A New Portal to SuFEx Click Chemistry: A Stable Fluorosulfuryl Imidazolium Salt Emerging as an “F−SO2 +” Donor of Unprecedented Reactivity, Selectivity, and Scope

Pyridinium-Based Fluorosulfonamide Reagents Enabled Photoredox-Catalyzed Radical Fluorosulfonamidation

Sulfamoyl fluorides, as a crucial building block of SuFEx, have garnered extensive research interest due to their unique properties. However, the direct radical fluorosulfonamidation process for the synthesis of sulfamoyl fluorides has been overlooked. We herein disclosed a practical procedure for constructing a redox-active fluorosulfonamide radical reagent named fluorosulfonyl-N-pyridinium tetrafluoroborate (PNSF) from SO2F2. These reagents can facilitate a range of reactions, including the N-(fluorosulfonyl) sulfonamidation of (hetero)arenes, sequential radical stereoselective fluorosulfonamidation, and 1,2-difunctionalization of alkenes.

Activation of SO2F2 at a Rhodium PNP Pincer Complex: Ligand Supported S-F Bond Cleavage to Generate NSO2F Derivatives

The κ2-(P,N)-phosphine ligand precursor NH(CH2CH2PCy2)2 can be used for the synthesis of the rhodium(I) complex [Rh(CO){ĸ3-(P,N,P)-Cy2PC2H4NHC2H4PCy2}][Cl] (1). The deprotonated complex [Rh(CO){ĸ3-(P,N,P)-Cy2PC2H4NC2H4PCy2}] (2) shows a cooperative reactivity of the PNP ligand in the activation reaction of SO2F2 to yield the rhodium fluorido complex trans-[Rh(F)(CO){ĸ2-(P,P)-Cy2PC2H4N(SO2F)C2H4PCy2}]2 (3) by S-F bond cleavage. It is remarkable that no reaction was observed when 3 was treated with hydrogen sources e. g. dihydrogen, organosilicon compounds such as triethylsilane or TMS-CF3 and different fluorine sources such as SF4 or Selectfluor®. However, the treatment of complex 3 with XeF2 in the presence of CsF resulted in the formation of the unique fluorido rhodium(III) complex cis,trans-[Rh(F)3(CO){ĸ2-(P,P)-Cy2PC2H4N(SO2F)C2H4PCy2}]2 (4). In the presence of pyridine(HF)X or BF3 the fluorido complex 3 converted into the dicationic complexes [Rh(CO){ĸ2-(P,P)-Cy2PC2H4N(SO2F)C2H4PCy2}]2[XF]2, X=HF (5) or BF3 (6), respectively.

2-Methylimidazole-1-(N-tert-octyl)sulfonimidoyl Fluoride: A Bench-Stable Alternative to SOF4 as Precursor to N,O-Substituted S(VI) Compounds

S(VI) compounds with multiple N or O substituents are often difficult to make and several crucial routes, such as multimodal SuFEx (Sulfur (VI) Fluoride Exchange) chemistry, rely on the highly useful but hazardous SOF4 gas. Safety issues and inaccessibility of SOF4 strongly hamper the developments of these organic compounds. Here we describe the synthesis and applications of 2-methylimidazole-1-(N-tert-octyl)sulfonimidoyl fluoride (ImSF), a novel bench-stable analogue of SOF4. ImSF is synthesized on a gram scale via a double fluorination of t-OctNSO. We show ImSF can undergo substitution reactions with phenols and amines, which lead to sulfurimidates and sulfuramidimidates, respectively, the intrinsically chiral analogous of medicinally relevant sulfates and sulfamates in which an S=O moiety is replaced by S=NR unit. Finally we demonstrate that such substitutions can occur enantiospecifically, providing the first entry to chiral sulfurimidates and sulfuramidimidates.

Radical Fluorosulfonamidation: A Facile Access to Sulfamoyl Fluorides

Recently, the introduction of fluorosulfonyl (-SO2F) groups have attracted considerable research interests, as this moiety could often afford enhanced activities and new functions in the context of chemical biology and drug discovery. Herein, we report the design and synthesis of 1-fluorosulfamoyl-pyridinium (FSAP) salts, which could serve as an effective photoredox-active precursor to fluorosulfamoyl radicals and enable the direct radical C-H fluorosulfonamidation of a variety of (hetero)arenes. This method features mild conditions, visible light, broad substrate scope, good group tolerance, etc., and a metal-free protocol is also viable by using organic photocatalysts. Further, FSAP can also be applied to the radical functionalization of alkenes via 1,2-difunctionalization, radical distal migration, tandem radical-polar crossover reactions, etc. In addition, a formal C-H methylamination of (hetero)arenes by combining this radical C-H fluorosulfonamidation with subsequent hydrolysis as well as product derivatization are also demonstrated.

Palladium-Catalyzed Esterification of Aryl Fluorosulfates with Aryl Formates

An efficient palladium-catalyzed carbonylation of aryl fluorosulfates with aryl formates for the facile synthesis of esters was developed. The cross-coupling reactions proceeded effectively in the presence of a palladium catalyst, phosphine ligand, and triethylamine in DMF to produce the corresponding esters in moderate to good yields. Of note, functionalities or substituents, such as nitro, cyano, methoxycarbonyl, trifluoromethyl, methylsulfonyl, trifluoromethoxy, fluoro, chloro, bromo, methyl, methoxy, N,N-dimethyl, and [1,3]dioxolyl, were well-tolerated in the reactions, which could be kept for late-stage modification. The reactions employing readily available and relatively robust aryl fluorosulfates as coupling electrophiles could potentially serve as an attractive alternative to traditional cross-couplings with the use of aryl halides and pseudohalides as substrates.

N-Fluorosulfonyl Guanidine: An Entry to N-Guanyl Sulfamides and Sulfamates

Here, we present the straightforward synthesis of N-fluorosulfonyl guanidine (1) from two industrial feedstocks, guanidine hydrochloride and sulfuryl fluoride (SO2F2), using SuFEx chemistry. Compound 1 exhibits excellent stability under ambient conditions and displays unique SuFEx reactivity toward amines and phenols to generate N-guanyl sulfamides and sulfamates that have rarely been accessed. Notably, water serves as an effective solvent in this process. Our protocol provides a reliable pathway for the synthesis and investigation of these novel guanidine-containing molecules.

One-Flow Syntheses of Unsymmetrical Sulfamides and N-Substituted Sulfamate Esters

We developed one-flow syntheses of unsymmetrical sulfamides and N-substituted sulfamate esters by changing a nucleophile and a tertiary amine from inexpensive and commercially available chlorosulfonic acid. In the synthesis of N-substituted sulfamate esters, unexpected symmetrical sulfite formation was suppressed by changing the tertiary amine. The effect of tertiary amines was proposed using linear regression. Our approach rapidly (≤90 s) provides desired products containing acidic and/or basic labile groups without tedious purification under mild (20 °C) conditions.

Stereoselective Fluorosulfonylation of Vinylboronic Acids for (E)-Vinyl Sulfonyl Fluorides with Copper Participation

A practical synthetic method for the synthesis of vinyl sulfonyl fluorides through copper-promoted direct fluorosulfonylation has been developed. The reaction of the vinylboronic acids with DABSO and then NFSI is performed under mild reaction conditions. This transformation efficiently affords aryl or alkyl vinyl sulfonyl fluorides with good reaction yields, exclusive E-configuration, broad substrate scope, excellent compatibility, and operational simplicity.

Desmethyl SuFEx-IT: SO2F2-Free Synthesis and Evaluation as a Fluorosulfurylating Agent

Access to SuFExable compounds was remarkably simplified by introduction of the solid FO2S-donor SuFEx-IT. However, the published process for preparation of this reagent relies on the use of sulfuryl fluoride (SO2F2), which is difficult to obtain and highly toxic. Herein, we disclose a simple protocol for SO2F2-free, hectogram-scale preparation of the analogous desmethyl SuFEx-IT from inexpensive starting materials. The reagent was prepared in a high (85%) total yield and without chromatographic purification steps. In addition, we demonstrate the utility of desmethyl SuFEx-IT by successful preparation of a series of fluorosulfates and sulfamoyl fluorides in high to excellent yields. As such, our work recognizes desmethyl SuFEx-IT as a valuable alternative to common FO2S-donors and enables cost-efficient access to substrates for SuFEx click chemistry.

Discovery of Arylfluorosulfates as Novel Fungicidal Agents against Plant Pathogens

A series of arylfluorosulfates were synthesized as fungicide candidates through a highly efficient sulfur fluoride exchange (SuFEx) reaction. A total of 32 arylfluorosulfate derivatives with simple structures have been synthesized, and most of them exhibited fungal activities in vitro against five agricultural pathogens (Rhizoctonia solani, Botrytis cinerea, Fusarium oxysporum, Pyricularia oryzae, and Phytophthora infestans). Among the target compounds, compound 31 exhibited great antifungal activity against Rhizoctonia solani (EC50 = 1.51 μg/mL), which was comparable to commercial fungicides carbendazim and thiabendazole (EC50 = 0.53 and 0.70 μg/mL, respectively); compounds 17 and 30 exhibited antifungal activities against Pyricularia oryzae (EC50 = 1.64 and 1.73 μg/mL, respectively) comparable to carbendazim (EC50 = 1.02 μg/mL). The in vitro antifungal effect of compound 31 was also evaluated on rice plants against Rhizoctonia solani. Significant preventive and curative efficacies were observed (89.2% and 91.8%, respectively, at 200 μg/mL), exceeding that of thiabendazole. Primary study on the mechanism of action indicated that compound 31 could suppress the sclerotia formation of Rhizoctonia solani even at a very low concentration (1.00 μg/mL), destroy the cell membrane and mitochondria, trigger the release of cellular contents, produce excessive reactive oxygen species (ROS), and suppress the activity of several related enzymes. This work could bring new insights into the development of arylfluorosulfates as novel fungicides.

Discovery of Molecular Glue Degraders via Isogenic Morphological Profiling

Molecular glue degraders (MGDs) are small molecules that degrade proteins of interest via the ubiquitin-proteasome system. While MGDs were historically discovered serendipitously, approaches for MGD discovery now include cell-viability-based drug screens or data mining of public transcriptomics and drug response datasets. These approaches, however, have target spaces restricted to the essential proteins. Here we develop a high-throughput workflow for MGD discovery that also reaches the nonessential proteome. This workflow begins with the rapid synthesis of a compound library by sulfur(VI) fluoride exchange chemistry coupled to a morphological profiling assay in isogenic cell lines that vary in levels of the E3 ligase CRBN. By comparing the morphological changes induced by compound treatment across the isogenic cell lines, we were able to identify FL2-14 as a CRBN-dependent MGD targeting the nonessential protein GSPT2. We envision that this workflow would contribute to the discovery and characterization of MGDs that target a wider range of proteins.

An efficient and mild oxidative approach from thiols to sulfonyl derivatives with DMSO/HBr

A mild and practical method for synthesizing sulfonyl derivatives, which have a wide range of applications in pharmaceuticals, materials, and organic synthesis, was described through the oxidative functionalization of thiols with DMSO/HBr. The simple conditions, low cost and ready availability of DMSO/HBr, as well as the versatility of the transformations, make this strategy very powerful in synthesizing a variety of sulfonyl derivatives including sulfonamides, sulfonyl fluorides, sulfonyl azides, and sulfonates. Mechanistic studies revealed that DMSO served as the terminal oxidant, and HBr acted as both a nucleophile and a redox mediator to transfer the oxygen atom.

Recent Advances of S-18F Radiochemistry for Positron Emission Tomography

The click chemistry of sulfur(VI) fluoride exchange (SuFEx) has facilitated the widespread application of sulfur-fluoride compounds such as sulfonyl fluorides, fluorosulfates, and sulfamoyl fluorides in various fields, especially in the development of 18F ligands for PET (positron emission tomography) imaging. In recent years, the prominent progress of sulfur-[18F]fluoride compounds has been achieved through the combination of 18F and sulfur-fluoride chemistry. These compounds serve as potential 18F tracers, 18F synthons, and reagents for 18F-fluorination, thereby complementing the range of 18F ligands, typically C-18F structures, used in PET studies. This review aims to provide an overview of S-18F labeling reactions through examples of relevant 18F compounds and highlight the advancements and breakthroughs achieved in the past decade.

Click Chemistry and Targeted Degradation: A Winning Combination for Medicinal Chemists?

Click chemistry is universally recognized as a powerful strategy for the fast and precise assembly of diverse building blocks. Targeted Protein Degradation (TPD) is a new therapeutic modality based on heterobifunctional small-molecule degraders that provides new opportunities to medicinal chemists dealing with undruggable targets and incurable diseases. Here, we highlight how very recently the TPD field and that of click chemistry have merged, opening up the possibility for fine-tuning the properties of a degrader, chemically assembled through a "click" synthesis. By reviewing concrete examples, we want to provide the reader with the insight that the application of click and bioorthogonal chemistry in the TDP field may be a winning combination.

The Certainty of a Few Good Reactions

The impact of click chemistry was recently recognized with the 2022 Nobel Prize in Chemistry. The breadth of areas where click chemistry has accelerated discovery is prodigal. In one of the most written about subjects in chemistry over recent years, this short perspective zones in on a small fragment of what we, the authors, consider are some of the most critical developments in synthetic chemistry, which have expanded access to the click chemistry toolbox. In addition, we touch upon areas within medicinal chemistry and novel approaches to drug discovery enabled by click chemistry, where we believe there is untapped potential for biological function to be found and exploited.

Harnessing Sulfur(VI) Fluoride Exchange Click Chemistry and Photocatalysis for Deaminative Benzylic Arylation

While among the most common functional handles present in organic molecules, amines are a widely underutilized linchpin for C-C bond formation. To facilitate C-N bond cleavage, large activating groups are typically used but result in the generation of stoichiometric amounts of organic waste. Herein, we report an atom-economic activation of benzylic primary amines relying on the Sulfur(VI) Fluoride Exchange (SuFEx) click chemistry and the aza-Ramberg-Bäcklund reaction. This two-step sequence allows the high-yielding generation of 1,2-dialkyldiazenes from primary amines via loss of SO2. Excitation of the diazenes with blue light and an Ir photocatalyst affords radical pairs upon expulsion of N2, which can be coaxed into the formation of C(sp3)-C(sp2) bonds upon diffusion and capture by a Ni catalyst. This arylative strategy relying on a traceless click approach was harnessed in a variety of examples and its mechanism was investigated.

Advances in the construction of diverse SuFEx linkers

Sulfur fluoride exchange (SuFEx), a new generation of click chemistry, was first presented by Sharpless, Dong and co-workers in 2014. Owing to the high stability and yet efficient reactivity of the S^VI-F bond, SuFEx has found widespread applications in organic synthesis, materials science, chemical biology and drug discovery. A diverse collection of SuFEx linkers has emerged, involving gaseous SO₂F₂ and SOF₄ hubs; SOF₄-derived iminosulfur oxydifluorides; O-, N- and C-attached sulfonyl fluorides and sulfonimidoyl fluorides; and novel sulfondiimidoyl fluorides. This review summarizes the progress of these SuFEx connectors, with an emphasis on analysing the advantages and disadvantages of synthetic strategies of these connectors based on the SuFEx concept, and it is expected to be beneficial to researchers to rapidly and correctly understand this field, thus inspiring further development in SuFEx chemistry.

Covalent drug discovery using sulfur(VI) fluoride exchange warheads

INTRODUCTION

Covalent drug discovery has traditionally focused on targeting cysteine, but the amino acid is often absent in protein binding sites. This review makes the case to move beyond cysteine labeling using sulfur (VI) fluoride exchange (SuFEx) chemistry to expand the druggable proteome.

AREAS COVERED

Recent advances in SuFEx medicinal chemistry and chemical biology are described, which have enabled the development of covalent chemical probes that site-selectively engage amino acid residues (including tyrosine, lysine, histidine, serine, and threonine) in binding pockets. Areas covered include chemoproteomic mapping of the targetable proteome, structure-based design of covalent inhibitors and molecular glues, metabolic stability profiling, and synthetic methodologies that have expedited the delivery of SuFEx modulators.

EXPERT OPINION

Despite recent innovations in SuFEx medicinal chemistry, focused preclinical research is required to ensure the field moves from early chemical probe discovery to the delivery of transformational covalent drug candidates. The authors believe that covalent drug candidates designed to engage residues beyond cysteine using sulfonyl exchange warheads will likely enter clinical trials in the coming years.

High-Throughput Diversification of Complex Bioactive Molecules by Accelerated Synthesis in Microdroplets

Late-stage diversification of drug molecules is an important strategy in drug discovery that can be facilitated by reaction screening using high-throughput experimentation. Here we present a rapid method for functionalizing bioactive molecules based on accelerated reactions in microdroplets. Reaction mixtures are nebulized at throughputs better than 1 reaction/second and the accelerated reactions occurring in the microdroplets are followed by desorption electrospray ionization mass spectrometry (DESI-MS). Because the accelerated reactions occur on the millisecond timescale, they allow an overall screening throughput of 1 Hz working at the low nanogram scale. Using this approach, an opioid agonist (PZM21) and an antagonist (naloxone) were diversified using three reactions important in medicinal chemistry: sulfur fluoride exchange (SuFEx) click reactions, imine formation reactions, and ene-type click reactions. Some 269 functionalized analogs of naloxone and PZM21 were generated and characterized by tandem mass spectrometry (MS/MS) after screening over 500 reactions.

Direct 18F-Fluorosulfurylation of Phenols and Amines Using an [18F]FSO2+ Transfer Agent Generated In Situ

We report the direct radiofluorosulfurylation method for the synthesis of ¹⁸F-labeled fluorosulfuryl derivatives from phenols and amines using an [¹⁸F]FSO₂⁺ transfer agent generated in situ. Nucleophilic radiofluorination is achieved even in a hydrous organic medium, obviating the need for azeotropic drying and the use of cryptands. This unprecedented, operationally simple isotopic functionalization facilitates the reliable production of potential radiotracers for positron emission tomography, rendering facile access to SuFEx radiochemistry.

Sulfur(VI) fluorides as tools in biomolecular and medicinal chemistry

Recent advances in the synthesis of sulfur(VI)-fluorides has enabled incredible growth in their application in biomolecular chemistry. This review aims to serve as a primer highlighting synthetic strategies toward a diversity of S(VI) fluorides and their application in chemical biology, bioconjugation, and medicinal chemistry.

Sulfur(iv) reagents for the SuFEx-based synthesis of substituted sulfamate esters

Sulfur(vi) fluoride exchange chemistry has been reported to be effective at synthesizing valuable sulfur(vi) functionalities through sequential nucleophilic additions, yet oxygen-based nucleophiles are limited in this approach to phenolic derivatives. Herein, we report a new sulfur(iv) fluoride exchange strategy to access synthetically challenging substituted sulfamate esters from alkyl alcohols and amines. We also report the development of a non-gaseous, sulfur(iv) fluoride exchange reagent, N-methylimidazolium sulfinyl fluoride hexafluorophosphate (MISF). By leveraging the reactivity of the sulfur(iv) center of this novel reagent, the sequential addition of alcohols and amines to MISF followed by oxidation afforded the desired substituted sulfamates in 40-83% yields after two steps. This new strategy expands the scope of SuFEx chemistry by increasing the accessibility of underdeveloped -S(O)F intermediates for future explorations.

Selective Fluorosulfonylation of Thianthrenium Salts Enabled by Electrochemistry

A practical electrochemically driven method for fluorosulfonylation of both aryl and alkyl thianthrenium salts has been disclosed. The strategy does not need external redox reagents or metal catalysts. In combination with C-H thianthrenation of aromatics, this method provides a new tool for the site-selective fluorosulfonylation of drugs.

Acid-Mediated Imidazole-to-Fluorine Exchange for the Synthesis of Sulfonyl and Sulfonimidoyl Fluorides

Sulfur(VI) fluoride motifs are important entities in organic chemistry. Typically, their syntheses involve the corresponding chlorides, which are often difficult to prepare and characterized by a poor storability due to the inherently weak S-Cl bond. Here, a single-step procedure for the preparation of sulfur(VI) fluorides starting from sulfonyl imidazoles as stable S(VI) reservoirs is described. By using a simple combination of AcOH and potassium bifluoride (KF₂H), an imidazole-to-fluorine exchange furnishes a variety of sulfonyl, sulfonimidoyl, sulfoxyl, and sulfamoyl fluorides in good to excellent yields.

The stable "F-SO2 +" donor provides a mild and efficient approach to nitriles and amides

In this update, we developed a mild, efficient and practical method using fluorosulfuryl imidazolium salt A as an environment friendly promoter for conversion of oximes to nitriles or amides via β-elimination or Beckmann rearrangement in almost quantitative yield in 10 minutes. The target products were generated in gram-scale and could be collected through crystallization without silica gel column purification in excellent yield.

Sulfur–Phenolate Exchange: SuFEx‐Derived Dynamic Covalent Reactions and Degradation of SuFEx Polymers

The products of the SuFEx reaction between sulfonimidoyl fluorides and phenols, sulfonimidates, are shown to display dynamic covalent chemistry with other phenols. This reaction was shown to be enantiospecific, finished in minutes at room temperature in high yields, and useful for both asymmetric synthesis and sustainable polymer production. Its wide scope further extends the usefulness of SuFEx and related click chemistries.

Introducing SuFNucs: Sulfamoyl-Fluoride-Functionalized Nucleosides That Undergo Sulfur Fluoride Exchange Reaction

The reaction between ribonucleosides and ex situ generated sulfonyl fluoride has been developed. The reaction takes place at the −NH₂ groups of nucleobases, and the resulting nucleosides are equipped with a sulfamoyl fluoride moiety, dubbed SuFNucs. These species undergo a selective sulfur fluoride exchange (SuFEx) reaction with various amines, leading to sulfamide-functionalized derivatives of adenosine, guanosine, and cytidine (SulfamNucs). The scope and examples of further SuFNucs fuctionalization leading to nucleotides, oligonucleotides, and peptide–nucleoside conjugates are presented.

Cell-Active, Reversible, and Irreversible Covalent Inhibitors That Selectively Target the Catalytic Lysine of BCR-ABL Kinase

Despite recent interests in developing lysine-targeting covalent inhibitors, no general approach is available to create such compounds. We report herein a general approach to develop cell-active covalent inhibitors of protein kinases by targeting the conserved catalytic lysine residue using key SuFEx and salicylaldehyde-based imine chemistries. We validated the strategy by successfully developing (irreversible and reversible) covalent inhibitors against BCR-ABL kinase. Our lead compounds showed high levels of selectivity in biochemical assays, exhibited nanomolar potency against endogenous ABL kinase in cellular assays, and were active against most drug-resistant ABL mutations. Among them, the salicylaldehyde-containing A5 is the first-ever reversible covalent ABL inhibitor that possessed time-dependent ABL inhibition with prolonged residence time and few cellular off-targets in K562 cells. Bioinformatics further suggested the generality of our strategy against the human kinome.

A practical fluorosulfonylating platform via photocatalytic imidazolium-based SO2F radical reagent

Sulfonyl fluorides are key components in the fields of chemical biology, materials science and drug discovery. In this line, the highly active SO₂F radical has been employed for the construction of sulfonyl fluorides, but the utilization of gaseous ClSO₂F as radical precursor is limited due to the tedious and hazardous preparation. Meanwhile, the synthesis of sulfonyl fluorides from inert SO₂F₂ gas through a fluorosulfonyl radical (·SO₂F) process has met with inevitable difficulties due to the high homolytic bond dissociation energy of the S(VI)-F bond. Here we report a radical fluorosulfonylation strategy for the stereoselective synthesis of alkenyl sulfonyl fluorides and functional alkyl sulfonyl fluorides with an air-stable crystalline benzimidazolium fluorosulfonate cationic salt reagent. This bench-stable redox-active reagent offers a useful and operational protocol for the radical fluorosulfonylation of unsaturated hydrocarbons with good yield and high stereoselectivity, which can be further transformed into valuable functional SO₂F moieties.

Sulfonyl fluorides have potential application in chemical biology, materials science, and drug discovery, but their preparation remains challenging. Here, the authors report an air-stable fluorosulfonylating reagent that enables the radical fluorosulfonylation, hydrofluorosulfonylation and migratory SO₂F-difunctionalization of unsaturated hydrocarbons to construct a variety of sulfonyl fluoride compounds.

Photoredox catalytic radical fluorosulfonylation of olefins enabled by a bench-stable redox-active fluorosulfonyl radical precursor

Sulfonyl fluorides have attracted considerable and growing research interests from various disciplines, which raises a high demand for novel and effective methods to access this class of compounds. Radical flurosulfonylation is recently emerging as a promising approach for the synthesis of sulfonyl fluorides. However, the scope of applicable substrate and reaction types are severely restricted by limited known radical reagents. Here, we introduce a solid state, redox-active type of fluorosulfonyl radical reagents, 1-fluorosulfonyl 2-aryl benzoimidazolium triflate (FABI) salts, which enable the radical fluorosulfonylation of olefins under photoredox conditions. In comparison with the known radical precursor, gaseous FSO₂Cl, FABI salts are bench-stable, easy to handle, affording high yields in the radical fluorosulfonylation of olefins with before challenging substrates. The advantage of FABIs is further demonstrated in the development of an alkoxyl-fluorosulfonyl difunctionalization reaction of olefins, which forges a facile access to useful β-alkoxyl sulfonyl fluorides and related compounds, and would thus benefit the related study in the context of chemical biology and drug discovery in the future.

Sulfonyl fluorides are compounds with potential application in chemical biology and drug discovery, but their preparation can be challenging. Here, the authors present a type of bench-stable fluorosulfonyl radical reagents that enable radical fluorosulfonylation reactions via photoredox catalysis.

(Hetero)aryl-SVI Fluorides: Synthetic Development and Opportunities

(Hetero)arylsulfur compounds where the S atom is in the oxidation state VI represent a large percentage of the molecular functionalities present in organic chemistry. More specifically, (hetero)aryl‐S^VI fluorides have recently received enormous attention because of their potential as chemical biology probes, as a result of their reactivity in a simple, modular, and efficient manner. Whereas the synthesis and application of the level 1 fluorination at S^VI atoms (sulfonyl and sulfonimidoyl fluorides) have been widely studied and reviewed, the synthetic strategies towards higher levels of fluorination (levels 2 to 5) are somewhat more limited. This Minireview evaluates and summarizes the progress in the synthesis of highly fluorinated aryl‐S^VI compounds at all levels, discussing synthetic strategies, reactivity, the advantages and disadvantages of the synthetic procedures, the proposed mechanisms, and the potential upcoming opportunities.

Selectivity Controlled Hydroamination of Alkynes to Sulfonyl Fluoride Hubs: Development and Application

A hydroamination of unactivated alkynes and lithium bis(fluorosulfonyl)imide (LiN(SO₂F)₂) is described under mild conditions, affording a single regioisomer of the sulfonyl fluorides. This method features broad functional group compatibility and delivers the target vinyl fluorosulfonimides in good to excellent yields. Moreover, gram-scale hydroamination of terminal and internal alkynes is achieved. Further transformations exploiting the reactivity of the vinyl fluorosulfonimide are subsequently developed for the synthesis of fluorosulfates and diphenyl sulfate.

An N-Fluorinated Imide for Practical Catalytic Imidations

Catalytic imidation using NFSI as the nitrogen source has become an emerging tool for oxidative carbon-nitrogen bond formation. However, the less than ideal benzenesulfonimide moiety is incorporated into products, severely detracting its synthetic value. As a solution to this challenge, we report herein the development of a novel N-fluorinated imide, N-fluoro-N-(fluorosulfonyl)carbamate (NFC), by which the attached imide moiety acts as a modular synthetic handle for one-step derivatization to amines, sulfonamides, and sulfamides. Furthermore, this study revealed the superior reactivity of NFC as showcased in a copper-catalyzed imidation of benzene derivatives and imidocyanation of aliphatic alkenes, overcoming the limitation of NFSI-mediated reactions.

Sulfonyl fluorides as targets and substrates in the development of new synthetic methods

The advent of sulfur(VI)-fluoride exchange (SuFEx) processes as transformations with click-like reactivity has invigorated research into electrophilic species featuring a sulfur-fluorine bond. Among these, sulfonyl fluorides have emerged as the workhorse functional group, with diverse applications being reported. Sulfonyl fluorides are used as electrophilic warheads by both medicinal chemists and chemical biologists. The balance of reactivity and stability that is so attractive for these applications, particularly the resistance of sulfonyl fluorides to hydrolysis under physiological conditions, has provided opportunities for synthetic chemists. New synthetic approaches that start with sulfur-containing substrates include the activation of sulfonamides using pyrilium salts, the deoxygenation of sulfonic acids, and the electrochemical oxidation of thiols. Employing non-sulfur-containing substrates has led to the development of transition-metal-catalysed processes based on palladium, copper and nickel, as well as the use of SO₂F₂ gas as an electrophilic hub. Selectively manipulating molecules that already contain a sulfonyl fluoride group has also proved to be a popular tactic, with metal-catalysed processes again at the fore. Finally, coaxing sulfonyl fluorides to engage with nucleophiles, when required, and under suitable reaction conditions, has led to new activation methods. This Review provides an overview of the challenges in the efficient synthesis and manipulation of these intriguing functional groups.

Photocatalytic fluorosulfonylation of aliphatic carboxylic acid NHPI esters

SO2 radical insertion/fluorination via a photocatalytic redox strategy is developed, providing an efficient and reliable approach for the synthesis of alkylsulfonyl fluorides.

Aliphatic sulfonyl fluoride synthesis via reductive decarboxylative fluorosulfonylation of aliphatic carboxylic acid NHPI esters

A general and efficient approach to various aliphatic sulfonyl fluorides by the reductive decarboxylative fluorosulfonylation of aliphatic carboxylic acids via a radical sulfur dioxide insertion and fluorination strategy was developed.

SuFEx modification of silk fibroin silicon aerogel and its adsorption behavior and antibacterial performance

A silk fibroin silicon-based composite aerogel (SSA) has been modified via a SuFEx reaction for application in the adsorption of anionic pollutants and antimicrobials in water. The tyrosine fragment in the silk fibroin was modified by a high yielding SuFEx click reaction. A quaternary ammonium salt functionality was introduced into the silk fibroin protein and the modified silk fibroin protein was crosslinked with tetraethyl orthosilicate. The aerogel was then prepared by freeze-drying. The aerogel obtained has biocompatibility and biodegradability properties. Four types of dyes (Methyl orange, Rhodamine B, Methylene blue and Acid red) were applied as targets and the saturated adsorption amounts were calculated. The adsorption behavior of the dyes towards SSA was studied by fitting Langmuir and Freundlich adsorption models. A pseudo-first order kinetic model and a pseudo-second order kinetic model were used to study the kinetics of the adsorption process. After 6 cycles, the removal rate of methyl orange by SSA remained at 81.25%. The adsorption capacity and anti-interference ability of SSA on some other polluting anions such as PO₄^3- and CrO₄^2- were also measured and the efficiency adsorption reached up to 70.94% and 77.91%, respectively. The antibacterial effect of SSA was evaluated with Escherichia coli and Staphylococcus aureus as representative examples.

Fluorosulfonyl radicals: new horizons for the synthesis of sulfonyl fluorides

Recent advances in the generation of fluorosulfonyl radicals toward sulfonyl fluorides are highlighted.

Redox-Neutral Organometallic Elementary Steps at Bismuth: Catalytic Synthesis of Aryl Sulfonyl Fluorides

A Bi-catalyzed synthesis of sulfonyl fluorides from the corresponding (hetero)aryl boronic acids is presented. We demonstrate that the organobismuth(III) catalysts bearing a bis-aryl sulfone ligand backbone revolve through different canonical organometallic steps within the catalytic cycle without modifying the oxidation state. All steps have been validated, including the catalytic insertion of SO₂ into Bi-C bonds, leading to a structurally unique O-bound bismuth sulfinate complex. The catalytic protocol affords excellent yields for a wide range of aryl and heteroaryl boronic acids, displaying a wide functional group tolerance.

Long-Life and High-Rate-Charging Lithium Metal Batteries Enabled by a Flexible Active Solid Electrolyte Interphase Layer

Commercially, lithium metal batteries are still limited by the growth of lithium dendrites and excessive consumption of the electrolyte. A stable multifunctional solid electrolyte interface is the development strategy of lithium metal batteries in the future. However, most of the artificial solid electrolyte interphases (SEIs) cannot meet the original intention of multifunctional design and cannot form an SEI film with a high conductivity and low nucleation potential. In this work, we report a universal and simple method of adding multifunctional fluorosulfonate to a commercial electrolyte, so increasing the inorganic LiF in the SEI. In addition, the imidazole ring in the fluorosulfonate combines with the alkyl group in the electrolyte to form a flexible interface layer, which inhibits the growth of lithium dendrites and makes lithium deposition more uniform, thereby realizing a stable fast charge cycle. With an ultralow capacity of 2 mAh/cm² deposited, the symmetrical battery can be deposited stably for nearly 300 h at a high current density of 20 mA/cm². The capacity retention rate of the Li-LiFePO₄ (LFP) full cell was still at 90.6% after 1000 cycles at 5 C. Even with 5 C high-rate fast charging, the capacity was maintained at 76.56% after 200 cycles, which is four times that of commercial electrolytes. This simple addition strategy gives insights into the practical application of the new electrolyte and provides a new idea for the construction of a stable SEI for commercial lithium metal batteries.

Rapid and column-free syntheses of acyl fluorides and peptides using ex situ generated thionyl fluoride

Thionyl fluoride (SOF₂) was first isolated in 1896, but there have been less than 10 subsequent reports of its use as a reagent for organic synthesis. This is partly due to a lack of facile, lab-scale methods for its generation. Herein we report a novel protocol for the ex situ generation of SOF₂ and subsequent demonstration of its ability to access both aliphatic and aromatic acyl fluorides in 55-98% isolated yields under mild conditions and short reaction times. We further demonstrate its aptitude in amino acid couplings, with a one-pot, column-free strategy that affords the corresponding dipeptides in 65-97% isolated yields with minimal to no epimerization. The broad scope allows for a wide range of protecting groups and both natural and unnatural amino acids. Finally, we demonstrated that this new method can be used in sequential liquid phase peptide synthesis (LPPS) to afford tri-, tetra-, penta-, and decapeptides in 14-88% yields without the need for column chromatography. We also demonstrated that this new method is amenable to solid phase peptide synthesis (SPPS), affording di- and pentapeptides in 80-98% yields.