Recent advances of transition-metal catalyzed radical oxidative cross-couplings

Photocatalytic regioselective C-H bond functionalizations in arenes

The direct functionalization of C-H bonds has revolutionized the field of synthetic organic chemistry by enabling efficient and atom-economical modification of arenes by avoiding prefunctionalization. However, the inherent challenges of inertness and regioselectivity in different C-H bonds, particularly for distal positions, necessitate innovative approaches. In this aspect, photoredox catalysis by utilizing both transition metal and organic photocatalysts has emerged as a powerful tool for addressing these challenges under mild reaction conditions. This review provides a comprehensive overview of recent progress in regioselective C-H functionalization in arenes via photocatalysis. Emphasizing the strategies for achieving ortho-, meta-, and para-selectivity, we explore the mechanistic insights, catalyst designs, and the novel methodologies that have expanded the scope of C-H bond functionalization. This discussion aims to offer valuable perspectives for advancing the field and developing more efficient and sustainable synthetic methodologies.

Electrochemical α-C(sp3)-H/N-H Cross-Coupling of Isochromans and Azoles

Isochroman and azole moieties are both present in a wide variety of biologically active molecules. Their efficient combination under mild reaction conditions is beneficial for obtaining small-molecule drug candidates. In this paper, we describe electrochemical α-C(sp3)-H/N-H cross-coupling reactions between isochromans and azoles, yielding products in moderate to excellent yields. This protocol does not require any catalysts or exogenous oxidants and can be performed at room temperature under air. Control experiments and cyclic voltammetry showed that the reaction may proceed through both radical coupling and nucleophilic addition processes.

Synchronous recognition of amines in oxidative carbonylation toward unsymmetrical ureas

Unsymmetrical ureas are commonly found in pharmaceuticals and bioactive compounds. However, devising strategies to introduce two distinct amines selectively in the construction of unsymmetrical ureas remains a challenge. In this work, we use a synchronous recognition strategy that takes advantage of radical and nucleophilic activation to discriminate between secondary and primary amines. Specifically, a copper catalyst preferentially oxidizes secondary amines to radical species, whereas a cobalt catalyst carbonylates primary amines to produce cobalt amides. Coupling these fragments by cooperative catalysis produces unsymmetrical ureas with high selectivity, as showcased by the modification of 41 biologically active compounds and six drugs.

α-Halocarbonyls as a Valuable Functionalized Tertiary Alkyl Source

This review introduces the synthetic organic chemical value of α-bromocarbonyl compounds with tertiary carbons. This α-bromocarbonyl compound with a tertiary carbon has been used primarily only as a radical initiator in atom transfer radical polymerization (ATRP) reactions. However, with the recent development of photo-radical reactions (around 2010), research on the use of α-bromocarbonyl compounds as tertiary alkyl radical precursors became popular (around 2012). As more examples were reported, α-bromocarbonyl compounds were studied not only as radicals but also for their applications in organometallic and ionic reactions. That is, α-bromocarbonyl compounds act as nucleophiles as well as electrophiles. The carbonyl group of α-bromocarbonyl compounds is also attractive because it allows the skeleton to be converted after the reaction, and it is being applied to total synthesis. In our survey until 2022, α-bromocarbonyl compounds can be used to perform a full range of reactions necessary for organic synthesis, including multi-component reactions, cross-coupling, substitution, cyclization, rearrangement, stereospecific reactions, asymmetric reactions. α-Bromocarbonyl compounds have created a new trend in tertiary alkylation, which until then had limited reaction patterns in organic synthesis. This review focuses on how α-bromocarbonyl compounds can be used in synthetic organic chemistry.

Strategies and Mechanisms of First-Row Transition Metal-Regulated Radical C-H Functionalization

Radical C-H functionalization represents a useful means of streamlining synthetic routes by avoiding substrate preactivation and allowing access to target molecules in fewer steps. The first-row transition metals (Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) are Earth-abundant and can be employed to regulate radical C-H functionalization. The use of such metals is desirable because of the diverse interaction modes between first-row transition metal complexes and radical species including radical addition to the metal center, radical addition to the ligand of metal complexes, radical substitution of the metal complexes, single-electron transfer between radicals and metal complexes, hydrogen atom transfer between radicals and metal complexes, and noncovalent interaction between the radicals and metal complexes. Such interactions could improve the reactivity, diversity, and selectivity of radical transformations to allow for more challenging radical C-H functionalization reactions. This review examines the achievements in this promising area over the past decade, with a focus on the state-of-the-art while also discussing existing limitations and the enormous potential of high-value radical C-H functionalization regulated by these metals. The aim is to provide the reader with a detailed account of the strategies and mechanisms associated with such functionalization.

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.

Development of novel transition metal-catalyzed synthetic approaches for the synthesis of a dihydrobenzofuran nucleus: a review

The synthesis of dihydrobenzofuran scaffolds bears pivotal significance in the field of medicinal chemistry and organic synthesis. These heterocyclic scaffolds hold immense prospects owing to their significant pharmaceutical applications as they are extensively employed as essential precursors for constructing complex organic frameworks. Their versatility and importance make them an interesting subject of study for researchers in the scientific community. While exploring their synthesis, researchers have unveiled various novel and efficient pathways for assembling the dihydrobenzofuran core. In the wake of extensive data being continuously reported each year, we have outlined the recent updates (post 2020) on novel methodological accomplishments employing the efficient catalytic role of several transition metals to forge dihydrobenzofuran functionalities.

Sustainable Aerobic Allylic C-H Bond Oxidation with Heterogeneous Iron Catalyst

Emerging techniques are revolutionizing the realm of chemical synthesis by introducing new avenues for C-H bond functionalization, which have been exploited for the synthesis of pharmaceuticals, natural compounds, and functional materials. Allylic C-H bond oxidation of alkenes serves as possibly the most employed C-H bond functionalization reaction. However, sustainable and selective approaches remain scarce, and the majority of the existing conditions still hinge on hazardous oxidants or costly metal catalysts. In this context, we introduce a heterogeneous iron catalyst that addresses the above-mentioned concerns by showcasing the aerobic oxidation of steroids, terpenes, and simple olefins to the corresponding enone products. This novel method provides a powerful tool for the arsenal of allylic C-H bond oxidation while minimizing the environmental concerns.

Hydroxytrifluoroethylation and Trifluoroacetylation Reactions via SET Processes

Hydroxytrifluoroethyl and trifluoroacetyl groups are of utmost importance in biologically active compounds, but methods to tether these motifs to organic architectures have been limited. Typically, the preparation of these compounds relied on the use of strong bases or multistep routes. The renaissance of radical chemistry in photocatalytic, transition metal mediated, and hydrogen atom transfer (HAT) processes have allowed the installation of these medicinally relevant fluorinated motifs. This review provides an overview of the methods available for the direct synthesis of hydroxytrifluoroethyl- and trifluoroacetyl-derived compounds governed by single-electron transfer processes.

Cu(ii)-catalyzed aerobic oxidative coupling of furans with indoles enables expeditious synthesis of indolyl-furans with blue fluorescence

With the purpose of incorporating sustainability in chemical processes, there has been a renewed focus on utilizing earth-abundant metal catalysts to expand the repertoire of organic reactions and processes. In this work, we have explored the atom-economic oxidative coupling between two important electron-rich heterocycles - indoles and furans - using commonly available, inexpensive metal catalyst CuCl2·2H2O (<0.25$ per g) to develop an expeditious synthesis of indolyl-furans. Moreover, the reaction proceeded well in the presence of the so-called 'ultimate oxidant' - air, without the need for any external ligand or additive. The reaction was found to be scalable and to work even under partially aqueous conditions. This makes the methodology highly economical, practical, operationally simple and sustainable. In addition, the methodology provides direct access to novel indole-furan-thiophene (IFT)-based electron-rich π-conjugated systems, which show green-yellow fluorescence with large Stokes shift and high quantum yields. Mechanistic investigations reveal that the reaction proceeds through chemoselective oxidation of indole by the metal catalyst followed by the nucleophilic attack by furan.

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp3)-H to construct C-C bonds

Ether derivatives are widespread as essential building blocks in various drugs, natural products, agrochemicals, and materials. Modern economy requires developing green strategies with improved efficiency and reduction of waste. Due to its atom and step-economy, the cross-dehydrogenative coupling (CDC) reaction has become a major strategy for ether functionalization. This review covers C-H/C-H cross-coupling reactions of ether derivatives with various C-H bond substrates via non-noble metal catalysts (Fe, Cu, Co, Mn, Ni, Zn, Y, Sc, In, Ag). We discuss advances achieved in these CDC reactions and hope to attract interest in developing novel methodologies in this field of organic chemistry.

Enantioselective catalytic radical decarbonylative azidation and cyanation of aldehydes

Empowered by the ubiquity of carbonyl functional groups in organic compounds, decarbonylative functionalization was prevalent in the construction of complex molecules. Under this context, asymmetric decarbonylative functionalization has emerged as an efficient pathway to accessing chiral motifs. However, ablation of enantiomeric control in a conventional 2e transition metal-catalyzed process was notable because of harsh conditions (high temperatures, etc.) that are usually required. To address this challenge and use readily accessible aldehyde directly, we report the asymmetric radical decarbonylative azidation and cyanation. Diverse aldehydes were directly used as alkyl radical precursor, engaging in the subsequent inner-sphere or outer-sphere ligand transfer where functional motifs (CN and N3) could be incorporated in excellent site- and enantioselectivity. Mild conditions, broad scope, excellent regioselectivity (driven by polarity-matching strategy), and enantioselectivity were shown for both transformations. This radical decarbonylative strategy using aldehydes as alkyl radical precursor has offered a powerful reaction manifold in asymmetric radical transformations to construct functional motifs regio- and stereoselectively.

Cyclization of Azobenzenes Via Electrochemical Oxidation Induced Benzylic Radical Generation

An electrochemical oxidation-induced cyclization of ortho-alkyl-substituted azobenzenes has been developed. The direct electrochemical benzylic C-H functionalization with respect to azobenzenes could proceed in the absence of any catalyst or external chemical oxidant to afford a number of 2H-indazole derivatives in moderate to good yields. This protocol enables the reuse of the byproduct to the same 2H-indazoles, thus significantly reducing pollution discharge in synthetic chemistry.

Late-stage Functionalization for Improving Drug-like Molecular Properties

The development of late-stage functionalization (LSF) methodologies, particularly C-H functionalization, has revolutionized the field of organic synthesis. Over the past decade, medicinal chemists have begun to implement LSF strategies into their drug discovery programs, allowing for the drug discovery process to become more efficient. Most reported applications of late-stage C-H functionalization of drugs and drug-like molecules have been to rapidly diversify screening libraries to explore structure-activity relationships. However, there has been a growing trend toward the use of LSF methodologies as an efficient tool for improving drug-like molecular properties of promising drug candidates. In this review, we have comprehensively reviewed recent progress in this emerging area. Particular emphasis is placed on case studies where multiple LSF techniques were implemented to generate a library of novel analogues with improved drug-like properties. We have critically analyzed the current scope of LSF strategies to improve drug-like properties and commented on how we believe LSF can transform drug discovery in the future. Overall, we aim to provide a comprehensive survey of LSF techniques as tools for efficiently improving drug-like molecular properties, anticipating its continued uptake in drug discovery programs.

Metal-free sulfonylation of quinoxalinones to access 2-sulfonyl-oxylated quinoxalines via oxidative O-S cross coupling

The C2 sulfonylation of quinoxalinones via a metal-free oxidative S-O cross-coupling strategy for synthesizing 2-sulfonyloxylated quinoxalines is established. It effectively solved the long-standing problems in the C2 transformation of quinoxalinones via a metal-free oxidative O-S coupling strategy. Compared with the traditional C2 transformed quinoxalinones-C2 chlorination method, this protocol is mild, facile, and environmentally friendly and exhibits good atomic economy and excellent functional group tolerance. Moreover, the utility of this methodology and the sulfonyloxyl handles was demonstrated through the synthesis of 2-substituted quinoxaline-based bioactive molecules.

Pd-catalyzed Aerobic Cross-Dehydrogenative Coupling of Catechols with 2-Oxindoles and Benzofuranones: Reactivity Difference Between Monomer and Dimer

Persistent radicals, which are generated from 2-oxindole or benzofuranone dimers, are useful tools for designing the radical-based cross-coupling reaction to provide molecules containing a quaternary carbon. The persistent radical is accessible from both the dimer and monomer; however, the reactivity difference between these substrates for the oxidative cross-coupling reaction is not fully understood, most likely because of the mechanistic complexity. Here, we present details of an aerobic cross-dehydrogenative coupling (CDC) reaction using various monomers and catechols. UV-Vis analysis and mechanistic control experiments showed that the monomer is less reactive than the dimer under aerobic conditions. Our Pd(II)-BINAP-μ-hydroxo complex significantly improved the reactivity of the monomers for the aerobic CDC reaction with catechols, yielding results comparable to those of the corresponding dimer. The procedure, which enables the generation of the persistent radical in situ, is particularly useful when employing the monomer that is not readily converted to the corresponding dimer.

Organophotoredox-Catalyzed Sulfurization of Alkenes and Alkynes: Selective and Controlled Synthesis of Sulfoxides, β-Hydroxysulfoxides, and β-Keto Sulfides

A visible-light organophotoredox-catalyzed sulfurization of alkenes and alkynes with aromatic and heteroaromatic thiols using eco-friendly air (O₂) as the sole oxidant has been demonstrated. The established method delivers a novel, benign, and metal-free strategy for the difunctionalization of alkenes and alkynes using organophotoredox catalyst Eosin Y. The selective and controlled synthetic approach shows good substrate generality to afford sulfoxides, β-hydroxysulfoxides, and β-keto sulfides in high yield and excellent regioselectivity.

Copper-Catalyzed Oxidative C-C Bond Cleavage of Alkyl-(Hetero)arenes Enabling Direct Access to Nitriles

The cleavage and functionalization of C-C bonds has emerged as a powerful tool for discovery of new transformations. Herein, we report a protocol that enables direct synthesis of nitriles via copper-catalyzed oxidative cleavage and cyanation of C-C bonds in a wide variety of multicarbon alkyl-substituted (hetero)arenes. Detailed mechanistic studies reveal that a tandem oxidative process is involved in this transformation.

Thermal Hydroquinone Oxidation on Co/N-doped Carbon Proceeds by a Band-Mediated Electrochemical Mechanism

Molecular metal complexes catalyze aerobic oxidation reactions via redox cycling at the metal center to effect sequential activation of O₂ and the substrate. Metal surfaces can catalyze the same transformations by coupling independent half-reactions for oxygen reduction and substrate oxidation mediated via the exchange of band-electrons. Metal- and nitrogen-doped carbons (MNCs) are promising catalysts for aerobic oxidation that consist of molecule-like active sites embedded in conductive carbon hosts. Owing to their combined molecular and metallic features, it remains unclear whether they catalyze aerobic oxidation via the sequential redox cycling pathways of molecules or band-mediated pathways of metals. Herein, we simultaneously track the potential of the catalyst and the rate of turnover of aerobic hydroquinone oxidation on a cobalt-based MNC catalyst in contact with a carbon electrode. By comparing operando measurements of rate and potential with the current-voltage behavior of each constituent half-reaction under identical conditions, we show that these molecular materials can display the band-mediated reaction mechanisms of extended metallic solids. We show that the action of these band-mediated mechanisms explains the fractional reaction orders in both oxygen and hydroquinone, the time evolution of catalyst potential and rate, and the dependence of rate on the overall reaction free energy. Selective poisoning experiments suggest that oxygen reduction proceeds at cobalt sites, whereas hydroquinone oxidation proceeds at native carbon-oxide defects on the MNC catalyst. These findings highlight that molecule-like active sites can take advantage of band-mediated mechanisms when coupled to conductive hosts.

N,N-Diethyl-3-methylbenzamide

The development of new techniques for the preparation of organic compounds is important, with catalytic processes being key to this innovation. The development of copper-based metal-organic frameworks to promote oxidative couplings has allowed the synthesis of amides in a very effective manner. This methodology has been successfully applied to the unique preparation of the bioactive compound N,N-diethyl-3-methylbenzamide, with excellent performance (>99% conversion and 95% yield of pure isolated product) on a preparative scale. The described procedure can be classified as an excellent synthesis (EcoScale) considering environmental and economic factors based on different “green metrics” (atom economy, reaction mass efficiency, materials recovery factor, stoichiometric factor, E-factor).

Nickel-Catalyzed Thermal Redox Functionalization of C(sp3 )-H Bonds with Carbon Electrophiles

C(sp³ )-H bond coupling with carbon electrophiles remains rarely explored under thermo-driven hydrogen atom transfer (HAT) conditions due to the challenge of integrating oxidation and reduction in a single operation. We report here a Ni-catalyzed arylation and alkylation of C(sp³ )-H bonds with organohalides to forge C(sp³ )-C bonds by merging economical Zn and tBuOOtBu (DTBP) as the external reductant and oxidant. The mild and easy-to-operate protocol enables facile carbofunctionalization of N-/O-α- and cyclohexane C-H bonds, and preparation of a few intermediates of bioactive compounds and drug derivatives. Preliminary mechanistic studies implied addition of an alkyl radical to a Ni^II salt.

Ni-Catalyzed Reductive 1,2-Cross-Dialkylation of Unactivated Alkenes with Two Alkyl Bromides

Cross-dialkylation of unactivated alkenes represents a significant challenge due to competitive β-hydride elimination and associated selectivity issues. Herein, a Ni-catalyzed reductive 1,2-dialkylation of unactivated aliphatic alkenes has been developed using two different alkyl bromides. The reaction proceeds smoothly under mild conditions to install two C_sp3-C_sp3 bonds onto directed aliphatic alkenes, demonstrating excellent chemo- and regioselectivity with good functional group tolerance.

A novel quinoline-based NNN-pincer Cu(II) complex as a superior catalyst for oxidative esterification of allylic C(sp3)-H bonds

We report for the first time that the quinoline-based NNN-pincer Cu(II) complex acts as an air stable superior catalyst for the oxidative cross-coupling of the allyl sp³ C-H bond with an acid for the synthesis of allyl esters in a homogeneous system at ambient temperature. The synthesized catalyst, 1, has been well characterized by various analytical techniques (HRMS, single crystal X-ray diffraction, CV, EPR, UV-vis spectroscopy) and showed excellent catalytic activity for the oxidative esterification of allylic C(sp³)-H bonds at 40 °C within a very short period of time (1 h) using only 1 mol% of the catalyst. A wide variety of aromatic allylic esters were synthesized in moderate to good yields, which could be extended to aliphatic allyl esters as well.

A radical-radical cross-coupling reaction of xanthene with sulfonyl hydrazides: facile access to xanthen-9-sulfone derivatives

A straightforward strategy for direct incorporation of sulfonyl units into a xanthene moiety for accessing xanthen-9-sulfone derivatives in good to excellent yields has been established via metal-free radical-radical cross-coupling reaction of xanthenes and sulfonyl hydrazides. Using easily accessible starting materials, this methodology proceeds efficiently with a high degree of functional group compatibility and with a wide scope of both xanthenes and sulfonyl hydrazides under operationally simple reaction conditions. Mechanistic investigations revealed that sulfonyl radicals could be generated from sulfonyl hydrazides in the presence of TBHP under an oxygen atmosphere.

Recent advances in photochemical and electrochemically induced thiocyanation: a greener approach for SCN-containing compound formation

Techniques utilizing photo- and electrochemically induced reactions have been developed to accelerate organic processes. These techniques use light or electrical energy (electron transfer) as a direct energy source without using an initiator or reagent. Thiocyanates are found in biologically active and pharmacological compounds and can be converted into various functional groups. It is one of the most prominent organic scaffolds. Significant development in photo- and electro-chemically induced thiocyanation procedures has been made in recent years for the conception of carbon-sulfur bonds and synthesis of pharmaceutically important molecules. This review discusses different photo- and electro-chemically driven thiocyanation C(sp3)-SCN, C(sp2)-SCN, and C(sp)-SCN bond conception processes that may be useful to green organothiocyanate synthesis. We focus on the synthetic and mechanistic characteristics of organic photo- and electrochemically accelerated C-SCN bond formation thiocyanation reactions to highlight major advances in this novel green and sustainable research field.

Visible-light-mediated defluorinative cyclization of α-fluoro-β-enamino esters catalyzed by 4-CzIPN

Using 4-CzIPN as an energy transfer (EnT) photocatalyst and α-fluoro-β-enamino esters as the substrates, a mild 6π-photocyclization/defluorination of N-aryl enamines was carried out to efficiently construct indoles without oxidant and...

Accessing oxy-functionalized N-heterocycles through rose bengal and TBHP integrated photoredox C(sp3)–O cross-coupling

A C(sp3)–O coupling strategy is described involving tautomerizable N-heterocycles (phthalazinone, pyridne, pyrimidinone and quinoxalinone) carbonyl employing rose bengal as the photocatalyst and TBHP.

Phosphorylation of arenes, heteroarenes, alkenes, carbonyls and imines by dehydrogenative cross-coupling of P(O)-H and P(R)-H

Organophosphorous compounds have recently emerged as a powerful class of compounds with widespread applications, such as in bioactive natural products, pharmaceuticals, agrochemicals and organic materials, and as ligands in catalysis. The preparation of these compounds requires synthetic techniques with novel catalytic systems varying from transition metal, photo- and electrochemical catalysis to transformations without metal catalysts. Over the past few decades, the addition of P-H bonds to alkenes, alkynes, arenes, heteroarenes and other unsaturated substrates in hydrophosphination and other related reactions via the above-mentioned catalytic processes has emerged as an atom economical approach to obtain organophosphorus compounds. In most of the catalytic cycles, the P-H bond is cleaved to yield a phosphorus-based radical, which adds onto the unsaturated substrate followed by reduction of the corresponding radical yielding the product.

Copper-Catalyzed Cyclization/Dimerization of Tryptamines with O2/Air as the Sole Oxidant: Direct Access to Complex Bispyrrolidino[2,3-b]indoline

The first transition metal catalytic one-step synthesis of the 3a, 3a'-bispyrrolidino [2,3-b] indoline scaffold via tandem cyclization/dimerization of tryptamines has been realized with the environmentally friendly O₂/air as the sole oxidant. Different from the traditional direct oxidation of indole "N-H" group by excess amount of metal salts, a copper-catalyzed oxidative cyclization reaction is developed for the formation of the radical pyrrolidinoindoline intermediate in the current strategy. The robustness and practicality of this methodology is demonstrated by the step-economic, divergent total synthesis of natural products (±)-folicanthine and meso-folicanthine.

High-Throughput Nano-Electrostatic-Spray Ionization/Photoreaction Mass Spectrometric Platform for the Discovery of Visible-Light-Activated Photocatalytic Reactions in the Picomole Scale

Visible-light-activated photocatalysis has emerged as a green and powerful tool for the synthesis of various organic compounds under mild conditions. However, the expeditious discovery of novel photocatalysts and synthetic pathways remains challenging. Here, we developed a bifunctional platform that enabled the high-throughput discovery and optimization of new photochemical reactions down to the picomole scale. This platform was designed based on a contactless nano-electrostatic-spray ionization technique, which allows synchronized photoreactions and high-throughput in situ mass spectrometric analysis with a near-100% duty cycle. Using this platform, we realized the rapid screening of photocatalytic reactions in ambient conditions with a high speed of less than 1.5 min/reaction using picomolar materials. The versatility was validated by multiple visible-light-induced photocatalytic reactions, especially the discovery of aerobic C-H thiolation with low-cost organic photocatalysts without any other additives. This study provided a new paradigm for the integration of ambient ionization techniques and new insights into photocatalytic reaction screening, which will have broad applications in the development of new visible-light-promoted reactions.

Recent advances in electrochemical oxidative cross-coupling with hydrogen evolution involving radicals

Oxidative cross-coupling has developed into a robust method for carbon-carbon (C-C), carbon-heteroatom (C-X), and heteroatom-heteroatom (X-Y) bond formation. Despite considerable advances in this field, the traditional oxidative cross-coupling reactions usually employ stoichiometric amounts of chemical oxidants to clean up surplus electrons from substrates to form new chemical bonds. Organic electrosynthesis is recognized as an environmentally benign and particularly powerful synthetic platform. Recent advancements have revealed that radical-involved electrochemical oxidative cross-coupling reactions can be achieved under exogenous-oxidant-free conditions. This tutorial review provides an overview of the most recent developments in electrochemical oxidative cross-coupling with hydrogen evolution involving radicals. Emphasis is mainly placed on synthetic and mechanistic aspects. We hope that this tutorial review can promote the development of radical chemistry, electrochemistry, and oxidative cross-coupling reactions.

The Rich Legacy and Bright Future of Transition-Metal Catalyzed Peroxide Based Radical Reactions

This personal account is mainly focused on the author's involvement in the field of transition metal-catalyzed peroxide based radical reactions. Over the past decades, radical chemistry has flourished and become crucial in contemporary synthetic organic chemistry. Owing to the presence of a single electron in one orbital, radicals are very unstable and react very fast. To carry out desired transformations and to control the side reactions the stabilizations of these radicals is essential. Fortunately, the implementation of a suitable transition metal and peroxide combination into the radical reactions have proved beneficial. Transition metals not only stabilizes the radicals but also protects them from being quenched by undesired homo-coupling or fragmentation. Transition metal-catalyzed radical-radical reactions provide an innovative way for the construction and derivatization of carbocycles and heterocycles. The objective of this review is to give an overview of the construction and derivatization of heterocycles through the lens of radical chemistry, mainly focusing on research work done by our group.

Photoredox-Catalyzed Benzylic Esterification via Radical-Polar Crossover

Photoredox-catalyzed C-O bond formation reactions are reported. The decarboxylative esterification reaction allows the conversion of a variety of arylacetic acids into the corresponding benzyl carboxylates. Furthermore, the use of (diacetoxyiodo)benzene allows the conversion of the benzylic C-H bond through hydrogen atom transfer. The reactions were applied to the divergent transformation of pharmaceuticals via decarboxylative or C-H esterification reactions.