Natural flavin coenzymes, featuring simple structure, non-toxicity, and the ability of absorbing and utilizing visible light, frequently act as electron carriers in biological redox reactions. Inspired by the biological function of flavins, great progress has been made in the two-electron oxidation reactions catalyzed by flavins with molecular oxygen or hydrogen peroxide as the terminal oxidant over the past two decades. Due to the versatile and tunable photochemical properties of artificial flavins, in recent years, more and more interests have been drawn to the photoinduced single electron transfer reactions with biomimetic flavins, promoting the rapid developments in the corresponding organic synthetic methodologies. Herein, the advances until July 2023 in bioinspired flavins-catalyzed one-electron oxidation of organic substrates bearing aromatic rings, nitrogen-, oxygen-, and sulfur-based groups under visible-light irradiation, delivering the corresponding radical cations which subsequently take part in the following reactions and enabling various of chemical transformations, are summarized. In addition, selected substrate scopes and possible reaction mechanisms involving single electron transfer process are discussed. Meanwhile, future challenges and opportunities of flavin photocatalysis are also prospected.

The structure of 3-sulfenyl indoles widely exists in many drug molecules and natural product molecules. Its derivatives have extensive biological activities such as antibacterial, antiviral and anti-tumor, and are also important intermediates of organic synthesis and structural units of drug synthesis. Therefore, 3-sulfenyl indole compounds have great application value in the field of medicine. The research of its synthesis method has also become one of the current research hotspots. In this paper, the research progress in the synthesis of 3-sulfenyl indoles compounds in recent years is reviewed, and some reaction mechanisms are also discussed.

Selenocysteine (Sec) is important in maintaining the functioning of living systems and its abnormal concentration will lead to a variety of physiological disorders. Fluorescent probes offer the advantages of high sensitivity, high spatial and temporal resolution, nondestructive and visual detection. However, the construction of highly selective selenocysteine probes for in vivo imaging is challenging due to the interference of biothiols. In recent years, various design strategies have been adopted to improve probe selectivity, accuracy and fluorescence properties. The research progress of Sec fluorescent probes in terms of design principles, performance characteristics and imaging applications based on the type of recognition mechanism is reviewed, and the challenges and development trends in this field are predicted.

Secondary and tertiary alcohols are important structural motifs that often exist in a large number of bioactive natural products and pharmaceuticals. Moreover, they can also be used as upstream raw material for preparation of various highly valuable chemicals. Among the existing synthetic methodologies for preparation of these compounds, the nucleophilic addition of nucleophiles to aldehydes and ketones represents one of the most operative ways. However, pre-functionalized substrates are always needed for this protocol, resulting in low efficiency and poor atom economy. The growing area of photocatalysis has provided a mild and effective approach for inert C—H bond activation. As a result, the photocatalytic straight addition of inert C—H bond to carbonyls has been developed, which affords the synthesis of secondary and tertiary alcohols in a new manner. The visible-light induced addition reaction of inert C—H bond to carbonyls was classified by three different mechanisms: reductive radical-polar crossover (RRPCO), radical-radical cross coupling as well as radical addition, and reviewed, respectively. Finally, the limitations and future developments of this research field are discussed.

The unique properties of difluorinated compounds have attracted widespread attention in the fields of medicine and material sciences. The conversion of inexpensive and easily available trifluoromethyl groups into difluoro groups is of great importance in organic synthesis. However, there still exist great challenges in the selective cleavage of C—F bonds, because the dissociation energy of single C—F bond in trifluoromethyl group is much higher than that of the C—F bond in the difluoro unit of the generated product. Thus, the selective cleavage of C—F bond is difficult to control, which can easily lead to excessive defluorination. Compared with the traditional thermal reaction, the visible-light irradiated reaction provides an alternative pathway to achieve C—F cleavage more efficiently and selectively. The research progress on the selective cleavage of C—F bonds mediated by visible light in the past three years is summarized and its future perspective is prospected.

Carbon dioxide (CO₂) is a green and renewable C1 synthon, and the direct carboxylation of inert chemical bonds with CO₂ could afford high value-added carboxylic acid derivatives from simple molecules, which feature both atomic and step economies. Organic electrosynthesis is a green synthesis technology using electrons as "reagents", and the development of electrochemical carboxylation of inert bonds with CO₂ has become a hot research topic in recent years. The recent progress on the electroreductive carboxylation of inert bonds with CO₂ is summarized, including C—H, C—C, C—O, and C—F single bonds. The mechanism and application of these reactions are emphatically discussed, and the challenges and development trends in this field are also covered.

Organic electrosynthesis replaces traditional chemical oxidants or reductants with traceless electrons, which has the advantages of sustainability and easy to scale up. The functionalization of unactivated C(sp³)—H bond can directly introduce the target functional group into the molecules, avoiding pre-functionalization and possessing both atomic and step economies. With the development of organic electrosynthesis, electrochemical-promoted functionalization of unactivated C(sp³)—H bond has become one of the hotspots in organic synthesis. The functional groups are classified according to the types of functional groups, and the recent achievements related to the functionalization of unactivated C(sp³)—H bond are summarized, with emphasis on analyzing reaction advantages, substrate scope, and reaction mechanism. Finally, the current challenges and future development are briefly discussed.

With the increasing importance of peptides in the treatment of oncological diseases and biomedical applications, the development and construction of new methods for peptide molecules have become a hot research topic for organic synthetic chemists. As a green and efficient reaction tool, organic electrochemistry has been gradually utilized in the field of organic small molecule synthesis in recent years, and its mild and controllable features are suitable for solving the chemo- and regioselectivity problems of the existing bioconjugation strategies, which provide an important synthetic means for the selective modification of peptide molecules. The electrochemical approaches to amino acids and peptides modification developed in the last five years are reviewed, and the distinct advantages of electrochemical synthesis techniques and its applicability in the development of novel biocompatible methodologies are described.

Asymmetric synthesis is one of the most important and valuable frontiers in exploratory research of synthetic organic chemistry. With the renaissance and vigorous development of organic electrochemistry in recent years, combining electrochemical organic synthesis and asymmetric catalytic strategies can be used to expand the reaction types, activation modes, bond formation systems, and substrate adaptability of asymmetric catalysis using the benefits of organic electrochemistry, which brought new opportunities for the asymmetric transformation that is difficult or impossible to be achieved by traditional methods. Thus, the development of novel, efficient, precise and sustainable electrochemical asymmetric catalytic strategies under mild and eco-friendly conditions is of great research significance. Although there are many advantages and key advances in asymmetric electrocatalysis, major challenges remain. Until now, relatively few examples of asymmetric electrochemical transformations with high enantioselectivity have been reported. In recent years, scholars in the field of organic chemistry around the world have carried out a series of original works in the field of asymmetric electro- chemical catalysis, and achieved remarkable results. The theoretical innovation, technical breakthrough, and difficult challenges in asymmetric electrochemical synthesis in recent decades are summarized. Examples of enantioselective electro-organic synthesis using transition metal catalysts, organocatalysts, biological enzyme catalysts, chemically modified chiral electrodes, chiral electrolytes, chiral solvents and chiral auxiliaries are discussed, along with their related reaction machanistic aspects. Finally, perspectives on this cutting-edge area are also briefly discussed.

Aniline and its derivatives are widely used and consumed in human life and industrial production, which inspires the direct aromatic C(sp²)—N construction from the corresponding C(sp²)—H bond. In recent years, as a controllable, sustainable, ambient, and highly scalable methodology, organic electrochemistry has received greater attention and also combined aromatic C(sp²)—N amination, presenting novel reactions. In this review, the common mechanism manifolds of electrochemical aromatic C(sp²)—H amination reactions are summarized, and the reactions examples are classified according to the type of amine sources. The prospects and challenges in this field are provided.

Organic electrophotocatalysis synthesis is recognized as a powerful and scalable methodology for organic synthesis combining photocatalysis and electrolysis synthesis. However, the research in organic electrophotocatalytic synthesis is still in an early stage. In recent years, with the emergence of this strategy, an increasing number of reports have demonstrated the viability and potential of this new methodology to achieve unprecedented transformations. By harnessing light energy and electric energy as driving forces for the reaction, without relying on stoichiometric oxidants or reductants, it enables effective and highly selective redox reactions under relatively mild conditions. Consequently, it finds wide applications in various reaction systems including redox and cross coupling reactions. A comprehensive overview of the latest advancements in organic electrophotocatalysis synthesis in recent years while categorizing the reactions based on their bonding types is provided. The reaction mechanism, advantages and characteristics are also introduced. Finally, the future development direction of organic electrophotocatalytic synthesis is prospected.

Compounds containing carbon-nitrogen bonds, such as amines, imines, nitriles, and N-heterocycles, are widespread in nature and play essential roles in pharmaceuticals, pesticides, materials, and other fields. The investigation of reactions involving carbon-nitrogen bonds is of paramount significance. In organic synthesis, the reduction of carbon-nitrogen bonds can be used for the removal of protecting groups, conversion of functional groups, and construction of biologically active molecules. However, carbon-nitrogen bonds, especially carbon-nitrogen single bonds, are renowned for their notable stability, thus requiring the harsh conditions for their reductions. As the renaissance of organic electrosynthesis in recent years, the electrochemical cathodic reductive reactions of carbon-nitrogen bonds under mild conditions have garnered considerable attention. According to the molecular structure of the substrates, electrochemical cathodic reductive reaction involving carbon-nitrogen bonds can be classified into two major categories: reductions of saturated carbon-nitrogen bonds, and unsaturated carbon-nitro- gen bonds. For compounds with saturated carbon-nitrogen bonds, such as ammonium salts, amides, aziridines, and nitro compounds, their cathodic reductions usually involve the cleavage of carbon-nitrogen bonds and substitution of the N-contained functional group. Compounds with unsaturated carbon-nitrogen bonds, such as imines, oximes, and N-heterocycles, are typically reduced into intermediates containing carbon-nitrogen single bonds, followed by addition reactions. A concise overview of the cathodic reductive reactions of above two kinds of substrates is provided and the possible reaction mechanisms is summarized.

Organic electrosynthesis can be traced back to the 19th century. The development of electroorganic synthesis has a long history. The combination of asymmetric catalysis and organic electrosynthesis opens up a new avenue for asymmetric organic synthesis. Thus, it has gradually emerged as a crucial approach for chiral compounds synthesis in recent years. Therefore, asymmetric electrosynthesis has garnered major attention of many organic synthetic researchers, and achieved considerable advances. Asymmetric electrosynthesis can transcend the limitations of traditional synthesis, controlling selectivity of the reaction through current and voltage adjustments. Moreover electrochemical synthesis is a novel sustainable methodology by replaced toxic and costly chemicals with renewable electricity. At present, asymmetric electrochemistry has been combined with organocatalysis, metal catalysis, photocatalysis, enzyme catalysis and other fields, showcasing significant potential in the synthesis of drug molecules. However, the asymmetric electrochemistry still presents several challenges to control the chemo-, regio-, and enantioselectivities. In this review, the breakthroughs and advances of asymmetric electrochemistry in the past 20 years are summarized. This overview of the field is organized by reaction types: metal reduction catalysis, metal oxidation catalysis, organic reduction catalysis and organic oxidation catalysis.

Direct and selective functionalization of relatively inert C—H bonds is a long-standing challenge in synthetic chemistry. While many strategies have been developed to date, new approach that does not require the use of transition-metals and oxidants is in high demand. Recently, electrophotocatalysis has emerged as a powerful means to effect direct C—H functionalization and other types of challenging transformations under mild reaction conditions. The recent advances on electrophotocatalytic C—H functionalization via anode oxidation are highlighted with a focus on mechanistic aspects. Challenges and opportunities of this emerging field are also discussed.

Electrocatalytic reduction and oxidation processes offer an efficient and sustainable platform for synthesizing valuable chemicals. Particularly, coupling the cathodic reduction and anodic oxidation processes via paired electrolysis can efficiently lower the reaction overpotential as well as selectively synthesize various high-value chemicals, which has drawn ever-growing attention in recent years. Herein, the recent advancements in paired electrolysis are summarized, focusing on the reduction of inorganic small molecules including carbon dioxide, nitrogen-containing substances, and water coupled with alternative oxidation reactions. Additionally, major challenges as well as potential solutions of paired electrolysis are proposed in this review, which may provide some guidance for researchers in the future.

As a class of common and important compounds, carboxylic acids are widely used in areas of medicine, pesticides and polymers. Therefore, development of facile and efficient methods for the synthesis of carboxylic acids is of great significance. Electrochemical synthesis of carboxylic acids has attracted widespread attentions due to its environmentally friendly and mild conditions. This article mainly reviews the relevant research in electrochemical synthesis of carboxylic acids in recent years from two aspects: electrochemical oxidation for carboxylation and electrochemical reduction of carbon dioxide for carboxylation.

Organosilicon compounds are widely applied in synthesis, materials, medicine and other fields due to their unique physical and chemical properties, and have attracted widespread attention from chemists. Therefore, it is particularly important to develop mild and efficient synthesis methods to construct organosilicon compounds. In recent years, the rapid development of electrochemistry provided a new strategy for the synthesis of organosilicon compounds. Due to its advantages of green and mild conditions, simple and efficient reactions, and no need for additional redox reagents, significant progress has been made in the synthesis of organosilicon compounds through electrochemical silylation reactions. The latest progress in electro- chemical silylation is mainly reviewed from two aspects: electrochemical silylation reactions via cathodic reduction, and electrochemical silylation reactions via anodic oxidation.

Carbon dioxide (CO₂) exerts a significant influence on climate change as a potent greenhouse gas. From a chemical standpoint, CO₂ serves as an abundant and cost-effective “carbon one (C1)” resource with non-toxicity, renewability, and easy obtainability. The utilization of CO₂ for synthesizing high-value-added chemicals represents an important avenue for addressing national strategic requirements and aligning with China’s objectives of peaking carbon emissions by 2030 and achieving carbon neutrality by 2060. Organic photocatalysis can harness light energy to induce electron transfer in organic chemical reactions, facilitating bond cleavage and recombination processes. This approach offers advantages such as mild reaction conditions, environmental friendliness and exceptional selectivity. By integrating CO₂ resource utilization with organic photocatalysis, novel opportunities arise for enriching carboxylation reactions. Two distinct types of photocatalytic carboxylation reactions, those involving carbon anions as pivotal intermediates and those featuring CO₂ radical anions as key intermediates, are systematically elucidated.

The pursuit of cleanliness, energy efficiency, and resource preservation through photochemical reactions has led to the emergence of novel pathways and methodologies in synthetic chemistry, rendering it one of the most dynamic research domains within modern organic synthesis. Carbon dioxide (CO₂), owing to its non-toxic, cost-effective, abundant, and recyclable attributes, serves as an optimal C1 precursor in synthetic chemistry. Recent years have witnessed rapid advancements in the photochemical conversion of CO₂ into carboxylic acid compounds, offering a gentle and highly efficient synthetic approach for their production. An overview of the research progress on the synthesis methodologies of carboxylic acid compounds through photochemical CO₂ conversion is provided, while certain associated reaction mechanisms are also elucidated.

N-Heterocyclic aromatics are among the most prevalent motifs in natural products, pharmaceuticals, and organic materials. Therefore, the selective functionalization of N-heterocyclic aromatics, represented by the Minisci reaction, has always been a hot topic for chemists. Meanwhile, in recent years, photocatalysis has sparked a new research trend as a green, safe, clean, and renewable catalytic method. Although a review has been conducted on photoinduced Minisci reactions in recent years, the exploration of asymmetric Minisci reactions is limited. The research progress on visible-light photocatalytic asymmetric Minisci reactions in recent years from the classification of free radical precursors and different reaction pathways is summarized. Furthermore, prospects for future development are also discussed.

The synthesis and transformations of alkynes have held an important position in the field of organic synthesis. How to rapidly introduce alkynyl into organic molecules has been of great interest. Photoredox catalysis has been widely used in organic synthesis because it can generate high reactive free radical intermediates under mild conditions using green and clean energy. Visible light photocatalytic alkynylation has flourished in the last decade, which is believed to be a significant complement to the classic transition-metal-catalyzed Sonogashira reaction. This alkynylation could take place via in situ generated copper acetylide complex from terminal alkynes and copper, which also occurs through alkynyl radical species or radical addition elimination of non-terminal alkynes. Moreover, it was a good supplement to Sonogashira reaction that various radical precursors could be applied to alkynylation by visible-light photoredox catalysis. Based on the type of bonding of alkynylation, the research progress of alkynylation reactions by visible-light photoredox catalysis is reviewed, and the future development of this field is prospected.

Organosilicon compounds play important roles in the fields of material science and pharmaceutical chemistry. The transformations involving organosilicon reagents have therefore attract extensive interest from synthetic community. The burgeoning visible light photocatalysis has provided a new opportunity for organic synthesis. Under the photoredox system, organosilicon compounds could be transformed into silicon or carbon radicals to participate in a variety of reactions. Generally, these reactions bear the merits, such as mild conditions, good selectivity, as well as high atom economy. According to the types of reactions, the recent progress in visible-light mediated hydrosilylation and difunctionalization of alkenes and alkynes, C—H bond silylation of N-aromatic heterocycles using organosilicon compounds as silicon radical precursors, and nucleophilic addition, Minisci reaction, homolytic substitution, as well as transition metal mediated cross-coupling reactions using organosilicon compounds as carbon radical precursors is reviewed primarily herein.

In recent years, the photochemical organic transformation promoted by visible light has aroused the interest of organic chemists. Compared with traditional methods, photoredox catalysis using visible light as renewable energy has been proved to be a mild and powerful tool, which can promote the activation of organic molecules by single electron transfer (SET) process. There are a lot of amino functional groups in the structures of many natural products, and amino groups are also important structural units of some drug molecules and functional materials. Therefore, by activating the C—N bond in these substances and carrying out some coupling reactions of C—C bond formation, the structure of these compounds can be effectively modified, so as to obtain compounds with various structures and functionalization. Therefore, this study has become an important research field of organic synthesis. The research results of C—N bond breaking promoted by visible light and its application in the study of C—C bond formation reaction in recent years are reviewed, and representative examples and reaction mechanisms are discussed.

The construction of C—S bond is of great significance in organic synthesis, in viewing that organic compounds containing C—S bonds are widely present in various natural products, drugs and functional materials. At present, transition metal-catalyzed C—S bond formation reactions have been well developed. However, in recent years, the visible-light-mediated C—S bond formation reactions have received more and more attention due to the characteristics of milder conditions, greener and higher reactivity. According to the classification of the reaction mechanisms, the methods of C—S bond construction based on photo-mediated redox catalysis, electron donor-acceptor complexes and energy transfer are summarized and a future perspective is made.

Organoboron compounds are important building blocks in organic synthesis and have been widely applied in materials and pharmaceutical science. The development of practical and concise borylation reactions to synthesize organoboron compounds has always been one of the core topics of organoboron chemistry. Recently, photochemical and electrochemical borylation reactions have gained rapid development and emerged as important methods towards the synthesis of organoboron compounds. The recent research progress concerning photochemical, electrochemical and photoelectrochemical borylation involving aryl and alkyl compounds from the view of energy resources and substrates is reviewed. Additionally, research trends of this area are also discussed.

Thiocyano and selenocyano are both important functional groups with broad application in organic synthesis. Such functional structures also occur frequently in molecules possessing valuable biological and pharmaceutical activities, optical functions, and catalytic profiles. Therefore, developing synthetic methods toward diverse organo thio-/selenocyanates as well as the tandem annulation for the construction of diverse heterocyclic scaffolds keep receiving high interests. The advances on the synthesis of organo thio-/selenocyanates via transition metal-free C—H thiocyanation or selenocyanation as well as the tandem annulation reactions based on such C—H functionalization are reviewed.

The cheap and readily available olefin substrates have received much attention for the synthesis of structurally rich and high value-added ketones, aldehydes, carboxylic acids and their derivatives via α-acylation. Multicomponent tandem α-acylation of olefins achieves high efficiency and selectivity by N-heterocyclic carbene or transition metal catalysis, albeit with narrow reaction modes and substrates. Rapid growth of photocatalysis in organic transformation has introduced new methodologies to undergo the α-acylation of olefins with broad substrate scope. The research progress and prospect for the future development in this active research field is highlighted.

Ethers are widely used in organic chemistry, materials science, biomedicine and other fields due to their excellent physicochemical properties. Among them, tetrahydrofuran/tetrahydrothiophene and their derivatives are the core backbones for building biologically active molecules and complex natural products. In recent years, photo/electrocatalysis has gradually become an important tool for chemists to synthesize novel compounds due to its compliance with the requirements of green chemistry and the unique pathway that mostly involves radical intermediates. The functionalization of α-positions of ethers using photo/electrocatalysis is a green and efficient synthetic strategy. Therefore, the research progress of photo/electro- catalytic functionalization of ether compounds at the α-position is reviewed with ether/sulfide as examples, and a detailed description of some of the mechanisms is provided.

As important organic molecular frameworks, spirocycles exist widely in organic chemistry, medicinal chemistry, material science and other fields. Since the spirocyclic skeleton has a large three-dimensional space structure, which meets the demand for conformational rigidity in drug design, it is particularly important to develop efficient synthetic methods for spirocyclic compounds. In recent years, photocatalysis and electrocatalysis have injected new potential into the synthesis of spirocyclic compounds as green and efficient synthetic methods. This article is mainly classified by the construction of snail [4.5] skeleton, snail [5.5] skeleton, snail [2.3] skeleton, and spiro-indoles skeleton. Moreover, the construction of spirocyclic compounds is reviewed from two aspects: photocatalysis and electrocatalytic synthesis.

CO₂ is an important C1 source in organic synthesis due to its abundant, non-toxic and low-cost properties. There- fore, it is of great significance to use CO₂ as a C1 source to synthesize compounds with high added value. This review focuses on the recent progress in the carboxylation of organic compounds using CO₂ as an electrophile under electrochemical conditions. The electrochemical carboxylation of non-activated organic halides, unsaturated alkene compounds and some special compounds are mainly introduced. And the use of sacrificial anodes and non-sacrificial anodes is classified in detail. The reaction mechanisms of these reactions are also discussed. This review provides a reference for the application of such reactions in organic synthesis in the future.

Sulfonyl compounds are important organic sulfur compounds, which are widely used in the fields of medicine, pesticides, functional materials and so on. Therefore, efficient strategies for the synthesis of sulfonyl compounds have become the focus of extensive research. Organic electrochemical synthesis is a green, mild and efficient synthesis strategy, which shows great potential in the synthesis of sulfonyl compounds. The reactions of electrochemical synthesis of C-sulfonyl compounds in recent years are introduced. The reactions of electrochemical synthesis of C(sp)-sulfonyl compounds, C(sp²)-sulfonyl compounds and C(sp³)-sulfonyl compounds are classified, summarized and discussed, and the corresponding reaction mechanism is described, so as to provide reference for the application of such reactions in organic synthesis in the future.