Synthesis of Aryl Alkyl Thioethers via a Copper-Catalyzed Three-Component Reaction with DABSO, Aryldiazonium Salts, and Alkyl Bromides

We developed a method for synthesizing aryl alkyl thioether compounds via a three-component reaction involving aryldiazonium salts, 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide), and alkyl bromides. Optimal yields were achieved when a copper catalyst was used in conjunction with zinc and tetrabutylammonium bromide in an acetonitrile solvent at 130 °C for 10 h. This methodology demonstrates good functional group tolerance and enables the successful synthesis of various aryl alkyl thioethers with moderate to high yields.

Photo-Driven Regiodivergent Arylation/Cyclization and Arylation/Hydroxylation of N-Aryl Methacrylamides with Aryltriazenes: Access to Functionalized 3,3-Disubstituted Oxindoles and α-Hydroxylamides

A metal-free, light-induced regiodivergent functionalization of α,β-unsaturated amides with aryltriazenes under ambient conditions was developed. The visible light and B(C6F5)3 cocatalyzed radical cascade arylation/cyclization of N-alkyl-N-arylmethacrylamides can obtain functionalized 3,3-disubstituted oxindoles with the assistance of photocatalyst eosin Y-Na2. In the absence of any catalyst, with purple light irradiation and electron-donor-acceptor (EDA) complex initiation, the radical cascade arylation/hydroxylation of N-arylmethacrylamides affords α-hydroxylamides. This methodology highlights the arts in accessing different regioisomers by altering the substrates and photocatalytic strategies.

Visible-Light-Promoted Thiolation of Benzyl Chlorides with Thiosulfonates via a Photoactive Electron Donor-Acceptor Complex

Visible-light-promoted thiolation of benzyl chlorides with thiosulfonates is disclosed via an electron donor-acceptor complex strategy. In addition to efficiently delivering a series of arylbenzylsulfide compounds, versatile thioglycosides were also successfully constructed by applying the metal- and photocatalyst-free protocol. Preliminary mechanistic studies suggest that a radical-radical coupling process was involved in this transformation.

Photoinduced Catalyst-Free Deuterodefunctionalization of Aryltriazenes with CDCl3

A photoinduced deuterodetriazenation of aryltriazenes with CDCl3 under catalyst-free conditions is reported. The reactions featured simple operation, ecofriendly conditions, readily available reagents, inexpensive D sources, precise site selectivity, and a wide range of substrates. Since aryltriazenes could be readily synthesized from arylamine, this protocol can be used as a general method for easily and accurately incorporating deuterium into aromatic systems by using CDCl3 as a D source.

Ambient Temperature Metal-Free Thiomethylation of Chloroheteroarenes and Chloropurines

Herein, we report an in-situ mild and metal-free protocol for thiomethylation of heteroarenes in high yields. The thiomethylation of various chloropurines, nucleosides, and chloroheteroarenes has been accomplished offering easy access to agrochemicals and synthetic molecules useful for drug discovery.

Pd-Catalyzed C-7 Arylation of Indolines with Aryltriazenes under Mild Conditions

A palladium-catalyzed direct C-H arylation of indolines at C-7 position has been achieved at near-ambient temperature. The reaction was carried out with aryltriazene as a stable aryl source and electron shuttle to sustainably release aryl radical in situ under the action of promoter, and pyrimidine as a detachable directing group for the synthesis of 7-arylindolines under oxidant- and ligand-free conditions. Notably, this catalytic system can also be applied to the direct and site-selective arylation of tetrahydroquinolines (C-8) and carbazoles (C-1).

One-pot synthesis of 11-sulfenyl dibenzodiazepines via tandem sulfenylation/cyclization of o-isocyanodiaryl amines and diaryl disulfides

A one-pot sulfenylation/cyclization of o-isocyanodiaryl amines has been described for the preparation of 11-sulfenyl dibenzodiazepines. This AgI-catalyzed reaction covers an unexplored tandem process to give seven-membered N-heterocycles. This transformation shows a broad range of substrate scope, simple operation, and moderate to good yields under aerobic conditions. Diphenyl diselenide can also be produced in an acceptable yield.

Recent advances in the chemistry of aryltriazene

Triazene is one of the most versatile building blocks in organic synthesis. Generally, it is viewed as a safe equivalent of diazonium salt, thus immediately finding numerous applications in preparative chemistry and medicinal chemistry. Besides, it can be used as a removable directing group in C-H functionalization or play a smart role as a precursor for aryl cation/radical generation. In this review, we will highlight recent noteworthy developments in this field.

Direct methylthiolation of C-, S-, and P-nucleophiles with sodium S-methyl thiosulfate

A practical and efficient methylthiolation that employed the typical Bunte salt sodium S-methyl sulfothioate as the sulfur source was described. This reagent could react with a variety of compounds such as alkynes, 1,3-diketones, thiols, selenol and H-phosphine oxides, affording methylthiolated products in moderate to excellent yields. The advantages such as easy preparation, air- and moisture-stability and high tolerance of functional groups demonstrated the potential of this reagent to be widely applied in organic synthesis. Notably, the robustness of this reagent was demonstrated by the late-stage modification of drug molecules of erlotinib.

Magnetic mesocellular foams with nickel complexes: as efficient and reusable nanocatalysts for the synthesis of symmetrical and asymmetrical diaryl chalcogenides

In this work, magnetic mesocellular foam (M-MCF) silica nanoparticles were prepared via inserting magnetic nanoparticles into the pores of mesocellular foams, the inner surface of which was functionalized with a methionine-nickel complex (M-MCF@Met-Ni). The structure of the as-prepared nanocatalysts was studied by FT-IR spectroscopy, BET, TGA, VSM, SEM, HR-TEM, EDS, WDX, XRD, and ICP-OES techniques. Thereafter, this nanocatalyst was used as a new, effective, and magnetically reusable catalyst for C-S and C-Se bond formation under mild conditions. All corresponding products were prepared with good yields and appropriate turnover number (TON) and turnover frequency (TOF), which reveals the high activity of this magnetic nanocatalyst in both reactions. In addition, the recovery and hot filtration tests indicated that this catalyst could be simply separated from the reaction mixture using an outside magnet and reused five consecutive times without any significant loss of its catalyst activity or metal leaching.

Synthesis of Four-Membered BN3 Heterocycles by the Borylation of Triazenes

Borylated triazenes were synthesized by the dehydrocoupling of triazenes with 9-borabicyclo(3.3.1)nonane, by the condensation of triazenes with BEt₃, or by the reaction of sodium triazenides with dialkyl- or diarylboron halides. The structures of the products were found to depend on the size of the substituents. Sterically demanding mesityl groups at boron or nitrogen gave rise to open-chain structures, whereas smaller substituents led to the formation of novel BN₃ heterocycles.

Copper catalyzed reaction of alcohols, alkyl halides and Na2S2O3: An odorless and ligand-free rout to unsymmetrical thioether synthesis

A CuI-catalyzed condensation reaction between alcohols, alkyl halides, and Na2S2O3 leading to structurally diverse thioethers is reported. A variety of alkyl halides and electron-rich benzyl alcohols were employed successfully in...

Aerobic Oxidative Cascade Thiolation and Cyclization to Construct Indole-Fused Isoquinolin-6(5H)-one Derivatives in EtOH

A practical method to construct sulfenylated indole-fused isoquinolin-6(5H)-one derivatives has been developed. Using eco-friendly ethanol as the solvent and air as the oxidant, this reaction could be compatible with sensitive molecular framework. The utility of the product was well illustrated by further transformations. Moreover, the reaction mechanism was investigated by control experiments.

Palladium-catalyzed bisthiolation of terminal alkynes for the assembly of diverse (Z)-1,2-bis(arylthio)alkene derivatives

An efficient and straightforward palladium-catalyzed three-component cascade bisthiolation of terminal alkynes and arylhydrazines with sodium thiosulfate (Na₂S₂O₃) as the sulfur source for the assembly of functionalized (Z)-1,2-bis(arylthio)alkene derivatives is described. Using 0.5 mol% IPr–Pd–Im–Cl₂ as the catalyst, a wide range of terminal alkynes and arylhydrazines are well tolerated, thus producing the desired products in good yields with good functional group tolerance and excellent regioselectivity. Moreover, this protocol could be readily scaled up, showing potential applications in organic synthesis and material science.

An efficient palladium-catalyzed bisthiolation of terminal alkynes and arylhydrazines with Na₂S₂O₃ as the sulfur source for the assembly of (Z)-1,2-bis(arylthio)alkene derivatives is described.

From aniline to phenol: carbon-nitrogen bond activation via uranyl photoredox catalysis

Carbon-nitrogen bond activation, via uranyl photoredox catalysis with water, enabled the conversion of 40 protogenetic anilines, 8 N-substituted anilines and 9 aniline-containing natural products/pharmaceuticals to the corresponding phenols in an ambient environment. A single-electron transfer process between a protonated aniline and uranyl catalyst, which was disclosed by radical quenching experiments and Stern-Volmer analysis, facilitated the following oxygen atom transfer process between the radical cation of protonated anilines and uranyl peroxide originating from water-splitting. ¹⁸O labeling and ¹⁵N tracking unambiguously depicted that the oxygen came from water and amino group left as ammonium salt. The 100-fold efficiency of the flow operation demonstrated the great potential of the conversion process for industrial synthetic application.

Unusual Deoxidative Coupling Reaction of β-Sulfinyl Esters with Benzylic Trimethylammonium Salts

A KOH-promoted unusual deoxidative coupling reaction of β-sulfinyl esters with benzylic trimethylammonium salts to produce thioethers is discovered for the first time. If quaternary ammonium salts synthesized from enantiomerically enriched amines are adopted, highly enantiomerically enriched benzyl thioethers (>95-99% ee) with configurations opposite to those of the enantiomerically enriched amines are obtained.

Unusual Application for Phosphonium Salts and Phosphoranes: Synthesis of Chalcogenides

A novel strategy for the synthesis of sulfides and selenides from phosphonium salts and thio- or selenesulfonates, commercially available compounds, is described. When phosphoranes were used in the reaction, different products were obtained. The methodology does not require the use of metals, reactive species, or anhydrous conditions to be performed.

Metal-catalyzed C-S bond formation using sulfur surrogates

Sulfur-containing compounds are present in a wide range of biologically important natural products, drugs, catalysts, and ligands and they have wide applications in material chemistry. Transition metal-catalyzed C-S bond-forming reactions have successfully overcome the obstacles associated with traditional organosulfur compound syntheses such as stoichiometric use of metal-catalysts, catalyst-poisoning and harsh reaction conditions. One of the key demands in metal-catalyzed C-S bond-forming reactions is the use of an appropriate sulfur source due to its odor and availability. The unpleasant odor of many organic sulfur sources might be one of the reasons for the metal-catalyzed C-S bond-forming reactions being less explored compared to other metal-catalyzed C-heteroatom bond-forming reactions. Hence, employing an appropriate sulfur surrogate in the synthesis of organosulfur compounds in metal-catalyzed reactions is still of prime interest for chemists. This review explores the recent advances in C-S bond formation using transition metal-catalyzed cross-coupling reactions and C-H bond functionalization using diverse and commercially available sulfur surrogates. Based on the different transition metal-catalysts, this review has been divided into three major classes namely (1) palladium-catalyzed C-S bond formation, (2) copper-catalyzed C-S bond formation, and (3) other metal-catalyzed C-S bond formation. This review is further arranged based on the different sulfur surrogates. Also, this review provides an insight into the growing opportunities in the construction of complex organosulfur scaffolds covering natural product synthesis and functional materials.

Polysulfuration via a Bilateral Thiamine Disulfurating Reagent

An efficient moduling disulfuration was developed for polysulfide construction via a bilateral six-membered thiamine disulfurating reagent. Under the control of energy release of ring strain, diverse unsymmetrical trisulfides and tetrasulfides were generated through the assembly of nucleophiles on both sides of the sulfur-sulfur motif. This strategy exhibits features of high efficiency, mild conditions, and general scope.

Design, synthesis and biological evaluation of thioether-containing lenalidomide and pomalidomide derivatives with anti-multiple myeloma activity

Lenalidomide and its analogs are well-known for treating multiple myeloma. In this work, designed sulfide-modified lenalidomide and pomalidomide were synthesized and evaluated. The anti-proliferative activity against MM.1S cell line of 3ak (IC₅₀ = 79 nM) was similar to lenalidomide (IC₅₀ = 81 nM). Compared to benzylic thioether substituted lenalidomide 3a, the half-live (T_1/2) of 4-F-phenyl-thioether analogs 3ak in human liver microsomes was promoted from 3 min to 416.7 min. The corresponding metabolic factor of 3ak was increased from 2.8% to 79.5%, which was slightly lower than lenalidomide (91.5%). Moreover, the IKZF1 degradation of 3y and 3ak was well related with corresponding IC₅₀ values, which suggested the IKZF1 degradation efficiency is correlated to the responses of MM1. S cells. Furthermore, the oral administration of compounds 3y and 3ak at dosages of 60 mg/kg could delay tumor growth in female CB-17 SCID mice. This research helped to prompt the stability of thioether lenalidomide analogs, which paved the way for developing better molecules for treating multiple myeloma.

Silver-promoted oxidative sulfonylation and ring-expansion of vinylcyclopropanes with sodium sulfinates leading to dihydronaphthalene derivatives

Silver-promoted sulfonylation and ring-expansion of vinylcyclopropanes with sodium sulfinates is established for the construction of 1-sulfonylmethylated 3,4-dihydronaphthalenes. This sulfonylation process involves a radical pathway, including sulfonyl radical formation, radical addition, ring-opening and cyclization. The 1-sulfonylmethylated 3,4-dihydronaphthalenes can be converted into other useful products.

Iodine-Catalyzed Synthesis of 3-Arylthioindoles Employing a 1-Aryltriazene/CS2 Combination as a New Sulfenylation Source

A practical approach for the regioselective synthesis of 3-arylthioindoles has been accomplished using a combination of 1-aryltriazene/CS₂ as a new sulfenylation source. The methodology employs molecular iodine as a catalyst and is compatible with a variety of structurally diverse reactants.

Brønsted and Lewis acid adducts of triazenes

Spectroscopy and crystallographic data show that triazenes are protonated at N1 position.

Visible-light photoredox-catalyzed dual C–C bond cleavage: synthesis of 2-cyanoalkylsulfonylated 3,4-dihydronaphthalenes through the insertion of sulfur dioxide

A novel visible-light photoredox-catalyzed dual C–C bond cleavage of methylenecyclopropanes and cycloketone oximes for accessing 2-cyanoalkylsulfonated 3,4-dihydronaphthalenes is established.

Promoting Effect of Crystal Water Leading to Catalyst-Free Synthesis of Heteroaryl Thioether from Heteroaryl Chloride, Sodium Thiosulfate Pentahydrate, and Alcohol

It is observed the crystal water in sodium thiosulfate pentahydrate (Na₂S₂O₃·5H₂O) can promote its multicomponent reaction with heteroaryl chlorides and alcohols, providing a facile, green, and specific synthesis of unsymmetrical heteroaryl thioethers via one-step formation of two C-S bonds under catalyst-, additive-, and solvent-free conditions. Mechanistic studies suggest that the crystal water in Na₂S₂O₃·5H₂O is crucial in generating the key thiol intermediates and byproduct NaHSO₄, which then catalyzes the dehydrative substitution of alcohols with thiols to afford thioethers.

Aryl Methyl Sulfone Construction from Eco-Friendly Inorganic Sulfur Dioxide and Methyl Reagents

A three-component cross-coupling protocol of boronic acid, sodium metabisulfite, and dimethyl carbonate was developed for the construction of significant functional methyl sulfones, in which introduction of sulfur dioxide at the last stage was successfully achieved in one step. Inorganic sodium metabisulfite was used as an eco-friendly sulfur dioxide source. Green dimethyl carbonate was employed as methyl reagent in this transformation. Diverse functional methyl sulfones were obtained from various readily available boronic acids. Notably, the last-stage modification of pharmaceuticals and the synthesis of Firocoxib were efficiently established through this strategy.

Direct C-S bond formation via C-O bond activation of phenols in a crossover Pd/Cu dual-metal catalysis system

A dual-metal catalysis system including a newly prepared nanoparticle [SiO2@organic-linker(OL)@Pd(II)] and CuI was introduced with ultra-high catalytic activity (high turnover number (TON), up to 19 000) to a one-pot and odorless synthesis of unsymmetrical aryl sulfides by crossover C-S bond formation. The reaction proceeds via C-O bond activation of phenols and direct C-S bond formation in the presence of S8 as an oddorless sulfur source and aryl boronic acids under mild conditions (room temperature). The catalyst could be recycled up to five times without an obvious change in its activity.

Copper-Catalyzed Electrophilic Thiolation of Organozinc Halides by Using N-Thiophthalimides Leading to Polyfunctional Thioethers

(Hetero)aryl, benzylic, and alkyl zinc halides were thiolated with N-thiophthalimides at 25 °C within 1 h in the presence of 5-10 % Cu(OAc)₂ ⋅H₂ O to furnish the corresponding polyfunctionalized thioethers in good yields. This electrophilic thiolation was extended to the introduction of trifluoromethylthio (SCF₃ ), thiocyanate (SCN), and selenophenyl (SePh) groups. The utility of this method was shown in a seven-step synthesis of a potent cathepsin D inhibitor in 34 % overall yield.

Silver-mediated oxidative C–C bond sulfonylation/arylation of methylenecyclopropanes with sodium sulfinates: facile access to 3-sulfonyl-1,2-dihydronaphthalenes

The novel AgNO₃-mediated sulfonylation/arylation of a C–C σ-bond in MCPs with sodium sulfinates to synthesize 3-sulfonylated 1,2-dihydronaphthalenes is reported.

Visible-light-induced cascade sulfonylation/cyclization of N-propargylindoles with aryldiazonium tetrafluoroborates via the insertion of sulfur dioxide

A simple and efficient visible-light-catalyzed cascade sulfonylation/cyclization of N-propargylindoles with K₂S₂O₅ and aryldiazonium tetrafluoroborates for the construction of 2-sulfonyl-substituted 9H-pyrrolo[1,2-a]indoles is developed.