Sulfur-Arylation of Sulfenamides via Ullmann-Type Coupling with (Hetero)aryl Iodides

Heteroarylation of Sulfenamides for Modular Synthesis of Antimicrobial Sulfilimines via Sulfinimidoyl Fluoride Intermediates

We herein disclose a mild metal-free strategy for the construction of heteroaryl-derived sulfilimines. Central to this approach is the in situ generated sulfinimidoyl fluoride intermediate that exhibits an optimal balance of reactivity and stability for efficient S(IV)-derived SuFEx reactions with heteroarenes without Lewis acids or base additives. This protocol enables the rapid incorporation of a broad range of heteroarenes to afford diverse sulfilimine scaffolds with potent antimicrobial activities against plant pathogens.

Visible-Light-Mediated Copper-Catalyzed S-Arylation of Sulfenamides with Aryl Thianthrenium Salts

The site-selective incorporation of sulfilimine functionalities into aromatic compounds provides a vital strategy for drug discovery in medicinal chemistry. However, green and sustainable methods for realizing the goal are still limited. Here, we report a copper-catalyzed S-arylation of sulfenamides with aryl thianthrenium salts irradiated by visible light without the photocatalyst, which exhibited fine functional-group compatibility and gave the desired products in high yields. Mechanistic investigations revealed that the key to achieving these results is the generation of an electron donor-acceptor (EDA) complex between sulfenamides and aryl thianthrenium salts under basic conditions.

Cu-Catalyzed Enantioselective S-Arylation of Sulfenamides Enabled by Confined Ligands

Chiral sulfilimines, aza analogues of sulfoxides, are essential in natural products and pharmaceuticals, highlighting the importance of their synthesis in asymmetric catalysis. However, efficient approaches for synthesizing chiral diaryl sulfilimines are still rare and challenging, particularly for those with two sterically similar aryl groups. Herein, we present a mild and efficient protocol for generating diverse enantioenriched diaryl and aryl alkyl sulfilimines via copper-catalyzed enantioselective S-arylation of N-acyl sulfenamides with diaryliodonium salts. A bulky PyBox ligand is crucial for stereocontrol, delivering various sulfilimines with up to 95% ee (51 examples).

Assembly of (Hetero)aryl Sulfoximines via Copper-Catalyzed S-Arylation of Sulfinamides with (Hetero)aryl Halides

The combination of CuI and 4-(dimethylamino)picolinamide offers an effective catalytic system for the successful coupling of (hetero)aryl halides (I and Br) with sulfinamides for the first time. A large number of functional groups and heterocycles were tolerated under the coupling conditions, providing a powerful approach for diverse synthesis of pharmaceutically important (hetero)aryl sulfoximines. The efficiency of the coupling reaction was highly dependent upon the electronic nature of (hetero)aryl halides and the substituents at the amide part of sulfinamides. By using enantioenriched sulfinamides as the coupling partners, the reaction proceeds in a highly stereospecific manner to afford (hetero)aryl sulfoximines with excellent enantioselectivity.

Sulfilimines from a Medicinal Chemist's Perspective: Physicochemical and in Vitro Parameters Relevant for Drug Discovery

While sulfoximines are nowadays a well established functional group for medicinal chemistry, the properties of sulfilimines are significantly less well studied, and no sulfilimine has progressed to the clinic to date. In this account, the physicochemical and in vitro properties of sulfilimines are reported and compared to those of sulfoximines and other more traditional functional groups. Furthermore, the impact on the physicochemical and in vitro properties of real drug scaffolds is studied in two series of sulfilimine-containing analogs of imatinib and hNE inhibitors. We show that sulfilimines can be chemically and configurationally stable under physiologically relevant conditions and that they are basic and highly polar and thus are often beneficial for solubility and metabolic stability, although at the cost of reduced permeability. We conclude that S-cyclopropyl,S-(hetero)aryl and S,S-di(hetero)aryl sulfilimines are so far neglected but potentially valuable S(IV) based pharmacophores that deserve to be considered as part of the medicinal chemistry toolbox.

Nitrene-mediated glycosylation with thioglycoside donors under metal catalysis

Glycosylation chemistry plays a pivotal role in glycoscience. Recent substantial developments have poised the field to address emerging challenges related to sustainability, cost efficiency, and robust applicability in complex substrate settings. The transition from stoichiometric activation to metal-catalyzed methods promises enhanced chemoselectivity and greater precision in controlling glycosidic bond breakage and formation, key to overcoming existing obstacles. Here, we report a nitrene-mediated glycosylation strategy using regular aryl sulfide glycosyl donors and easily accessible 3-methyl dioxazolone as an activator under the catalysis of iron or ruthenium. The iron-catalyzed system demonstrates exceptional catalytic reactivity, requiring as little as 0.1 mole % of catalyst at room temperature, and works well for complex peptide substrates. The ruthenium-catalyzed system can accommodate acid-sensitive functional groups and challenging low-reactivity acceptors. Mechanistic investigations have unveiled unusual multistep pathways involving sulfur imidation of sulfide donors via nitrene transfer and sulfur-to-oxygen rearrangement of N-acyl sulfilimines for the nitrene-mediated activation of sulfide donors.

Asymmetric Catalytic Synthesis of Allylic Sulfenamides from Vinyl α-Diazo Compounds by a Rearrangement Route

The asymmetric rearrangement of allylic sulfilimines is an effective route to synthetically attractive targets, such as allylic sulfenamides. The current methods are limited to chirality transfer from chiral allylic sulfilimine precursors. Herein, we report a general and fundamentally new rearrangement route to access optically enriched allylic sulfenamides and their derivatives. The process involves S-alkylation and an unusual S-to-N rearrangement step. A chiral nickel complex enables the transformation of a broad scope of sulfenamides and vinyl α-diazo pyrazoleamides under mild conditions. Various allylic sulfenamides have been synthesized with excellent γ-regioselectivity and enantioselectivity, and can be efficiently converted into sulfinamide and 4-aminobutenoic acid derivatives. In addition, DFT calculations demonstrate the connection between the spin state and conformation of the nickel vinyl carbenoid, as well as an unknown rearrangement process.

Base-Promoted Sulfur Arylation of Sulfenamides to Oxonium Aryne Precursors: Chemoselective Synthesis of Sulfilimines and o-Sulfanylanilines

In this study, a metal-free and efficient method for the synthesis of sulfilimines and o-sulfanylanilines in high yields with excellent chemoselectivities from oxonium aryne precursors with sulfenamides has been developed. This method features mild reaction conditions, simple operations, a general substrate scope, and good tolerance of functional groups. In addition, scale-up synthesis, related applications, and preliminary mechanistic explorations were also investigated.

Synthesis of Sulfinamidines via Iron-Catalyzed Nitrene Transfer Reaction with Sulfenamides

An iron-catalyzed nitrene transfer reaction for the rapid synthesis of sulfinamidines from readily available sulfenamides is reported. This method features mild conditions, short reaction times, and a broad substrate scope, allowing the preparation of a variety of sulfinamidines in good to excellent yields. The synthetic utility of the sulfinamidine products was further demonstrated through their conversion to other valuable sulfur(VI) compounds, such as sulfondiimidoyl fluorides, sulfinamidiate esters, and sulfonimidamides. Preliminary efforts in the development of an asymmetric variant showed moderate enantioselectivity.

Identification of O-arylated huperzinines as novel cholinergic anti-inflammatory pathway agonists against gout arthritis

Lycodine alkaloids are important natural products with diverse biological effects. In this manuscript, we set out the first structural optimization of the 2-pyridone moiety of Lycodine alkaloid via selective O-arylation under metal-free conditions and obtained a series of potent bioactive molecules against monosodium urate (MSU)-induced IL-1β production. Further investigations demonstrated that these natural product derivatives could activate the neuro-immunomodulatory cholinergic anti-inflammatory pathway (CAP) to block the initial phase of NLRP3 inflammasome activation. Compared with the clinical drugs hydrocortisone and indomethacin, as well as commercially available CAP agonists GTS-21 and pnu282987, 3k and 3q possessed greater potency against MSU-induced IL-1β production. Meanwhile, these molecules possessed less cytotoxicity against promonocytic THP-1 macrophages when compared with colchicine. This work reports a concise strategy for direct modification of 2-pyridone moiety from natural Lycodine alkaloids, and provides novel frameworks for discovering CAP activators and drugs for gout arthritis.

Ligand-Enabled Copper-Catalyzed Ullmann-Type S-C Bond Formation to Access Sulfilimines

A copper-catalyzed Ullmann-type cross-coupling reaction of sulfenamides with aryl iodides is developed. The key to success is the use of a 2-methylnaphthalen-1-amine-derived amide ligand, which enables the formation of an S-C bond to access functionalized sulfilimines in good to excellent yields at room temperature. This method has the advantages of mild conditions, a broad substrate scope, good functional group compatibility, and high chemoselectivity. The utility of this protocol is highlighted through late-stage modification of drug-relevant molecules and sulfilimine product derivatization.

Synthesis of chiral sulfilimines by organocatalytic enantioselective sulfur alkylation of sulfenamides

Sulfilimines are versatile synthetic intermediates and important moieties in bioactive molecules. However, their applications in drug discovery are underexplored, and efficient asymmetric synthetic methods are highly desirable. Here, we report a transition metal-free pentanidium-catalyzed sulfur alkylation of sulfenamides with exclusive chemoselectivity over nitrogen and high enantioselectivity. The reaction conditions were mild, and a wide range of enantioenriched aryl and alkyl sulfilimines were obtained. The synthetic utility and practicability of this robust protocol were further demonstrated through gram-scale reactions and late-stage functionalization of drugs.

Synthesis of Sulfilimines via Visible-Light-Mediated Triplet Energy Transfer to Sulfonyl Azides

Sulfilimines and their derivatives have garnered considerable interest in both synthetic and medicinal chemistry. Photochemical nitrene transfer to sulfides is known as a conventional synthetic approach to sulfilimines. However, the existing methods have a limited substrate scope stemming from the incompatibility of singlet nitrene intermediates with nucleophilic functional groups. Herein, we report the synthesis of N-sulfonyl sulfilimines via visible-light-mediated energy transfer to sulfonyl azides, uncovering the previously overlooked reactivity of triplet nitrenes with sulfides. This reaction features broad functional group tolerance, water compatibility, and amenability to the late-stage functionalization of drugs. Thus, this work represents an important example of energy transfer chemistry that overcomes challenges in traditional synthetic methods.

Enantioselective Synthesis of Sulfinamidines via Asymmetric Nitrogen Transfer from N-H Oxaziridines to Sulfenamides

Sulfinamidines are promising aza-SIV chiral building blocks in asymmetric synthesis and drug discovery. However, no report has documented their enantioselective synthesis. Here we present an enantioselective synthesis of sulfinamidines via electrophilic amination of sulfenamides using an enantiopure N-H oxaziridine. The resulting enantiomerically enriched primary sulfinamidines are configurationally stable at 90 °C in solution and show remarkable stability against organic acids and bases under non-aqueous conditions. We also demonstrate a one-pot, three-component, enantioselective synthesis of sulfinamides using N-H oxaziridine reagents.

Trideuteromethylthiolation through Reaction of Arynes, S-Methyl-d3 Sulfonothioate with Sulfonamides or Amides: Access to Trideuteromethylated Sulfilimines

A direct and practical three-component tandem reaction of arynes, S-methyl-d3 sulfonothioate with sulfonamides or amides is developed. The reaction is highly efficient and chemoselective, which allows mild synthesis of trideuteromethylated sulfilimines with broad substrate scope and good functional group compatibility, giving the products in good to excellent yields with 92%-99% deuterium incorporation. Mechanism studies disclosed sulfenamide that generated in situ is the key intermediate for the reaction. This protocol provides potential method for introduction of -SCD3 moiety for deuteration of marked drugs and drug candidates containing sulfilimine skeleton.

Decarboxylative Radical Sulfilimination via Photoredox, Copper, and Brønsted Base Catalysis

Sulfilimines, the aza-variants of sulfoxides, are key structural motifs in natural products, pharmaceuticals, and agrochemicals; and sulfilimine synthesis is therefore important in organic chemistry. However, methods for radical sulfilimination remain elusive, and as a result, the structural diversity of currently available sulfilimines is limited. Herein, we report the first protocol for decarboxylative radical sulfilimination reactions between sulfenamides and N-hydroxyphthalimide esters of primary, secondary, and tertiary alkyl carboxylic acids, which were achieved via a combination of photoredox, copper, and Brønsted base catalysis. This novel protocol provided a wide variety of sulfilimines, in addition to serving as an efficient route for the synthesis of S-alkyl/S-aryl homocysteine sulfilimines and S-(4-methylphenyl) homocysteine sulfoximine. Moreover, it could be used for late-stage introduction of a sulfilimine group into structurally complex molecules, thereby avoiding the need to preserve labile organosulfur moieties through multistep synthetic sequences. A mechanism involving photocatalytic substrate transformation and copper-mediated C(sp3 )-S bond formation is proposed.

Synthesis of N-Acylsulfenamides from (Hetero)Aryl Iodides and Boronic Acids by One-Pot Sulfur-Arylation and Dealkylation

A general one-pot approach to diverse N-acylsulfenamides from a common S-phenethylsulfenamide starting material is reported. This approach was demonstrated by C-S bond formation utilizing commercially abundant (hetero)aryl iodides and boronic acids to provide sulfilimine intermediates that undergo thermal elimination of styrene. In contrast, all prior approaches to N-acylsulfenamides rely on thiol inputs to introduce sulfenamide S-substituents. A broad scope of reaction inputs was demonstrated including for approved drugs and drug precursors with dense display of functionality. Several different types of sulfur functionalization were performed on a sulfenamide derived from a complex precursor of the blockbuster anticoagulant drug apixaban, highlighting the utility of this approach for the introduction of high oxidation state sulfur groups in complex bioactive compounds. Mechanistic studies established that the key styrene elimination step proceeds by a concerted elimination that does not require reagents or catalysts, and therefore, this one-pot approach should be applicable to the synthesis of N-acylsulfenamides utilizing diverse electrophiles and reaction conditions for C-S bond formation.

Selective S-Arylation of Sulfenamides with Arynes: Access to Sulfilimines

Sulfilimines, the aza analogues of sulfoxides, are of increasing interest in medicinal and agrochemical research programs. However, the development of efficient routes for their synthesis has remained relatively unexplored. In this study, we report a transition metal-free, selective S-arylation reaction between sulfenamides and arynes, enabling the facile preparation of structurally diverse sulfilimines under mild and redox-neutral conditions in good yields. The application value of our method was further demonstrated by scale-up synthesis, downstream derivatization, and robustness screen.

Synthesis of Sulfilimines via Multicomponent Reaction of Arynes, Sulfamides, and Thiosulfonates

In this work, a facile and efficient method for the synthesis of sulfilimines through multicomponent reaction of arynes, sulfamides, and thiosulfonates was developed. A variety of structurally diverse substrates and functional groups were very compatible in the reaction, giving the corresponding sulfilimines in good to high yields. This protocol could be conducted on a gram scale, and the product was easily converted to sulfide and sulfoximine. Mechanism studies revealed that sulfenamide generated in situ is the key intermediate for the reaction.