Synthesis of Sulfilimines via Aryne and Cyclohexyne Intermediates

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.

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.

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.

Unlocking Chiral Sulfinimidoyl Electrophiles: Asymmetric Synthesis of Sulfinamides Catalyzed by Anionic Stereogenic-at-Cobalt(III) Complexes

Asymmetric catalysis involving a sulfoxide electrophile intermediate presents an efficient methodology for accessing stereogenic-at-sulfur compounds, such as sulfinate esters, sulfinamides, etc., which have garnered increasing attention in modern pharmaceutical sciences. However, as the aza-analog of sulfoxide electrophiles, the asymmetric issues about electrophilic sulfinimidoyl species remain largely unexplored and represent a significant challenge in sulfur stereochemistry. Herein, we exhibit an anionic stereogenic-at-cobalt(III) complex-catalyzed asymmetric synthesis of chiral sulfinamides via chiral sulfinimidoyl iodide intermediates. Mechanistic investigations reveal that the catalytic cycle is initiated by asymmetric oxidative iodination, generating sulfinimidoyl iodides. These active intermediates subsequently undergo an enantiospecific nucleophilic substitution with water, affording a diverse array of enantioenriched sulfinamides. Notably, these sulfinamides exhibit promising antifungal activities against Sclerotinia sclerotiorum and serve as ideal platform molecules facilitating the stereospecific transformation into various stereogenic aza-sulfur compounds.

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.

A Rapid, Mild and Direct Route to Sulfonimidoyl Fluoride from Sulfenamide

We develop a rapid and mild protocol to access sulfonimidoyl fluoride-[S(VI)] from sulfenamide-[S(II)] directly. The transformation occurs via the reaction of sulfenamide with NCS (N-chlorosuccinimide), water, and TBAF in acetonitrile. Water and TBAF act as the source for S═O bond formation and fluoride, respectively. The reaction takes a very short time (within 5 min). The drug molecules, such as Carbamazepine and Levetiracetam attached sulfonimidoyl fluorides are also achieved following this protocol. Furthermore, sulfonimidoyl fluoride is transformed into sulfonimidamide in the presence of AlCl3. To the best of our knowledge, it is the first report detailing the synthesis of sulfonimidoyl fluoride-[S(VI)] directly from S(II)-sulfenamide.

Bifunctional Lewis Base-Catalyzed (3 + 2) Cycloadditions of Pyrazolone-Derived MBH Carbonates with Arynes

The (3 + 2) cycloaddition of arynes with allylic ylides remains a formidable challenge because both intermediates are highly reactive and prone to spontaneous quenching. Here, we report a (3 + 2) cycloaddition of pyrazolone MBH carbonates with arynes, enabling the efficient synthesis of diverse indene-fused spiropyrazolones. The key is employing a new bifunctional Lewis base catalyst to facilitate the cycloaddition of in situ generated allylic pyridinium ylides with arynes.

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.

Arynes Promoted Dehydrosulfurization of Thioamides: Access to Nitriles and Diaryl Sulfides

An aryne-promoted dehydrosulfurization reaction of thioamides to give nitriles and diaryl sulfides in a one-pot manner is presented. Aromatic, heteroaromatic, and aliphatic natural products and drug-derived nitriles and diaryl sulfides were obtained in good to excellent yields. Especially, selenoamide was also a suitable substrate and produced diaryl selenide and nitrile in high yields. The D-labeled experiments indicated that the protons of thioamides transfer to diaryl sulfides.

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.

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.

Bromothiolation of Arynes for the Synthesis of 2-Bromobenzenethiol Equivalents

A new method to synthesize o-bromobenzenethiol equivalents through aryne intermediates is disclosed. Various o-bromobenzenethiol equivalents are prepared by the bromothiolation of aryne intermediates with potassium xanthates. Aryl xanthates serve in the synthesis of diverse organosulfurs involving phenothiazines and thianthrenes by further transformations.

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.