Sulfur-Arylation of Sulfenamides via Chan-Lam Coupling with Boronic Acids: Access to High Oxidation State Sulfur Pharmacophores

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.

Electrochemically Promoted Synthesis of N-Sulfonyl Sulfinimidate Esters and Sulfilimines from Sulfonamides, Thiophenols, Thioethers, and Alcohols

In this work, we report an electrochemical method for the straightforward preparation of scarcely accessible sulfinimidate esters from readily available sulfonamides, thiophenols, and alcohols. Mechanistic experiments show that sulfur oxidation at the anodic surface generates an electrophilic intermediate, which subsequently undergoes nucleophilic substitution. Moreover, sulfilimines can be obtained in moderate-to-excellent yields when thioethers are used as the S-donor instead of thiophenols via a dehydrogenateive imination process. This method is also characterized by mild reaction condition, operational simplicity, high atomic economic efficiency, easy later drug synthesis, and modification, as well as scaling up to a gram scale.

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.

Regioselective N-arylation of N-Acylsulfenamides Enabled by o-Quinone Diimides

The functionalization of N-acylsulfenamides is a research focus in organosulfur chemistry, as the N-S array has unique properties and versatile applications. Although great progress has been made in S-functionalization, the N-functionalization, especially the N-arylation of N-acylsulfenamides, has rarely been explored because of the lower nucleophilicity of the N-site. Herein, we report a Brønsted acid-catalyzed regioselective N-arylation reaction of N-acylsulfenamides with o-quinone diimides. Under mild and metal-free conditions, a wide range of N-arylated N-acylsulfenamides have been prepared in good yields with excellent regioselectivity. The ease of gram-scale synthesis and transformations into useful sulfonamides demonstrates their synthetic practicality.

Anionic Stereogenic-at-Cobalt(III) Complex-Enabled Asymmetric Oxidation of N,N-Dialkyl Sulfenamides

An asymmetric oxidation of N,N-dialkyl sulfenamides is exhibited by using anionic stereogenic-at-cobalt(III) complexes as catalysts. This protocol provides an alternative approach to access a diverse set of chiral tertiary sulfinamides with high enantioselectivities (24 examples, up to 94:6 e.r.). Additionally, control experiments suggest that this protocol could be accomplished through a chiral cationic S(IV) intermediate.

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.

Asymmetric S-Arylation of Sulfenamides to Access Axially Chiral Sulfilimines Enabled by Anionic Stereogenic-at-Cobalt(III) Complexes

An efficient enantioselective coupling reaction between sulfenamides and cyclic diaryliodonium salts is established via adaptive Cu/anionic stereogenic-at-Co(III) complex combined catalysis, precisely synthesizing a broad range of axially chiral sulfilimines with excellent enantioselectivities, diastereoselectivities, regioselectivities, and chemoselectivities (67 examples under same conditions, up to 98 % ee). The following thermodynamically controlled pyramidal inversion enables efficient stereodivegent synthesis of all four stereoisomers. Mechanistic studies suggest that anionic stereogenic-at-cobalt(III) complexes serve as counteranions of diaryliodonium and anionic ligand of Cu(I) catalyst simultaneously, which could be regarded as an explanation for outstanding selectivities.

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.

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.

Photoredox-Catalyzed Difunctionalization of Alkenes with Sulfilimines

Herein, we disclose a facile photoinduced difunctionalization of alkenes, enabling the synthesis of valuable β-amino alcohols, β-amino ethers, and 1,2-diamines with diverse nucleophiles. The protocol relies on the use of readily accessible dibenzothiophene-based sulfilimines as novel N-radical precursors, showcasing high functional-group tolerance and exclusive regioselectivity under mild reaction conditions.

Enantioselective Arylation of Sulfenamides to Access Sulfilimines Enabled by Palladium Catalysis

Sulfur-containing functional groups have garnered considerable attention due to their common occurrence in ligands, pharmaceuticals, and insecticides. Nevertheless, enantioselective synthesis of sulfilimines, particularly diaryl sulfilimines remains a challenging and persistent goal. Herein we report a highly enantio- and chemoselective cross-coupling of sulfenamides with aryl diazonium salt to construct diverse S(IV) stereocenters by Pd catalysis. Bisphosphine ligands bearing sulfinamide groups play a crucial role in achieving high reactivity and selectivity. This approach provides a general, modular and divergent framework for quickly synthesizing chiral sulfilimines and sulfoximines that are otherwise challenging to access. In addition, the origins of the high chemoselectivity and enantioselectivity were extensively investigated using density functional theory calculations.

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.

1,2-Difunctionalization of Aryne with Sulfenamide and Organohalide: Mild and Metal-Free Access to S-(o-Halo)aryl Sulfilimine

A mild and metal-free approach has been developed for 1,2-difunctionalization of aryne using sulfenamides as a nucleophile and a halogen source (CX4) as an electrophile to synthesize S-(o-halo)aryl sulfilimines. The late-stage functionalizations of halide handles via Suzuki-Miyaura and Buchwald-Hartwig reactions exhibit the synthetic utilities of the products. The chemoselectivity, regioselectivity, rapidity, and use of economical CCl4 are the advantages of this protocol.

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.

Diphenylphosphinylhydroxylamine (DPPH) Affords Late-Stage S-imination to access free-NH Sulfilimines and Sulfoximines

Sulfilimines, as potential aza-isosteres of sulfoxides, are valued as building blocks, auxiliaries, ligands, bioconjugation handles, and as precursors to versatile S(VI) scaffolds including sulfoximines and sulfondiimines. Here, we report a thioether imination methodology that exploits O-(diphenylphosphinyl)hydroxyl amine (DPPH). Under mild, metal-free, and biomolecule-compatible conditions, DPPH enables late-stage S-imination on peptides, natural products, and a clinically trialled drug, and shows both excellent chemoselectivity and broad functional group tolerance. This methodological report is extended to an efficient and high-yielding one-pot reaction for accessing free-NH sulfoximines with diverse substrates including ones of potential clinical importance. In the presence of a rhodium catalyst, sulfoxides are S-iminated in higher yields to afford free-NH sulfoximines. S-imination was validated on an oxidatively delicate amatoxin to give sulfilimine and sulfoximine congeners. Interestingly, these new sulfilimine and sulfoximine-amatoxins show cytotoxicity. This method is further extended to create sulfilimine and sulfoximine-Fulvestrant and buthionine analogues.

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.

Copper-Catalyzed Aerobic S-Amination of Sulfenamides for the Synthesis of Sulfinamidines

Herein, we present a copper-catalyzed oxidative amination of sulfenamides for the synthesis of sulfinamidines. By the employment of air as the terminal oxidant, a diverse array of secondary and primary amines can be efficiently transformed into their corresponding products. This method is well-suited for last-stage functionalization, and the underlying mechanism has been investigated. The transformation is characterized by exceptional chemoselectivity, mild conditions, facile operation, and broad substrate compatibility, which have significant implications for the fields of pharmaceuticals and organic synthesis.

Synthesis of Sulfoximines by Copper-Catalyzed Oxidative Coupling of Sulfinamides and Aryl Boronic Acids

A novel copper-catalyzed cross-coupling reaction of sulfinamides and aryl boronic acids is developed. The reaction is highly chemoselective and stereospecific, which allows mild synthesis of optically pure sulfoximines with broad scope and functional group tolerance. The utility of this method is demonstrated by the asymmetric synthesis of pharmaceutical intermediates.

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.

Hypervalent Iodine Mediated Synthesis of Sulfinamidines from Sulfenamides

In this study, we present a novel, efficient method for the oxidative amination of sulfenamides using diacetoxyiodobenzene (PhI(OAc)2) and amines under basic conditions. This innovative technique streamlines the synthesis of sulfinamidines under mild, metal-free conditions, achieving outstanding yields of up to 99%. Furthermore, we propose possible pathways that elucidate the observed molecular sequence of events in this reaction. This cutting-edge approach not only advances the synthesis of valuable sulfinamidine compounds but also expands the synthetic toolbox available to chemists, paving the way for future discoveries in organic synthesis and potential applications in medicinal chemistry.

Synthesis of Sulfilimines via Aryne and Cyclohexyne Intermediates

An efficient and metal-free approach for the synthesis of sulfilimines from sulfenamides with aryne and cyclohexyne precursors has been developed. The reaction proceeds through unusual S-C bond formation, which offers a novel and practical entry to access a wide range of sulfilimines in moderate to good yields with excellent chemoselectivity. Moreover, this protocol is amenable to gram-scale synthesis and is applicable to the transformation of the products into useful sulfoximines.

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

Sulfur-(hetero)arylation of sulfenamides with commercially abundant (hetero)aryl iodides by Ullmann-type coupling with inexpensive copper(I) iodide as the catalyst is reported. A broad scope of reaction inputs was demonstrated, including both aryl and alkyl sulfenamides and highly sterically hindered aryl and 5- and 6-membered ring heteroaryl iodides. Relevant to many bioactive high oxidation state sulfur compounds, the (hetero)arylation of S-methyl sulfenamides is reported, including for complex aryl iodides. Smiles rearrangement of electron-deficient S-heteroaryl sulfilimines is also disclosed.

Metal-Free Chemoselective S-Arylation of Sulfenamides To Access Sulfilimines

A novel and efficient S-arylation of sulfenamides with diaryliodonium salts for the synthesis of sulfilimines is developed. The reaction proceeds smoothly under transition-metal-free and air conditions, giving rapid access to sulfilimines in good to excellent yields via selective S-C bond formation. This protocol is scalable and exhibits a broad substrate scope, good functional group tolerance, and excellent chemoselectivity.

Preparation of Sulfilimines by Sulfur-Alkylation of N-Acyl Sulfenamides with Alkyl Halides

Sulfur alkylation of N-acyl sulfenamides with alkyl halides provides sulfilimines in 47% to 98% yields. A broad scope was established with a variety of aryl and alkyl sulfenamides, including for different N-acyl groups. Alkyl halides with different steric and electronic properties were effective inputs, including methyl, primary, secondary, benzyl, and propargyl halides. A proof-of-concept asymmetric phase-transfer alkylation was also demonstrated. A sulfilimine product was readily converted to an N-acyl and to a free sulfoximine, which represent important motifs in medicinal chemistry.

Base-Promoted S-Arylation of Sulfenamides for the Synthesis of Sulfilimines

Sulfilimines are key intermediates to common motifs in medicines and agrochemicals. Typically, this class of compounds are prepared by imidation of thioethers, transition-metal-catalyzed or base-promoted sulfur alkylation and transition-metal-catalyzed sulfur arylation. Here, we report a practical and efficient base-mediated sulfur arylation reaction for the preparation of sulfilimines. A wide range of N-acyl and N-aryl sulfenamides react with various diaryliodonium salts smoothly to afford the sulfilimines in high yields with excellent chemoselectivities.