Organochlorides have been widely used in medicine, pesticides, materials and other fields. In addition, organochlorides are also important synthetic building blocks. They have participated in a variety of reactions, such as free radical reactions, substitution reactions and cross-coupling reactions. The hydrochlorination of olefins is one of the most direct and efficient methods for the synthesis of organochlorides, and remakable breakthroughs have been made in the past thirty years. The research progress of olefin hydrochlorination in the past three decades is introduced. According to whether metal catalysis is involved, it is mainly classified into two categories: metal-free alkene hydrochlorination and metal-catalyzed alkene hydrochlorination. Different type of hydrochlorination reactions and related mechanisms are summarized. In addition, the future development direction of alkene hydrochlorination is prospected.

Allyl groups, as a kind of universal protective groups in organic synthesis, are easily introduced, and stable under acidic, basic and reductive conditions. Moreover, the deallylation may occur efficiently and selectively under mild conditions. Therefore, functional group protection with allyl moiety plays a significant role in organic synthesis, especially in the synthesis of natural products and pharmaceutical industry. In recent decades, various methods of deallylation have been developed. Herein, the comprehensive development on the deallylation reaction with base and reductant, oxidation and free radical, Lewis-acid, iodine, transition metals, and electrochemical methods is reviewed.

Coupling or condensation reagents are compounds that can be used to promote the direct condensation of carboxylic acids with amines or alcohols to furnish amide or ester bond, respectively. Since their discovery, coupling reagents have been widely used in the manufacture of drugs, materials, cosmetics and other fine chemicals containing amide or ester bond. In particular, coupling reagent plays a crucial role in the chemical synthesis of peptides which involves the iterative amide bond formation between proteinogenic α-amino acids. However, current peptide synthesis methods and strategies are mainly relied on the reagents and techniques developed in 1950~1980s, and are reaching a high standard and their inherent limits. For example, the impurities and racemization/epmimerization caused by over activation of conventional coupling reagents have become major concerns of peptide drug manufacture. Moreover, the poor atom economy of the solid phase peptide synthesis results in large amount of chemical waste, and thus posing formidable challenge to the sustainable development. Only disruptive innovations involving new reagents and novel condensation mechanism can solve the notorious issues that plague current peptide synthesis. In this context, our research group disclosed that ynamide could be used as a novel coupling reagent to promote amide and ester bond formation via the condensation of carboxylic acids with amines or alcohols. More importantly, ynamide coupling reagents could also be used for peptide bond formation in a racemization free manner. Herein, the discovery as well as the application of ynamide coupling reagent in the construction of amide and ester bonds is systematically summarized.

Chiral organosulfur compounds have a wide range of applications in the fields of medicinal chemistry and asymmetric synthesis. The development of new methods for the preparation of these compounds is an important task in organic synthetic chemistry. Enantioselective electrophilic thiolation of alkenes has emerged as a straightforward pathway for the synthesis of chiral sulfides. By this fashion, both the thio group and another valuable functional group can be introduced simultaneously into the parent alkene molecules. We designed and synthesized a series of chiral bifunctional chalcogenide catalysts and successfully applied them to intra- and inter-molecular enantioselective trifluoromethylthiolation, alkylthiolation, arylthiolation of different kinds of alkenes. A variety of chiral sulfides were obtained with high enantioselectivities. The recent advances in chiral bifunctional chalcogenide catalyzed enantioselective thiofunctionalization of alkenes developed by our group are summarized, and the prospect of this field is also discussed.

Because of its excellent controlled release properties, stimulus-responsive drug carriers have attracted extensive attention in the field of biomedicine and have achieved extremely rapid development. Boronate bonds have been widely used as a stimulus-responsive site in the construction of drug carriers because of its simple construction conditions, good biocompatibility, and fast responsiveness to various micro-environmental changes such as pH, glucose and 5'-adenosine triphosphate (ATP) concentration in vivo. The types of drug carriers based on boronate bonds include drug-polymer conjugate, polymer micelles, linear-hyperbranched polymers and mesoporous silica, which could load anticancer drugs and deliver insulin and genes. Besides, drugs could be integrated into carrier by covalent bonding, physical encapsulation, and electrostatic interactions, which could be released at specific sites via endogenous stimuli. The application of boronate bond in drug delivery system is reviewed from four aspects: drug types, carrier types, combination mode of drug and carrier as well as breaking mechanism of boronate bond. The main challenges and future advances in this field are also detailed.

Biothiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play an important role in life activities, and the fluctuation of their concentrations is closely related to many diseases. Therefore, it is of great importance to detect the content of biothiols. Among all varieties of techniques, the fluorescent probe demonstrates tremendous advantages ascribed to its good sensitivity, high temporal-spatial resolution, noninvasiveness and visualization. Taking advantage of the commonality and differences among the three thiols, namely, the similar reactive groups of sulfhydryl group and amino group, and the different molecular size, nucleophilicity, steric hindrance and intracellular contents, various recognition mechanisms, such as Michael addition, aromatic nucleophilic reaction and concerted addition and cyclization reaction, are all implemented to realize the specific detection of biothiols. The research progress of thiol fluorescent probes in recent three years is reviewed. The fluorescent probes that can selectively respond to biothiols as well as to Cys, Hcy and GSH are systemically analyzed and summarized. The molecular design, recognition mechanism, fluorescence properties and imaging applications are emphasized,, and the application of biothiol fluorescent probe on monitoring life activities is preliminary introduced. In addition, a perspective of future development in this area is also presented.

Proton-coupled electron transfer (PCET) reactions are a kind of unconventional redox reactions, which exhibit special reactivities and selectivities due to their unique interdependent electron-proton transfer mechanisms. There are three possible pathways of PCET processes, including stepwise electron transfer followed by proton transfer (ETPT), proton transfer followed by electron transfer (PTET), and concerted pathway in which electron and proton transfer synchronously (CEPT), avoiding intermediates with high energy. These reactions have been playing a key role in numerous areas in organic chemistry, inorganic chemistry, bioorganic chemistry, organometallic and material chemistry, including the redox processes in natural and artificial systems, such as the activation for small molecules. Recently, the application of PCET reactions in organic synthesis has received a great deal of attentions and interests. Being accompanied by the development of electrochemical methods and photocatalysts, more and more novel reactions in electrochemistry and photochemistry involve PCET processes have been reported. Applying these electrochemical and photochemical methods, the activation of X—H bond has been achieved via PCET processes, including C—H bond, N—H bond, P—H bond, S—H bond or O—H bond. Thus, based on these crucial processes, a number of vital structures and fundamental frameworks can be synthesized, and various synthetic building blocks and natural products have been attained. For example, pharmaceutical building blocks like 2°-piperidines can be cyanated at their α-position; substituted dimeric pyrroloindolines such as (–)-calycanthidine, (–)-chimonanthine, and (–)-psychotriasine have also been successfully synthesized via PCET mechanism. Moreover, not only the products of reduction of multiple bonds (C=Y bond such as C=C bond, C=N bond and C=O bond), but also the products of self/cross-coupling have been achieved via PCET mechanism. In this review, the recent applications and developments of PCET mechanism in organic synthesis are summarized, including new catalyst systems and new reagents, especially with electrochemical and photochemical methodologies. The future of this area has also been demonstrated from both experimental and theoretical aspects.

The halogenation of organic compounds is one of the most important transformations in organic synthesis. However, there are some problems in traditional batch halogenation, such as high exothermicity, poor selectivity and the use of highly toxic and corrosive halogenating agents. Flow chemistry has its unique advantages such as high mixing efficiency, fast heat and mass transfer performance, accurate control over process parameters and enhanced process safety, reduced energy input and so on. According to the classification of halogenation of organic compounds, the main progress of flow chemistry in fluorination, chlorination, bromination and iodization is summarized systematically, and its development trend is prospected.

The critical step for the synthesis of disulfide-containing peptides is the efficient construction of one or multiple disulfide bridges. Generally, the folding of disulfide bonds could be achieved by three chemical strategies,i.e. one-step oxidative folding strategy, multi-step oxidative folding strategy, and one-pot oxidative folding strategy. Because few comparative studies have been conducted on efficiencies of three strategies, the systematical research is desirable. Three folding strategies were separately applied for the preparation of centipede toxin RhTx. The results showed that the isolated yield of two-step oxidative folding strategy was higher than those of one-step and one-pot oxidative folding strategies. Besides, the one-pot oxidative folding strategy may induce severe misfoldings. The circular dichroism (CD) and activity tests indicated that disulfide bonds are critical for the structure and activity of RhTx. In addition, the efficient preparation of RhTx on tens of milligrams scale was achieved, affording molecular tools for the further biological and biophysical studies of RhTx targeting TRPV1. Overall, three mainstream oxidative folding strategies were systematically studied, which provided a valuable reference for the synthesis of disulfide-containing peptides.

As the smallest unsaturated cyclic compounds in nature, cyclopropenes serve as important synthetic intermediates in organic chemistry as well as unique monomers in polymerization. While cyclopropenes are mostly explored in the domain of organic chemistry, the polymerization reaction of cyclopropenes has gradually attracted the attentions of chemists in recent years. The research progress of cyclopropene polymerization is reviewed, including addition polymerization and ring-opening metathesis polymerization (ROMP), and prospects for the future development of this field from the perspective of polymer synthesis methodolody.

Medium-sized rings (8~11 membered ring) and macrocycles (12-membered rings and above) are extremely important parts of drug and natural products. Meanwhile, they are widely used in the field of medicinal chemistry, organic chemistry and other fields. Developing simple, green and efficient protocol to synthesize medium-sized rings and macrocycles has attracted great interests from chemists in the recent years. The latest ring expansion/cyclization reaction in the synthesis of medium-sized ring and macrocyclic compounds in the past five years is reviewed, and the prospect of their future and development is also outlined.

C—N bonds are widely existed in drugs, natural products, and functional materials. Thus, the construction of C—N bonds is one of the most important research areas in academia and industry. Recently, the renaissance in organic electrochemistry has promoted the electrochemical C—N bond formations to be a special branch of organic synthesis. The most recent advances in the electrochemical C—N bond formations since 2015 are summarized. The reaction mechanisms of these transformations are discussed, and the challenges and future directions of this important filed are included. We hope that this review can give references to the researchers, graduate students and other related people.

The triphenylamine fluorophore with propeller-structure can be used not only as a strong electron donor, but also as a potential aggregation-induced emission (AIE) framework. At the same time, triphenylamine derivatives with different substituted groups (e.g. formyl, amino, halogen, boronic acid group, alkynyl) can easily be modified for further functionalization by simple reactions, such as condensation and metal coupling reaction. Thus, the functional triphenylamine derivatives are widely applied in the molecular design of solar cells, fluorescent dyes, solid-state luminescent materials and fluorescent probes. According to the detected analytes, such as cations, anions, and neutral small molecules, the triphenylamine-based fluorescent probes reported in the past five years are divided into three types. And on the viewpoint of their structures and performances, the new progress on the molecular design, synthesis and detecting application is reviewed. The developing potential of triphenylamine-based fluorescent probes is also envisioned, and the AIE-type probes with the properties of near-infrared and high photoluminescence quantum yield should be highlighted in the future.

Dearomatization reaction is one of the most popular research areas in organic chemistry. It could build highly functionalized three-dimensional molecules from readily available planar aromatic compounds. In recent years, arynes as reactive intermediates have been extensively investigated in dearomatization reactions, and a series of synthetic protocols have been reported. The mechanisms of the dearomatization reaction of azaarenes with arynes, the [4+2] cycloaddition dearomatization reactions of arynes with dienes, and the dearomatization of arynes in other pathways are reviewed. The insights and outlooks regarding this rapid developing field are also provided.

Transition-metal-catalyzed chelation-assisted C—H functionalization has been increasingly explored as an efficient and atom-economical strategy for construction of C—C bonds. In particular, employing the carbene synthons as a coupling partner in C—H activation has been significantly developed. Compared with the traditional carbene precursors such as diazo compounds, sulfoxonium ylides are easier to synthesize and safer in reaction, which can be employed as practical alternatives in metal-carbene reactions. Recently, the coupling reactions of sulfoxonium ylides with organometallic intermediates, generated via C—H bond activation, have been reported. They have served as privileged synthetic skeletons to accessortho-C—H acylmethylated or cyclized compounds. The recent progress on the application of sulfoxonium ylides in C—H activation is summarized and the future research direction is prospect.

During the past several decades, Suzuki-Miyaura cross-coupling reaction has emerged and flourished as one of the most remarkable and practical methods to construct C—C bond. The substrates, organoboronic compounds, are usually more stable, less toxic and easier to obtain compared with other metal or metalloid alternatives. Suzuki-Miyaura cross-coupling reaction possesses extraordinary merits of demonstrated efficiency, broad functional group compatibility and mild reaction conditions. It has been the premier method to construct C—C bond for organic synthetic chemists and has been widely applied in the industrial syntheses. The rapid development of Suzuki-Miyaura cross-coupling reaction is accompanied with the progress of mechanism studies. It is well accepted that the catalytic cycle of Suzuki-Miyaura cross-coupling reaction contains three main steps: oxidative addition of organic halides to Pd catalysts, transmetalation between oxidative addition intermediates and organoboronic compounds, and reductive elimination from transmetalation intermediates to form C—C bond along with regenerating Pd catalysts. However, these three main steps can be influenced by diverse reaction conditions, and different reaction pathways may occur within each single step. Furthermore, beyond the oxidative addition and transmetalation intermediates, other transient but crucial intermediates may exist. To figure out these issues and discover more insights into Suzuki- Miyaura cross-coupling reaction, numerous researchers have designed and conducted systematic investigations. Herein, the recent progress of mechanism studies is summarized and discussed. The steps of oxidative addition, transmetalation and reductive elimination are discussed in detail. Moreover, a brief introduction of transition-metal-free and base-free Suzuki- Miyaura cross-coupling reactions which show more possibilities of the reaction mechanism is given. Besides summary of precedent research works, our opinions about future development of the mechanism studies are also given. Although breakthroughs have been made in the mechanism studies, further investigations are needed to bring comprehensive knowledge of this reaction and help us further optimize the reaction conditions.

Chiral propargyl amines are key intermediates in the asymmetric total synthesis of natural products and bioactive compounds. The asymmetric alkynylation of imine and its analogues can provide a highly efficient and enantioselective synthetic route for these chiral building blocks. In addition, through rational substrate and reaction design, the asymmetric alkynylation of imines can be used as the starting point of a series of cascade reactions to synthesize a variety of novel nitrogen-heterocyclic compounds. Therefore, highly efficient and enantioselective alkynylation of imines and their analogues has attracted the continuous attention of synthetic chemists. According to the types of substrate, the research progress in asymmetric alkynylation of imines and their analogues over the past decade is introduced, which is divided into two parts: asymmetric alkynylation of aldimines and asymmetric alkynylation of ketoimines. The reaction mechanism and their advantages and disadvantages, together their synthetic applications will be briefly introduced, hoping to provide some useful inspiration for expanding the application of this reaction in synthesis.

Because of its low cost and environmental friendliness, visible light catalysis has been widely used in organic synthesis in recent years. Among them, α-aminoalkyl radical plays an important role because of its high activity and accessibility. The development and application of this active radical in visible light catalysis are mainly summarized and its outlook in the future is given.

N-Heteroarenes are present in a wide variety of natural products, small-molecule drugs, organic materials, and ligands. Therefore, the methods for selective C—H functionalization of N-heteroarenes are highly sought-after for late-stage modification of pharmaceuticals. A useful tool for the synthesis of alkyl-substituted nitrogen-containing aromatic rings is the Minisci reaction, in which a protonated N-heteroarene is attacked by an alkyl radical under oxidative and acidic conditions. Classic Minisci reactions often require the use of excess oxidant, excess acid, and high temperature, which greatly limits the scope of the substrates. With the rapid development of photocatalysis in organic synthesis, in recent years, a variety of photocatalytic Minisci reactions have been reported, and successfully been applied to the synthesis of drugs. In this paper, the visible light mediated Minisci reactions in recent years are briefly reviewed.

Nitrogen-containing organic compounds are ubiquitous in natural products, drug molecules and organic intermediates. Therefore, the introduction of nitrogenous functional groups into organic compounds is of great significance. Despite transition metal-catalyzed C—N coupling reaction provided an effcient strategy to access these ntrogen-containing compounds, extra steps are generally required to obtain the pre-functionalized starting materials. Recently, transition metal-catalyzed C—H amination has emerged as a more atom- and step-economical strategy to construct C—N bonds. Compared to the noble metals (e.g. palladium and rhodium), base metal catalysts, such as copper, cobalt and nickel, have attracted dramatic attentions, due to their earth abundance, cost effectiveness, and unique catalytic activities. Herein, the recent advances in copper-, cobalt- and nickel-catalyzed C—H amination reactions assisted by directing groups were summmarized according to the types of base metals, C—H bonds, and amination reagents with an emphasis on the discussion of various amination reagents and their application. Finally, the limitations and development trend of this research field are analyzed and prospected.

The incorporation of trifluoromethyl functional groups can effectively improve the chemical stability, metabolic stability and liposolubility of functional molecules. Therefore, the development of efficient methods to synthesize trifluoromethyl compounds is of significant importance. In recent years, great progress has been made in the reaction of a trifluoromethyl radical and alkene, in which alkyl radical species was first formed, followed to promote intramolecular functional groups migration. The novel pathways not only provide practical strategy for the functionalization of alkenes, which can realize the rapid construction of diverse molecules, but also promote the development of organic radical chemistry. The recent advances in alkene trifluoromethylation-initiated functional group migration including functionalized allylic compounds and non-activated alkenes are sumarrized. According to different types of migrating functional groups, the reaction in the two different sections are classified, in which the pathways of free radical generation, the scope and limits of the reaction and the reaction mechanism in different catalytic systems are discussed and highlighted in detail. Finally, a perspective on the further development of this research area is made.

Streptomyces are important sources of natural products. However, it is more challenging to discover novel compounds from Streptomyces strains isolated from common environmental samples, such as typical soil samples. Due to the unique climates, varying geological and nutrition conditions, deep-sea, desert, volcanic and polar environments are extreme habitats for Streptomyces. These unique habitats are regarded as rare and under-explored niches of new Streptomyces strains and their natural products. The recent advancement of the structures and bioactivities of 155 natural products is reviewed, produced by various Streptomyces strains isolated from these extreme environments from 2009 to 2020.

Porous organic materials have found many applications, such as catalysis, energy, adsorption and separation., owing to the high specific surface area, pore channel tunability, easy functionalization and structural diversity. The careful selection of specific monomers with polyfunctionality and highly efficient polymerization provides powerful tools for creating novel porous organic materials, and it has become a research topic in this field. Herein the latest progress in the efficient construction of novel porous organic materials is reviewed taking C₃ symmetrical phloroglucinol and its derivatives as examples.

Minisci reaction, an important method for the construction of new carbon-carbon bonds, refers to one kind of the radical substitution reactions between a nucleophilic carbon radical and an electron-deficient nitrogen-containing aromatic heterocycle. Besides, organic electrosynthesis is experiencing a renaissance as a green synthesis technology and means. This review focuses on the recent advances in Minisci reactions under electrochemical conditions.

Berberine is an important natural drug and a kind of benzyl isoquinoline alkaloid, which has unique four-ring structure. In recent years, pharmacological research has found berberine is expected to be used in the clinical treatment of cancer, diabetes and other frequently occurring diseases. Based on the Woodward’s biosynthetic hypothesis, a schematic review on the synthetic studies towards berberine is provided.

Fe-catalyzed borylation of ketones to access tertiary α-hydroxyboronates has been demonstrated. In this transformation, commercially available FeBr₂ was used as the catalyst, alcohols have been added to accelerate the transformation and avoid the side reaction. Various aliphatic ketones with different functional groups have been converted into tertiary α-hydroxyboronates. This transformation showed a particular tolerance for ketones with steric hinderance, which was distinguished from the traditional Cu catalyst. A gram scale reaction was also available. The alcoholic C—O functionalizations based onα-hydroxyboronates have been realized to access tertiary alkyl boronic esters, gem-diborylalkanes and gem- silylborylalkanes.

(Hetero)Aryl boronic acids and their derivatives have been widely used in synthetic chemistry, material sciences, and drug discovery. Accordingly, the development of novel synthetic methods towards these structures has received a great deal of attention. In particular, Ir-catalyzed C—H borylation represents one of the most efficient methods. Due to the restriction of the reaction mechanism, regioselective controllable C—H borylation of Ir catalysis is a formidable challenge, and it is also an important development direction in this area. In this review, the recent progress in Ir-catalyzed remote selective C—H borylation of arenes is systematically discussed.

The application and research of 2-substituted benzothiazoles in biomedicine, materials science and other fields have made their synthetic methods widely concerned. Based on the research of traditional synthetic methods, the development of new methods such as elemental sulfur-mediated redox reaction and dehydroaromatization of saturated compounds could provide more possibilities for the synthesis of benzothiazole derivatives. In addition, the application of new metal-organic framework catalysts, combined ionic liquids/gels, ultrasound and microwave assist in recent years have greatly enriched the synthesis of benzothiazole derivatives. The synthetic method of 2-substituted benzothiazoles in recent years is analyzed.

Isatin is a natural small molecule compound of the indole class. Due to its unique structure, low cost and easy availability, the use of isatin as a starting material to construct complex and diverse heterocyclic compounds has been a research hotspot in the field of organic synthesis. Since isatin possess rich reaction sites, it has a significant step advantage in converting it into similar heterocycles. In recent years, the great progress has been made in the construction of heterocyclic compounds based on domino reactions involving isatins. According to the different types of heterocycles, the research progress in the synthesis of benzoheterocyclic compounds by the domino reactions related to isatins is briefly discussed.

The unique chemical and physical advantages conferred by incorporation of F-atoms/perfluoroalkyl groups (R_f) into organic compounds have gained widespread recognition throughout drug discovery, crop protection, polymer chemistry, and materials science. The past decades have witnessed a boom in organofluorine chemistry and heterocyclic chemistry mainly owing to the importance of fluorine-containing heterocycles. As a result, the exploitation of readily available fluorinated building blocks to attach R_f groups to various heterocycles has become an important topic in synthetic chemistry. On the other hand, perfluoroalkyl halide, as a low-toxic and environmentally friendly perfluoroalkyl building block, has been extensively utilized as a unique reagent in the heterocycle construction. Considering the great influence and synthetic potential of these novel avenues, we summarize the recent advances for the synthesis of fluoroalkylated heterocycles by using perfluoroalkyl halides as key fluorine-containing building blocks. One or three C—X bonds of perfluoroalkyl halides are cleaved/functiona- lized during the perfluoroalkylation and cyclization process, and a series of perfluoroalkylated heterocycles such as quinoxalines, phenanthridines, hydrazones, thiazoles, pyrimidines, aza-tricycles, isoxazoles,etc. were synthesized in moderate to good yields. With a specific emphasis on their proposed mechanism, we hope this review will be useful for medicinal and synthetic organic chemists who are interested in radical-mediated perfluoroalkylation.

Fluorine chemistry has been widely used in all walks of life, and the combination of fluorine chemistry and organic chemistry is blooming everywhere. Since the introduction of fluorine atoms or fluorine groups into drugs is of great significance, it is essential to seek an effective fluoroalkylation pathway. With the development of electrochemistry, people combine electrochemistry and fluoroalkylation reaction skillfully. In turn, a safer, more economical, environmentally friendly and efficient fluoroalkylation pathway is obtained. The fluoroalkylation reaction pathway under the guidance of electrochemistry has not only reformed the reaction method, but also has advantages in terms of substrate universality. Fluoroalkylation of unsaturated aliphatic compounds their derivatives and aromatic compounds under electrochemical catalysis has been reported. According to the nature of the substrate and its reaction mechanism, the progress of electrocatalytic fluoroalkylation methods is summarized.

Molecular nanocarbon materials with well-defined structures constructed through organic synthesis have attracted much attention in recent years, exhibiting unique properties and broad applications in many areas. The combination of helicenes and molcular nanocarbons generates a fancinating type of chiral molecular nanocarbons with potential applications in the fields of chiral optics, chiral optoelectronics and spintronics etc. However, it is of greart challenge to synthesize these molecules due to the large intramolecular strain and the special helical structure. Among various synthetic strategies, the Scholl reaction possesses the advantages of mild conditions and high efficiency. In this review, recent advances in the syntheses of helicene-based molecular nanocarbons via the Scholl reaction are summarized, and our perspectives to stimulate further development of the chiral nanocarbon materials are also provided.

Carbon monoxide (CO), as an important cell signaling molecule, is involved in important physiological and pathological functions in organism. A new fluorescence enhanced CO fluorescent probe NaLy-CO was developed by using naphthalimide dye as fluorescence platform and nitro group as the recognition site. The results of spectrum test in solution showed that the fluorescent probe NaLy-CO had good selectivity and sensitivity to CO. The fluorescent probe NaLy-CO was successfully used to detect exogenous and endogenous CO in living HeLa cells by using confocal fluorescence imaging technology. In addition, the colocation imaging experiments showed that the fluorescent probe NaLy-CO could detect CO in the lysosome of living cells.

Imidazo[1,2-a]pyridines are a special nitrogen-containing compounds, which play an important role in the fields of pesticides biomedicine, optical and electrical materials. In recent years, the synthesis of functional imidazo[1,2-a]pyridines has become a hot topic for organic scientists and pharmaceutical chemists, and great progress has been made. Among them, the synthesis of functionalized imidazo[1,2-a]pyridines via visible-light catalysis and electrochemistry based on green chemistry has become the powerful tool for the synthesis of these compounds. Based on the types of canbon-hetero bonds of imidazo- [1,2-a]pyridines, the research on the construction of imidazo[1,2-a]pyridines C-3 canbon-hetero bonds by visible-light catalysis and electrochemical synthesis in recent 5 years is summarized.

Herein, the palladium-catalyzed allylic carbonylative Negishi cross-coupling reaction employing sterically bulky aromatic isocyanides as the CO surrogate was disclosed. The leverage of sterically bulky aromatic isocyanide minimizes the side β-H elimination in carboxylation reaction, affords synthetically important β,γ-unsaturated ketones with high regioselectivity and stereoselectivity, thereby tackles the long-standing challenge in Pd-catalyzed allylic carbonylative cross-coupling with CO gas. Moreover, this protocol exhibits the advantage including mild reaction conditions, as well as broad substrate scope due to the utilization of Negishi reagent as the carbon nucleophiles.

Selective activation of methane under mild conditions to produce functionalized products is highly lucrative but remains challenging. The photochemical reaction of anhydrous ferric chloride (FeCl₃) with methane at ambient temperature is an efficient process to selectively chlorinate methane to methyl chloride. An exclusive formation of methyl chloride instead of other multi-chlorinated products is observed, and a maximum initial productivity of 43 g_MeCl?(kg_Fe?h)^–1 was obtained under irradiation with a 300-watt high-pressure mercury lamp or solar light. Ferric chloride functions both as the source of reactive chlorine radicals and as the oxidant, and it was concomitantly reduced to ferrous chloride. The reaction rate increases with the power of the lamp and the concentration of ferric chloride. Interestingly, the reaction temperature from 25 to 75 ℃ and the methane pressure in the range of 1~4 MPa had little influence on the reaction rate. Methyl chloride was hydrolyzed to methanol with elimination of hydrogen chloride, and the ferrous product was re-oxidized to the ferric analog by oxygen in the air in the presence of hydrogen chloride, thus completing the loop of both iron and chlorine.

As a kind of soft materials promoted by multiple noncovalent interactions, supramolecular chiral assemblies own the distinctive confined chiral microenvironment and play an important role in material engineering, life science, optical devices and catalytic synthesis. In general, supramolecular chiral assembles can be fabricated through the assembly of chiral molecules, or a combination of achiral molecules and chiral inducements, or mere achiral molecules in symmetry breaking manner. In this paper, the general fabrication strategies of supramolecular chiral assemblies in recent years are summarized, and their improvements in chiral template, chiral recognition, circularly polarized luminescence and asymmetric catalysis are briefly reviewed, as well as the shortcomings in these fields. With the development of supramolecular chiral assemblies, the mechanism of chirality transfer will be explained in depth in future, which may help us understand the chirality phenomenon in organism and give a clue to answer to the origin of homochirality in nature.

Nitrogenous heterocyclic compounds are widely found in medicinal molecules, natural products and functional materials. Therefore, it has great significance to develop simple and efficient methods for the construction of these compounds. Recently, remarkable progress has been made in haloids mediated electrochemical synthesis of nitrogen heterocycles. Due to the relatively mild reaction condition and environmental protection, it provides a novel approach to construct nitrogen heterocycles. In this review, the recent developments in this area are summarized.

In modern organic synthesis, C—H functionalization can be used to construct various bioactive skeletons quickly and directly, and increase the complexity of the target molecular structure, which becomes an effective supplement to the traditional methods. Among them, C(sp³)—H functionalization has long been a big challenge in this field. Molecular iodine has been identified as an economically and ecologically harmless transition metal substitute, and tremendous progress has been made in the challenging C(sp³)—H functionalization reaction recently. The molecular iodine-catalyzed C(sp³)—H functionalization reactions under different oxidation systems have different reaction characteristics and mechanisms. The combination of molecular iodine and hypervalent aryl iodanes, dimethyl sulfoxide (DMSO), peroxide and oxygen can efficiently catalyze the functionalization of C(sp³)—H with different mechanisms. Recently, transition-metal/iodine co-cataly- sis and iodine-containing electrochemical catalysis have also made unprecedented progress in C(sp³)—H functionalization reaction. Herein, the progress of C(sp³)—H functionalization catalyzed by iodine under different oxidation systems from 2015 to now is summarized. The research on the green catalytic system of molecular iodine in the C(sp³)—H functionalization reaction is summarized and prospected.