyl thioethers that are formed in situ. This study expands the range of applications of ketones in chemical synthesis.

Asymmetric Sulfonylation from a Reaction of Cyclopropan-1-ol, Sulfur Dioxide, and 1-(Alkynyl)naphthalen-2-ol

Asymmetric sulfonylation from a reaction of cyclopropan-1-ol, sulfur dioxide, and 1-(alkynyl)naphthalen-2-ol in the presence of a catalytic amount of organocatalyst at room temperature is developed. Axially chiral (S)-(E)-1-(1-(alkylsulfonyl)-2-arylvinyl)naphthalen-2-ols are generated in moderate to good yields with excellent enantioselectivity and regioselectivity under mild conditions. During this transformation, γ-keto sulfinate generated in situ from cyclopropan-1-ol and sulfur dioxide acts as the key intermediate.

Synthesis of alkynyl sulfides via base-promoted nucleophilic ring-opening of α-bromostyrene sulfonium salt

An efficient method for the synthesis of alkynyl sulfides via a C(sp3)-S bond cleavage of α-bromostyrene sulfonium salts has been developed. This base-promoted nucleophilic ring-opening pathway allows the preparation of diverse alkynyl sulfide compounds using tetramethylene sulfoxide as the sulfur source. The reaction proceeds with good functional group tolerance and could be applied to the late-stage functionalization of bioactive molecules and drugs. Furthermore, the synthetic utility of this method was demonstrated by a one-pot synthesis, scale-up reaction and further modification of various alkynyl sulfide products.

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.

Pushing Boundaries: What's Next in Metal-Free C-H Functionalization for Sulfenylation?

The synthesis of thioether derivatives has been explored widely due to the potential application of these derivatives in medicinal chemistry, pharmaceutical industry and material chemistry. Within this context, there has been an increasing demand for the environmentally benign construction of C-S bonds via C-H functionalization under metal-free conditions. In the present article, we highlight recent developments in metal-free sulfenylation that have occurred in the past three years. The synthesis of organosulfur compounds via a metal-free approach using a variety of sulfur sources, including thiophenols, disulfides, sulfonyl hydrazides, sulfonyl chlorides, elemental sulfur and sulfinates, is discussed. Non-conventional strategies, which refer to the development of thioether derivatives under visible light and electrochemically mediated conditions, are also discussed. The key advantages of the reviewed methodologies include broad substrate scope and high reaction yields under environmentally benign conditions. This comprehensive review will provide chemists with a synthetic tool that will facilitate further development in this field.

Rh(III)-Catalyzed Diastereo- and Enantioselective Regiodivergent (Hetero)Arylamidation of (Homo)Allylic Sulfides

A rhodium-catalyzed 3-component conjunctive diastereo- and regioselective arylamidation of (homo)allylic sulfides, organon boronic acids, and dioxazolones is reported. These reactions deliver the 1,2-insertion and 2,1-insertion arylamidation products, respectively, for allylic sulfides and homoallylic sulfides. The enantioselective arylamidation of terminal and internal allylic sulfides is achieved, furnishing various 1,3-N,S compounds featuring one or two contiguous stereocenters in high yields and with high diastereo- and enantioselectivities. Mechanistic studies suggest a change in the turnover-limiting and selectivity-determining steps induced by the native and easily removable sulfide group.

Platform for Multiple Isotope Labeling via Carbon-Sulfur Bond Exchange

In this work, we explore a nickel-catalyzed reversible carbon-sulfur (C-S) bond activation strategy to achieve selective sulfur isotope exchange. Isotopes are at the foundation of applications in life science, such as nuclear imaging, and are essential tools for the determination of pharmacokinetic and dynamic profiles of new pharmaceuticals. However, the insertion of an isotope into an organic molecule remains challenging, and current technologies are element-specific. Despite the ubiquitous presence of sulfur in many biologically active molecules, sulfur isotope labeling is an underexplored field, and sulfur isotope exchange has been overlooked. This approach enables us to move beyond standardized element-specific procedures and was applied to multiple isotopes, including deuterium, carbon-13, sulfur-34, and radioactive carbon-14. These results provide a unique platform for multiple isotope labeling and are compatible with a wide range of substrates, including pharmaceuticals. In addition, this technology proved its potential as an isotopic encryption device for organic molecules.

Intramolecular Friedel-Crafts Reaction with Trifluoroacetic Acid: Synthesizing Some New Functionalized 9-Aryl/Alkyl Thioxanthenes

In this study, a series of halogen-substituted thioxanthenes were synthesized because the most important and biologically active derivatives of xanthenes are thioxanthenes. In order to obtain new thioxanthene derivatives, first, the starting molecules were synthesized by the appropriate reaction methods in two steps. The intramolecular Friedel-Crafts alkylation (FCA) method was used to convert the prepared three aromatic substituted starting alcohol compounds to their corresponding thioxanthenes by cyclization. For the intramolecular FCA reaction of secondary alcohols, which are the starting compounds (1a-1t), organic Bro̷nsted acids, which require more innovative, easier, and suitable reaction conditions, were used instead of halide reagents with corrosive effects as classical FCA catalysts. Trifluoroacetic acid was determined to be the organocatalyst with the best yield. Therefore, some original 9-aryl/alkyl thioxanthene derivatives (2a-2t) were synthesized using the optimized FCA method. In addition, a new sulfone derivative of thioxanthene 3i was prepared by performing the oxidation reaction with one of the obtained new thioxanthene 2i. Thioxanthenes and their derivatives are important heterocyclic structures that contain pharmacologically valuable sulfur and are used in the treatment of psychotic diseases such as Alzheimer's or schizophrenia, as well as a number of potent biological activities.

N-Heterocyclic Carbene-Catalyzed Facile Synthesis of Phthalidyl Sulfonohydrazones: Density Functional Theory Mechanistic Insights and Docking Interactions

N-heterocyclic carbene catalysis reaction protocol is disclosed for the synthesis of phthalidyl sulfonohydrazones. A broad range of N-tosyl hydrazones react effectively with phthalaldehyde derivatives under open-air conditions, enabling the formation of a new C-N bond via an oxidative path. The reaction proceeds under mild reaction conditions with broad substrate scopes, wide functional group tolerance, and good to excellent yields. The mechanistic pathway is studied successfully using control experiments, competitive reactions, ESI-MS spectral analyses of the reaction mixture, and computational study by density functional theory. The potential use of one of the phthalidyl sulfonohydrazone derivatives as the inhibitor of β-ketoacyl acyl carrier protein synthase I of Escherichia coli is investigated using molecular docking.

Chemoselective Heterogeneous Hydrogenation of Sulfur Containing Quinolines under Mild Conditions

Sulfur, alongside oxygen and nitrogen, holds a prominent position as one of the key heteroatoms in nature and medicinal chemistry. Its significance stems from its ability to adopt different oxidation states, rendering it valuable as both a polarity handle and a hydrogen bond donor/acceptor. Nevertheless, the poisonous nature of its free electron pairs makes sulfur containing substrates inaccessible for many catalytic protocols. Strong and (at low temperatures) irreversible chemisorption to the catalyst's surface is in particular detrimental for heterogeneous catalysts, possessing only few catalytically active sites. Herein, we present a novel heterogeneous Ru-S catalyst that tolerates multiple sulfur functionalities, including thioethers, thiophenes, sulfoxides, sulfones, sulfonamides, and sulfoximines, in the hydrogenation of quinolines. The utility of the products was further demonstrated by subsequent diversifications of the sulfur functionalities.

Enantioselective Synthesis of Planar-Chiral Sulfur-Containing Cyclophanes by Chiral Sulfide Catalyzed Electrophilic Sulfenylation of Arenes

An efficient catalytic asymmetric electrophilic sulfenylation reaction for the synthesis of planar-chiral sulfur-containing cyclophanes has been developed for the first time. This was achieved by using a new Lewis base catalyst and a new ortho-trifluoromethyl-substituted sulfenylating reagent. Using the substrates with low rotational energy barrier, the transformation proceeded through a dynamic kinetic resolution, and the high rotational energy barrier of the substrates allowed the reaction to undergo a kinetic resolution process. Meanwhile, this transformation was compatible with a desymmetrization process when the symmetric substrates were used. Various planar-chiral sulfur-containing cyclophanes were readily obtained in moderate to excellent yields with moderate to excellent enantioselectivities (up to 97 % yield and 95 % ee). This approach was used to synthesize pharmaceutically relevant planar-chiral sulfur-containing molecules. Density functional theory calculations showed that π-π interactions between the sulfenyl group and the aromatic ring in the substrate play a crucial role in enantioinduction in this sulfenylation reaction.

Base-Promoted Ring-Opening Hydroxylation of Cyclic Sulfonium Salts

Herein, we reported a general strategy for the synthesis of sulfur-containing primary alcohol derivatives by base-promoted ring-opening hydroxylation of cyclic sulfonium salts. A variety of sulfonium salts were successfully transformed into the desired hydroxylated products in moderate to excellent yields with good functional group tolerance. Moreover, the one-pot synthesis, scale-up reaction, and late-stage functionalization of complex molecules demonstrated the practicability of this synthetic protocol in the field of synthetic chemistry.

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.

Lewis acid-catalyzed one-pot thioalkenylation of donor-acceptor cyclopropanes using in situ generated dithiocarbamates and propiolates

Lewis acid-catalyzed one-pot 1,3-thioalkenylation of donor-acceptor (D-A) cyclopropanes has been demonstrated employing in situ generated dithiocarbamates (from amines and CS2) as nucleophilic triggers and alkyl propiolates as electrophiles. This method addresses the limitations of previously known carbothiolation approach, eliminating the need for extra filtration prior to the subsequent trapping with electrophiles. The anticipated thioalkenylated products were obtained in good to excellent yields with a moderate to good E/Z ratio. Three new bonds (C-N, C-S, and C-C) are formed during this 1,3-bisfunctionalization reaction. Notably, employing enantiomerically pure D-A cyclopropanes resulted in enantiopure 1,3-thioalkenylated products, underscoring the stereospecific nature of the developed reaction.

Construction of C-S and C-Se Bonds from Unstrained Ketone Precursors under Photoredox Catalysis

A mild photoredox catalyzed construction of sulfides, disulfides, selenides, sulfoxides and sulfones from unstrained ketone precursors is introduced. Combination of this deacylative process with SN 2 or coupling reactions provides novel and convenient modular strategies toward unsymmetrical or symmetric disulfides. Reactivity studies favor a bromine radical that initiates a HAT (Hydrogen Atom Transfer) from the aminal intermediate resulting in expulsion of a C-centered radical that is intercepted to make C-S and C-Se bonds. Gram scale reactions, broad substrate scope and tolerance towards various functional groups render this method appealing for future applications in the synthesis of organosulfur and selenium complexes.

Photochemical Organocatalytic Synthesis of Thioethers from Aryl Chlorides and Alcohols

Thioethers, often found in pharmaceuticals and natural compounds, typically involve metal cross-coupling reactions, high temperatures, and the use of disagreeable thiols for their synthesis. Here we present a straightforward, thiol-free organocatalytic protocol that uses mild conditions to stitch together inexpensive alcohols and aryl chlorides, yielding a diverse array of aryl alkyl thioethers. Central to this approach was the discovery that tetramethylthiourea can serve as a simple sulfur source upon intercepting photochemically generated aryl radicals. To form radicals, we used a readily available indole thiolate organocatalyst that, when excited with 405 nm light, gained a strongly reducing power, enabling the activation of typically unreactive aryl chlorides via single-electron transfer. Radical trapping by the thiourea, followed by an alcohol attack via a polar path, resulted in the formation of thioether products.

Nitro-sulfinate Reductive Coupling to Access (Hetero)aryl Sulfonamides

A method to assemble (hetero)aryl sulfonamides via the reductive coupling of aryl sulfinates and nitroarenes is reported. Various reducing conditions with sodium bisulfite and with or without tin(II) chloride in DMSO were developed using an ultrasound bath to improve reaction homogeneity and mixing. A range of (hetero)aryl sulfonamides bearing a selection of functional groups were prepared, and the mechanism of the transformation was investigated. These investigations have led us to propose the formation of nitrosoarene intermediates, which were established via an independent molecular coupling strategy.

Asymmetric synthesis of sulfoximines, sulfonimidoyl fluorides and sulfonimidamides enabled by an enantiopure bifunctional S(VI) reagent

An increased interest to expand three-dimensional chemical space for the design of new materials and medicines has created a demand for isosteric replacement groups of commonly used molecular functionality. The structural and chemical properties of chiral S(VI) functional groups provide unique spatial and electronic features compared with their achiral sulfur- and carbon-based counterparts. Manipulation of the S(VI) centre to introduce structural variation with stereochemical control has remained a synthetic challenge. The stability of sulfonimidoyl fluorides and the efficiency of sulfur fluorine exchange chemistry has enabled the development of the enantiopure bifunctional S(VI) transfer reagent t-BuSF to overcome current synthetic limitations. Here, we disclose a reagent platform that serves as a chiral sulfur fluorine exchange template for the rapid asymmetric synthesis of over 70 sulfoximines, sulfonimidoyl fluorides and sulfonimidamides with excellent enantiomeric excess and good overall yields. Furthermore, the practical utility of the bifunctional S(VI) transfer reagent was demonstrated in the syntheses of enantiopure pharmaceutical intermediates and analogues.

The vinyl sulfone motif as a structural unit for novel drug design and discovery

INTRODUCTION

Vinyl sulfones are a special sulfur-containing structural unit that have attracted considerable attention, owing to their important role in serving as key structural motifs of various biologically active compounds as well as serving as versatile building blocks for organic transformations. The synthetic strategy of vinyl sulfone derivatives has been substantially upgraded over the past 30 years, and the wide application of this functional group in drug design and discovery has been promoted.

AREA COVERED

In this review, the authors review the application of vinyl sulfones in drug discovery and select optimized compounds which might have significant impact or potential inspiration for drug design.

EXPERT OPINION

Vinyl sulfones have been reported to target various macromolecular targets via non-covalent or covalent interactions, including multiple kinases, tubulin, cysteine protease, transcription factor, and so on. Thus, it has been significantly applied as a privileged scaffold in the design of anticancer, anti-infective, anti-inflammatory, and neuroprotective agents. However, much work remains to be done to improve the drug-like properties, such as chemical and metabolic stability, ADME, and toxicity. Besides, the chemical space of vinyl sulfones needs to be expanded, including but not limited to the design of constrained endocyclic and exocyclic vinyl sulfones.

A General Platform for Visible Light Sulfonylation Reactions Enabled by Catalytic Triarylamine EDA Complexes

Catalytic electron donor-acceptor (EDA) complexes have recently emerged as a powerful and sustainable alternative to iridium- and ruthenium-based photoredox synthetic methods. Yet, these complexes remain underexplored and reliant on the use of meticulously designed acceptors that require previous installation. Herein, we report a novel EDA complex employing tris(4-methoxyphenyl) amine as a catalytic donor for the sulfonylation of alkenes using inexpensive and readily available sulfonyl chlorides. Applying this operationally simple, visible-light-mediated general platform, we report both the redox-neutral and net-reductive functionalization of more than 60 substrates, encompassing vinylic or allylic sulfonylation, hydrosulfonylation, and sulfamoylation of activated and unactivated alkenes and alkynes.

Visible-Light-Induced Decarboxylative Aminosulfonylation of (Hetero)aryl Carboxylic Oxime Esters

Sulfonamides are important structures in pharmaceuticals, agrochemicals, and organocatalysts, yet the rapid and benign synthesis of these compounds is still a great challenge. Herein we report a photoinduced method for synthesizing sulfonamides from (hetero)aryl carboxylic acid oxime esters. This reaction proceeds via one-pot cascade radical-radical cross-coupling by energy-transfer-mediated photocatalysis. A wide substrate scope including (hetero)aryl substrates and late-stage modification of pharmaceutical molecular entities reveal its generality.

Organophotocatalyzed Alkyl/Arylsulfonylation of Vinylcyclopropanes

Allyl sulfones are an essential pharmacophore in many bioactive compounds. To combat their synthetic barrier, we report a practical, straightforward organophotocatalyzed methodology for accessing miscellaneously functionalized allyl sulfone derivatives using inexpensive and bench-stable sodium sulfinate salts under mild conditions. This photo-catalyzed radical sulfonylation provides access to a variety of allyl sulfones in good to excellent yields with high E : Z selectivity. A wide range of vinyl cyclopropanes, as well as aryl/hetero and alkyl sodium sulfinates, were tolerated and reliable in gram-scale synthesis. Later on, further functionalization of allyl sulfones was demonstrated. A plausible mechanism for radical sulfonylation is proposed from the control experiments.

Advances in Difunctionalization of Olefins with Diorganyl Dichalcogenides

Organochalcogen molecules have extensive applications in various fields. They serve as pharmaceuticals, ligands, organocatalysts, agrochemicals, and other functional materials. Difunctionalization of olefins, which belong to a class of multicomponent reactions, is a successful technique for introducing two functional moieties in a single-step reaction, both in terms of atom economy and step economy. The difunctionalization of olefins with diorganyl dichalcogenides may effectively increase the molecular complexity, which has achieved significant advancements in recent decades. This article describes recent advancements in the difunctionalization of olefins with diorganyl diselenides and diorganyl disulfides.

Simultaneous Preparation of Sulfides/Selenides and Sulfones via Synergistic Nickel-Catalyzed Reductive Coupling and SN2 Reaction

Sulfone compounds and thioether compounds are two highly valuable classes of compounds, but it is challenging to prepare sulfone and thioether compounds simultaneously and efficiently. Here we report that sulfides/selenides and sulfones can be obtained simultaneously using allyl bromide/benzyl bromide-activated alkyl bromides and thiosulfonates/selenosulfonates using a nickel-catalyzed reductive coupling and SN2 synergistic strategy, which is characterized by excellent atom and step economy, mild reaction conditions, broad functional group compatibility, and excellent yields.

Formation of C-B, C-C, and C-X Bonds from Nonstabilized Aryl Radicals Generated from Diaryl Boryl Radicals

With the development of organoboron chemistry, boron-centered radicals have become increasingly attractive. However, their synthetic applications remain limited in that they have been used only as substrates for addition reactions or as initiators for catalytic reactions. We have achieved a new reaction pathway in which tetraarylborate salts are used as precursors for aryl radicals via boron radicals, by introducing a simple activation reagent. In addition, we carried out a diverse array of transformations involving these aryl radical precursors, which allowed the construction of new C-B, C-C, and C-X bonds in the presence of visible light.

Copper-Catalyzed Remote Enantioselective Sulfonylation of Yne-Allylic Esters with Sodium Sulfinates

Impressive progress has been made in the copper-catalyzed asymmetric propargylic substitution (APS) reaction, but its use in remote asymmetric yne-allylic substitution remains a challenging topic. Herein, we report the first remote enantioselective copper-catalyzed sulfonylation of yne-allylic esters with sodium sulfinates. The reaction is assumed to occur via a copper-vinylvinylidene species as the key reactive intermediate. The use of readily available starting materials, the mild reaction conditions, and the excellent regio-, enantio- and stereoselectivity, as well as broad substrate scope (>70 examples), show the practicality and attractiveness of this method.

Nickel-Catalyzed Enantioselective Synthesis of Dienyl Sulfoxide

Sulfoxides are widely used in the pharmaceutical industry and as ligands in asymmetric catalysis. However, the efficient asymmetric synthesis of this structural motif remains limited. In this study, we disclosed a Ni-catalyzed enantioconvergent reaction that utilizes both racemic allenyl carbonates and β-sulfinyl esters. Our method employs cheap and more sustainable Ni(II) as a precatalyst and successfully overcomes the challenging poisoning effect and instability of sulfenate generated in situ. This enables the synthesis of a series of dienyl sulfoxides with enantioselectivity of up to 98 % ee. The product exhibits tremendous potential in various applications, including diastereoselective Diels-Alder reactions, coordination with transition metals, and incorporation into medicinal compounds, among others. Using a combination of experimental and computational methods, we have uncovered an interesting associated outersphere mechanism that contrasts with conventional mechanisms commonly observed in asymmetric transition metal catalysis.