Syntheses and Transformations of Sulfoximines

Stereoselective Preparation and Palladium-Catalyzed Suzuki-Miyaura Cross-Coupling of Alkenyl Sulfoximines

Although numerous transition-metal catalyzed cross-coupling reactions of alkenyl electrophiles with a sulfur(VI) leaving group, mainly alkenyl sulfones, have been developed, most rely heavily on highly nucleophilic Grignard reagents, and the use of organoboron reagents remains challenging. We report herein facile preparation and the following Pd-catalyzed Suzuki-Miyaura cross-coupling reaction of alkenyl sulfoximine, a monoaza analog of sulfone. The condensation of alkyl sulfoximine with aldehydes, developed in this study, makes alkenyl sulfoximines more readily available. The resulting alkenes undergo an unprecedented oxidative addition of the C-S bond to the Pd center. This cross-coupling proceeds with retention of its original stereochemistry and provided alkenes bearing three different functionalities in a stereoselective fashion. DFT calculations highlight the critical role of boronic acid and in situ-generated boroxines in facilitating this transformation.

Palladium(II)-Catalyzed Regioselective Hydroamination of Allylamines to N-Alkyl Sulfoximines

An intermolecular coupling between sulfoximines and allyl amines, linked to the picolinamide directing group, is developed by leveraging a nucleopalladation-guided regioselective hydroamination strategy, enabling the production of a range of valuable N-alkyl sulfoximines in high yields. The protocol features operational simplicity and a broad substrate scope and was also amenable to aniline nucleophiles. Synthetic utilities were showcased through scale-up reactions and product diversifications, leading to biorelevant molecules.

Gold-Catalysed Intramolecular Reaction of Alkynes with Sulfoximines Acting as N- and O-Transfer Reagents

Among the nucleophilic oxidants employed in the gold-catalysed oxidation of alkynes, sulphur-based reagents have played a substantial role since the beginning, granting access to the respective gold carbene intermediates. Herein, we describe the first example of the substance class of sulfoximines being used as atom transfer reagents to alkynes in gold catalysis. Based on the transformation of N-(2-alkynylphenyl) sulfoximines to 3H-indol-3-ones, it is demonstrated that the sulfoximine functionality is capable of selectively transferring first its nitrogen moiety to the alkyne, forming the α-imino gold carbene, which is then oxidised by the released sulfoxide moiety in a second step via a pseudo-intramolecular mechanism-a distinctive feature that differentiates this work mechanistically from earlier studies. A combination of extensive experimental and theoretical studies provides evidence for this mechanistic rationale. As no external reagents for the 1,2-difunctionalisation of the alkyne unit are required, a wide variety of functional groups are tolerated in the transformation, affording the desired 3H-indol-3-ones in mostly good yields. It was further also showcased that it is possible to combine our methodology with additional transformations of the 3H-indol-3-one core in one-pot procedures, allowing facile access to C2-quaternary indolin-3-one structures.

Paired Electrocatalysis-Enabled Cross Coupling of Sulfinamides with Olefins toward the Synthesis of Vinyl Sulfoximines

We present here a novel paired electrocatalysis-enabled convenient synthesis of the (E)-vinyl sulfoximines through the cross-coupling reaction of sulfinamides and olefins. This protocol showed a broad substrate scope and excellent E selectivity of products under metal- and oxidant-free conditions. A preliminary mechanistic study suggested that fluorinated sulfoximine generated from anodic oxidation of sulfinamide was the key intermediate that was then converted into the sulfonimidoyl radical at the cathode with the help of DBU in this reaction.

Zinc-Catalyzed N-Aroylation of Sulfoximines with Carboxylic Acids

A zinc-catalyzed C(sp2)-N dehydrative cross-coupling between carboxylic acids and NH-sulfoximines to afford N-aroylated sulfoximines under mild reaction conditions is described. Various NH-sulfoximines were coupled with readily available carboxylic acids to provide the corresponding N-aroylated sulfoximines in good to excellent yields.

InCl3 catalyzed simultaneous reductive sulfoximination and O-silylation: synthesis of silyloxy benzylsulfoximine

This article describes the synthesis of ortho-silyloxy benzylsulfoximine via the reaction of salicylaldehyde and sulfoximine in the presence of silane and InCl3. The steps include simultaneous reductive sulfoximination and an O-silylation process. To the best of our knowledge, this is the first report of this kind of reaction, where both reductive amination (here sulfoximination) and O-silylation occur concurrently.

Synthesis of N-Sulfinyl Sulfoximines from 5-(Sulfoximido)dibenzothiophenium Triflates and Sodium Sulfinates

A transition-metal-free and efficient S-O/S-N bond interconversion reaction has been developed. The protocol facilitates an efficient synthesis of N-sulfinyl sulfoximines by reacting sulfoximido-substituted sulfonium salts with a wide range of sodium sulfinates, featuring broad substrate scope, including a plethora of heterocyclic and fluoroalkyl substrates, high functional group tolerance, and mild conditions.

Syntheses of Sulfilimines by Iron-Catalyzed Iminations of Sulfides with 2,2,2-Trichloroethyl Sulfamate

N-protected sulfilimines are prepared by imination of sulfides with a combination of 2,2,2-trichloroethyl sulfamate (H2NTces), (diacetoxyiodo)benzene (PIDA), and a catalytic amount of iron triflate. The reaction proceeds at room temperature, and after only 3 h a wide range of acyclic and cyclic NTces-sulfilimines with various functional groups and (hetero)aryl substituents can be obtained. By subsequent oxidation followed by deprotection, the products are converted into NH-sulfoximines.

Organocatalytic skeletal reorganization for enantioselective synthesis of S-stereogenic sulfinamides

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

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

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

Generation of sulfones utilizing β-sulfinyl esters as masked aryl sulfinates under redox-neutral conditions

A method for generation of SVI sulfones from β-sulfinyl esters (SIV) under transition-metal-free non-oxidative mild conditions is presented. Various sulfones have been achieved with moderate to excellent yields. The advantage of using β-sulfinyl esters as masked aryl sulfinates has also been exemplified using brominated substrates. Oxygen isotope-labeling experiments indicated that the oxygen atoms incorporated into the sulfone product come from the sulfoxide of the β-sulfinyl ester. Successive β-elimination/O-addition/sulfinate esterification/β-elimination processes are proposed for the mechanism of generating SVI from SIV.

PIDA/I2-mediated photo-induced aerobic N-acylation of sulfoximines with methylarenes

A visible-light-promoted, PIDA/I2-mediated acylation of NH-sulfoximines with methylarenes as an acyl source has been achieved. This transition metal and photosensitizer-free approach provides easy access to N-acylsulfoximines via oxidative coupling of sulfoximines with easily available methylarenes without using any peroxide source. Mechanistic investigations suggest the intermediacy of radicals and the importance of molecular oxygen.

Kinetic Resolution of Sulfoximines via Asymmetric Organocatalyzed Formation of Benzothiadiazine-1-oxides

A catalytic kinetic resolution of sulfoximines has been developed through chiral phosphoric acid-catalyzed intramolecular dehydrative cyclizations. A variety of racemic sulfoximines bearing an ortho-amidophenyl moiety underwent asymmetric dehydrative cyclizations using this method, yielding both the recovered sulfoximines and benzothiadiazine-1-oxide products with good to high enantioselectivities (with s-factor up to 61). The diverse derivatizations of the chiral products into a wide range of S-stereogenic center-containing S,N-heterocycles have demonstrated the value of this method.

Thermal Nickel-Catalyzed N-Arylation of NH-Sulfoximines with (Hetero)aryl Chlorides Enabled by PhPAd-DalPhos Ligation

We report a versatile method for cross-coupling of NH-sulfoximines with (hetero)aryl chlorides, as well as bromide and sulfonate electrophiles, that makes use of the air-stable, commercial precatalyst (PhPAd-DalPhos)Ni(o-tol)Cl. Under optimized conditions a diverse electrophile scope is established, including the N-arylation of the pharmaceutical Clozapine. While 5 mol % Ni and 80 °C are commonly employed in this chemistry, successful examples utilizing 1 mol % Ni and/or 25 °C are presented. Competition experiments establish the superiority of NH-sulfoximine over primary sulfonamide as nucleophiles under these conditions.

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.

Facile synthesis of N-(α-furanyl) alkyl sulfoximines via gold catalyzed Michael addition/cyclization of enynones and sulfoximines

Herein, we prepare a new array of N-(α-furanyl) alkyl sulfoximines via a gold catalyzed reaction of enynone with sulfoximine in moderate to very good yields. The reaction involves Michael addition of sulfoximine to enynone, followed by intramolecular cyclization. The presence of two chiral centres led to the formation of a mixture of diastereomers approximately in a 1 : 1 ratio. The salient features of the protocol include broad substrate scope, high efficiency and high yields. The synthetic utility of the protocol is explored using Suzuki-Miyaura cross-coupling and mild, metal-free opening of the furan ring.

Electro-oxidative coupling of Bunte salts with aryldiazonium tetrafluoroborates: a benign access to unsymmetrical sulfoxides

An electrochemical strategy for the synthesis of unsymmetrical sulfoxides has been explored using Bunte salts and aryldiazonium tetrafluoroborates under constant current electrolysis at room temperature. In addition to being eco-safe and using mild conditions, the present protocol is free from the use of metal/oxidant, and is endowed with a broad substrate scope and good functional group tolerance.

Rapid Access to Densely Functionalized Cyclopentenyl Sulfoximines through a Sc-Catalyzed Aza-Piancatelli Reaction

Sulfoximines make up a class of compounds of growing interest for crop science and medicinal chemistry, but methods for directly incorporating them into complex molecular scaffolds are lacking. Here we report a scandium-catalyzed variant of the aza-Piancatelli cyclization that can directly incorporate sulfoximines as nucleophiles rather than the classical aniline substrates. Starting from 2-furylcarbinols and sulfoximines, the reaction provides direct access to 4-sulfoximinocyclopentenones, a new scaffold bearing cyclopentenone and sulfoximine motifs, both of interest for bioactive compounds.

Discovery of piperonyl-tethered sulfoximines as novel low bee-toxicity aphicides targeting Amelα1/ratβ2 complex

Nicotinic acetylcholine receptor (nAChR) is recognized as a significant insecticide target for neonicotinoids and some agonists. In this study, the nAChR α1 subunit from Apis mellifera was first found to be narrowly tuned to different bee toxicity insecticides, namely, sulfoxaflor (SFX) and flupyradifurone (FPF). Hence, novel sulfoximine derivatives 7a-h were rationally designed and synthesized by introducing a benzo[d][1,3]dioxole moiety into a unique sulfoximine skeleton based on the binding cavity characteristics of Amelα1/ratβ2. The two electrode voltage clamp responses of 7a-h were obviously lower than that of SFX, indicating their potentially low bee toxicity. Besides, representative compounds 7b and 7g exhibited low bee toxicity (LD50 > 11.0 μg/bee at 48 h) revealed by acute contact toxicity bioassays. Molecular modelling results indicated that Ile152, Ala151, and Val160 from honeybee subunit Amelα1 and Lys144 and Trp80 from aphid subunit Mpα1 may be crucial for bee toxicity and aphicidal activity, respectively. These results clarify the toxic mechanism of agonist insecticides on nontargeted pollinators and reveal novel scaffold sulfoximine aphicidal candidates with low bee toxicity. These results will provide a new perspective on the rational design and highly effective development of novel eco-friendly insecticides based on the structure of the nAChR subunit.

Nickel-Catalyzed Enantioselective Synthesis of Dienyl Sulfoxide

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

Electrochemical N-Acylation of Sulfoximine with Hydroxamic Acid

Despite the widespread applications of sulfoximines, green and efficient access to functionalized sulfoximines remains a challenge. By employing an electrochemical strategy, we describe an approach for the construction of N-aroylsulfoximines, which features a broad substrate scope, mild reaction conditions, safety on a gram scale, and no need for an external oxidant and transition metal catalysts.

Chromatographic Enantioseparation of Chiral Sulfoximines on Polysaccharide-Based Chiral Stationary Phases

Chiral sulfoximines have significant roles in pharmaceutical industry and agricultural chemicals. Furthermore, chiral structurally related sulfoximines are used for their wide potential applications in some uncharted territory. However, chromatographic study on these compounds has not been systematically performed. Herein, this paper describes the enantioseparation of 12 chiral sulfoximines on polysaccharide-based chiral stationary phases (CSPs). Separation factors of chiral column, high-performance liquid chromatography parameters such as mobile phase composition and column temperature were carefully investigated. Chiralcel OJ-H column can resolve all of the 12 compounds, while Chiralpak AD-H column and Chiralpak AS-H column can separate eight and nine molecules, respectively. The sulfoximines are effectively resolved with Chiralcel OJ-H column with a mixture of n-hexane/2-propanol (80:20) as the mobile phase.

Electrochemical Oxidative Carbonylation of NH-Sulfoximines

The electrochemical synthesis of N-aroylsulfoximines features the use of tetra-n-butylammonium iodide (TBAI) as the medium and a broad substrate scope, thus affording a wide range of N-aroylated sulfoximines in moderate to good yields. The advantages of this electrochemical strategy are augmented by mild reaction conditions that are external oxidant-free, ligand-free, and easy to scale up to gram scale. Both the control experiments and the mechanistic studies revealed that the whole electrochemical process proceeded through a palladium (II/IV/II) catalytic cycle.

Progress in the Enantioselective Synthesis of Sulfur (VI) Compounds

In recent years, there has been a notable surge in the prominence of enantioenriched sulfur(VI) compounds within the chemical science, particularly in the realm of bioactive molecules. However, the synthesis of these enantioenriched sulfur(VI) compounds has posed significant challenges, necessitating the exploration of diverse synthetic methods. Accordingly, this review aims to provide an in-depth analysis of the latest advancements in the synthesis of sulfoximines, sulfonimidate esters, sulfonimidamides, and sulfonimidoyl halides, with a focus on developments since 1971.

Green One-Pot Syntheses of 2-Sulfoximidoyl-3,6-dibromo Indoles Using N-Br Sulfoximines as Both Brominating and Sulfoximinating Reagents

A green one-pot 2,3,6-trifunctionalization of N-alkyl/aryl indoles was achieved by adding three equivalents of N-Br sulfoximine to the indole solution. A variety of 2-sulfoximidoyl-3,6-dibromo indoles were prepared with 38-94% yields using N-Br sulfoximines as both brominating and sulfoximinating reagents. Based on the results of controlled experiments, we propose that a radical substitution involving 3,6-dibromination and 2-sulfoximination occurs in the reaction process. This is first time that 2,3,6-trifunctionalization of indole in one pot has been achieved.

Asymmetric Synthesis of S(IV) and S(VI) Stereogenic Centers

Sulfur can form diverse S(IV) and S(VI) stereogenic centers, of which some have gained significant attention recently due to their increasing use as pharmacophores in drug discovery programs. The preparation of these sulfur stereogenic centers in their enantiopure form has been challenging, and progress made will be discussed in this Perspective. This Perspective summarizes different strategies, with selected works, for asymmetric synthesis of these moieties, including diastereoselective transformations using chiral auxiliaries, enantiospecific transformations of enantiopure sulfur compounds, and catalytic enantioselective synthesis. We will discuss the advantages and limitations of these strategies and will provide our views on how this field will develop.

One-Pot Tandem Oxidative Bromination and Amination of Sulfenamide for the Synthesis of Sulfinamidines

The sulfinamidines as aza analogues of sulfinamides received limited attention from both organic chemists and pharmaceutical chemists. Herein, we present a tandem oxidative/nucleophilic substitution approach for the synthesis of sulfinamidines in high yield (up to 98%). This cascade reaction method is enabled by N-bromosuccinimide (NBS) as an oxidant and diverse readily available amines as nucleophiles without any additives or catalysts. Notably, this method is highly time-economical, safe to operate, and easy to scale up and has excellent functional group compatibility.

Electrochemically Driven Selective Removal of the S═N Bond-Directing Group Using Cyclohexanone Oxime as the Mediator

An inexpensive electrochemical induction system was used for the efficient reductive defunctionalization of sulfoximines through a radical pathway. This practical and robust strategy could be used for the removal of the S═N bond-directing group from various sulfoximines. The practicability of this method was demonstrated by its mild conditions, simple operation, one-pot procedure, gram-scale synthesis, and the undivided cell. Furthermore, preliminary mechanistic studies suggested that the reaction might proceed via a homocoupling reaction and a denitrification procedure.

A One-Pot Domino Reaction Providing Fluorinated 5,6-Dihydro-1,2-thiazine 1-Oxides from Sulfoximines and 1-Trifluoromethylstyrenes

N-Trifluoroacetylated (N-TFA) sulfoximines react with 1-trifluoromethylstyrenes in a one-pot domino reaction to give fluorinated 5,6-dihydro-1,2-thiazine 1-oxides in good to high yields. The process involves three sequential reaction steps that can be characterized as (1) nucleophilic allylic substitution (S_N2'), (2) hydrolysis, and (3) intramolecular nucleophilic vinylic substitution (S_NV). The products can further be modified by defluorination. The molecular structure of the resulting product was confirmed by X-ray crystallographic analysis.

A Copper-Catalyzed Interrupted Domino Reaction for the Synthesis of Fused Triazolyl Benzothiadiazine-1-oxides

Copper(I)-catalyzed domino reactions of 2-azido sulfoximines with 1-iodoalkynes yield fused triazolyl-containing benzothiadiazine-1-oxides. The protocol features the synthesis of two fused heterocyclic rings in one step with good to excellent yields and a broad functional group tolerance. Detailed mechanistic investigations indicate that a copper π-complex initiates a cycloaddition and oxidative C-N coupling reaction sequence. The results suggest an interrupted domino process involving an iodinated triazole as a key intermediate.

Dehydrogenative Imination of Low-Valent Sulfur Compounds-Fast and Scalable Synthesis of Sulfilimines, Sulfinamidines, and Sulfinimidate Esters

Herein, we describe an electrochemical pathway for the synthesis of sulfilimines, sulfoximines, sulfinamidines, and sulfinimidate esters from readily available low-valent sulfur compounds and primary amides or their analogues. The combination of solvents and supporting electrolytes together act both as an electrolyte as well as a mediator, leading to efficient use of reactants. Both can be easily recovered, enabling an atom-efficient and sustainable process. A broad scope of sulfilimines, sulfinamidines, and sulfinimidate esters with N-EWGs is accessed in up to excellent yields with broad functional group tolerance. This fast synthesis can be easily scaled up to multigram quantities with high robustness for fluctuation of current densities of up to 3 orders of magnitude. The sulfilimines are converted into the corresponding sulfoximines in an ex-cell process in high to excellent yields using electro-generated peroxodicarbonate as a green oxidizer. Thereby, preparatively valuable NH sulfoximines are accessible.

Recent Advances in the Synthesis of Cyclic Sulfoximines via C-H Bond Activation

Sulfoximines, a ubiquitous class of structural motifs, are widely present in bioactive molecules and functional materials that have received considerable attention from modern organic chemistry, pharmaceutical industries, and materials science. Sulfoximines have proved to be an effective directing group for C-H functionalization which was widely investigated for the synthesis of cyclic sulfoximines. Within the last decade, great progress has been achieved in the synthesis of cyclic sulfoximines. Thus, this review highlights the recent advances in the synthesis of cyclic sulfoximines via the C-H activation strategy and is classified based on the substrate types.

Synthesis of Sulfoximines and Sulfonimidamides Using Hypervalent Iodine Mediated NH Transfer

The development of NH transfer reactions using hypervalent iodine and simple sources of ammonia has facilitated the synthesis of sulfoximines and sulfonimidamides for applications across the chemical sciences. Perhaps most notably, the methods have been widely applied in medicinal chemistry and in the preparation of biologically active compounds, including in the large-scale preparation of an API intermediate. This review provides an overview of the development of these synthetic methods involving an intermediate iodonitrene since our initial report in 2016 on the conversion of sulfoxides into sulfoximines. This review covers the NH transfer to sulfoxides and sulfinamides, and the simultaneous NH/O transfer to sulfides and sulfenamides to form sulfoximines and sulfonimidamides, respectively. The mechanism of the reactions and the identification of key intermediates are discussed. Developments in the choice of reagents, and in the reaction conditions and setups used are described.

Electro-mechanochemical approach towards the chloro sulfoximidations of allenes under solvent-free conditions in a ball mill

An electro-mechanochemical protocol for the synthesis of vinylic sulfoximines has been developed. Utilising mechanochemically strained BaTiO₃ nanoparticles, the catalytic active system is generated in situ by the reduction of copper(II) chloride. Various combinations of electron-donating and -withdrawing groups are tolerated, and the approach leads to products with difunctionalised double bonds in good to excellent yields. Attempts to add a sulfoximidoyl chloride to an alkyne proved difficult. Additions of a sulfonyl iodide to allenes and alkynes proceeded smoothly in the presence of silica gel without the need for activation by a piezoelectric material.

Decarboxylative sulfoximination of benzoic acids enabled by photoinduced ligand-to-copper charge transfer

Sulfoximines are synthetically important scaffolds and serve important roles in drug discovery. Currently, there is no solution to decarboxylative sulfoximination of benzoic acids; although thoroughly investigated, limited substrate scope and harsh reaction conditions still hold back traditional thermal aromatic decarboxylative functionalization. Herein, we realize the first decarboxylative sulfoximination of benzoic acids via photo-induced ligand to copper charge transfer (copper-LMCT)-enabled decarboxylative carbometalation. The transformation proceeds under mild reaction conditions, has a broad substrate scope, and can be applied to late-stage functionalization of complex small molecules.

The Preparation of Diaryl Sulfoxinium Triflates and Their Application in Palladium-Catalyzed Cross-Coupling Reactions

Treatment of N-methyl-S,S-diaryl sulfoximines with methyl trifluoromethanesulfonate provides bench-stable sulfoxinium salts in excellent yields. Applying them in Sonogashira-, Heck- and Suzuki-type cross-coupling reactions leads to the corresponding products by sequential C-S bond cleavage and C-C bond formation. Electronic factors induced by substituents on the S-aryl groups govern the coupling efficiency.

Superbase-Mediated gem-Difluoroalkenylations of Sulfoximines

At ambient temperature, deprotonated sulfoximines react with 1-trifluoromethylalkenes to provide either N- or C-gem-difluoroalkenylated products. The reaction site depends upon the N substituent of the starting material. The optimal conditions involve the use of a superbasic system NaOH in dimethyl sulfoxide. The reactions are characterized by a broad substrate scope and medium to high yields. Scale-up experiments of both the N- and C-gem-difluoroalkenylations proceeded well. Treatment of a N-difluoroallyl sulfoximine with an aryl thiol under dioxygen afforded the corresponding oxygenated addition product.

Synthesis of β-Arylseleno Sulfoximines: A Metal-Free Three-Component Reaction Mediated by Tetrabutylammonium Tribromide

A tetrabutylammonium tribromide-mediated three-component reaction of alkenes, diselenides, and sulfoximines has been established herein, providing direct and metal-free access to diverse β-arylseleno sulfoximine derivatives. This regioselective sulfoximido-selenization protocol proceeds efficiently under mild and ambient conditions with generally good yields. This strategy is featured by step and atom economy, practicability, a broad substrate scope, and gram-scale synthesis.

Iron(II)-Catalyzed Nitrene Transfer Reaction of Sulfoxides with N-Acyloxyamides

An iron(II)-catalyzed nitrene transfer reaction of sulfoxides with N-acyloxyamides has been developed, leading to the efficient construction of N-acyl sulfoximines with high functional-group compatibility. The current catalytic transformation was carried out under an air atmosphere at ambient temperature and could be scaled up to gram scale with a catalyst loading of 1 mol %. Application of the methodology was demonstrated by facile C-H acetoxylation and olefination using the N-acyl sulfoximine as the directing group.

Organocatalytic atroposelective construction of axially chiral N, N- and N, S-1,2-azoles through novel ring formation approach

1,2-Azoles are privileged structures in ligand/catalyst design and widely exist in many important natural products and drugs. In this report, two types of axially chiral 1,2-azoles (naphthyl-isothiazole S-oxides with a stereogenic sulfur center and atropoisomeric naphthyl pyrazoles) are synthesized via modified vinylidene ortho-quinone methide intermediates. Diverse products are acquired in satisfying yields and good to excellent enantioselectivities. The vinylidene ortho-quinone methide intermediates bearing two hetero atoms at 5-position have been demonstrated as a platform molecule for the atroposelective synthesis of axially chiral 1,2-azoles. This finding not only enrich our knowledge of vinylidene ortho-quinone methide chemistry but also provide the easy preparation method for diverse atropisomeric heterobiaryls that were inaccessible by existing methodologies. The obtained chiral naphthyl-isothiazole S-oxides and naphthyl-pyrazoles have demonstrated their potential application in further synthetic transformations and therapeutic agents.

Visible-Light-Induced N-Acylation of Sulfoximines

A metal-, base-, and additive-free N-acylation of sulfoximines was developed under mild conditions using organic photoredox catalyst. This green strategy featured broad substrate scope, good compatibility with air, and high yields (up to 96%). It could be further applied to amino acid modifications and α-keto N-acyl sulfoximine synthesis without any complicated transformations or operations.

1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP)-Assisted Catalyst-Free Sulfonation of Allylic Alcohols with Sulfinyl Amides

A highly regioselective and catalyst-free sulfonation of allylic alcohols with sulfinyl amides has been realized. Such a mix-and-go procedure provides a convenient approach to synthetically various allylic sulfones under mild reaction conditions. Furthermore, this novel reaction shows ample substrate scope and outstanding functional group tolerance and could also be scaled-up. Meanwhile, it is the first example that sulfinyl amides act as a powerful sulfur nucleophile in the reactions. 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP) as a solvent plays a critical role in allylic sulfonation.

Visible Light-Promoted Synthesis of β-Keto Sulfoximines from N-Tosyl-Protected Sulfoximidoyl Chlorides

Under visible light, N-tosyl-protected sulfoximidoyl chlorides react with aryl alkynes to give β-keto sulfoximines. The reaction is characterized by a high functional group tolerance and good yields. It can be improved by the presence of a ruthenium photocatalyst. Air is the source of the ketonic oxygen in the products.

Accessing Perfluoroaryl Sulfonimidamides and Sulfoximines via Photogenerated Perfluoroaryl Nitrenes: Synthesis and Application as a Chiral Auxiliary

Sulfonimidamides (SIAs) and sulfoximines (SOIs) have attracted attention due to their potential in agriculture and in medicinal chemistry as bioisosteres of biologically active compounds, and new synthetic methods are needed to access and explore these compounds. Herein, we present a light-promoted generation of perfluorinated aromatic nitrenes, from perfluorinated azides, that subsequently are allowed to react with sulfinamides and sulfoxides, generating achiral and chiral SIAs and SOIs. One of the enantiopure SIAs was evaluated as a novel chiral auxiliary in Grignard additions to the imines yielding the product in up to 96:4 diastereomeric ratio.

Rhodium-catalyzed C-H activation/cyclization of aryl sulfoximines with iodonium ylides towards polycyclic 1,2-benzothiazines

The synthesis of 1,2-benzothiazine derivatives through rhodium-catalyzed C-H activation/cyclization of S-aryl sulfoximines with iodonium ylides was developed for the first time. In this report, C-H and N-H bond functionalization was realized towards a series of tricyclic and tetracyclic sulfoximine derivatives with moderate to excellent yields under simple reaction conditions.

Three-Dimensional Heterocycles by 5-exo-dig Cyclizations of S-Methyl-N-ynonylsulfoximines

Upon treatment with Cs₂CO₃, S-methyl-N-ynonylsulfoximines undergo 5-exo-dig cyclizations to give three-dimensional heterocycles. The reactions proceed at ambient temperature with a wide range of substrates affording the corresponding products in good to excellent yields.