Nickel Phosphite/Phosphine-Catalyzed C-S Cross-Coupling of Aryl Chlorides and Thiols

Nucleophilic Aromatic Substitution of Heteroaryl Halides with Thiols

The nucleophilic aromatic substitution (SNAr) between heteroaryl halides (Cl, Br) and thiols proceeds smoothly in DMAc under the action of K2CO3 at rt-100 °C. For most electron-deficient heteroarenes, reaction takes place without introducing an additional electron-withdrawing group. For electron-rich heteroarenes, an additional electron-withdrawing group such as a simple ester, keto, cyano, and nitro group is required to ensure the reaction completes. The reactivity trend of heteroaryl halides is highly dependent on the electronic nature of the heteroarenes and orientation of halogens. Besides thiols, a couple of functionalized thioureas and thioamides are compatible with these conditions, providing the corresponding heteroaryl thioethers in good yields.

Mechanochemical Nickel-Catalyzed Carbon-Sulfur Bond Formation between Aryl Iodides and Aromatic Sulfur Surrogates

The formation of aromatic thioethers from C-S coupling is of great importance in synthetic chemistry. Traditional solution strategies through transition-metal catalysis generally require bulk solution, heat, and longer reaction time. Herein, a mechano-promoted sulfenylation of aryl iodides with nickel catalysis is described. The active aromatic sulfide agents are in-situ generated from aromatic thiol or disulfide and subsequently adapted in the nickel catalytic cycle, with a tolerance of broad substituted groups under optimized conditions. In addition to the gram-scale synthesis that reveals the application potential of the method, the radical trapping and competitive experiments are also conducted for the mechanistic study, thus providing a plausible mechanism rationally. Furthermore, the proposed methodology is certificated as being versatile and following the green principles with ideal calculated values of green chemistry metrics, and the comparison with other approaches for C-S bond formation is also demonstrated.

Copper-Catalyzed Direct Thiolation of Ketones Using Sulfonohydrazides: A Synthetic Route to Benzylic Thioethers

A facile copper-catalyzed sustainable thiolation of ketones with sulfonohydrazides has been designed for the efficient construction of benzylic thioethers in excellent yield under mild reaction conditions. The current approach avoids the widely used thiolation reagent, thiols. The commercial availability of the base and reagents, broad substrate scope, and convenient reaction procedure make it an attractive method for benzylic thioether synthesis.

Nickel Catalyzed Cross-Coupling of Aryl and Alkenyl Triflates with Alkyl Thiols

We report a nickel catalyzed C-S cross-coupling of aryl and alkenyl triflates with alkyl thiols. A variety of the corresponding thioethers were synthesized using an air-stable nickel precatalyst under mild reaction conditions with short reaction times. A broad substrate scope, including pharmaceutically relevant compounds, could be demonstrated.

Access to Sterically Hindered Thioethers (α-Thioamides) Under Mild Conditions Using α-Halohydroxamates: Application toward 1,4-Benzothiazinones and 4,1-Benzothiazepinones

Herein, we report a new and highly efficient approach for synthesizing congested α-thioamides under mild reaction conditions (mild base, room temperature, and short duration) using α-halo hydroxamates as direct alkylating agents. The reaction works well with both (hetero)aryl and alkyl thiols, tolerating a broad functional group and diverse substrate scope, including benzeneselenol for selenoether construction. The strategy enables efficient synthesis of biologically relevant 1,4 benzothiazinone and 4,1-benzothiazepinone cores, along with various other functionalized sulfur-based scaffolds of biological importance.

Copper-Catalyzed Thiolation of Hydrazones with Sodium Sulfinates: A Straightforward Synthesis of Benzylic Thioethers

A facile and sustainable protocol for the thiolation of hydrazones with sodium sulfinates has been developed in the presence of CuBr₂ and DBU in DMF to afford diverse benzylic thioethers. Control experiments reveal a radical pathway involving a thiyl radical as a key intermediate.

Ni-catalyzed C-S bond construction and cleavage

Sulfur-containing compounds have attracted considerable interest due to their wide-ranging applications in pharmaceuticals, agriculture, natural products, and organic materials. The development of efficient and rapid methods for the construction and transformation of sulfur-containing compounds is of great importance. Since nickel is inexpensive and has a variety of valence states, strong nucleophilicity and low energy barriers for oxidative addition, the construction and transformation of sulfur-containing compounds by nickel-catalyzed cross-coupling have become important strategies. In addition, sulfur-containing compounds have also been playing increasingly important roles in the field of cross-coupling due to their thermodynamically stable but dynamic activity. This review will focus on nickel-catalyzed construction and transformation of various sulfide-containing compounds, such as sulfides, disulfides, and hypervalent sulfur-containing compounds.

Metal-free photo-induced sulfidation of aryl iodide and other chalcogenation

A photo-induced C-S radical cross-coupling of aryl iodides and disulfides under transition-metal and external photosensitizer free conditions for the synthesis of aryl sulfides at room temperature has been presented, which features mild reaction conditions, broad substrate scope, high efficiency, and good functional group compatibility. The developed methodology could be readily applied to forge C-S bond in the field of pharmaceutical and material science.

Nickel-Catalyzed Regioselective Thiolation of Anilides with Thiols

An efficient method for direct thiolation of anilides with thiols using NiCl2·6H2O as the catalyst is developed. Using this method, the desired products were successfully synthesized in moderate to good yields. Initial mechanistic studies suggest that this reaction proceeds through a radical pathway.

Stepwise synthesis and catalysis in C-S cross-coupling of pyridine-functionalized N-heterocyclic carbene nickel (II) complexes by mechanochemistry

The synthesis of three N-heterocyclic carbene complexes by stepwise grinding was described in this paper. The benzimidazolium salts ([H2L]Br2 and [H2L](PF6)2 ([H2L] =1,1’-di(2-picolyl)-3,3’-methylenedibenzoimidazolium) were initially prepared. Their reactions with Ni(OAc)2·4H2O...

Catalyst-free aerobic radical cascade reactions of o-vinylphenylisocyanides with thiols to access 2-thio-substituted quinolines

We herein report an efficient and green aerobic radical cascade reaction of o-vinylphenylisocyanides with thiols to access a broad range of 2-thio-substituted quinolines without the need for additional catalysts or oxidants.

A Ni(ii)-catalyzed reductive cross-coupling reaction of oxalates and thiosulfonates/selenosulfonates

A Ni(ii)-catalyzed reductive cross-coupling reaction of oxalates and thiosulfonates/selenosulfonates to synthesize benzylic sulfides/selenides under mild conditions is developed.

Dimsyl Anion Enables Visible‐Light‐Promoted Charge Transfer in Cross‐Coupling Reactions of Aryl Halides

A methodology is reported for visible-light-promoted synthesis of unsymmetrical chalcogenides enabled by dimsyl anion in the absence of transition-metals or photoredox catalysts. The cross-coupling reaction between aryl halides and diaryl dichalcogenides proceeds with electron-rich, electron-poor, and heteroaromatic moieties. Mechanistic investigations using UV-Vis spectroscopy, time-dependent density functional theory (TD-DFT) calculations, and control reactions suggest that dimsyl anion forms an electron-donor-acceptor (EDA) complex capable of absorbing blue light, leading to a charge transfer responsible for generation of aryl radicals from aryl halides. This previously unreported mechanistic pathway may be applied to other light-induced transformations performed in DMSO in the presence of bases and aryl halides.

Ni(II) Precatalysts Enable Thioetherification of (Hetero)Aryl Halides and Tosylates and Tandem C-S/C-N Couplings

Ni‐catalyzed C−S cross‐coupling reactions have received less attention compared with other C‐heteroatom couplings. Most reported examples comprise the thioetherification of most reactive aryl iodides with aromatic thiols. The use of C−O electrophiles in this context is almost uncharted. Here, we describe that preformed Ni(II) precatalysts of the type NiCl(allyl)(PMe₂Ar’) (Ar’=terphenyl group) efficiently couple a wide range of (hetero)aryl halides, including challenging aryl chlorides, with a variety of aromatic and aliphatic thiols. Aryl and alkenyl tosylates are also well tolerated, demonstrating, for the first time, to be competent electrophilic partners in Ni‐catalyzed C−S bond formation. The chemoselective functionalization of the C−I bond in the presence of a C−Cl bond allows for designing site‐selective tandem C−S/C−N couplings. The formation of the two C‐heteroatom bonds takes place in a single operation and represents a rare example of dual electrophile/nucleophile chemoselective process.

Nickel-Catalyzed Thiolation of Aryl Nitriles

A nickel-catalyzed thiolation of aryl nitriles has been developed to access functionalized aryl thioethers. The ligand dcype (1,2-bis(dicyclohexylphosphino)ethane) as well as the base KOt Bu (potassium tert-butoxide) are essential to achieve this transformation. This scalable and practical process involves both a C-C bond activation and a C-S bond formation. Furthermore, this reaction shows a high functional-group tolerance and enables the late-stage functionalization of important molecules.

Ag-Cu copromoted direct C2-H bond thiolation of azoles with Bunte salts as sulfur sources

A direct C2-H thiolation of azoles with Bunte salts was achieved under the combined action of copper and silver salts. This protocol could furnish various substituted 2-thioazoles in moderate to good yields. This method has a broad substrate scope and shows good functional group tolerance.

Nickel-Catalyzed Reductive Thiolation of Unactivated Alkyl Bromides and Arenesulfonyl Cyanides

The cross-electrophile coupling between unactivated alkyl bromides with arenesulfonyl cyanides catalyzed by Ni(acac)₂ under reductive conditions to form unsymmetrical sulfides is developed. This approach for sulfide synthesis is practical, relies on available, unfunctionalized materials such as alkyl (pseudo)halides, and is scalable. This catalytic strategy provides a complementary method for the preparation of unsymmetrical alkyl-aryl sulfides under mild conditions with good functional group tolerance.

Streamlined construction of peptide macrocycles via palladium-catalyzed intramolecular S-arylation in solution and on DNA

A highly efficient and versatile method for construction of peptide macrocycles via palladium-catalyzed intramolecular S-arylation of alkyl and aryl thiols with aryl iodides under mild conditions is developed. The method exhibits a broad substrate scope for thiols, aryl iodides and amino acid units. Peptide macrocycles of a wide range of size and composition can be readily assembled in high yield from various easily accessible building blocks. This method has been successfully employed to prepare an 8-million-membered tetrameric cyclic peptide DNA-encoded library (DEL). Preliminary screening of the DEL library against protein p300 identified compounds with single digit micromolar inhibition activity.

Safe, Scalable, Inexpensive, and Mild Nickel-Catalyzed Migita-Like C-S Cross-Couplings in Recyclable Water

A new approach to C-S couplings is reported that relies on nickel catalysis under mild conditions, enabled by micellar catalysis in recyclable water as the reaction medium. The protocol tolerates a wide range of heteroaromatic halides and thiols, including alkyl and heteroaryl thiols, leading to a variety of thioethers in good isolated yields. The method is scalable, results in low residual metal in the products, and is applicable to syntheses of targets in the pharmaceutical area. The procedure also features an associated low E Factor, suggesting a far more attractive entry than is otherwise currently available, especially those based on unsustainable loadings of Pd catalysts.

Highly economical and direct amination of sp3 carbon using low-cost nickel pincer catalyst

Developing more efficient routes to achieve C-N bond coupling is of great importance to industries ranging from products in pharmaceuticals and fertilizers to biomedical technologies and next-generation electroactive materials. Over the past decade, improvements in catalyst design have moved synthesis away from expensive metals to newer inexpensive C-N cross-coupling approaches via direct amine alkylation. For the first time, we report the use of an amide-based nickel pincer catalyst (1) for direct alkylation of amines via activation of sp3 C-H bonds. The reaction was accomplished using a 0.2 mol% catalyst and no additional activating agents other than the base. Upon optimization, it was determined that the ideal reaction conditions involved solvent dimethyl sulfoxide at 110 °C for 3 h. The catalyst demonstrated excellent reactivity in the formation of various imines, intramolecularly cyclized amines, and substituted amines with a turnover number (TON) as high as 183. Depending on the base used for the reaction and the starting amines, the catalyst demonstrated high selectivity towards the product formation. The exploration into the mechanism and kinetics of the reaction pathway suggested the C-H activation as the rate-limiting step, with the reaction second-order overall, holding first-order behavior towards the catalyst and toluene substrate.

Iodine/DMSO-Promoted Selective Direct Arylthiation of Anilines with Thiols under Metal-Free Conditions

An iodine-promoted divergent thiolation of unprotected anilines with thiols for the synthesis of sulfide anilines has been described. The combinational use of I₂ and DMSO played an important role to realize this kind of transformation without the aid of a metal catalyst and strong oxidants. The reaction selectivity was well controlled to provide mono-, bis-, and trisubstituted diaryl sulfide derivatives. More importantly, iodination and sulfenylation can occur simultaneously to provide useful multifunctionalized iodoaniline products. This method afforded an efficient protocol for the construct C-S and C-I bonds from the C-H bond under mild reaction conditions.

Redox-active benzimidazolium sulfonamides as cationic thiolating reagents for reductive cross-coupling of organic halides

Redox-active benzimidazolium sulfonamides as thiolating reagents have been developed for reductive C–S bond coupling. The IMDN-SO₂R reagent provides a bench-stable cationic precursor to generate a portfolio of highly active N–S intermediates, which can be successfully applied in cross-electrophilic coupling with various organic halides. The employment of an electrophilic sulfur source solved the problem of catalyst deactivation and avoided odorous thiols, featuring practical conditions, broad substrate scope, and excellent tolerance.

Redox-active benzimidazolium sulfonamides as thiolating reagents have been developed for reductive C–S bond coupling.

Nickel-Catalyzed Cross-Electrophile Coupling of Aryl Chlorides with Primary Alkyl Chlorides

Alkyl chlorides and aryl chlorides are among the most abundant and stable carbon electrophiles. Although their coupling with carbon nucleophiles is well developed, the cross-electrophile coupling of aryl chlorides with alkyl chlorides has remained a challenge. We report here the first general approach to this transformation. The key to productive, selective cross-coupling is the use of a small amount of iodide or bromide along with a recently reported ligand, pyridine-2,6-bis(N-cyanocarboxamidine) (PyBCam^CN). The scope of the reaction is demonstrated with 35 examples (63 ± 16% average yield), and we show that the Br^- and I^- additives act as cocatalysts, generating a low, steady-state concentration of more-reactive alkyl bromide/iodide.

Thiol Activation toward Selective Thiolation of Aromatic C-H Bond

Direct C-S bond coupling is an attractive way to construct aryl sulfur ether, a building block for a variety of biological active molecules. Herein, we disclose an effective model for regioselective thiolation of the aromatic C-H bond by thiol activation instead of arene activation. Strikingly, this method has been applied into anisole derivatives that are not available in the arene activation approach to forge a single thioether isomer with high reactivity.

CuMoO4 Bimetallic Nanoparticles, An Efficient Catalyst for Room Temperature C-S Cross-Coupling of Thiols and Haloarenes

Cu^II catalyst is less efficient at room temperature for C-S cross-coupling. C-S cross-coupling by Cu^II catalyst at room temperature is not reported; however, doping of copper with molybdenum metal has been realized here to be more efficient for C-S cross-coupling in comparison to general Cu^II catalyst. The doped catalyst CuMoO₄ nanoparticle is found to be more efficient than copper. The catalyst works under mild conditions without any ligand at room temperature and is recyclable and effective for a wide range of thiols and haloarenes (ArI, ArBr, ArF) from milligram to gram scale. The copper-based bimetallic catalyst is developed and recognized for C-S cross-coupling of haloarenes with alkyl and aryl thiols.

Bimetallic BaMoO4 nanoparticles for the C–S cross-coupling of thiols with haloarenes

The C–S cross-coupling of alkyl/aryl thiols with haloarenes using BaMoO₄ nanoparticles was accomplished with high yields, and good functional group tolerance and selectivity. Unactivated bromo and 4-acetyl fluoroarenes can afford thioethers in high yields.

Room temperature nickel-catalyzed cross-coupling of aryl-boronic acids with thiophenols: synthesis of diarylsulfides

A mild and easy to operate NiCl₂/2,2′-bipyridine-catalyzed cross-coupling of thiophenols with arylboronic acids has been developed for the synthesis of symmetric and unsymmetric diarylsulfides at room temperature and in air.

Highly active mesoionic chalcogenone zinc(ii) derivatives for C–S cross-coupling reactions

Mesoionic heavier chalcogenone complexes of zinc(ii) have been isolated and utilized as catalysts in C–S cross coupling reactions between thiophenols and aryl halides under convenient reaction conditions.

Advances in Cu and Ni-catalyzed Chan–Lam-type coupling: synthesis of diarylchalcogenides, Ar2–X (X = S, Se, Te)

Advances in the Cu and Ni-catalyzed Chan–Lam-type coupling of aryl/heteroarylboronic acids with various chalcogen sources for diarylsulfide, diarylselenide and diaryltelluride synthesis are covered in this review.