Chemistry with Electrochemically Generated N-Centered Radicals

Phosphorus-Doped Single Atom Copper Catalyst as a Redox Mediator in the Cathodic Reduction of Quinazolinones

The use of clean electric energy to activate inert compounds has garnered significant attention. Homogeneous redox mediators (RMs) in organic electrosynthesis are effective platforms for this purpose. However, understanding the RM's electronic structure under operational conditions, electron transport processes at the electrode surface, and substrate adsorption-desorption dynamics remains challenging. Here, we synthesized a Cu single-atom catalyst (SAC, named Cu─N─P@NC) with a CuN3P1 micro-coordination structure, employing it as a unique cathode redox mediator. Introducing phosphine atoms into the coordination system allowed modulation of the SAC's electronic metal-support interaction, optimizing catalyst-substrate adsorption-desorption dynamics and accelerating electrochemical reactions. Utilizing the heterogeneous SAC strategy, we achieved a novel electro-reduction coupling ring-opening reaction of inert quinazolinone frameworks. The Cu-SAC exhibited exceptionally high catalytic activity and substrate compatibility, operating smoothly at gram-scale production. Additionally, we applied the SAC to modify 11 natural product molecules. Integrating micro-coordination environment regulation and theoretical adsorption models elucidated the significant influence of electrode-RMs-substrate interactions on reaction kinetics and catalytic efficiency-a feat challenging for homogeneous RMs. This approach offers a novel pathway for advancing efficient organic electrosynthesis reactions and provides critical insights for mechanistic studies.

Electrochemical Conversions of Sulfenamides into Sulfonimidoyl- and Sulfondiimidoyl Fluorides

The invention of versatile linkage agents provides the chemical basis for SuFEx chemistry. Sulfonimidoyl fluorides and sulfondiimidoyl fluorides are aza-isosteres of sulfonyl fluorides with diverse reactivity through the fine-tuning of N-substituents. However, limited synthetic approaches impede their wide applications in SuFEx chemistry. Herein, we develop a straightforward electrochemical strategy for sulfonimidoyl- and sulfondiimidoyl fluorides through sequential oxidations of the readily available sulfenamides via sulfinamide and iminosulfinamide intermediates, respectively. The previously rarely investigated (bis)-sulfondiimidoyl fluorides are now easily accessible and readily participate in SuFEx chemistry with diverse oxygen and nitrogen nucleophiles, macrocyclization, and polymerization.

Rapid Access to a Cyclobutane-Containing Skeleton Fused with Chromane through In(III)-Catalyzed Intramolecular Annulation of 5-Hydroxy Benzochromene

Intramolecular oxidative annulation of 5-hydroxy benzochromene via In(OTf)3 and DDQ catalysis, through an ortho-quinone methide radical intermediate, afforded various cyclobutane-containing products in good to excellent yields. This oxidative annulation pathway reveals great group tolerance and broad compatibility with benzochromene. In addition, this method exhibits an excellent ability to synthesize cyclobutane-containing products in gram-scale experiments, providing a novel approach to synthesize a series of natural products, such as cannabicyclol, isoeriobrucinol A, and ranhuadujuanine A.

Energy-Transfer-Enabled 1,4-Amino Migration and C-O Diradical Recombination for Norrish-Yang-Type Epoxidation

An energy-transfer-enabled photochemical strategy merges 1,4-nitrogen migration with Norrish-Yang-type epoxidation to achieve skeletal editing of molecular frameworks. This approach bypasses classical di-π-methane rearrangements, providing an oxidant-free and atom-economical route to epoxides via controlled C-O diradical recombination. The protocol accommodates >40 diverse substrates, including arenes, heterocycles, and bioactive motifs, enabling late-stage functionalization of complex architectures. Scalability is demonstrated through gram-scale synthesis (84% yield) and one-pot cascades. Mechanistic studies reveal a triplet energy-transfer pathway distinct from radical chain processes, with nitrogen migration directing regioselective diradical recombination.

Electrooxidative synthesis of 1,2,3-triazolone 1-amines

A new method for the synthesis of newly reported heterocycles, namely 1,2,3-triazolone 1-amines, via electrochemically induced intramolecular N-N bond formation was developed. The process involves electrooxidative cyclization of readily available α-aminocarbonyl hydrazones, occurs under mild conditions and enables the preparation of a diverse series of target compounds, although nitrophenyl-substituted substrates undergo decomposition upon electrolysis. Cyclic voltammetry (CV) measurements were also conducted to determine the reaction mechanism and to explain the observed scope limitations. In addition, thermal behavior studies demonstrated moderate thermal stability of several synthesized 1,2,3-triazolone 1-amines in the range of 110-140 °C. Overall, this study represents a promising contribution to the electroorganic synthesis of neglected nitrogen heterocycles for various biomedical and materials science applications.

Recent advances in electrochemical utilization of NHPI esters

Electrochemical methods employing N-hydroxyphthalimide (NHPI) esters have emerged as powerful tools for sustainable organic synthesis. Derived from abundant and stable alkyl carboxylic acids, NHPI esters enable the generation of alkyl radicals through single-electron transfer (SET) and decarboxylation, facilitating carbon-carbon (C-C) and carbon-heteroatom (C-X) bond formation. These reactions are vital for synthesizing complex molecules used in pharmaceuticals, agrochemicals, and advanced materials, yet traditional approaches often depend on harsh conditions, toxic reagents, or costly metals. This review explores recent progress in electrochemical applications of NHPI esters, highlighting their role in both metal-catalyzed (e.g., Ni, Cr) and metal-free systems.

Dual-nickel/photoredox-catalyzed acylation of spiro-dihydroquinazolinones with carboxylic acids via an aromatization-driven deconstructive strategy

Dual-nickel/photoredox-catalyzed aromatization-mediated deconstruction and acylation of spiro-dihydroquinazolinones with carboxylic acids serving as acyl electrophiles is described. A series of synthetical ketone scaffolds with functional group tolerance could be obtained under mild conditions. A radical pathway involving an N-centered radical inducing β-scission to form a C-centered radical is proposed for these transformations.

Room Temperature Access to Bridged Nitrogen Ligands via Electroreductive Annulation of 1,10-Phenanthrolines and Imines

An electroreductive annulation reaction of 1,10-phenanthrolines and imines has been developed. This method proceeds with broad substrate and functionality tolerance, high selectivity, and no need for pressurized H2 gas or transition metal catalysts. Mechanistic studies reveal that the products are formed via simultaneous electroreduction of both proton-activated reactants followed by radical cross-coupling and intramolecular cyclization of the coupling adduct.

A dual-radical process for tri/di-fluoromethylarylation of alkenes enabled by indirect electroreduction

This study presents a stable and mild electrochemical dual-radical strategy for tri/di-fluoromethylarylation of alkenes. The synergistic combination of cyanoarene and phenanthrene as dual redox mediators constructs an efficient catalytic system.

Organo-mediator enabled electrochemical transformations

Electrochemistry has emerged as a powerful means to facilitate redox transformations in modern chemical synthesis. This review focuses on organo-mediators that facilitate electrochemical reactions via outer-sphere electron transfer (ET) between active mediators and substrates, offering advantages over direct electrolysis due to their availability, ease of modification, and simple post-processing. They prevent overoxidation/reduction, enhance selectivity, and mitigate electrode passivation during the electrosynthesis. By modifying the structure of organo-mediators, those with tunable redox potentials enable electrosynthesis and avoid metal residues in the final products, making them promising for further application in synthetic chemistry, particularly in pharmacochemistry, where the maximum allowed level of the metal residue in synthetic samples is extremely strict. This review highlights the recent advancements in this rapidly growing area within the past two decades, including the electrochemical organo-mediated oxidation (EOMO) and electrochemical organo-mediated reduction (EOMR) events. The organo-mediator enabled electrochemical transformations are discussed according to the reaction type, which has been categorized into oxidation and reduction organic mediators.

Synthesis of Rare 1,2,3-Triazolium-5-olates by Electrooxidative Cyclization of α-Aminocarbonyl Hydrazones

A new method for the synthesis of rare mesoionic heterocycles, namely, 1,2,3-triazolium-5-olates, via electrochemically induced intramolecular N-N bond formation was realized. The process involves electrooxidative cyclization of the readily available α-aminocarbonyl hydrazones, occurs under mild conditions, and enables the preparation of a diverse series of target mesoionics. Additionally, 1,2,3-triazolium-5-olates demonstrated high thermal stability (up to 275 °C) and feature prominent Stokes shifts (7600-8050 cm-1), which enables their application potential for analytical systems and materials science.

Electrochemically promoted tandem cyclization of functionalized methylenecyclopropanes: synthesis of tetracyclic benzazepine derivatives

In this study, an electrocatalytic tandem cyclization reaction of amide-tethered methylenecyclopropanes has been developed, which can realize the rapid construction of tetracyclic benzazepine derivatives in moderate yields with good functional group compatibility under relatively mild conditions. In this transformation, the catalytic amount of ferrocene serves as the electrocatalytic medium, and electron transfer on electrodes can replace oxidants or reducing agents, which is more environmentally friendly than and economically comparable to traditional photocatalysis or metal catalysis. Moreover, the origin of the regiochemistry is well elucidated through density functional theory (DFT) calculations.

Electrochemical Benzylic C-H Carboxylation

Direct benzylic C-H carboxylation stands as a high atom economy, efficient, and convenient route for the synthesis of valuable benzylic carboxylic acids, which are of great significance in many pharmaceuticals and bioactive molecules. However, the inherent inertness of both benzylic C-H bonds and carbon dioxide presents a great challenge for further transformations. Herein, we report our efforts to overcome this obstacle via halide-promoted linear paired electrolysis to generate various benzylic carboxylic acids. Remarkably, this process is transition-metal- and base-free, making it environmentally benign and cost-effective. Besides, it is suitable for constructing a wide range of primary, secondary, and tertiary benzylic carboxylic acids under mild reaction conditions, demonstrating broad substrate scopes and good functional group tolerance. Furthermore, our protocol enables the direct synthesis of some drug molecules, including Flurbiprofen, Ibuprofen, and Naproxen, and facilitates the late-stage modification of complex compounds, showcasing the practical application in synthetic chemistry and underscores its potential to advance the synthesis of benzylic carboxylic acids and related compounds.

Proton-Modulated Nickel Hydride Electrocatalysis for the Hydrogenation of Unsaturated Bonds and Olefin Isomerization

Transition-metal hydrides stand as indispensable intermediates in both energy conversion and organic synthesis. Their electrochemical generation represents a compelling sustainable approach, enabling precise control over the reactivity and expanding the scope of electrocatalytic hydrogenation and isomerization. However, a major challenge in Ni-catalyzed electrochemical hydrogenation is the competing hydrogen evolution reaction (HER), which has led to various innovative strategies aimed at circumventing Ni-H formation. Here, we pursued an alternative approach by designing a bifunctional ligand with a pendant amine moiety to promote Ni-H formation. This design enabled selective (semi)hydrogenation of a diverse range of substrates, including terminal and internal alkynes, alkenes, and aldehydes, achieving an unprecedented substrate scope. Remarkably, we also demonstrated tunable positional selectivity for olefin isomerization by employing different types of proton sources. Our hydrogenation and isomerization method also exhibits excellent functional group tolerance, streamlining access to pharmaceuticals and their derivatives. Computational studies revealed the crucial, noninnocent role of the proton source in modulating metal hydride selectivity, either through hydrogen bonding, direct protonation of the pendant amine, or facilitation of protodemetalation.

A TEMPO-N3 Complex Enables the Electrochemical C-H Azidation of N-Heterocycles through the Cleavage of Alkoxyamines

A TEMPO-N3 charge-transfer complex enables the electrochemical C-H azidation of various N-heterocycles. The TEMPO+ ion, generated from TEMPO, assists in producing N3 ⋅ by forming a TEMPO-N3 complex with N3 -. The formation of this complex is supported by UV-vis absorption spectra, cyclic voltammetry studies, and ESI-HRMS studies. The reaction likely proceeds by forming a highly labile azidooxygenation adduct, which undergoes oxidative alkoxyamine mesolytic cleavage. Subsequent deprotonation of the resulting carbocation exclusively produces the azidation product. It is important to note that substituted olefins generally yield azidooxygenation or diazidation as the final product. Our study demonstrates that N-heterocycles deliver a selective monoazidation product, possibly due to steric reasons. ESI-HRMS studies provide evidence for forming azidooxygenation and alkoxyamine radical cation adducts. The regio- and chemoselectivity of this azidation reaction using the TEMPO-N3 complex have been discussed.

Electrochemical Amination of Aryl Halides with NH3

Primary arylamines are the most pivotal class of organic motifs in pharmaceuticals, agrochemicals, ligands and natural products. Ammonia (NH3) is an ideal nitrogen source in terms of reactivity, atom economy, and environmental compatibility. Despite significant progress in the synthesis of primary arylamines, the development of a general method for rapid access to diversely functionalized primary arylamines is still urgent and necessary. Herein, we developed a method for the direct synthesis of primary arylamines through electrochemical amination of aryl halides with NH3. Notably, the weak nucleophilic reagent NH3 was directly used as an ammonia surrogate, allowing for efficient conversion of carbon-halogen bonds to diverse primary arylamines with good functional group tolerance. A broad scope of functionalized primary arylamines has been achieved in moderate to excellent yields.

Isolated Metal Centers Activate Small Molecule Electrooxidation: Mechanisms and Applications

Electrochemical oxidation of small molecules shows great promise to substitute oxygen evolution reaction (OER) or hydrogen oxidation reaction (HOR) to enhance reaction kinetics and reduce energy consumption, as well as produce high-valued chemicals or serve as fuels. For these oxidation reactions, high-valence metal sites generated at oxidative potentials are typically considered as active sites to trigger the oxidation process of small molecules. Isolated atom site catalysts (IASCs) have been developed as an ideal system to precisely regulate the oxidation state and coordination environment of single-metal centers, and thus optimize their catalytic property. The isolated metal sites in IASCs inherently possess a positive oxidation state, and can be more readily produce homogeneous high-valence active sites under oxidative potentials than their nanoparticle counterparts. Meanwhile, IASCs merely possess the isolated metal centers but lack ensemble metal sites, which can alter the adsorption configurations of small molecules as compared with nanoparticle counterparts, and thus induce various reaction pathways and mechanisms to change product selectivity. More importantly, the construction of isolated metal centers is discovered to limit metal d-electron back donation to CO 2p* orbital and reduce the overly strong adsorption of CO on ensemble metal sites, which resolve the CO poisoning problems in most small molecules electro-oxidation reactions and thus improve catalytic stability. Based on these advantages of IASCs in the fields of electrochemical oxidation of small molecules, this review summarizes recent developments and advancements in IASCs in small molecules electro-oxidation reactions, focusing on anodic HOR in fuel cells and OER in electrolytic cells as well as their alternative reactions, such as formic acid/methanol/ethanol/glycerol/urea/5-hydroxymethylfurfural (HMF) oxidation reactions as key reactions. The catalytic merits of different oxidation reactions and the decoding of structure-activity relationships are specifically discussed to guide the precise design and structural regulation of IASCs from the perspective of a comprehensive reaction mechanism. Finally, future prospects and challenges are put forward, aiming to motivate more application possibilities for diverse functional IASCs.

Iodoarene Activation: Take a Leap Forward toward Green and Sustainable Transformations

Constructing chemical bonds under green sustainable conditions has drawn attention from environmental and economic perspectives. The dissociation of (hetero)aryl-halide bonds is a crucial step of most arylations affording (hetero)arene derivatives. Herein, we summarize the (hetero)aryl halides activation enabling the direct (hetero)arylation of trapping reagents and construction of highly functionalized (hetero)arenes under benign conditions. The strategies for the activation of aryl iodides are classified into (a) hypervalent iodoarene activation followed by functionalization under thermal/photochemical conditions, (b) aryl-I bond dissociation in the presence of bases with/without organic catalysts and promoters, (c) photoinduced aryl-I bond dissociation in the presence/absence of organophotocatalysts, (d) electrochemical activation of aryl iodides by direct/indirect electrolysis mediated by organocatalysts and mediators acting as electron shuttles, and (e) electrophotochemical activation of aryl iodides mediated by redox-active organocatalysts. These activation modes result in aryl iodides exhibiting diverse reactivity as formal aryl cations/radicals/anions and aryne precursors. The coupling of these reactive intermediates with trapping reagents leads to the facile and selective formation of C-C and C-heteroatom bonds. These ecofriendly, inexpensive, and functional group-tolerant activation strategies offer green alternatives to transition metal-based catalysis.

Electrochemical Synergistic Ni/Co-Catalyzed Carbonylative Cross-Electrophile Coupling of Aryl and Alkyl Halides with CO

Accessing unsymmetric ketones and achieving their carbon isotope labeling are crucial yet challenging tasks in both synthetic and medicinal chemistry. We report here an efficient electrochemical nickel-/cobalt-catalyzed carbonylative cross-electrophile coupling reaction. This method allows for the modular synthesis of a library of unsymmetric ketones from simple building blocks, including aryl halides, alkyl halides, and gaseous CO. The simultaneous use of nickel and cobalt salts as concerted catalysts ensures the high efficiency of this three-component carbonylative coupling. Furthermore, electrochemical reduction avoids the use of stoichiometric reductants, making this protocol more sustainable and attractive. The broad substrate scope and late-stage 13C isotope labeling of complex molecules derived from biologically active compounds highlight the practicality of this method.

Enantioselective electrochemical nickel-catalyzed vinylogous radical reactions

Highly functionalized structural motifs with extended chiral carbon chains are prevalent in a wide range of bioactive compounds and play critical roles in the production of various functionalized molecules. Here, we describe a nickel-catalyzed asymmetric radical-based electrochemical functionalization of silyl polyenolates at α-, γ-, ε-, and η-positions. Driven by electric current, this methodology provides a sustainable route to access enantioenriched dicarbonyls via vinylogous radical pathways. It demonstrates excellent functional groups tolerance, mild reaction conditions, broad substrate compatibility, formation of quaternary stereocenters at remote positions, and high levels of regio- and enantioselectivity (up to 98% enantiomeric excess). Mechanistic investigations indicate that ferrocene-based electron transfer mediators are pivotal in the anodic oxidation process, facilitating the generation of nickel-bound α-carbonyl radicals while suppressing the undesired oxidation of silyl polyenolates, thus guiding the selection of mediators for electrocatalytic systems. The versatility of catalytic asymmetric electrosynthesis is highlighted by the preparation of valuable enantioenriched building blocks and the total synthesis of (-)-ethosuximide.

Concomitant (3 + 3) Annulation/Fragmentation of Triazinanes with Enamines: Electrosynthesis of Multisubstituted Dihydropyrimidines

An electro-oxidative formal (3 + 3) annulation of 1,3,5-triazinanes with enamines toward multisubstituted 1,2-dihydropyrimidines is reported. This metal-free mild protocol offers wide functional group tolerance, and heterocycles with an unexplored molecular scaffold were constructed in excellent yields. Mechanistically, the electro-oxidation of triazinane and nucleophilic reactivity of enamine result in a concomitant annulation-fragmentation process, leading to the six-membered heterocyclic product.

Electrochemical Synthesis of Vinyl Sulfonates Mediated by Bromine Radicals

Vinyl sulfonates are vital intermediates in organic synthesis, serving as versatile electrophiles in various cross-coupling reactions. Despite their significance, direct methods for synthesizing vinyl sulfonates from styrenes have been limited. In this study, we introduce an innovative electrochemical approach that leverages bromine radical mediation to facilitate the direct synthesis of vinyl sulfonates, cheap nBu4NBr acts as both an electrolyte and a catalytic amount. This process involves the reaction of styrenes with sodium sulfinates and water under electrochemical conditions, offering a straightforward pathway to these compounds. The developed strategy is characterized by its high efficiency, operational simplicity, and environmentally benign nature, adhering to the principles of green chemistry while ensuring high atom economy and remarkable regioselectivity. Furthermore, this methodology proves effective for gram-scale synthesis and allows for the subsequent functionalization of vinyl sulfonate products with pharmaceutical derivatives, thus broadening the potential applications of electrochemical techniques in styrene functionalization.

Remote Migratory Reductive Arylation of Unactivated Alkenes Enabled by Electrochemical Nickel Catalysis

Transition metal-catalyzed cross-coupling reaction between organometallic reagents and electrophiles is a potent method for constructing C(sp2)-C(sp3) bonds. Given the characters of organometallic reagents, cross-reductive coupling is emerging as an alternative strategy. The resurgence of electrochemistry offers an ideal method for electrochemical reductive of cross-coupling electrophiles. Inspired by the mechanism of electrochemical metal hydride, our study proposed that Ni-H electrochemically catalyze the hydroarylation coupling of unactivated alkenes with aryl halides. 1,1-Diarylalkanes can be produced effectively. This method have advantages including mild conditions, excellent regioselectivity, and satisfactory yields.

Electrochemical cobalt-catalyzed semi-deuteration of alkynes to access deuterated Z-alkenes

Deuterium labeling has found extensive applications across various research fields, including organic synthesis, drug design, and molecular imaging. Electrocatalytic semi-hydrogenation of alkynes offers a viable route for the synthesis of Z-alkenes, yet it falls short in achieving the semi-deuteration of these compounds. In this study, we report an electrochemical cobalt-catalyzed transfer deuteration reaction that proficiently accomplishes the semi-deuteration of alkynes, yielding Z-configuration deuterated alkene products. This reaction utilizes cost-effective cobalt salts as catalysts and employs D2O and AcOD (acetic acid-d) as economical and efficient deuterium sources, underscoring its practicality and feasibility. The reaction demonstrates a broad alkyne substrate scope, high reaction efficiency, good functional group compatibility, excellent Z-selectivity, and a remarkable degree of deuteration rate.

Electrochemical 1,2-Alkylarylation of Styrenes with Malonates and N-Heteroarenes via Direct C(sp3)-H/C(sp2)-H Functionalization

A general and atom-economical electrochemical dehydrogenative method for the intermolecular 1,2-alkylarylation of styrenes with malonates and nucleophilic N-heteroarenes (including indoles and pyrroles) has been developed. This transformation provides a regioselective route to construct highly valuable 1,1-diarylalkanes enabled by C(sp3)-H/C(sp2)-H functionalization under mild conditions, and H2 is the only theoretical byproduct. Mechanistic studies indicated that the reaction proceeded through the oxidative of the C(sp3)-H bond to generate alkyl radical, radical addition across the C═C bond, single electron oxidation and C(sp2)-H functionalization cascades.

Recent advances in electrochemical 1,2-difunctionalization of alkenes: mechanisms and perspectives

In recent years, significant achievements have been made in the field of electroorganic chemistry regarding the difunctionalization of alkenes. Researchers have developed innovative strategies utilizing the unique reactivity of electrochemical processes to synthesize complex molecules with high regioselectivity and stereoselectivity. This technology is widely applied in the total synthesis of natural products and in the pharmaceutical industry. This article reviews the research progress in the electrochemical difunctionalization of alkenes through three different radical-mediated pathways over the past five years. It includes discussions on 1,2-stereoselective and non-diastereoselective difunctionalization reactions, rearrangements, intramolecular migrations, and cyclization processes. The summary emphasizes innovative electrode designs, reaction mechanisms, and the integration with other emerging technologies, highlighting the potential of this method in modern organic chemistry. Additionally, it aims to address current challenges and propose possible solutions, providing a promising direction for electrochemically mediated difunctionalization reactions of alkenes.

Electrochemical Aminooxygenation of Enamides

Herein, we present an unprecedented electrochemical approach for aminooxygenation of enamides with azoles under transition-metal- and oxidizing-reagent-free conditions. This method affords 4-azolated oxazolines directly from readily available starting materials in up to 95% yield. Central to our success is the utilization of electrical energy as the primary driving force and NaBr as a mediator. Importantly, the resulting 4-azolated oxazolines exhibit potential utility as ligands (pyrazole-oxazoline ligands) in transition-metal-catalyzed reactions.

Enantioselective Multicomponent Electrochemical Difunctionalization of Terminal Alkynes

The direct functionalization of alkyne triple bonds using a radical strategy provides an efficient platform for creating a wide range of substituted alkenes. However, developing a multicomponent enantioselective radical reaction using feedstock alkynes to forge all-carbon quaternary stereocenters─while addressing challenges related to compatibility, selectivity, and efficiency─remains relatively rare. Here we report an enantioselective electrochemical nickel-catalyzed three-component cross-coupling of readily available terminal alkynes, diverse racemic alkyl radical precursors, and group transfer reagents (such as (TMS)3Si-H, RSe-SeR, RTe-TeR, and CHI3), achieving excellent regio-, stereo-, and enantioselectivities (more than 70 examples, up to 95% ee). Electricity-mediated difunctionalizations significantly expand the scope of both aliphatic and aromatic alkynes, demonstrating excellent functional group compatibility. The key to success lies in the rational design of anodically generated nickel-bound tertiary radical intermediates, which stereoselectively capture alkynes to form vinyl radicals and participate in subsequently diverse group transfer processes to enable the intermolecular and anti-stereoselective difunctionalization of alkynes. This approach allows the transformation of terminal alkynes into diverse structural entities with α-quaternary stereogenic centers.

Electrochemical Cyclopropanation of Unactivated Alkenes with Methylene Compounds

Cyclopropanes are prevalent in natural products, pharmaceuticals, and bioactive compounds, functioning as a significant structural motif. Although a series of methods have been developed for the construction of the cyclopropane skeleton, the development of a direct and efficient strategy for the rapid synthesis of cyclopropanes from bench-stable starting materials with a broad substrate scope and functional group tolerance remains challenging and highly desirable. Herein, we present an electrochemical method for the direct cyclopropanation of unactivated alkenes using active methylene compounds. The strategy shows a broad substrate scope with a high level of functional group compatibility, as well as potential application as demonstrated by late-stage cyclopropanation of complex molecules and drug derivatives. Further mechanistic investigations suggest that Cp2Fe (Fc) plays an essential role as an oxidative mediator in generating radicals from active methylene compounds.

Electrochemical Denitrative Cyclization Driven by Alternating Polarity

Alternating current electrolysis has emerged as a promising technique for addressing challenging redox reactions that are otherwise difficult or impossible for direct current electrolysis. Under mild and transition-metal-free reaction conditions, a general electrochemical denitrative cyclization of nitroarenes was developed to access various cyclic sulfone-containing derivatives of biological significance. The key to success lies in the facile manipulation of multiple redox events upon rapid alternating polarity switching to enhance the selectivity and efficiency.

Electrochemical Difunctionalization of Alkenes

Owing to their wide utilizations in synthesis and their products prevalence in numerous natural products, pharmaceuticals and functional materials, the alkene difunctionalization methods for the selective transformations of the olefins are important and have attracted much attention form the synthetic chemists. Among them, the electrochemical alkene difunctionalization reaction is particularly promising and has becoming a potent and sustainable tool for the selective transformations of alkenes into vicinal difunctionalized structures in organic synthesis through simultaneous incorporation of two functional groups. Herein, we summarize recent progress in the electrochemical alkene difunctionalization reactions according to the alkene difunctionalization types as well as the category of the radicals over the past five years. By selecting the remarkable synthetic examples, we have elaborately discussed the substrate scope and the mechanisms for the electrochemical olefin difunctionalization reaction.

Advances in cross-coupling and oxidative coupling reactions of NH-sulfoximines - a review

Due to the special structure and physicochemical properties of sulfoximines, research on sulfoximines has achieved great progress in recent decades, especially in chemical and medicinal fields. This review highlights recent advancements in the N-functionalization of NH-sulfoximines, focusing on classical cross-coupling reactions with electrophilic agents and oxidative coupling reactions with extensive organic compounds, including specific (hetero)arenes, alkenes (1,4-naphthoquinones), alkanes (cyclohexanes), nucleophiles (thiols, disulfides, sulfinates, diarylphosphine oxides), organyl boronic acids, and arylhydrazines. Transition metal-catalyzed, metal-free, electrochemical and radical oxidative coupling reactions are discussed. This review also reports and discusses the mechanistic pathways of some typical reactions.

Enantioselective reductive cross-couplings to forge C(sp2)-C(sp3) bonds by merging electrochemistry with nickel catalysis

Motivated by the inherent benefits of synergistically combining electrochemical methodologies with nickel catalysis, we present here a Ni-catalyzed enantioselective electroreductive cross-coupling of benzyl chlorides with aryl halides, yielding chiral 1,1-diaryl compounds with good to excellent enantioselectivity. This catalytic reaction can not only be applied to aryl chlorides/bromides, which are challenging to access by other means, but also to benzyl chlorides containing silicon groups. Additionally, the absence of a sacrificial anode lays a foundation for scalability. The combination of cyclic voltammetry analysis with electrode potential studies suggests that NiI species activate aryl halides via oxidative addition and alkyl chlorides via single electron transfer.

Electrochemical Dicarboxylation of Vinyl Epoxide with CO2 for the Facile and Selective Synthesis of Diacids

We present a novel electrochemical dicarboxylation of epoxides with CO2, characterized by the cleavage of two C-O single bonds. Not only are vinyl epoxides viable, but cyclic carbonates also serve as effective substrates, facilitating the synthesis of E-configured adipic and octanedioic acids with high chemo-, regio-, and stereoselectivity. The synthetic practicality is further highlighted by the diverse functionalizations of the resulting multifunctional diacids. Mechanistic studies support the single-electron transfer reduction of CO2 to its radical anion, which undergoes radical addition to the vinyl moiety of epoxides. The subsequent reductive cleavage of two C-O bonds, coupled with a nucleophilic attack on CO2, culminates in the formation of the desired diacid products.

Modular Access to C2'-Aryl/Alkenyl Nucleosides with Electrochemical Stereoselective Cross-Coupling

Chemically modified oligonucleotides have garnered significant attention in medicinal chemistry, chemical biology, and synthetic biology due to their enhanced stability in vivo compared to naturally occurring oligonucleotides. However, current methods for synthesizing modified nucleosides, particularly at the C2'-position, are limited in terms of efficiency, modularity, and selectivity. Herein, we report a new approach for the synthesis of highly functionalized C2'-α-aryl/alkenyl nucleosides via an electrochemical nickel-catalyzed cross-coupling of 2'-bromo nucleosides with a variety of (hetero)aryl and alkenyl iodides. This method affords a diverse array of C2'- α-aryl/alkenyl nucleosides with excellent stereoselectivity, broad substrate scope, and good functional group compatibility. We further synthesized oligonucleotides incorporating C2'-aryl-modified thymidine moieties and demonstrated that their annealed double-stranded DNAs exhibit decreased melting temperatures (Tm). Additionally, oligonucleotides with C2'-aryl modifications at the 3' end showed enhanced resistance to 3'-exonuclease degradation and C2'-aryl modifications did not impede the cellular uptake process, highlighting the potential of these modified oligonucleotides for therapeutic applications.

Cathodic tandem alkylation/dearomatization of heterocycles enabled by Al-facilitated carbonyl deoxygenation

Developing efficient strategies for the deoxygenative functionalization of carbonyl compounds is crucial for enhancing the effective utilization of biomass and the upgrading of chemical feedstocks. In this study, we present an elegant cathodic reduction strategy that enables a tandem alkylation/dearomatization reaction between quinoline derivatives and aryl aldehydes/ketones in a one-pot process. Our approach can be executed via two distinct paths: the aluminum (Al)-facilitated spin-center shift (SCS) path and the Al-facilitated direct deoxygenation path. Both paths are theoretically substantiated by DFT calculations. The crux of this protocol is the in-situ activation of the alcohol intermediates by Al salts, which substantially lowers the activation energy necessary for the formation of key transition states, thereby effectively facilitating the deoxygenation process. Control experiments have not only successfully identified the intermediates but also established that the hydrogen source for the reaction is derived from water and tetrabutylammonium salt. Notably, this method is transition metal-free and compatible with water and oxygen.

Electrochemical Cyclizative Carboxylation of Alkene-Tethered Aryl Isocyanides with Carbon Dioxide

Herein, we present an unprecedented electrochemical reductive cyclizative carboxylation of o-vinylphenyl isocyanides with carbon dioxide achieved without the use of metal catalysts. This protocol demonstrates a broad substrate scope and good functional group tolerance, facilitating the rapid assembly of 2-oxoindolin-3-acetic acids in good to high yields with excellent regioselectivity. Furthermore, these structural motifs may have potential applications in formal synthesis of bioactive natural products.

Electro-catalyzed, solvent-controlled divergent decarboxylative annulation and hydroaminomethylation of cyclic aldimines with N-arylglycines

Herein, we reported a sustainable and simple method involving electrochemical-catalyzed decarboxylative annulation and hydroaminomethylation of cyclic aldimines with N-arylglycines by switching the reaction solvents. When the reaction was carried out in MeCN/H2O or H2O, the resulting products included imidazolidine-fused sulfamidates and C4-aminomethylated cyclic aldimines, obtained in moderate to good yields, respectively. Mechanistically, a radical pathway was proposed to be involved in this approach.

Electrochemical Three-Component C-H Functionalization of Indoles with Sodium Bisulfite and Alcohols to Access Indole-Containing Sulfonate Esters

Herein, an efficient electrochemical three-component C-H functionalization of indoles with sodium bisulfite and alcohols is described, providing a sustainable and convenient synthetic route for the construction of structurally valuable indole-containing sulfonate esters in moderate to good yields. This protocol proceeds in an undivided cell without any metal catalysts or oxidants, features a broad substrate scope, and has an excellent functional group tolerance. Preliminary mechanistic studies suggest that a radical-radical pathway may be involved in this three-component reaction system.

Ruthenaelectro-catalyzed C-H phosphorylation: ortho to para position-selectivity switch

The position-selective C-H bond activation of arenes has long been a challenging topic. Herein, we report an expedient ruthenium-electrocatalyzed site-selective ortho-C-H phosphorylation of arenes driven by electrochemical hydrogen evolution reaction (HER), avoiding stoichiometric amounts of chemical redox-waste products. This strategy paved the way to achieve unprecedented ruthenaelectro-catalyzed para-C-H phosphorylation with excellent levels of site-selectivity. This electrocatalytic approach was characterized by an ample substrate scope with a broad range of arenes containing N-heterocycles, as well as several aryl/alkylphosphine oxides were well tolerated. Moreover, late-stage C-H phosphorylation of medicinal relevant drugs could also be achieved. DFT mechanistic studies provided support for an unusual ruthenium(iii/iv/ii) regime for the ortho-C-H phosphorylation.

Enantioselective nickel-catalyzed electrochemical reductive conjugate alkenylation of α,β-unsaturated ketones

Catalytic electrochemical asymmetric catalysis is emerging as a promising strategy for the synthesis of chiral compounds. Herein, we report an asymmetric electrochemical nickel-catalysed reductive conjugate addition of alkenyl bromides/aryl iodides to α,β-unsaturated ketones in an undivided cell, leading to addition products with high yields and excellent enantioselectivities (up to 96% yield and 96% ee).

Solid-Liquid-Gas Three-Phase Indirect Electrolysis Enabled by Affinity Auxiliary Imparted Covalent Organic Frameworks

The design of efficient heterogeneous redox mediators with favorable affinity to substrate and electrolyte are much desired yet still challenging for the development of indirect electrolysis system. Herein, for the first time, we have developed a solid-liquid-gas three-phase indirect electrolysis system based on a covalent organic framework (Dha-COF-Cu) as heterogeneous redox mediator for S-S coupling reaction. Dha-COF-Cu with the integration of high porosity, nanorod morphology, abundant hydroxyl groups and active Cu sites is much beneficial for the adsorption/activation of thiols, uniform dispersion and high wettability in electrolyte, and efficient interfacial electron transfer. Notably, Dha-COF-Cu as solid-phase redox mediator exhibits excellent electrocatalytic efficiency for the formation of value-added liquid-phase S-S bond product (yields up to 99 %) coupling with the generation of gas-phase product of H2 (~1.40 mmol g-1 h-1), resulting in a powerful three-phase indirect electrolysis system. This is the first work about COFs that can be applied in three-phase indirect electrolysis system, which might promote the development of porous crystalline materials in this field.

Asymmetric Synthesis of Chiral Calix[4]arenes with Both Inherent and Axial Chirality via Cobalt-Catalyzed Enantioselective Intermolecular C-H Annulation

Inherently chiral calixarenes have garnered significant attention due to their distinctive properties, yet the development of efficient catalytic asymmetric synthesis methods remains a critical challenge. Herein, we report the asymmetric synthesis of calix[4]arenes featuring inherent or both inherent and axial chirality via a cobalt-catalyzed C-H activation/annulation strategy in high yield with excellent enantio- and diastereoselectivity (up to >99 % ee and >20 : 1 dr). Electrooxidation was also suitable for this transformation to obviate the sacrificial metal oxidants, underscoring the environmentally friendly potential of this approach. A key octahedral cobaltacycle intermediate was synthesized and characterized, providing valuable insights into the mode of enantio- and diastereocontrol of this protocol. Noteworthy photoluminescence quantum yields of up to 0.94 were measured, underscoring the potential of these compounds in the domain of organic fluorescent materials.

N-Hydroxyphthalimides as Nitrogen Radical Precursors in the Copper-Catalyzed Radical Cross-Coupling Amination of Arylboronic Acids: Synthesis of Arylamines

A new and practical approach for the synthesis of arylamines via copper-catalyzed radical cross-coupling amination of arylboronic acids has been developed. The key enabling advance in this protocol is the design of N-hydroxyphthalimides as precursors to generate nitrogen-based radical intermediates for cross-coupling with arylboronic acids, providing the corresponding arylamines of a high yield of up to 98%. In addition, the procedure successfully demonstrated remarkable efficiency across a wide range of functional group tolerances. Mechanistic investigations suggested that a nitrogen radical cross-coupling pathway is possible via phosphite-mediated N-O bond scission.

Paired electrocatalysis enabled oxidative coupling of styrenes with alkyl radicals

A paired electrocatalysis strategy for intermolecular oxidative cross-dehydrocoupling between styrenes and ethers or p-methylphenol derivatives using ketone as a mild oxidant is described. This approach enables the generation of Csp3 carbon-centered radicals through anodic oxidation, followed by reductive coupling of ketones at the cathode, ultimately yielding valuable oxidative alkylation products.

Toward the Electrostatic Catalysis of Nucleophilic Substitutions: A Surface Chemistry Study of the Menshutkin Reaction

The catalysis of nonredox reactions by external electric fields is one of the most rapidly expanding areas of chemistry. The Menshutkin reaction, a classic example of bimolecular nucleophilic substitution (SN2), involves the conversion of a tertiary amine to a quaternary ammonium salt by coupling it with an alkyl halide. The reaction barrier of the Menshutkin reaction is theoretically predicted to be highly sensitive to the magnitude and direction of an external electric field experienced by the transition state. In this study, we investigate how near-surface electric fields can drive this prototypical nucleophilic substitution by examining the coupling of a diffusive redox-tagged tertiary amine with an electrode-tethered alkyl bromide under a variable external bias. Our findings reveal a competition between electrostatically assisted reactions, solvent effects, and electrochemically triggered side reactions involving radical intermediates. We estimate that only about 5% of the coupling events are attributable to the external field, while the majority of the reaction products originate from electrochemically generated radical intermediates.

Enantioselective Nickel-Electrocatalyzed Cross-Dehydrogenative α- and γ-Nitroalkylation

Asymmetric catalytic versions of electricity-driven processes hold immense potential for the sustainable preparation of chiral compounds. However, the involvement of anodic oxidative cross-dehydrogenative coupling events between two distinct nucleophiles makes it challenging for a chiral catalyst to regulate the stereochemistry of the products. Our current electrocatalytic strategy for enantioconvergent cross-dehydrogenative α- and γ-nitroalkylation via radical-based pathways produces an array of enantioenriched nitroesters without supplementary stoichiometric oxidants. Mechanistic investigations reveal that the nickel catalyst plays a key role in both the electrochemical activation of the substrates and the stereoselectivity-defining events, affording the electrochemically generated Lewis acid-bound α-carbonyl radicals to interact with in situ-generated nitronate anions in a stereoselective manner. This electrocatalytic approach enables transformations that are highly challenging under thermal conditions, such as umpolung reactivity with readily available substrates, all-carbon quaternary stereocenter creation, and the control of remote stereochemistry.

Electrochemical Synthesis of Quinazolines: N-H/C(sp3)-H Coupling of o-Carbonyl Anilines with Amino Acids and Amines

A mild and efficient electrochemical protocol for the synthesis of quinazolines through N-H/C(sp3)-H coupling of o-carbonyl anilines with natural amino acids/amines has been developed. The products quinazolines can easily be isolated in moderate to excellent yields under external chemical oxidant-free conditions. Moreover, this reaction can be safely conducted on gram scale.

A Multicomponent [2+2+1] Cascade Cyclization to Synthesize Thiazol-2(3H)-one

A multicomponent [2+2+1] tandem cyclization of alkynones with amines and water using potassium thiocyanate as electrolyte and raw material to access thiazol-2(3H)-ones has been developed. This transformation proceeded smoothly via electrocatalytic oxidative C-H bond thiolation, and nucleophilic cascade cyclization to build the (C-S/C-N) bonds to construct the C-O bond. The reaction avoided using transition metal catalysts or oxidation reagents, making it more sustainable and renewable.