Synthesis of Sulfoximine Carbamates by Rhodium-Catalyzed Nitrene Transfer of Carbamates to Sulfoxides

Selective N=S Coupling Reactions of N-Methoxy Arylamides and Sulfoxides Catalyzed by Iron Salt

An iron-catalyzed selective N=S coupling of N-methoxy amides and sulfoxides has been developed and was found to be a highly efficient method for the synthesis of N-acyl sulfoximines. Electron-donating as well as electron-withdrawing groups on the phenyl ring are tolerated, and even sensitive substituents are compatible. The current catalytic transformation was conducted under an air atmosphere and can be easily scaled up to a gram scale with a catalyst loading of only 1 mol %. In this case, both coupling partners are used in their native forms, thus obviating prior functionalization and activation.

Bifunctionality of dirhodium tetracarboxylates in metallaphotocatalysis

Metallaphotocatalysis has been recognized as a pivotal catalysis enabling new reactivities. Traditional metallaphotocatalysis often requires two or more separate catalysts and exhibits flaw in cost and substrate-tolerance, thus representing an await-to-solve issue in catalysis. We herein realize metallaphotocatalysis with a bifunctional dirhodium tetracarboxylate ([Rh2]) alone. The [Rh2] shows an photocatalytic activity of promoting singlet oxygen (1O2) oxidation. By harnessing its photocatalytic activity, the [Rh2] catalyzes a photochemical cascade reaction (PCR) via combination of carbenoid chemistry and 1O2 chemistry. The PCR is characterized by high atom-efficiency, excellent stereoselectivities, mild conditions, scalable synthesis, and pharmaceutically interesting products. DFT calculations-aided mechanistic study rationalizes the reaction pathway and interprets the origin of stereoselectivities of the PCR. The products show inhibitory activity against PTP1B, being promising in the treatment of type II diabetes and cancers. Overall, here we show the bifunctional [Rh2] merges Rh-carbenoid chemistry and 1O2 chemistry.

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.

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.

Redox-Neutral Strategy for Sulfilimines Synthesis via S-Arylation of Sulfenamides

In this investigation, an unprecedented transition-metal-free and redox-neutral synthesis of sulfilimines was realized through the S-arylation of readily obtainable sulfenamides employing diaryliodonium salts. The pivotal step encompassed the resonance between bivalent nitrogen-centered anions, engendered postdeprotonation of sulfenamides under alkaline conditions, and sulfinimidoyl anions. The experimental outcomes demonstrate that sulfinimidoyl anionic species function as efficacious nucleophilic reagents, affording sulfilimines with notable to exceptional yields and superlative chemoselectivity, all executed within a transition-metal-free protocol and under exceptionally mild conditions.

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.

Synthesis of Sulfoximine Propargyl Carbamates under Improved Conditions for Rhodium Catalyzed Carbamate Transfer to Sulfoxides

Sulfoximines provide aza-analogues of sulfones, with potentially improved properties for medicinal chemistry. The sulfoximine nitrogen also provides an additional vector for the inclusion of other functionality. Here, we report improved conditions for rhodium catalyzed synthesis of sulfoximine (and sulfilimine) carbamates, especially for previously low-yielding carbamates containing π-functionality. Notably we report the preparation of propargyl sulfoximine carbamates to provide an alkyne as a potential click handle. Using Rh₂(esp)₂ as catalyst and a DOE optimization approach provided considerably increased yields.

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.

Stereospecific reaction of sulfonimidoyl fluorides with Grignard reagents for the synthesis of enantioenriched sulfoximines

Sulfonimidoyl halides have previously shown poor stability and selectivity in reaction with organometallic reagents. Here we report the preparation of enantioenriched sulfonimidoyl fluorides and their stereospecific reaction at sulfur with Grignard reagents. Notably the first enantioenriched alkyl sulfonimidoyl fluorides are prepared, including methyl. The nature of the N-group is important to the success of the stereocontrolled sequence to sulfoximines.

Synthesis of Enantioenriched Primary tert-Butanesulfonimidamides via Imination-Hydrazinolysis of N'-tert-Butanesulfinyl Amidines

The first synthesis of primary tert-butanesulfonimidamides with high enantiopurity was realized by imination (or imination/N-functionalization) of enantioenriched N'-tert-butanesulfinyl amidines, followed by hydrazinolysis. N'-Sulfinyl amidines served as imination precursors during copper-catalyzed sulfonyl nitrene transfer or iodonitrene-based NH transfer. Further transformations allowed access to primary tert-butanesulfonimidamides with diverse substitutions on the nitrogen of S═N.

Stereospecific α-(hetero)arylation of sulfoximines and sulfonimidamides

The occurrence of sulfoximines and sulfonimidoyl groups in biologically active molecules within pharmaceuticals and agrochemicals has notably increased in the past decade. This increase has prompted a wave of discovery of methods to install S(VI) functionality into complex organic molecules. Traditional synthetic methods to form α-substituted sulfonimidoyl motifs rely on S-C bond disconnections and typically require control of the stereogenic S-centre or late-stage modification at sulfur, and comprise multistep routes. Here, we report the development of a stereospecific, modular S_NAr approach for the introduction of sulfonimidoyl functional groups into heterocyclic cores. This strategy has been demonstrated across 85 examples, in good to excellent yield, of complex and diverse heterocycles. Sulfoximines, sulfonimidamides and sulfondiimines are all compatible nucleophiles in the S_NAr reaction and hence, the methodology was applied to the synthesis of four sulfoximine-containing pharmaceuticals. Of these synthetic applications, most notably ceralasertib, an ATR inhibitor currently in clinical trials, was synthesized in an eight-step procedure on a gram-scale.

Flow Electrosynthesis of Sulfoxides, Sulfones, and Sulfoximines without Supporting Electrolytes

An efficient electrochemical flow process for the selective oxidation of sulfides to sulfoxides and sulfones and of sulfoxides to N-cyanosulfoximines has been developed. In total, 69 examples of sulfoxides, sulfones, and N-cyanosulfoximines have been synthesized in good to excellent yields and with high current efficiencies. The synthesis was assisted and facilitated through a supporting electrolyte-free, fully automated electrochemical protocol that highlights the advantages of flow electrolysis.

Synthesis and Configurational Assignment of Vinyl Sulfoximines and Sulfonimidamides

Vinyl sulfones and sulfonamides are valued for their use as electrophilic warheads in covalent protein inhibitors. Conversely, the S(VI) aza-isosteres thereof, vinyl sulfoximines and sulfonimidamides, are far less studied and have yet to be applied to the field of protein bioconjugation. Herein, we report a range of different synthetic methodologies for constructing vinyl sulfoximine and vinyl sulfonimidamide architectures that allows access to new areas of electrophilic chemical space. We demonstrate how late-stage functionalization can be applied to these motifs to incorporate alkyne tags, generating fully functionalized probes for future chemical biology applications. Finally, we establish a workflow for determining the absolute configuration of enantioenriched vinyl sulfoximines and sulfonimidamides by comparing experimentally and computationally determined electronic circular dichroism spectra, enabling access to configurationally assigned enantiomeric pairs by separation.

Photochemistry of N-Phenyl Dibenzothiophene Sulfoximine†

Sulfoximines are popular scaffolds in drug discovery due to their hydrogen bonding properties and chemical stability. In recent years, the role of reactive intermediates such as nitrenes has been studied in the synthesis and degradation of sulfoximines. In this work, the photochemistry of N-phenyl dibenzothiophene sulfoximine [5-(phenylimino)-5H-5λ⁴ -dibenzo[b,d]thiophene S-oxide] was analyzed. The structure resembles a combination of N-phenyl iminodibenzothiophene and dibenzothiophene S-oxide, which generate nitrene and O(³ P) upon UV-A irradiation, respectively. The photochemistry of N-phenyl dibenzothiophene sulfoximine was explored by monitoring the formation of azobenzene, a photoproduct of triplet nitrene, using direct irradiation and sensitized experiments. The reactivity profile was further studied through direct irradiation experiments in the presence of diethylamine (DEA) as a nucleophile. The studies demonstrated that N-phenyl dibenzothiophene sulfoximine underwent S-N photocleavage to release singlet phenyl nitrene which formed a mixture of azepines in the presence of DEA and generated moderate amounts of azobenzene in the absence of DEA to indicate formation of triplet phenyl nitrene.

One-Pot Synthesis of N-Iodo Sulfoximines from Sulfides

This is the first report on the synthesis and characterization of N-iodo sulfoximines. The synthesis was designed as a room temperature one-pot cascade reaction from readily available sulfides as starting compounds, converted into sulfoximines by reaction with ammonium carbonate and (diacetoxyiodo)benzene, followed by iodination with N-iodosuccinimide or iodine in situ, in up to 90% isolated yields, also at a multigram scale. Iodination of aryls with N-iodo sulfoximines, oxidation, and conversion to N-SCF₃ congeners have been demonstrated.

Synthesis of Highly Enantioenriched Sulfonimidoyl Fluorides and Sulfonimidamides by Stereospecific Sulfur-Fluorine Exchange (SuFEx) Reaction

Sulfonimidamides present exciting opportunities as chiral isosteres of sulfonamides, with potential for additional directional interactions. Here, we present the first modular enantioselective synthesis of sulfonimidamides, including the first stereoselective synthesis of enantioenriched sulfonimidoyl fluorides, and studies on their reactivity. A new route to sulfonimidoyl fluorides is presented from solid bench-stable, N-Boc-sulfinamide (Boc=tert-butyloxycarbonyl) salt building blocks. Enantioenriched arylsulfonimidoyl fluorides are shown to be readily racemised by fluoride ions. Conditions are developed, which trap fluoride and enable the stereospecific reaction of sulfonimidoyl fluorides with primary and secondary amines (100 % es, es=enantiospecificity) generating sulfonimidamides with up to 99 % ee. Aryl and alkyl sulfonimidoyl fluoride reagents are suitable for mild late stage functionalisation reactions, exemplified by coupling with a selection of complex amines in marketed drugs.

Synthesis of Sulfinamidines and Sulfinimidate Esters by Transfer of Nitrogen to Sulfenamides

In this work we report a new synthetic tactic for the straightforward preparation of hardly accessible sulfinamidines and sulfinamide esters, by using a simple metal-free protocol. The process is robust and uses readily available sulfenamides as the S-donor and sulfonyloxycarbamates as the N-source. The scope and mechanism have also been investigated.

An efficient imidation of thioethers with nitrene in water

The first imidation of thioethers with free nitrene in water was realized. N-Cbz sulfilimines are formed via imidation of thioethers with free nitrene generated from α elimination of nosyloxycarbamates. In this work, water is successfully applied as solvent for free nitrene, and transition metal catalyst is not needed.

Modern Stereoselective Synthesis of Chiral Sulfinyl Compounds

Chiral sulfinyl compounds, sulfoxides, sulfoximines, sulfinamides, and other derivatives, play an important role in asymmetric synthesis as versatile auxiliaries, ligands, and catalysts. They are also recognized as pharmacophores found in already marketed and well-sold drugs (e.g., esomeprazole) and used in drug design. This review is devoted to the modern methods of preparation of sulfinyl derivatives in enantiopure or enantiomerically enriched form. Selected new approaches leading to racemic products for which the asymmetric variant can be developed in the future are mentioned as well.

General Method for the Asymmetric Synthesis of N-H Sulfoximines via C-S Bond Formation

A versatile method for the synthesis of enantioenriched N-H sulfoximines is reported. The approach stems from the organomagnesium-mediated ring opening of novel cyclic sulfonimidate templates. The reactions proceed in high yield and with excellent stereofidelity with alkyl, aryl, and heteroaryl Grignard reagents. The chiral auxiliary is readily removed from the resultant sulfoximines via an unusual oxidative debenzylation protocol that utilizes molecular oxygen as the terminal oxidant. This provides a general strategy for the synthesis of highly enantioenriched N-H sulfoximines.

Synthesis of NH-Sulfoximines by Using Recyclable Hypervalent Iodine(III) Reagents under Aqueous Micellar Conditions

The synthesis of NH-sulfoximines from sulfides has been first developed under mild conditions in an aqueous solution with surfactant TPGS-750-M as the catalyst at room temperature. In this newly developed process, a simple and convenient recycling strategy to regenerate the indispensable hypervalent iodine(III) is used. The resulting 1,2,3-trifluoro-5-iodobezene can be recovered almost quantitively from the mixture by liquid-liquid extraction and then oxidized to give the corresponding iodine(III) species. This optimized procedure is compatible with a broad range of functional groups and can be easily performed on a gram scale, providing a green protocol for the synthesis of sulfoximines.

Transforming Oxadiazolines through Nitrene Intermediates by Energy Transfer Catalysis: Access to Sulfoximines and Benzimidazoles

Subtle differences in reaction conditions facilitated unprecedented photocatalytic reactions of oxadiazolines by energy transfer catalysis. A set of compounds, sulfoximines and benzimidazoles, were ingeniously prepared from oxadiazolines via nitrene intermediates by photocatalytic N-O/C-N bond cleavages. The synthesis of sulfoximines was realized through intermolecular N-S bond formation between nitrene intermediates and sulfoxides, whereas benzimidazoles were obtained via intramolecular aromatic substitution of the nitrene to the tethered aryl substituent.

N-(2,3,5,6-Tetrafluoropyridyl)sulfoximines: synthesis, X-ray crystallography, and halogen bonding

N-(Tetrafluoropyridyl)sulfoximines are obtained from NH-sulfoximines and pentafluoropyridine under solution-based or mechanochemical conditions, and the solid-state structures of 26 products have been determined by X-ray diffraction analysis.

Batch and Continuous-Flow Iron(II)-Catalyzed Synthesis of Sulfilimines and Sulfoximines using N-Mesyloxycarbamates

The synthesis of sulfilimines and sulfoximines with N-mesyloxycarbamates in presence of catalytic iron(II) chloride hydrate is described. The use of 1-butylimidazole as a base proved instrumental in enabling a homogeneous reaction mixture compatible with continuous flow processes. The amination is applicable to a wide range of substrates, and affords the desired product in good to excellent yields within 1 to 60 minutes.

Copper-promoted dehydrogenative cross-coupling reaction of dialkyl phosphites with sulfoximines

Synthesis of sulfoximine derived phosphoramidates was achieved in good to excellent yields from NH-sulfoximines and dialkyl phosphites.

Safer Synthesis of (Diacetoxyiodo)arenes Using Sodium Hypochlorite Pentahydrate

A practical method for the preparation of (diacetoxyiodo)arene ArI(OAc)₂ is described. The use of commercially available sodium hypochlorite pentahydrate (NaClO·5H₂O) enabled safe, rapid, and inexpensive oxidation of iodoarenes with electron-withdrawing and -donating substituents. The method allows tandem divergent access to synthetically useful organo-λ³-iodanes such as hydroxyl(tosyloxy)iodobenzene, iodosylbenzene, iodonium ylide, etc.

Sulfoximidoyl-Containing Hypervalent Iodine(III) Reagents: 1-Sulfoximidoyl-1,2-benziodoxoles

Treatment of NH-sulfoximines with pseudocyclic benziodoxole triflate results in N-I bond formation leading to a new type of sulfoximidoyl-containing hypervalent iodine(III) reagents in high yields. Degradation studies revealed a pronounced stability in both the solid state and in solution.

Novel Pieces for the Emerging Picture of Sulfoximines in Drug Discovery: Synthesis and Evaluation of Sulfoximine Analogues of Marketed Drugs and Advanced Clinical Candidates

Sulfoximines have gained considerable recognition as an important structural motif in drug discovery of late. In particular, the clinical kinase inhibitors for the treatment of cancer, roniciclib (pan-CDK inhibitor), BAY 1143572 (P-TEFb inhibitor), and AZD 6738 (ATR inhibitor), have recently drawn considerable attention. Whilst the interest in this underrepresented functional group in drug discovery is clearly on the rise, there remains an incomplete understanding of the medicinal-chemistry-relevant properties of sulfoximines. Herein we report the synthesis and in vitro characterization of a variety of sulfoximine analogues of marketed drugs and advanced clinical candidates to gain a better understanding of this neglected functional group and its potential in drug discovery.

Mechanistic investigation of the NH-sulfoximination of sulfide. Evidence for λ6-sulfanenitrile intermediates

One-pot synthesis of NH-sulfoximines from sulfides was reported through fully described acetoxy- and methoxy-λ⁶-sulfanenitrile intermediates (¹H, ¹³C, ¹⁵N NMR and HRMS).