Herein, a novel [4＋2] annulation of a wide range of sulfoxonium ylides and o-phenylenediamines was reported, which was catalyzed by cheap and commercially available copper catalyst. The research results indicated that under the optimal reaction conditions, the isolated yield was up to 93% with 10 mol% Cu(OAc)₂ as catalyst, 1.0 equiv. of NaOAc as additive and 1,2-dichloroethane (DCE) as solvent at 80 ℃ for 24 h. This method features cheap and commerial available catalyst, mild reaction conditions, broad substrate scope and excellent functional groups tolerance.

In recent years, multi-resonance thermally activated delayed fluorescence (MR-TADF) materials have attracted wide attention because of their excellent photophysical properties and electroluminescent performance. By introducing electron-deficient and electron-rich centers (such as boron and nitrogen atoms) in the framework of polycyclic aromatic hydrocarbons (PAHs), the HOMO and LUMO can be separated on different atoms due to the opposite resonance effects, which can reduce the singlet-triplet energy gap (ΔE_ST) to achieve TADF properties. Compared with conventional donor-acceptor type TADF materials, MR-TADF materials have rigid skeletons and show short-range charge transfer characteristics, which are conducive to realizing narrowband luminescence with high color purity and high quantum efficiency, making them ideal luminescent materials and widely used in organic light-emitting diodes (OLEDs). Since the first report of MR-TADF materials based on B,N-heteroarenes in 2016, significant progress has been achieved in the development of new materials. However, a timely summary on this topic is still lacking. In this review, the design strategy and synthetic method of MR-TADF materials based on B,N-heteroarenes are summarized, and the recent advances in the development of new molecular skeletons, the backbone modification strategy to tune the properties, and a novel type of chiral MR-TADF materials are discussed. It is expected that the current review would further promote the development and application of MR-TADF materials in the future.

Most of the traditional organic fluorescent molecules have notorious aggregation-induced quenching (ACQ) effect, which limits their application in many fields. Therefore, how to achieve the transition from ACQ to aggregation-induced emission (AIE) while maintaining the functional properties of traditional conjugated molecules is of great significance. In recent years, many research groups have done a lot of breakthrough works in this field. According to the construction method and structural characteristics of AIE luminogen (AIEgen), the ACQ to AIE transformation strategy can be divided into two types. Based on the restriction of intramolecular motion (RIM) mechanism, the first one is to decorate ACQphore with typical AIEgen (e.g. tetraphenylethene unit). As the second one, some functional units (e.g. triphenylamine and cyanoethylene moiety) are introduced to realize the construction of AIE molecules from zero starting point as the RIM mechanism. In the latter, the construction of other AIEgen systems involving isomerism and excited-state intramolecular proton transfer (ESIPT) mechanisms has also been prominent recently. Thus, according to these classifications, the new progress on the construction strategy of ACQ-to-AIE transformation in the past five years is summarized from the four aspects of AIEgens’ structure, performance, mechanism and application.

A green, efficient and catalyst-free synthesis of (E)-2-styrylquinoline-3-carboxylic acid derivatives via direct olefination of 2-methylquinoline-3-carboxylic acid with aromatic aldehydes has been accomplished successfully by using environmentally benign and non-toxic deep eutectic solvent (DES) of 1,3-dimethylurea (DMU)/L-(+)-tartaric acid (LTA) (n∶n=7∶3) as a dual catalyst and reaction medium. The synthetic strategy has the attractive features such as mild and environmentally benign reaction conditions, experimental simplicity, easy work-up procedure and good yields, which would contribute to the usefulness of this method.

A novel fluorescence probe N'-((2-(4'-(diphenyl)-[1,1'-biphenyl]-4-yl)-2H-1,2,3-triazole-4-yl)methylene) hydrazine- 1-thioamide (DBTMC) was designed and synthesized from (4-(diphenylamino)-phenyl)boronic acid, (4-bromophenyl)- 2H-[1,2,3]-triazole-4-carbaldehyde and thiosemicarbazide. DBTMC possessed excellent solvent effect and aggregation effect, and exhibited high selectivity, high sensitivity and rapid response to Cu²⁺ with detection limit of 4.48×10^–8 mol/L. The possible response mechanism was explored through job’s curve, ¹H NMR titration, HRMS and density functional theory (DFT) calculations. The test strip prepared with the probe DBTMC solution could be used for quick recognition of Cu²⁺. DBTMC was applied to HeLa cells to detect Cu²⁺ and excellent results were achieved, possessing potential application.

Aniline and its derivatives, as the basic aromatic amine compounds, are widely used in different fields such as chemistry, biology, medicine, dyes, polymer materials and agriculture. Moreover, hydrogenation reduction of nitrobenzene is a simple method for the synthesis of aniline. According to the difference of proton/electron donor, the reduction of nitrobenzene can be divided into Bechamp reduction, catalytic hydrogenation, catalytic hydrogen transfer and Zinin reduction. Zinin reduction is a method for preparing aniline by reducing nitro group by using sulfide as electron donor and protic solvent as hydrogen source, which is widely used in the laboratory research and industrial production. In this review, Zinin reduction method is systematically summarized. The principle of reduction of nitro group by sulfide is clarified from the types of sulfide reductants, the reduction mechanism of nitro group, and the application of nitro group reduction. Additionally, the reduction mechanism of nitro group by elemental sulfur, sulfide, polysulfide and hydrosulfide is detailly elucidated, and the regulatory mechanism of OH^- and H₂O in the reduction of nitro group by sulfide is explained in detail. Finally, the ability and application effect of different sulfides as reductants to reduce nitro group are analyzed in terms of atom economy.

Proteins are the most abundant biomolecules in nature and are involved almost in all living processes. Chemical modification of proteins is an efficient strategy to mediate and study the physical and chemical properties and biological functionalities of proteins. Most protein chemical modifications are based on the bioorthogonal reactivities of the side chain functional groups of certain amino acid residues. Among 20 proteinogenic amino acids, cysteine has become the best choice for chemical protein modification, owning to its relative low abundance in proteins, the unique nucleophilicity and low redox potential of its mercaptan group. The recent advances in chemical protein modification via cysteine are comprehensively reviewed and the challenges and applications for future development are discussed.

Diazo compounds have rich reactivity and are important synthetic intermediates in organic synthesis. Diazo compounds are commonly used as the precursors of transition metal carbenes, and the relative transition metal catalyzed reactions have achieved many important progresses in the past decades. In sharp contrast, radical reactions with diazo compounds as a key component are still less explored. Owing to the easy generation of diverse radical intermediates under mild conditions, visible-light photoredox catalysis has emerged as a powerful tool for organic synthesis. By the combination of visible light photoredox catalysis and diazo compounds, some novel reactions that different from the classical carbene processes have been developed, which further extend the synthetic applications of these reagents. The progresses of radical reactions of diazo compounds enabled by visible light photoredox catalysis in the past five years are summarized, including: (1) diazo compounds as the nucluophiles, (2) diazo compounds as the equivalents of carbyne precursors, (3) diazo compounds as the radical acceptors, and (4) diazo compounds as the radical precursors. We wish that the detailed discussion on the mechanism of the reactions would help the audiences to understand the features of radical reactions of diazo compounds and the realative visible light chemistry.

β-Naphthol is an important synthon in organic synthesis and can participate in various chemical reactions due to its active chemical property at α-site, which has attracted a great attention from chemists. β-Naphthol can undergo various chemical transformations at α-position, such as alkylation, arylation, cyclization, amination, halogenation and so on, which can be used to construct structurally diverse naphthol derivatives with various biological activities. These naphthol derivatives can be used not only as the privileged skeletons of natural active drugs, but also as the building blocks for the preparation of the important intermediates in chemical synthesis. In recent years, chemical reactions based on β-naphthol at α-site have emerged one after another. The reactions of β-naphthol at α-position are reviewed from the aspects of C-C, C-N, C-O, C-X, C-S, C-P bond constructions and so on.

Organosilanes are versatile intermediates and products in material chemistry, pharmaceutical chemistry and synthetic chemistry because of their unique physical, chemical and physiological properties. In the past century, the synthesis of organosilanes containing C—Si bonds has gradually become one of the research hotspots. Due to the high tolerance of functional groups, good atomic economy and chemoselectivity of radical chemistry, the construction of C—Si bond via free radical silylation reaction has achieved great progress in recent years. The research progress of the radical silylation reactions exploring silane as the precursor of silicon radical in the last decade is summarized, and the related reaction mechanism is discussed.

Sulfonium salts are one of the most important class of organosulfur (IV) compounds which have a positive charge on the sulfur center with three C—S bonds. Because of their bench-stable, easy synthesis, broad structural diversity, and rich reactivity, sulfonium salts are playing a significant role in synthetic chemistry. In recent years, visible-light promoted photoredox catalysis is rapidly developing into a powerful tool for organic synthesis. In this paper, the recent advances of different sulfonium salts in the radical type reactions induced by visible light are summarized. The formation reactions of C—C bond and C—X (X=B, N, O, S, Se, Te, F, Cl, I) bonds are introduced, and the applicable scope and mechanism of some reactions are also discussed.

Near-ultraviolet and visible light-induced organic synthesis without photosensitizer has attracted much attention for the organic chemists. Since no photosensitizer is needed in the reaction, it makes the reaction system more simple and feasible, and indicates the future development direction for visible-light-induced organic transformations. Visible-light-promoted organic synthesis without photosensitizer is reviewed in this paper. It covers organic photosyntheses in which the substrate/product as a light-absorbing substance, the electron donor acceptor (EDA) complex as a light-absorbing substance, and the homolysis of weak covalent chemical bonds under the visible-light irradiation conditions. Moreover, other organic photosynthetic reactions without external photocatalyst are also discussed.

Boron dipyrromethene (BODIPY) dyes are widely used in the fields of life sciences, chemical analysis and optoelectronic materials due to its excellent photophysical properties, favorable biocompatibility, facile synthesis and modification etc. The synthesis and derivative strategies of BODIPY provide the basis for its wide application and have attracted great attention from researchers. In this review, the modification strategies for different reaction positions of BODIPY have been discussed, and Pd-catalyzed cross-coupling reactions and oxidative coupling reactions about BODIPY are discussed individually. Finallly, the development of this field is prospected.

As a class of small organic molecules containing (NC) functional groups with high activity, isocyanide has been widely employed in organic synthesis, materials science, as well as coordination chemistry. In recent years, the transition metal-catalyzed isocyanide insertion reactions have attracted much attention due to the convenient and simple operations, the efficiency in the formation of diverse new bonds and good reaction selectivity. A series of highly useful chain or cyclic compounds have been successfully constructed using this strategy, such as functionalized ketones, amides, nitrogen heterocyclic compounds, etc. To study the most recent progress, the advances in transition metal-catalyzed isocyanide insertion reactions since 2017 to 2021 are briefly summarized according to different metal categories, and the future development has also been prospected in this review.

A Pd-catalyzed decarboxylation strategy for the efficient synthesis of cyclohepta[b]indoles in good yields with good to excellent enantioselectivities and moderate diastereoselectivities is reported. In this procedure, viny indoloxazolidones were activated by Pd catalyst to generate zwitterionic intermediates in situ, which were then trapped by the electro-deficient diene species via the asymmetric [3＋4] cycloaddition process.

Chirality is widely found in many natural products and drug molecules. It is of great significance to obtain optically pure chiral compounds because of the fact that different enantiomers have distinct or even opposite physiological activities. Deracemization is the most direct, efficient and atom-economic approach to obtain a single enantiomer, and the emerging photocatalytic deracemization attracts much attention because of its high efficiency. Herein, the recent advances in photocatalytic deracemization are summarized. The future research direction of this field is also prospected.

In recent years, visible-light photocatalytic asymmetric synthesis has shown considerable potential in the mild and rapid construction of optically active organic molecules with structural diversity. Chiral Lewis acids (CLA), including chiral borane compounds, lanthanum complexes, first-row transition metal complexes, and chiral-at-iridium or rhodium complexes, have been established as one class of the most effective catalysts being capable of controlling the stereochemistry in photo-induced chemical transformations. The recent advances in this emerging field were presented by classifying the reactions into bifunctional CLA photocatalytic reactions and reactions enabled by dual catalysis with a CLA catalyst and an external photosensitizer, expecting that these studies will stimulate progress in organic synthesis, photocatalysis and asymmetric catalysis.

Polycyclic aromatic hydrocarbons (PAHs) and their derivatives are widely used in the field of organic optoelectronic materials, and the photophyscial properties of polycyclic aromatic hydrocarbons can be effectively modified by heteroatomic doping. By replacing carbon carbon (CC) units with an isoelectronic and isostructural boron nitrogen (BN) units, the electronic structure and intermolecular interactions of PAHs can be fine-tuned, resulting in new BN-heteroaromatics with unique optoelectronic properties and bioactivity. BN/CC isosterism can not only enrich the famlily of heteroaromatics but also promote their applications in the fields of optoelectronic, catalysis and biomedical applications. In particular, the researchers from China have engaged and promoted the development of boron/nitrogen-doped heteroaromaics, leading to some great results. The recent advance of 1,2-BN heteroaromatics in China from the chemistry perspective is summarized, including the synthetic development of 1,2-BN heteroaromatics, as well as their applications in variety of research fields. In the end, the development prospects of BN-heteroaromatics are pointed out. Through highlighting these advances of boron/nitrogen-doped heteroaromaics in China, it is hoped that more researchers will be interested in the synthesis and application of boron/nitrogen-doped heteroaromaics. It is also hoped that this review would stimulate the conversation and cooperation between the chemists and material scientists in the related fields.

Phosphoramides or phosphates and their derivatives are a very important class of phosphorus-containing organic molecules, which are widely applied in medicinal chemistry, material chemistry and organic catalysis. As one of the most effective methods towards constructing phosphorus compounds, the Atherton-Todd reaction involves in situ halogenation of P(O)-H molecules with tetrachloromethane to generate the key intermediates of phosphoryl chlorides in the presence of bases, which subsequently react with amines or alcohols to form the corresponding phosphoramide or phosphate products. In recent years, this reaction has been widely explored by synthetic chemists due to its ease of operation, high atom economy, broad substrate versatility, and ease of incorporation of phosphorus units into active structural fragments. The research progress of the Atherton-Todd reaction and its application in organic synthesis in recent decades are summarized, and a brief outlook on the current research challenges is put forward, hoping to provide reference and thinking for the further development of the Atherton-Todd reaction.

Enantioenriched organophosphates are ubiquitous in a large array of chiral ligands, chiral catalysts and bioactive molecules. Over the past few decades, synthetic chemists have contributed substantial efforts to develop the efficient methodologies for the construction of P-chiral phosphine derivatives, considerably enriching the arsenal of chiral organophosphine ligands and the promising pharmaceutical molecules. Among them, a number of works are focused on the synthesis of P-chiral phosphine oxides because it is more stability than trivalent phosphines and the convenient reduction. In view of the rapid progress in this area and the currently available reviews, the progress in the last three years is summarized and discussed, namely from 2020 to 2022. The description of the synthetic strategy is divided into five segments, involving asymmetric induction, catalytic desymmetrization, catalytic asymmetric synthesis, catalytic kinetic resolution or dynamic kinetic asymmetric transformation, and enzyme catalysis.

Alkenes and their functionalized derivatives represent a versatile class of building blocks in organic synthesis. The traditional synthetic methods include Wittig olefination, Peterson olefination, Horner-Wadsworth-Emmons reaction and others, and many of these classic reactions have also become textbook knowledge. Most of these methods are based on ionic pathways and some still require pre-functionalization at the sites where C—C double bonds are formed, resulting some limitations on substrate scope or functional group tolerance. Over the past few years, photoredox catalysis has become a powerful platform for new reaction design owing to its green chemistry characteristics and unique activation modes. The recently developed and representative methods for the synthesis of alkenes under photochemical conditions are summarized. Moreover, the prospects of further developments are also discussed.

Quercetin, as a natural antioxidant, is mainly found in vegetables, fruits and other plants. It can regulate many intracellular and extracellular signaling pathways related to disease progression. It can be anti-inflammatory, antiviral, anticancer, prevention and treatment of cardiovascular and cerebrovascular diseases, thus has a wide range of pharmacological activities. Due to the structural characteristics of quercetin, its low bioavailability limits its clinical application. However, the low molecular mass and easily modifiable chemical groups of quercetin make it attractive for drug development. Therefore, researchers have designed and synthesized new quercetin derivatives through various methods to improve its unfavorable factors. Many quercetin derivatives with excellent properties, good solubility, high bioavailability, stable metabolism, low toxicity and significant biological activity have been synthesized. The recent progress in the synthesis of quercetin derivatives and their biological activities is reviewed, providing a reference for the further development of quercetin derivatives.

Copper-catalyzed Chan-Lam reaction represents an important and highly efficient method for the synthesis of organic molecules containing carbon-heteroatom (C—N, C—O, C—S) bonds, which has many advantages such as mild conditions, wide substrates range and high yields. Therefore, the Chan-Lam coupling reactions are extensively applied in organic synthesis, medicinal chemistry and material science, etc. Although many catalytic systems using different copper salt alone or in combination with various ligands for Chan-Lam coupling reaction have been extensively reported by different groups, the studies on the Chan-Lam coupling reaction employing well-defined copper complexes as catalysts were underdeveloped. In recent years, the Chan-Lam reactions catalyzed by copper complexes with different ligands have attracted more special attention from synthetic chemist and made many achievements. Some novel copper complexes have been designed and synthesized, which were further used as efficient catalysts for Chan-Lam coupling reactions of arylboronic acids with various nucleophiles. The recent progresses on Chan-Lam coupling reactions catalyzed by well-defined copper(II) complexes are summarized from two aspects of homogeneous catalysis and heterogeneous catalysis in detail. Then the homogeneous Chan-Lam reactions are classified by the different coordination mode of copper complexes, and the heterogeneous Chan-Lam reactions are described according to chronological order. The reaction mechanism on Chan-Lam coupling proposed by different research groups is also straightened out and discussed. Finally, the development prospects of this research field are pointed out.

The photo-transition metal synergistically catalyzed coupling reaction provides a new research strategy for the development of metal-catalyzed coupling reactions. In this catalytic system, the excited state photosensitizer controls the valence state of the transition metal intermediate through a single electron transfer process, there by regulating the coupling reaction process, especially for the process that is difficult to occur in traditional transition metal catalysis. In addition, the excited photosensitizers could also promote the coupling reaction through the energy transfer process. Simultaneously, the light-promoted transition metal-catalyzed C—X bond coupling reactions without external photosensitizers have also been rapidly developed. Light and transition metals synergistically catalyzed coupling reactions provide an important tool for the construction of C-heteroatom bonds, showcasing broad application prospects in synthetic chemistry.

Alkenes are cheap and easily available bulk industrial feedstocks. Difunctionalization of alkenes can rapidly construct complex molecules, which have broad applications in organic synthesis. Compared with traditional redox-neutral alkene difunctionalization, the reductive difunctionalization of alkenes can introduce two different electrophiles to both sides of the carbon-carbon double bond, which has the advantages of mild reaction conditions, high functional group tolerance, and no need for pre-prepared organometallic reagents. The latest research progress in nickel-catalyzed reductive difunctionalization of alkenes is summarized. The development prospect of the reaction is prospected.

Epoxides and aziridines are important three-membered cyclic compounds, which exhibit high reactivity due to their strong strain in molecules. The asymmetric ring-opening reactions of epoxides and aziridines catalyzed by transition metals are efficient strategies for the construction of chiral molecules containing O/N atoms. In this way, a series of chiral alcohols, chiral amines and chiral heterocycles can be constructed. The recent progress in transition metal-catalyzed asymmetric ring-opening reactions of epoxides and aziridines in the past two decades is reviewed with emphasis on the influence of the kinds of transition metal catalysts, nucleophiles, and ligands. Furthermore, the possible reaction mechanisms and applications for the asymmetric ring-opening reactions are discussed, and the future development in this field is also prospected.

The discovery of aggregation-induced emission (AIE) has created a new milestone and new situation in the research of organic luminescence materials. The research on AIE molecules has attracted enormous attention. Among them, trisubstituted olefinic AIE molecules, as new structural types in recent years, have made remarkable progress in their design, synthesis and application. In view of this, according to the structural characteristics of the substituents attached to the carbon-carbon double bond, these trisubstituted olefinic AIE molecules synthesized in recent years are divided into three categories: olefinic AIE molecules substituted (a) by multiple aryl rings, (b) by cyano group(s) and (c) by heteroatoms. As this classification, their molecular mechanisms and applications in the field of organic luminescence materials and fluorescent probes are reviewed, and the future design of the trisubstituted AIE molecules is also prospected.

Ortho-quinone methides (o-QMs) belong to a class of highly reactive organic intermediates, which play an important role in catalytic asymmetric formations of carbon-carbon bond and carbon-heteroatom bond. However, o-QMs are highly unstable, which led to the underdevelopment of catalytic asymmetric reactions involving o-QMs. The utilization of some precursors for in situ generating o-QMs is a solution to address this challenging issue. Therefore, the development of catalytic asymmetric reactions involving in situ generated o-QMs has absorbed great attention from the chemists. The key to develop such reactions is to exploit easily available and stable precursors of o-QMs. Ortho-hydroxybenzyl alcohols are a kind of o-QM precursors with unique advantages. Hence, the catalytic asymmetric [4+n] cycloadditions, tandem cyclizations and nucleophilic additions of o-hydroxybenzyl alcohols have developed very rapidly in recent years, which have become efficient strategies for the synthesis of chiral oxygen-containing heterocycles and arylmethane derivatives. The catalytic asymmetric reactions involving o-hydroxybenzyl alcohols are summarized, which will open a new window for the design of new type of o-hydroxybenzyl alcohols and their involved catalytic asymmetric reactions.

Chiral phosphoric acids derived from 1,1'-binaphthyl-2,2'-diol (BINOL) and 1,1'-spirobiindane-7,7'-diol (SPINOL) have been widely applied in asymmetric catalysis and displayed excellent enantioselectivities in hundreds of reactions. However, in catalytic asymmetric reactions that involve less sterically hindered nonaromatic substrates, these Brønsted acids usually provide unsatisfactory enantioselectivities due to the relatively loose chiral environment around the catalytically active site induced by the inherent orientational property of the 3,3'-substituents which extend outwardly. In order to develop chiral phosphoric acids that are compatible with these substrates, 9,9'-biphenanthryl-10,10'-diol (BIFOL)-based confined phosphoric acid was designed by introducing two aromatic substituents which extend inwardly onto the 1,1'-positions of BIFOL. By employing cheap and commercially available m-dibromobenzene as starting material, the key intermediate 8-bromophenanthren- 9-ol which undergoes oxidative coupling to afford 1,1'-dibromo-9,9'-biphenanthryl-10,10'-diol was first synthesized. After introducing two aryl substituents through Suzuki-Miyaura coupling, the obtained aryl-substituted BIFOL was converted to the targeted molecule by reacting with phosphoryl chloride and hydrolyzing. The structure of the obtained phosphoric acid was confirmed by single crystal X-ray diffraction analysis.

Indole-based chiral heterocycles constitute a class of important heterocyclic compounds that are found in numerous natural products, pharmaceuticals, pesticide, and functional materials. The efficient and highly enantioselective synthesis of chiral indole derivatives has become one of the most important issues in organic chemistry. Due to the simple reactivity of the traditional indoles, their involved catalytic asymmetric reactions are very limited, resulting in the limited types of constructed indole-based frameworks. To solve these challenging issues, chemists devised a strategy of introducing simple functional groups to the indole ring, so as to obtain a series of functionalized indole derivatives, namely indole-based platform molecules, as efficient building blocks for constructing chiral indole-related frameworks. Among them, 2-indolylmethanols are a class of important platform molecules, which were designed on the consideration that the introduction of a hydroxymethyl group to C2-position of the indole ring would change the reactivity and the reactive site of the indole ring. This class of platform molecules can act as either electrophiles or nucleophiles, and can act as multi-carbon building blocks in catalytic asymmetric reactions. Therefore, the design and development of 2-indolylmethanols as platform molecules have provided a new strategy for the efficient and highly enantioselective synthesis of chiral indole derivatives. The advances in catalytic asymmetric reactions using 2-indolylmethanols as platform molecules are summarized, which will open a new window for designing and application of new types of indole-based platform molecules.

Enaminones are versatile and extremely useful building blocks in organic synthesis with the advantages of easy availability, convenient storage, and distinct reactivity. In particular, such compounds are important precursors in heterocyclic chemistry. Recently, transition-metal-catalyzed or transition-metal-free α-functionalization of enaminones by C-H activation has emerged as a more atom- and step-economical strategy for the construction of functionalized enaminones or various heterocycles, and it has attracted the attention of many organic chemists. This review is divided into five sections based on the varied chemical bonds: C-C bond formation, C-O bond formation, C-N bond formation, C-X bond formation, and C-S/Se bond formation. The recent progress in functionalization of enaminone based on the reaction mechanism, reaction system, the scope of substrates, etc. is systematically reviewed.

In recent years, the development and application of transition metal ruthenium or iridium complexes based photocatalysts have opened up a new research field for organic synthesis, which provides mild and efficient strategies for the construction of chemical bonds and organic transformations. In order to enrich the types of photocatalysts, broaden the application scope of photocatalysis, and develop green and sustainable chemistry, some low-cost and easily available organometallic complexes with copper or iron were applied as photocatalysts recently. Iron-complexes feature non-toxicity, rich variety, and unique property of charge transfer from ligands to metals, which enable them show extraordinary capability in the field of photocatalytic synthesis. According to different reaction types, this review focuses on the recent development of photoinduced iron-catalysis in organic synthesis including C—H bond functionalization, C—C bond functionalization, bifunctionalization of alkenes, cross-coupling reaction, decarboxylative functionalization, selective oxidation and reduction.

Chiral αα-carbonyl compounds are important structural units in natural products and pharmaceuticals and versatile synthetic building blocks in organic synthesis. Transition metal-catalyzed asymmetric acylation reaction is one of the most straightforward methods for preparing these compounds. In particular, significant progress has been made in the area of nickel-catalyzed asymmetric acylation reaction, due to the unique properties of nickel catalysts. The latest progress of nickel-catalyzed asymmetric acylation reaction, including nickel-catalyzed asymmetric alkyl-acyl cross-coupling reaction, asymmetric hydroacylation of alkene and asymmetric acyl-functionalization alkene, is summarized.

Because of the broad substrate availability, high atom economy and efficient stereocontrol, palladium-catalzyed asymmetric hydrofunctionalizations of conjugated dienes have emerged as an efficient route to construct enantioenriched allylic motifs, including allylic C—C, C—N, C—S, C—P, C—Si and C—O bonds. The development, advance and mechanistic features of this area in the past decades are summarized. Based on the types of allylic stereogenic centers constructed via this strategy, the review is divided into six parts, including asymmetric hydroalkylation, hydroamination, hydrophosphinylation, hydrosulfonylation, hydrosilylation and hydroalkoxylation.

The difunctionalization of unsaturated hydrocarbons (alkenes or alkynes) is an important strategy to introduce functional groups, and is also an important method to synthesize polysubstituted hydrocarbons, which is widely used in the fields of total synthesis of natural products and drug synthesis. The latest research progress on the electrochemically enabled difunctionalization of alkenes or alkynes in recent five years is summarized. According to the classification of difunctionalization of alkenes and cyclization of unsaturated hydrocarbon, the application and the related reaction mechanism are introduced. It is hoped that this review can be referred to the future application in organic synthesis of electrochemic- mediated difunctionalization of alkenes/alkynes.

α-Chiral primary amine subunits are widespread structural units in a large number of pharmaceutical molecules and are key intermediates toward the preparation of numerous amine-containing drugs. Versatile functionalizations on the NH₂ group also supply a quick way to construct molecular complexity. Additionally, chiral primary amines can serve as ligands or organocatalysts which can be applied in organic synthesis. Therefore, efficient synthetic routes toward chiral primary amines have attracted tremendous attention. Asymmetric chemo-catalytic reactions that are capable of directly preparing chiral primary amines remain scarce. Transition-metal-catalyzed asymmetric reductive amination (ARA), a reaction type that transforms easily available ketones and amines into chiral amines in the presence of a chiral metal-catalyst and reductant, is among the most straightforward methods to access chiral amines. However, studies on ARA are still limited compared to that on imine hydrogenation, probably due to the presence of competitive ketone reduction as the side reaction. ARA using ammonium salts as the amine sources can directly yield chiral primary amines from prochiral ketones and are thus highly attractive and of great significance. In addition to competition with ketone reduction process, this reaction also faces some other challenges, including: (1) NH₃ or the produced primary amines can coordinate to the metal center which results in catalyst poisoning effect; (2) the coordination of amine ligand to the metal center may lead to ligand exchange that enhances the challenge on asymmetric control; (3) the produced primary amines may undergo further alkylation process via double reductive amination, thus providing more complicated outcome. The existing problems and challenges in ARA require urgent development of applicable catalytic systems. Aiming to solve some challenges in the field of ARA with ammonium salts, we have carried out systematic studies and will present the latest progress achieved from our team in this account.

Owing to the special chemical structure of the seven-membered heterocyclic skeleton and the unique chemical properties of the heteroatoms contained, it is widely used in natural products and drug molecules. However, the development of synthetic methodology for these structures is challenging due to the unique thermodynamic and kinetic characteristics of nitrogen/oxygen-containing seven-membered heterocyclic frameworks, as well as their own unique cross-ring forces. Therefore, it is of great significance to develop simple and efficient methods for the construction of seven-membered heterocyclic compounds. Compared with traditional synthetic methods, radical reactions can avoid the limitations of poor atom economy and harsh reaction conditions. In this review, the recent synthetic strategies for the construction of seven-membered nitrogen/oxygen-containing heterocyclic compounds using radical tandem cyclization reactions are summarized.

Polycyclic compounds, which exist widely in natural products, synthetic drugs, agrochemicals, fine chemicals, etc. have a wide range of biological activities. Therefore, efficient synthesis of polycyclic compounds is an important research direction in organic synthesis. In recent years, free radical cascade cyclization of polyenes has increasingly become a reliable and concise way to construct polycyclic skeletons. However, the research papers on free radical cascade cyclization, especially those initiated by the homolysis of epoxides, have not been summarized. Therefore, this paper mainly reviews the initiation methods of free radical polyene cascade cyclization and its application in the synthesis of polycyclic natural products, with an emphasis on the Ti(III)-mediated free radical cascade cyclization of polyene epoxides.

Circularly polarized thermally activated delayed fluorescence (CP-TADF) materials have the characteristics of easily modified molecular structure, high exciton utilization and circularly polarized luminescence, which are the promising luminescent materials for the application of optical information storage, 3D displays, light-emitting devices and data encryption. The circular-polarized organic light-emitting diodes (CP-OLED) prepared by using such materials as emitting layers can simultaneously achieve high luminescence dissymmetry factor and theoretical 100% exciton utilization, which is crucial for the development of low-power and high-performance OLED. Recently, through the design and optimization of molecular structure, electroluminescence efficiency of CP-TADF materials were improved, but the problems of low luminescence dissymmetry factor and serious efficiency roll-off still existed. On this basis, the reported CP-TADF materials is reviewed and the relationship between the design strategies of molecular structure and the characters of excellent photophysical properties, circular polarization properties and electroluminescent properties is summaried. Furthermore, the preparation of high-perfor- mance of CP-TADF materials and their applications in OLEDs are prospected.

The three component reaction has the advantages of simple operation and efficient reaction, in line with the principles of atomic economy and green environmental protection. At present, the arylation without transition metal catalyst is mainly divided into three types of as following: (1) the direct arylation, (2) the insertion of aryne into σ-bond or π-bond, and (3) the three-component reactions involving aryne. Compared with the direct arylation and the insertion of aryne into σ-bond or π-bond, the mechanism of three component reactions involving aryne is still unclear, and the published reviews are still lacking. In order to facilitate the scientific researchers to consult and understand the three-component reaction involved in aryne, the progresses in the three-component reaction involving aryne in recent years are reviewed.