Transition-metal-catalyzed C-S, C-Se, and C-Te bond formation via cross-coupling and atom-economic addition reactions

Iron-Mediated One-Pot Dehydroxylative Cross-Electrophile Coupling of Alcohol with Disulfide for Thioether Synthesis by Using TCT as a Hydroxyl-Activating Agent

An efficient dehydroxythiolation between alcohols and disulfides using the widely abundant and cheapest iron as a reaction mediator was developed. The one-pot thiolation proceeded effectively via C-O bond activation with the aid of cyanuric chloride (TCT) as a hydroxyl-activating agent to give the corresponding thioethers in modest to excellent yields, displaying both a wide substrate scope (applicable to benzyl alcohol, allyl alcohol, and primary alkyl alcohol) and good functional group tolerance. In addition, diselenide was also proven to be an appropriate substrate for the protocol, and the reaction could be subjected to scale-up synthesis. Preliminary mechanistic examination revealed that transiently formed TCT-derived ether A, which is generated in situ via the reaction of TCT with alcohol, possibly serves as the pivotal intermediate of the cross-electrophile thioetherification.

Enhanced Oxidative Coupling of Thiols to Disulfides Using the Visible-Light-Responsive POM@MOF Constructed with Ru Metalloligands

The photocatalytic oxidative coupling of thiols to disulfides by using visible light represents an economically viable and environmentally sustainable strategy. A novel POM@MOF photocatalyst (Ru-CdS-SiW) was synthesized through the encapsulation of Keggin-type [SiW12O40]4- within a MOF composed of Ru metalloligands and {Cd4S2O16} clusters. In this structure, the incorporation of POMs to the MOFs reduced the charge transport distance, facilitated the separation and transfer of photogenerated charges and holes, and prevented the recombination of electron-hole pairs. The Ru-CdS-SiW catalyst demonstrated exceptional catalytic performance, achieving a 98.1% yield in the S-S bond formation from 4-methylthiophenol coupling with an apparent quantum yield of 4.8% at 440 nm. Through comprehensive exploratory experiments and electron paramagnetic resonance (EPR) measurements, we elucidated the mechanism underlying the photoinduced oxidative coupling of thiols. Notably, this catalytic reaction operates under mild visible-light conditions and exhibits remarkable recyclability, presenting significant potential for applications in sensitive systems, such as protein disulfide bond formation.

NBS-promoted regioselective thiocyanatothiolation of alkenes with free thiols and NH4SCN

An efficient NBS-promoted three-component thiocyanatothiolation of alkenes with free thiols and NH4SCN has been developed. This protocol avoids tedious preactivation of thiols and employs a diverse range of accessible thiols directly as sulfur sources. Moreover, the reaction exhibits regioselectivity and shows high compatibility with styrenes and unactivated alkenes. Preliminary mechanism studies revealed that both a radical pathway and thiol-oxidation-coupling were involved in this protocol.

Copper-Mediated Enantioselective C-H Thiolation of Ferrocenes Enabled by the BINOL Ligand

Transition-metal-catalyzed enantioselective C-H activation has transformed the landscape of asymmetric synthesis, enabling the efficient conversion of C-H bonds into C-C and carbon-heteroatom (C-X) bonds. However, the formation of C-S bonds through enantioselective C-H thiolation remains underdeveloped due to challenges such as catalyst deactivation and competitive coordination of sulfur-containing compounds with chiral ligands. Herein, we report an unprecedented approach to constructing sulfur-substituted planar chiral ferrocenes (PCFs) through copper-mediated enantioselective C-H thiolation enabled by only a 2.5 mol % 1,1'-bi-2,2'-naphthol (BINOL) ligand. A variety of sulfur-substituted PCFs were obtained in good yields (up to 83%) with excellent enantioselectivity (up to >99% ee). Mechanistic studies reveal that the irreversible C-H activation serves as both the stereo- and rate-determining step and can be achieved with catalytic amounts of Cu species. Furthermore, the utility of this protocol is illustrated through gram-scale synthesis, removal of the directing group, and the synthesis of N,S-chiral ligands as well as chiral rotaxanes. This significant advancement not only expands the tool kit for constructing chiral organosulfur compounds but also highlights the potential of enantioselective C-H activation in asymmetric synthesis.

A stereochemical model and origins of selectivity for the rhodium-catalyzed hydroselenation of styrene

A deeper understanding of the mechanisms underlying transition metal-catalyzed transformation is crucial for developing innovative strategies to synthesize chiral organoselenium compounds. In this study, we developed and investigated a three-layer chirality relay model for the rhodium-catalyzed asymmetric hydroselenation of alkenes through density functional theory (DFT) calculations. In the back layer of this model, the four bulky substituents on the phosphorus atom of the bidentate chiral MeO-BIPHEP ligand were positioned on axial and equatorial bonds, thereby influencing the configuration of the middle layer. The middle layer involved the coordination of selenium to Rh(I) hydride. Carbon chirality in alkanes facilitated reductive elimination in the front layer. The independent gradient model based on the Hirshfeld partition (IGMH) analysis supports this model, and the origins of enantioselectivity were explained through the three-layer chirality relay mechanism. Additionally, computational results revealed that selenol exhibited higher reactivity compared with phenol and thiol. This difference was attributable to its lower bond dissociation energy.

Recent progress in C-S bond formation via electron donor-acceptor photoactivation

Recent advancements in C-S bond formation via electron donor-acceptor (EDA) complex photoactivation have been remarkable. EDA complexes, which are composed of electron donors and acceptors, facilitate C-S bond construction under mild conditions through single-electron transfer events upon visible light irradiation. This review highlights the utilization of various sulfur-containing substrates, including diacetoxybenzenesulfonyl (DABSO), sulfonic acids, sodium sulfinates, sulfonyl chlorides, and thiophenols, in EDA-promoted sulfonylation and thiolation reactions, covering the works published since 2017 to date. These reactions offer novel, environmentally friendly pathways for the synthesis of sulfur-containing compounds.

Exploring nickel-catalyzed organochalcogen synthesis via cross-coupling of benzonitrile and alkyl chalcogenols with computational tools

The preparation of organochalcogens has increased in recent times due to their promising biological activity properties. This work studies the reaction mechanism of a nickel(0)-catalyzed cross-coupling between benzonitrile and propanethiol to produce new C-S bonds by computational means. The proposed mechanism follows the classical oxidative addition/transmetalation/reductive elimination cross-coupling sequence, involving an unusual oxidative addition of a Ph-CN bond onto the active species. The computed catalytic cycle for thioether synthesis has been examined to determine whether the same protocol could be employed to build the analogous C-Se and C-Te bonds. The proposed mechanism for C-S coupling is validated by microkinetic modeling and shows a very good agreement with available experimental data. The extension of the proposed mechanism to C-Se and C-Te couplings indicates that these new reactions should be operative, although their reaction rates appear to be significantly slower.

Base-Promoted Annulation of o-(Cyanomethyl)aryl Thioester with Thiophenols to Access 3-Thiolated Isoquinolones

An efficient annulation approach to forming 3-thiolated isoquinolones from readily accessible o-(cyanomethyl)aryl thioesters and thiophenols has been established. This metal-free annulation is achieved by taking advantage of solvent-free reactions with no precaution to exclude water or air, enabling broad substrate scope and good functionality tolerance. Furthermore, the protocol is scalable and offers facile access to valuable isoquinolones without chromatography.

Bis(dialkylaminethiocarbonyl)disulfides Act as Electron Acceptors for EDA Complexes for the Synthesis of Dithiocarbamate Derivatives under Visible Light

This study proposes a green and efficient atom- and step-economical method for converting hazardous CS2 to dithiocarbamate derivatives under visible light irradiation and catalyst-free conditions. By the construction of novel C-S and C-N bonds, a series of β-dicarbonyl compounds and amines are incorporated into the products. Under light, CS2 and amine first form bis(dialkylaminethiocarbonyl)disulfides, which then react with K2CO3-activated β-dicarbonyl compounds to form electron donor-acceptor (EDA) complexes and subsequently generate the target products. This study confirms for the first time that bis(dialkylaminethiocarbonyl)disulfides can act as electron acceptors to form an EDA complex with β-dicarbonyl compounds, which are then coupled to form the target product under light.

Cross-Coupling Reactions with Nickel, Visible Light, and tert-Butylamine as a Bifunctional Additive

Transition metal catalysis is crucial for the synthesis of complex molecules, with ligands and bases playing a pivotal role in optimizing cross-coupling reactions. Despite advancements in ligand design and base selection, achieving effective synergy between these components remains challenging. We present here a general approach to nickel-catalyzed photoredox reactions employing tert-butylamine as a cost-effective bifunctional additive, acting as the base and ligand. This method proves effective for C-O and C-N bond-forming reactions with a diverse array of nucleophiles, including phenols, aliphatic alcohols, anilines, sulfonamides, sulfoximines, and imines. Notably, the protocol demonstrates significant applicability in biomolecule derivatization and facilitates sequential one-pot functionalizations. Spectroscopic investigations revealed the robustness of the dynamic catalytic system, while elucidation of structure-reactivity relationships demonstrated how computed molecular properties of both the nucleophile and electrophile correlated to reaction performance, providing a foundation for effective reaction outcome prediction.

Hemilabile and Redox-Active Quinone Ligands Unlock sp3-Rich Couplings in Nickel-Catalyzed Olefin Carbosulfenylation

A three-component coupling approach toward structurally complex dialkylsulfides is described via the nickel-catalyzed 1,2-carbosulfenylation of unactivated alkenes with organoboron nucleophiles and alkylsulfenamide (N-S) electrophiles. Efficient catalytic turnover is facilitated using a tailored N-S electrophile containing an N-methyl methanesulfonamide leaving group, allowing catalyst loadings as low as 1 mol %. Regioselectivity is controlled by a collection of monodentate, weakly coordinating native directing groups, including sulfonamides, amides, sulfinamides, phosphoramides, and carbamates. Key to the development of this transformation is the identification of quinones as a family of hemilabile and redox-active ligands that tune the steric and electronic properties of the metal throughout the catalytic cycle. Density functional theory (DFT) results show that the duroquinone (DQ) ligand adopts different coordination modes in different stages of the Ni-catalyzed 1,2-carbosulfenylation-binding as an η6 capping ligand to stabilize the precatalyst/resting state and prevent catalyst decomposition, binding as an X-type redox-active durosemiquinone radical anion to promote alkene migratory insertion with a less distorted square planar Ni(II) center, and binding as an L-type ligand to promote N-S oxidative addition at a relatively more electron-rich Ni(I) center.

Alkylthiolation of Aryl Halides under Electrochemical Conditions

An electrochemical protocol for the alkylthiolation of aryl halides was developed. By using dialkyl disulfides as the alkylthio sources, Mg plate as the sacrificial anode and graphite felt (GF) as the cathode, a series of aryl sulfides were obtained in moderate to good yields. The approach was also suitable for the synthesis of aryl selenides. This method has the features such as simple reaction conditions and good functional group compatibility, which makes it have a good application prospect in organic synthesis and drug synthesis.

Trifluoromethylthiolation Carbonylation of Unactivated Alkenes via Distal Migration

Sulfur-containing compounds represent a significant category of organic compounds, and the introduction of sulfur groups into organic compounds can effectively enhance their biological activity and synthetic diversity. Although a variety of difunctionalization reactions of alkenes based on sulfur radicals have been documented, significant challenges remain in the carbonylative difunctionalization of unactivated alkenes by the addition of a sulfur radical. Herein, we present a trifluoromethylthiolative carbonylation reaction of unactivated alkenes, which goes through the addition of a trifluoromethylthiol radical to unactivated alkenes and then carbonylation of the newly generated carbon radical intermediate. A heterocyclic/aryl migration in the presence of carbon monoxide is crucial for the success of this methodology and finally resulted in the formation of sulfur-containing carbonylated products in good yields.

Visible-light-driven catalyst-free C-S cross-coupling of thiol derivatives and aryl halides

A mild, scalable, and high-yielding visible-light-promoted C-S cross-coupling between alkyl thiol derivatives and (hetero)aryl halides without the need for metals, ligands, or photocatalysts is reported, offering advantages over traditional C-S bond forming strategies. The formation of an electron donor-acceptor (EDA) complex is supported by experimental and computational mechanistic studies, which undergoes visible-light-induced charge transfer to initiate C-S bond formation in the absence of a photoredox catalyst.

Construction of axially chiral 2-arylpyrroles using catalytic asymmetric Suzuki-Miyaura cross-coupling: an efficient approach to esaxerenone

A general and efficient method has been developed to access axially chiral 2-arylpyrroles using catalytic asymmetric Suzuki-Miyaura cross-coupling. A wide range of axially chiral arylpyrroles were obtained in high yields with good to excellent enantioselectivities. The key to success is the use of a combined catalytic system involving a palladium catalyst and chiral ferrocene diphosphine ligand for achieving effective enantiocontrol. More importantly, this axially chiral CF3-substituted 2-arylpyrrole serves as a key intermediate in the preparation of the anti-hypertensive and diabetic nephropathy drug esaxerenone. It was directly asymmetrically synthesized with high enantioselectivity (92% ee). Thus, a new strategy is provided for the catalytic asymmetric synthesis of esaxerenone.

Overriding Cage Effect in Electron Donor-Acceptor Photoactivation of Diaryliodonium Reagents: Synthesis of Chalcogenides

In recent times, diaryliodonium reagents (DAIRs) have witnessed a resurgence as arylating reagents, especially under photoinduced conditions. However, reactions proceeding through electron donor-acceptor (EDA) complex formation with DAIRs are restricted to electron-rich reacting partners serving as donors due to the well-known cage effect. We discovered a practical and high-yielding visible-light-induced EDA platform to generate aryl radicals from the corresponding DAIRs and use them to synthesize key chalcogenides. In this process, an array of DAIRs and dichalcogenides react in the presence of 1,4 diazabicyclo[2.2.2]octane (DABCO) as a cheap and readily available donor, furnishing a variety of di(hetero)aryl and aryl/alkyl chalcogenides in good yields. The method is scalable, features a broad scope with good yields, and operates under open-to-air conditions. The photoinduced chalcogenation technology is suitable for late-stage functionalizations and disulfide bioconjugations and facilitates access to biologically relevant thioesters, dithiocarbamates, sulfoximines, and sulfones. Moreover, the method applies to synthesizing diverse pharmaceuticals, such as vortioxetine, promazine, mequitazine, and dapsone, under amenable conditions.

Ru(II)-Catalyzed C7 Trifluoromethylthiolation and Thioarylation of Indolines Using Bench-Stable Reagents

A Ru(II)-catalyzed C(sp2)-H trifluoromethylthiolation and thioarylation of indolines using bench-stable reagents have been explored. Diversely substituted indolines were functionalized at C7 position in good to excellent yields. Radical quenching, deuterium labeling, KIE, and reaction order determination experiments were performed to support the proposed reaction pathway. Gram-scale synthesis and post-transformation of the synthesized products have also been carried out to demonstrate the applicability of the developed catalytic protocol.

Highly selective synthesis of selenium-containing (E)-N-propenolquinazolinones via FeCl3-mediated cascade reaction of propargyl quinazoline-4-yl ethers with diselenides

An effective approach for the highly selective synthesis of selenium-containing (E)-N-propenolquinazolinones via an FeCl3·6H2O mediated cascade reaction of propargyl quinazoline-4-yl ethers and diselenides has been developed. Mechanistic investigations revealed that the reaction of FeCl3 and (PhSe)2 generates, in situ, the electrophilic species PhSe[FeCl4]·6H2O, which triggers the cascade reaction.

Cobalt-catalyzed reductive cross-coupling: a review

Transition-metal-catalyzed reductive cross-coupling is highly efficient for forming C-C bonds. It earns its limelight from its application by coupling unreactive electrophilic substrates to synthesize a variety of carbon-carbon bonds with various hybridizations (sp, sp2, and sp3), late-stage functionalization, and bioactive molecules' synthesis. Reductive cross-coupling is challenging to bring selectivity but promising approach. Cobalt is comparatively more affordable than other highly efficient metals e.g., palladium and nickel but cobalt catalysis is still facing efficacy challenges. Researchers are trying to harness the maximum out of cobalt's catalytic properties. Shortly, with efficiency achieved combined with the affordability of cobalt, it will revolutionize industrial applications. This review gives insight into the core of cobalt-catalyzed reductive cross-coupling reactions with a variety of substrates forming a range of differently hybridized coupled products.

Facile Synthesis of β-trifluoromethyl thioethers via DBN-catalyzed Hydrothiolation of α-(Trifluoromethyl)styrenes with Thiols

A very simple and atom-economical method for the synthesis of vicinal trifluoromethyl thioethers via DBN-catalyzed hydrothiolation of α-(trifluoromethyl)styrenes with thiols was reported. The reaction proceeded smoothly under mild reaction conditions and provided the β-CF3-thioethers in moderate to good yields in an anti-Markovnikov manner. Furthermore, this method features several remarkable advantages, such as the use of a catalytic amount of DBN, broad substrate scope, excellent functional group compatibility, and easy scalability.

Fe(III)-catalyzed p-selective C-H bond chalcogenation of phenols

An efficient, eco-friendly, and scalable protocol has been introduced for the p-selective C-X (X = Se/S) bond formation of phenols employing earth-abundant, less-toxic Fe(III)-catalysts and the green solvent ethanol without using any directing template, stabilizing ligands, oxidants, or additives. The key attraction lies in the impressive p-selectivity with moderate to good yields, wide functional group compatibility under mild aerobic reaction conditions, and the synthetic modification of the products towards value-added molecules.

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.

Ultra-Fast Selenol-Yne Click (SYC) Reaction Enables Poly(selenoacetal) Covalent Adaptable Network Formation

The emergence of covalent adaptable networks (CANs) based on dynamic covalent bonds (DCBs) presents a promising avenue for achieving resource recovery and utilization. In this study, we discovered a dynamic covalent bond called selenacetal, which is obtained through a double click reaction between selenol and activated alkynes. Density functional theory (DFT) calculations demonstrated that the ΔG for the formation of selenoacetals ranges from 12 to 18 kJ mol-1, suggesting its potential for dynamic reversibility. Dynamic exchange experiments involving small molecules and polymers provide substantial evidence supporting the dynamic exchange properties of selenoacetals. By utilizing this highly efficient click reaction, we successfully synthesized dynamic materials based on selenoacetal with remarkable reprocessing capabilities without any catalysts. These materials exhibit chemical recycling under alkaline conditions, wherein selenoacetal (SA) can decompose into active enone selenide (ES) and diselenides. Reintroducing selenol initiates a renewed reaction with the enone selenide, facilitating material recycling and yielding a newly developed dynamic material exhibiting both photo- and thermal responsiveness. The results underscore the potential of selenoacetal polymers in terms of recyclability and selective degradation, making them a valuable addition to conventional covalent adaptable networks.

Cross-Electrophile Couplings of Benzyl Sulfonium Salts with Thiosulfonates via C-S Bond Activation

A zinc-mediated cross-electrophile coupling of benzyl sulfonium salts with thiosulfonates via C-S bond cleavage was achieved. The reductive thiolation proceeded well under transition metal-free conditions to afford the desired benzyl sulfides in good yields, exhibiting both broad substrate scope and good functionality tolerance. In addition, the reaction could be applied to the use of selenosulfonate as an effective selenylation agent and be subjected to scale-up synthesis.

Dual Ligand Enabled Pd-Catalyzed Ortho-Alkylation of Iodoarenes

The synthesis of complex polysubstituted aromatic molecules from simple precursors is a central goal in organic chemistry. In this study, we developed an approach for the ortho-alkylation of iodoarenes utilizing a dual ligand catalytic system. By combining Pd/olefin ligand cooperative catalysis with bulky trialkylphosphine ligand-promoted C(sp2)-I reductive elimination, we have established an ortho-alkylative Catellani-type reaction with the aryl-iodine bond reconstruction as the final step, which opens new synthetic opportunities within the Catellani-type reactions. Through in-depth mechanistic investigations, we have isolated and characterized key organopalladium intermediates, revealing the synergistic interaction of the dual ligands in merging the Catellani-type process with C(sp2)-I reductive elimination. The present study showcases the unique advantages of Pd/olefin ligand catalysis and emphasizes the effectiveness of the dual ligand system in expanding the chemical space of the Catellani chemistry.

Metal-organic frameworks for organic transformations by photocatalysis and photothermal catalysis

Organic transformation by light-driven catalysis, especially, photocatalysis and photothermal catalysis, denoted as photo(thermal) catalysis, is an efficient, green, and economical route to produce value-added compounds. In recent years, owing to their diverse structure types, tunable pore sizes, and abundant active sites, metal-organic framework (MOF)-based photo(thermal) catalysis has attracted broad interest in organic transformations. In this review, we provide a comprehensive and systematic overview of MOF-based photo(thermal) catalysis for organic transformations. First, the general mechanisms, unique advantages, and strategies to improve the performance of MOFs in photo(thermal) catalysis are discussed. Then, outstanding examples of organic transformations over MOF-based photo(thermal) catalysis are introduced according to the reaction type. In addition, several representative advanced characterization techniques used for revealing the charge reaction kinetics and reaction intermediates of MOF-based organic transformations by photo(thermal) catalysis are presented. Finally, the prospects and challenges in this field are proposed. This review aims to inspire the rational design and development of MOF-based materials with improved performance in organic transformations by photocatalysis and photothermal catalysis.

Cobalt-catalyzed hydrothiolation of alkynes for the diverse synthesis of branched alkenyl sulfides

Alkenyl sulfides have gained increasing prominence in medicinal chemistry and materials. Hydrothiolation of alkynes for the diverse synthesis of alkenyl sulfides is an appealing method. Herein, we report a cobalt-catalyzed Markovnikov hydromethylthiolation of alkynes to afford branched alkenyl methylsulfanes with good yields and high regioselectivity. This method also enables the diverse synthesis of branched alkenyl sulfides. The reaction shows good functional group tolerance and could be scaled up. The mechanistic studies including control experiments, deuterium-labeling experiments, and Hammett plot indicated alkynes insertion followed by electrophilic thiolation pathway.

Enantioselective Arylation of Sulfenamides to Access Sulfilimines Enabled by Palladium Catalysis

Sulfur-containing functional groups have garnered considerable attention due to their common occurrence in ligands, pharmaceuticals, and insecticides. Nevertheless, enantioselective synthesis of sulfilimines, particularly diaryl sulfilimines remains a challenging and persistent goal. Herein we report a highly enantio- and chemoselective cross-coupling of sulfenamides with aryl diazonium salt to construct diverse S(IV) stereocenters by Pd catalysis. Bisphosphine ligands bearing sulfinamide groups play a crucial role in achieving high reactivity and selectivity. This approach provides a general, modular and divergent framework for quickly synthesizing chiral sulfilimines and sulfoximines that are otherwise challenging to access. In addition, the origins of the high chemoselectivity and enantioselectivity were extensively investigated using density functional theory calculations.

Electrosynthesis of Cyclic Isoureas and Ureas Through Contiguous Heterofunctionalizations

An efficient synthetic protocol for the selenylated cyclic isoureas was developed using electrochemical activation of diselenides. This sustainable approach permitted transition metal and chemical oxidant-free difunctionalization of olefins and overall access to distinct 1,2,3 triheterofunctionalized carbon skeletons. Excellent functional group tolerance was noticed, allowing the synthesis of a series of cyclic isourea derivatives. In addition, an acid-triggered skeletal isomerization facilitated the synthesis of cyclic urea derivatives from the corresponding cyclic isoureas. Mechanistic investigations, along with voltammetric studies, enabled the postulation of the reaction mechanism.

Reactions of alkynes with C-S bond formation: recent developments

Alkynes are important in organic synthesis. This review mainly focuses on recent advances (2013-2023) on alkynes with C-S bond formation, based on more than 30 types of sulfur reagents. The reactions of alkynes with various sulfur-containing compounds including RSSR (disulfides), RSH (thiols), S8 (elemental sulphur), alkynyl thioethers, RSCN, AgSCF3, K2S, Na2S, dithiane, RSCl, NFSI, RNCS, EtOCS2K, thiocarbamate, RSONH2, thiourea, sulfoxide, RSO2N3, CS2, RSO2NH2, RSO2NHNH2, RSO2Cl, RSO2Oar, RSO2SR', DABCO·(SO2)2, Na2S2O5, K2S2O5, RSO2H, RSO2Na and related compounds are discussed. Diverse mechanisms such as radical, electrophilic/nucleophilic addition, rearrangement, C-C bond cleavage, and CuAAC are discussed. The content is organized by substrates and reactivity patterns. We hope it will help in future research in this area.

Asymmetric Synthesis and Applications of Chiral Organoselenium Compounds: A Review

The synthesis and application of organoselenium compounds have developed rapidly, and chiral organoselenium compounds have become an important intermediate in the field of medicine, materials, organic synthesis. The strategy of developing a green economy is still a challenge in the synthesis of chiral organoselenium compounds with enantioselective properties. This review covers in detail the synthesis of chiral organoselenium compounds from 1979 to 2024 and their application in the fields of asymmetric synthesis and catalysis.

Electrophotocatalytic Tellurosulfonylation of Alkynes for the Synthesis of β-(Telluro)vinyl Sulfones

Difunctionalization of alkynes has gained a lot of interest in current organic chemistry. Herein, we developed an electrophotocatalytic multicomponent cascade reaction of alkynes and indoles with sulfinic acid sodium salts using elemental tellurium as the tellurium source. Using synergistic anodic oxidation and visible-light irradiation, various β-(telluro)vinyl sulfones have been prepared. This strategy features mild reaction conditions, excellent substrate scope, readily available starting materials, and great functional group tolerance.

Metal-free oxidative coupling of aryl acetylene with elemental sulphur and amines: facile access to α-ketothioamides

A simple and efficient oxidative coupling of aromatic alkynes with elemental sulphur and secondary amines has been reported. The iodine/DMSO system easily promoted the transformations, affording thioglyoxamides via C-S, C-O, and C-N bond formations. In this context, acetylenic C-H bond oxidation has occurred through iodination, leading to the desired products. Moreover, this metal-free, one-pot protocol is accomplished by using readily available starting materials, without external oxidants, and under aerobic conditions, providing a variety of α-ketothioamide compounds in moderate to good yields.

C(sp)-H, S-H, and Sn-H Bond Activation with a Cobalt(I) Pincer Complex

This study focuses on the stoichiometric reactions of {2,6-(iPr2PO)2C6H3}Co(PMe3)2 with terminal alkynes, thiols, and tin hydrides as part of an effort to develop catalytic, two-electron processes with cobalt. This specific Co(I) pincer complex proves to be effective for cleaving the C(sp)-H, S-H, and Sn-H bonds to give oxidative addition products with the general formula {2,6-(iPr2PO)2C6H3}CoHX(PMe3) (X = alkynyl, thiolate, and stannyl groups) along with the free PMe3. These reactions typically reach completion when the substituents on acetylene, sulfur, and tin are electron-withdrawing groups (e.g., phenyl, pyridyl, and alkenyl groups). In contrast, alkyl-substituted acetylenes, 1-pentanethiol, and tributyltin hydride are partially converted due to the equilibria with the corresponding oxidative addition products. The Co(I) pincer complex is not a hydrothiolation catalyst but capable of catalyzing the hydrostannation of terminal alkynes with Ph3SnH to produce β-(Z)-alkenylstannanes selectively.

Rh-Catalyzed Asymmetric Hydrogenation of 2-Substituted 4H-(Thio)chromenes for Synthesis of Chiral (Thio)chromanes

Rh-catalyzed asymmetric hydrogenation of 2-substituted 4H-thiochromenes and 4H-chromenes was successfully developed. This method provided highly efficient access to a series of chiral 2-substituted thiochromanes and chromanes in high yields with excellent enantioselectivities (up to 99% yield, 86-99% ee). The obtained chiral 2-substituted thiochromane products were also successfully transformed to corresponding chiral α-substituted sulfoxides and sulfones with excellent enantioselectivities. Furthermore, this highly enantioselective hydrogenation process could be successfully applied to the concise and practical synthesis of the chiral pharmaceutical BW683C.

Electrochemical selenylative ipso-annulation of N-benzylacrylamides to construct seleno-azaspiro[4.5]decadienones

Herein, we present the electrochemical synthesis of selenylated azaspiro[4.5]decadienones through domino selenylation/ipso-annulation of N-benzylacrylamides with diselenides. The method showed a wide substrate scope under mild and external oxidant-free reaction conditions, involving the construction of C-Se and C-C bonds. Gram-scale synthesis and further functional group conversion of the product are also demonstrated.

Metal-catalyzed Markovnikov-type selective hydrofunctionalization of terminal alkynes

Metal-catalyzed highly Markovnikov-type selective hydrofunctionalization of terminal alkynes provides a straightforward and atom-economical route to access 1,1-disubstituted alkenes, which have a wide range of applications in organic synthesis. However, the highly Markovnikov-type selective transformations are challenging due to the electronic and steric effects during the addition process. With the development of metal-catalyzed organic synthesis, different metal catalysts have been developed to solve this challenge, especially for platinum group metal catalysts. In this perspective, we review homogeneous metal-catalyzed Markovnikov-type selective hydrofunctionalization of terminal alkynes according to the classified element types as well as reaction mechanisms. Future avenues for investigation are also presented to help expand this exciting field.

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.

t-BuOLi promoted regioselective N-thiolation of indoles with N-arylthio phthalimide

The selective N-thiolation of indole substrates poses a challenge due to their diminished nucleophilicity at nitrogen. Herein, we present a novel method for the thiolation of the NH group in indole derivatives by using N-arylthio phthalimide as the sulfur source, t-BuOLi as the base and MeCN as the solvent. The process was successfully conducted under transition metal catalyst-free and room temperature conditions with a high product yield and a short reaction time. The developed protocol exhibited excellent regioselectivity and broad substrate tolerance in the preparation of N-thioindoles with diverse functional groups.

Transition-Metal-Catalyzed Transformations for the Synthesis of Marine Drugs

Transition metal catalysis has contributed to the discovery of novel methodologies and the preparation of natural products, as well as new chances to increase the chemical space in drug discovery programs. In the case of marine drugs, this strategy has been used to achieve selective, sustainable and efficient transformations, which cannot be obtained otherwise. In this perspective, we aim to showcase how a variety of transition metals have provided fruitful couplings in a wide variety of marine drug-like scaffolds over the past few years, by accelerating the production of these valuable molecules.

Sulfur in Waste-Free Sustainable Synthesis: Advancing Carbon-Carbon Coupling Techniques

This review explores the pivotal role of sulfur in advancing sustainable carbon-carbon (C-C) coupling reactions. The unique electronic properties of sulfur, as a soft Lewis base with significant mesomeric effect make it an excellent candidate for initiating radical transformations, directing C-H-activation, and facilitating cycloaddition and C-S bond dissociation reactions. These attributes are crucial for developing waste-free methodologies in green chemistry. Our mini-review is focused on existing sulfur-directed C-C coupling techniques, emphasizing their sustainability and comparing state-of-the-art methods with traditional approaches. The review highlights the importance of this research in addressing current challenges in organic synthesis and catalysis. The innovative use of sulfur in photocatalytic, electrochemical and metal-catalyzed processes not only exemplifies significant advancements in the field but also opens new avenues for environmentally friendly chemical processes. By focusing on atom economy and waste minimization, the analysis provides broad appeal and potential for future developments in sustainable organic chemistry.

Reaction Pattern and Mechanistic Aspects of Iodine and Iodine-Based Reagents in Selenylation of Aliphatic, Aromatic, and (Hetero)Cyclic Systems

Organoselenium compounds have been the subject of extensive research since the discovery of the biologically active compound ebselen. Ebselen has recently been found to show activity against the main protease of the virus responsible for COVID-19. Other organoselenium compounds are also well-known for their diverse biological activities, with such compounds exhibiting interesting physical properties relevant to the fields of electronics, materials, and polymer chemistry. In addition, the incorporation of selenium into various organic molecules has garnered significant attention due to the potential of selenium to enhance the biological activity of these molecules, particularly in conjunction with bioactive heterocycles. Iodine and iodine-based reagents play a prominent role in the synthesis of organoselenium compounds, being valued for their cost-effectiveness, non-toxicity, and ease of handling. These reagents efficiently selenylate a broad range of organic substrates, encompassing alkenes, alkynes, and cyclic, aromatic, and heterocyclic molecules. They serve as catalysts, additives, inducers, and oxidizing agents, facilitating the introduction of different functional groups at alternate positions in the molecules, thereby allowing for regioselective and stereoselective approaches. Specific iodine reagents and their combinations can be tailored to follow the desired reaction pathways. Here, we present a comprehensive review of the progress in the selenylation of organic molecules using iodine reagents over the past decade, with a focus on reaction patterns, solvent effects, heating, microwave, and ultrasonic conditions. Detailed discussions on mechanistic aspects, such as electrophilic, nucleophilic, radical, electrochemical, and ring expansion reactions via selenylation, multiselenylation, and difunctionalization, are included. The review also highlights the formation of various cyclic, heterocyclic, and heteroarenes resulting from the in situ generation of selenium intermediates, encompassing cyclic ketones, cyclic ethers, cyclic lactones, selenophenes, chromones, pyrazolines, pyrrolidines, piperidines, indolines, oxazolines, isooxazolines, lactones, dihydrofurans, and isoxazolidines. To enhance the reader's interest, the review is structured into different sections covering the selenylation of aliphatic sp2/sp carbon and cyclic sp2 carbon, and then is further subdivided into various heterocyclic molecules.

Synthesis of Diaryl Tellurides with Sodium Aryltellurites under Mild Conditions

A highly efficient new protocol has been developed for the formation of C-Te bonds, leading to both symmetrical and unsymmetrical diaryl tellurides. This protocol utilizes sodium aryltellurites (4), which can be easily prepared from low-cost aryltelluride trichlorides and NaOH. The synthesis involves the use of 4 and arylazo sulfones as starting materials in the presence of (MeO)2P(O)H. A variety of diaryl tellurides are obtained in moderate to good yields using this method. Importantly, this innovative protocol eliminates the need for traditional, highly toxic aryltellurolating reagents such as diaryl ditellurides and elemental tellurium. This study will bring new vitality to the synthesis of tellurides.

Recent trends in the synthesis and applications of β-iodovinyl sulfones: a decade of progress

Direct vicinal difunctionalization of π-systems has emerged as a powerful platform for constructing multiple bonds in a single synthetic operation using simple chemical feedstocks. Over the past decade, there has been exponential growth in the direct construction of successive C-S and C-I bonds using a wide variety of sulfonyl and iodide reactants through 1,2-iodosulfonylation of alkynes in a regio- and stereo-selective manner. In this review, we mainly focus on the recent developments in the preparation of β-iodovinyl sulfones and their practical applications in organic synthesis. The most promising photoredox and electrochemical transformations for synthesizing β-iodovinyl sulfones are also reviewed. The multifunctional β-iodovinyl sulfones have recently been burgeoning as versatile synthetic precursors due to the combination of vinyl iodide and vinyl sulfone moieties, essential building blocks for diverse synthetic manipulations. We hereby present the chemistry of β-iodovinyl sulfones, which can be classified into numerous sections based on the sulfonyl surrogates, and potential synthetic approaches are systematically outlined.

Development and synthesis of a novel salen-type ligand based on phenylalanine for Mizoroki-Heck, and S-arylation cross-coupling reactions

In this article, we introduced a novel salen-type ligand precursor and applied it in the Pd-catalyzed Mizoroki-Heck and Cu-catalyzed S-arylation cross-coupling reactions. For the preparation of this structure, (DL)-phenyl alanine was employed as a starting material. These ligand precursor and related catalytic system can be readily synthesised. Various aryl halides (-I, -Br) and alkenes were applied successfully in this protocol to give the corresponding Mizoroki-Heck cross-coupling and S-arylated products in high to excellent yields.

Direct Access to Thio- and Seleno-acetamides Bearing (Benzo)thiazoles by a Base-Promoted One-Pot Two-Step Three-Component Reaction of 2-Amino(benzo)thiazoles with Aryl Acetyl Chlorides and Dichalcogenides

Highly efficient and practical carbon-chalcogen (S, Se) and amide bonds formation methodologies for the synthesis of thio- and seleno-acetamides were developed, via the base-promoted one-pot two-step reactions of 2-amino(benzo)thiazoles and aryl acetyl chlorides with dichalcogenides. This cross-coupling reaction afforded the goal products that had been chalcogenated regioselectively in moderate to good yields. Further transformations of the new synthesized compounds, DFT calculations and preliminary mechanism studies are discussed as well.

Recent advances in selective mono-/dichalcogenation and exclusive dichalcogenation of C(sp2)-H and C(sp3)-H bonds

Organochalcogen compounds are prevalent in numerous natural products, pharmaceuticals, agrochemicals, polymers, biological molecules and synthetic intermediates. Direct chalcogenation of C-H bonds has evolved as a step- and atom-economical method for the synthesis of chalcogen-bearing compounds. Nevertheless, direct C-H chalcogenation severely lags behind C-C, C-N and C-O bond formations. Moreover, compared with the C-H monochalcogenation, reports of selective mono-/dichalcogenation and exclusive dichalcogenation of C-H bonds are relatively scarce. The past decade has witnessed significant advancements in selective mono-/dichalcogenation and exclusive dichalcogenation of various C(sp2)-H and C(sp3)-H bonds via transition-metal-catalyzed/mediated, photocatalytic, electrochemical or metal-free approaches. In light of the significance of both mono- and dichalcogen-containing compounds in various fields of chemical science and the critical issue of chemoselectivity in organic synthesis, the present review systematically summarizes the advances in these research fields, with a special focus on elucidating scopes and mechanistic aspects. Moreover, the synthetic limitations, applications of some of these processes, the current challenges and our own perspectives on these highly active research fields are also discussed. Based on the substrate types and C-H bonds being chalcogenated, the present review is organized into four sections: (1) transition-metal-catalyzed/mediated chelation-assisted selective C-H mono-/dichalcogenation or exclusive dichalcogenation of (hetero)arenes; (2) directing group-free selective C-H mono-/dichalcogenation or exclusive dichalcogenation of electron-rich (hetero)arenes; (3) C(sp3)-H dichalcogenation; (4) dichalcogenation of both C(sp2)-H and C(sp3)-H bonds. We believe the present review will serve as an invaluable resource for future innovations and drug discovery.

Cleavage and Noncleavage Chemistry in Reactive Oxygen Species (ROS)-Responsive Materials for Smart Drug Delivery

The design and development of advanced drug delivery systems targeting reactive oxygen species (ROS) have gained significant interest in recent years for treating various diseases, including cancer, psychiatric diseases, cardiovascular diseases, neurological diseases, metabolic diseases, and chronic inflammations. Integrating specific chemical bonds capable of effectively responding to ROS and triggering drug release into the delivery system is crucial. In this Review, we discuss commonly used conjugation linkers (chemical bonds) and categorize them into two groups: cleavable linkers and noncleavable linkers. Our goal is to clarify their unique drug release mechanisms from a chemical perspective and provide practical organic synthesis approaches for their efficient production. We showcase numerous significant examples to demonstrate their synthesis routes and diverse applications. Ultimately, we strive to present a comprehensive overview of cleavage and noncleavage chemistry, offering insights into the development of smart drug delivery systems that respond to ROS.

Heterogeneously catalyzed decarbonylation of thioesters by supported Ni, Pd, or Rh nanoparticle catalysts

Decarbonylation of thioesters has been actively studied using homogeneous metal catalysts as an attractive approach for synthesizing thioethers, which are widely utilized in various fields, because decarbonylation ideally requires no additives and produces CO as the sole theoretical byproduct. However, heterogeneously catalyzed decarbonylation of thioesters has not been reported to date, despite its importance for the construction of environmentally-friendly and practical catalytic systems. This study demonstrated a heterogeneously catalyzed system for the decarbonylation of various aryl thioesters to produce thioethers and CO by utilizing CeO2- or hydroxyapatite-supported Ni, Pd, or Rh nanoparticle catalysts. The Ni catalysts showed high catalytic activity, while the Pd catalysts possessed excellent functional group tolerance. The Rh catalysts were suitable for the selective decarbonylation of unsymmetrically substituted thioesters.

Bidentate Ligand Driven Intramolecularly Te…O Bonded Organotellurium Cations from Synthesis, Stability to Catalysis

A new series of unsymmetrical phenyl tellurides derived from 2-N-(quinolin-8-yl) benzamide ligand has been synthesized in a practical manner by the copper-catalyzed method by using diaryl ditelluride and Mg as a reductant at room temperature. In order to augment the Lewis acidity of these newly formed unsymmetrical monotellurides, these have been transformed into corresponding unsymmetrical 2-N-(quinolin-8-yl)benzamide tellurium cations. Subsequently, these Lewis acidic tellurium cations were used as chalcogen bonding catalysts, enabling the synthesis of various substituted 1,2-dihydroquinolines by activating ketones with anilines under mild conditions. Moreover, the synthesized 2-N-(quinolin-8-yl)benzamide phenyl tellurium cation has also catalyzed the formation of β-amino alcohols in high regioselectivity by effectively activating epoxides at room temperature. Mechanistic insight by 1 H and 19 F NMR study, electrostatic surface potential (ESP map), control reaction in which tellurium cation reacted explosively with epoxide, suggested that the enhanced Lewis acidity of tellurium center seems responsible for efficient catalytic activities under mild conditions enabling β-amino alcohols with excellent regioselectivity and 1,2-dihydroquinolines with trifluoromethyl, nitro, and pyridylsubstitution, which were difficult to access.