Eight-membered carbocycles are widely found in natural products with significant biological activities and other molecules ranging from perfumes to potential materials. Therefore, accessing these eight-membered carbocycle embedded molecules is important for drug discovery, biological investigation, fragrance industry, material development and many other fields. However, the synthesis of eight-membered carbocycles is still posing challenges to synthetic chemists. Hence, tremendous efforts have been endeavored by many leading chemists to discover and develop new reactions in order to synthesize eight-membered carbocycles. Among these reactions, transition-metal-catalyzed cycloadditions of [m+n], [m+n+o], [m+ n+o+p] have evolved as powerful tools to achieve this aim. This topic has been reviewed in 2010. Summarized here are many new developments in this field and applications of the previously developed reactions in natural product synthesis since then.

Enantioselective hydroboration of ketones and imines provides a powerful method to access valuable chiral alcohols and amines which are widely used in organic synthesis, materials science, pharmaceutical, agrochemistry and fine chemical industry. After invented in 1991, pinacolborane (HBpin) as a stable, commercially available and measurably simple reductive reagent has been widely applied in hydroboration of carbonyl derivatives, imines and nitriles and relevant mechanistic investigation. In the past 5 years, HBpin has also been employed for asymmetric catalytic hydroboration (CHB) to access chiral alcohols and amines. The enantioselective CHB reactions of ketones and imines using HBpin are outlined according to the classification of different catalysts, such as earth abundant transition metals, main group elements, and rare-earth metals.

Among various 1,3-dipoles of cyclic azomethine imines, C,N-cyclic azomethine imines are the most widely used reagents in the construction of diverse tetrahydroisoquinoline derivatives. The developments of reactions with C,N-cyclic azomethine imines including [3+2], [3+3], [3+4], [5+1], [3+1] cycloaddition reactions and miscellaneous reactions are summarized. The properties of reactions, reaction processes and synthetic applications are discussed. Finally, the prospects of the reaction with this reagent are also proposed.

Organoboron compounds are valuable synthetic intermediates and widely used in the synthesis of medicine, pesticide and organic optoelectronic materials due to their extensive resouce and highly transformable ability. Among various organoboron compounds, the synthesis and transformation of alkylboron compounds have attracted much attention. As a sustainable and green energy, visible light shows an important effect in organic systhesis. Tetracoordinated alkylboron compounds could occur single electron transfer (SET) process to generate alkyl radical for further transformations. Herein, the recent advances in the photoinduced transformation of alkyl boron compounds are summarized.

As a typical representative of thiopeptide antibiotics, nosiheptide (NOS) possesses very good antibacterial activity. However, due to poor water solubility and low bioavailability, its clinical application is hampered. Due to its complex structure, it is difficult to obtain analogues with improved physical and chemical properties via total chemical synthesis. Based on the previous studies on the biosynthesis of nosiheptide, the side-ring 3-methyl-2-indoleic acid (MIA) analogues were used as chemical small molecule probes to explore the substrate tolerance of enzymes involved in NOS biosynthesis pathway in NOS-producing bacteria via the co-fermentation of probe molecules with mutant strain and the combination of high resolution mass spectrometry data of fermentation products. The results showed that enzymes involved in NOS biosynthesis pathway had a considerable tolerance to MIA analogues substituted by F, Cl and CH₃, however, MIA analogues substituted by large steric hindrance group, such as NO₂, CF₃ and Ph, were not tolerated. The position, the size and the property of the substituted groups of MIA also affected the steps of identification, transport and upload of the related enzymes involved in NOS biosynthesis. The present study not only explored the substrate tolerance of enzymes involved in NOS biosynthesis pathway, but also was expected to obtain NOS analogues via biosynthetic pathway engineering. What’s more, it provides valuable information for using directed evolution technology to improve the substrate tolerance of enzymes in the rate-limiting steps of NOS biosynthesis and to expand the use of NOS-producing bacteria to obtain more analogues.

In recent years, decatungstate [W₁₀O₃₂]^4- as a catalyst has attracted much attention in the field of photocatalytic organic synthesis. With the catalysis of decatungstate, the C—H bond of substrate can be converted into the corresponding radical via a hydrogen atom transfer (HAT) progress under light irradiation. In this review, we summarized the recent advances of the application of decatungstate as a photocatalyst for the C—H functionalization to construct C—C, C—N, C—F bonds.

A catalytic system capable of selectively promoting the cyclopropanation reaction and C—S bond cleavage reaction was established. For the reactions between phenyl vinyl sulfide and diazoacetonitrile (generated by in situ method), the cyclopropanation reaction products were obtained under the catalysis of hemin chloride, and the C—S bond cleavage reaction products were generated in the presence of FePc. All the reations were operated without inert gas protection or high temperature, and the target products were obtained by stirring at room temperature for 1 h in moderate to excellent yields.

In recent years, mechanoluminescence, as a unique luminescence phenomenon, exhibited huge potential applications and rapid development in stress detection, anti-counterfeiting, encryption, light sources and bio-imaging, etc. Recently, great efforts have been made on molecular aggregation science, molecular packing and intermolecular interaction in the solid state have been deeply understood, directly promoting the development and application of mechanoluminescence and photoluminescence materials. The phenomenon and mechanism of mechanoluminescence were firstly introduced, the relationship between mechanoluminescence and aggregation behaviors of organic compounds were discussed in detail. The measurement and characterization of mechanoluminescence, the relationship between applied stress and mechanoluminescence intensity, and the color of mechanoluminescence were briefly introduced, then, the current application of mechanoluminescence was highlighted. In the end, the prospect of organic mechanoluminescence materials was afforded.

A mild method for the conversion of alkyl iodides to alcohols was developed. The transformation was promoted by tris(trimethylsilyl)silane/O₂ and accelerated by photoredox catalysis under visible light irradiation conditions. Various alkyl iodides, including primary, secondary and tertiary iodides, can be smoothly converted to the corresponding alcohols in 38%~99% yields.

Methylation of arenes is one of the versatile approaches to achieve structural modification in organic and medicinal chemistry. Installation of a methyl group onto an aromatic ring can lead to significant improvenent of the physical properties and biological activity of this molecule, thusly the effect oftentimes is called the“magic methyl effect”. During the past few years, visible-light-induced photocatalysis has emerged as a powerful tool for the development of efficient transformations in organic synthesis. Compared to traditional radical mediated reactions, the use of visible light as energy input is more environmentally benign. Recently, a series of aryl methylation reactions enabled by visible light photoredox catalysis have been reported and applied in the synthesis of pharmaceutically-interested products. In this review, the recent progress of visible-light-induced aryl methylation reactions is briefly summaried, with discussions of different reaction pathways.

Due to the potential applications of fullerene derivatives in materials science and biological science, chemists have been devoted to their synthesis over the past 30 years, and have reported a great diversity of synthetic protocols to fun-ctionalize fullerenes. Among the numerous methods, electrochemical synthesis has been considered to be a novel and efficient strategy due to its mild reaction conditions, good regioselectivity and relatively high yield. The electrochemical functionalizations of [60]fullerene-fused heterocycles have recently attracted wide interest, because electroreduction results in the carbon-heteroatom bond breaking and rearrangement of the heterocyclic moieties on the fullerene skeleton, consequently providing new addition patterns of fullerene derivatives. The electrochemical reactions of [60]fullerene-fused heterocycles since 2011 are reviewed.

Inspired by enzyme allosteric catalysis, the study on artificial stimuli-responsive asymmetric catalytic systems has attracted more and more attentions in recent years. In order to precisely control the catalytic activity and stereoselectivity, stimuli-responsive functionalities have been introduced into the catalyst design. A variety of asymmetric reactions featuring on/off-switchable catalysis and/or stereodivergent catalysis have been successfully achieved by using light-, coordination-, pH-and redox-driven chiral switchable catalysts. By selecting representative examples, the catalyst design principles, allosteric mechanism and their applications in switchable asymmetric reactions sre mainly introduced. At the same time, advantages and limitations of this emerging field are summarized, and perspectives for its future development are given.

Cinchona alkaloids widely exist in nature, which have attracted extensive interest of researchers because of their readily availability, biological activity, unique structural properties, and easy modification. With the development of asymmetric synthetic chemistry, cinchona alkaloids and their derivatives have been used as a privileged class of chiral catalysts or ligands in many catalytic asymmetric reactions. In particular, a variety of cinchona alkaloid-derived chiral catalysts and ligands have been developed and applied by organic chemists in catalytic asymmetric synthesis in rencent years. The recent progress made in this field over the past few years is summarized. Moreover, the related reaction mechanisms and future development prospects are also discussed.

A convenient K₂S₂O₈-initiated radical cascade cyclization for the construction of 4-sulfonated cyclopenta[gh]-phenanthridines from 2-alkynylnitriles and sodium sulfinates has been explored under metal-free conditions. This protocol features mild conditions, good functional group tolerance and broad substrate scope. A variety of potentially bioactive 4-sulfonated cyclopenta[gh]phenanthridines were facilely synthesized via direct annulation.

Among the more than 800 alkaloids isolated from skins of arrow poison-frog, batrachotoxin had attracted the most widespread attention of scientists from several fields, due to its potent cardio and nerve toxicities and challenging structure. A new strategy, which is different from all the previous total syntheses (one racemic and two enantioselective), is disclosed. This strategy features the formation of the CDE skeleton and then the ABCDE core of batrachotoxin by a key Diels-Alder reaction between A ring and CDE framework. Because A ring segment is a known compound, the first key of synthesis resides in the construction of the CDE framework. Thus, in addition to the new synthetic strategy, the synthesis of a functionalized CD ring system is developed. The synthesis started from the preparation of 2-allylcyclopentane-1,3-dione and its Michael addition with hex-1-en-3-one. The Hajos-Wiechert-type reaction of the adduct was investigated under optimized conditions using L-phenylalanine as an organocatalyst and D-camphorsulfonic acid (D-CSA) as an additive, the desired Robinson annulation proceeded smoothly to give the desired cyclization product in 75% yield and 81% ee. The latter was converted into a functionalized CD skeleton that bears all elements for elaborating to CDE framework in seven steps.

The enantioselective syntheses of (-)-indolizidine 167B and (+)-coniine were described based on the asymmetric hydrogenation of racemic δ-hydroxy esters via kinetic resolution. With optically active chiral δ-hydroxy ester (S)-4 and chiral 1,5-diol (R)-5 obtained by asymmetric hydrogenation of racemic ethyl 5-hydroxyoctanoate (rac-4) with chiral spiro iridium catalyst Ir-(R)-SpiroPAP as chiral starting materials, the efficient enantioselective syntheses of (-)-indolizidine 167B and (+)-coniine were achieved by using intramolecular reductive amination and N-substitution/cyclization, respectively, as a key step to construct the chiral aza-bicyclic[4.3.0]nonane skeleton and chiral piperidine ring. This provides new efficient methods for enantioselective syntheses of indolizidine and piperidine alkaloids.

Driven by nowadays’ computing power, big data technology as well as learning algorithm, artificial intelligence (AI) has gained trenmendous attentions and become a transformative approach in many research areas. One of the most extensively explored AI approaches in chemistry is (deep) machine learning, which provides new twists in the fields of organic chemistry. The workflow of machine learning (ML) study in organic chemistry is briefly introduced. Meanwhile, the application of ML in the accurate prediction of chemical properties, molecular de novo design, chemical reaction prediction, retrosynthetic analysis and artificial intelligence synthetic machine are also summarized. In the end, the current challenges in this field are analyzed and discussed.

Supramolecular polymers are regarded as a new kind of dynamic materials. The study of supramolecular polymers not only helps to understand the law of self-assembly, but also provides theoretical support for the development of smart materials. Herein, three dioxyphenylene bridged ditopic ureidopyrimidinone (UPy) derivatives M1~M3 are studied. These molecules could undergo supramolecular polymerization via quadruple hydrogen bonding. The only difference in their structure is the length of the oligo(ethylene oxide) chain as spacers. The supramolecular polymerization based on ring-chain equilibrium of these molecules were studied by a series of experiments including concentration-dependent ¹H NMR, NOESY, and viscosity measurement, which showed that the spacer length has a big impact on the ring-opening supramolecular polymerization process. And the main reason for this is the different strengths of π-π interaction between the dioxyphenylene unit and the dimerized UPy motif in the cyclic monomer form. M1 with the shortest spacer lacks this kind of π-π interaction while M3 with the longest spacer possesses a weak π-π interaction, both leading to small value of CPCs. By contrast, M2 with a moderate length of spacer has a strong π-π interaction, resulting in a high CPC value (189 mmol·L^-1). Finally, the host-guest complexation between M1~M3 with the π-electron deficient bipyridinium-based cyclophane “blue-box” were further investigated, which shows that only M3 could perform host-guest complexation. From this interesting model, new insight into the relationship between molecular structure and supramolecular polymerization is discovered, which is important for creating tailor-made supramolecular polymeric materials.

gem-Difluoroalkenes have wide applications in the drug designs and act as the synthon of molecules containing fluoride. The current researches on the electrochemical syntheses of gem-difluoroalkenes are limited to the silylation of enolated trifluoromethyl ketones. Herein, by using graphite felt as electrodes, the electrochemical allylic hydrodefluorination of α-trifluoromethyl cinnamates is realized using gaseous ammonia as hydrogen source, giving gem-difluorostyrenes in moderate to good yields. The usage of ammonia and graphite felt cathode is important to inhibit the cathodic hydrogen evolution, keeping the electron transfer from cathode to substrate with high selectivity. The cyclic voltammetry (CV) and square wave voltammetry (SWV) analyses support a stepwise electron transfer process to achieve the C—H bond formation and C—F bond cleavage.

The introduction of methyl group into aromatic compounds is a valuable transformation. A large number of known methods use organohalides as the starting materials. However, those methods require pre-synthesized methyl metal reagents or toxic methyl electrophiles. Herein, a palladium-catalyzed reductive coupling reaction between aryl bromides and trimethylsilyl-diazomethane is developed, and the following desilicification process can afford the methylated products. This transformation has broad functional group tolerance and allows methylation of (hetero)aryl halides in moderate to good yields. Thus, it has the potential to be an attractive approach for methylation of organic. In addition, this reductive coupling can also serve as an efficient way for the introduction of silylmethyl group.

By using sulfonyl hydrazines and ketene dithioacetals as starting materials, the regioselective annulation providing 3-alkylthiolated pyrazoles has been realized in the low cost and easily available NaHSO₄ catalytst. The reactions were realized in 1,4-dioxane medium and 80 ℃ heating, whereby a seris of 3-alkylthiol pyrazoles possessing N-sulfonyl structure have been efficiently synthesized.

Although the chiral separation techniques represented by the polysaccharides-based chiral stationary phases are almost matured, the chiral separation for complex samples remains a challenge. To this end, two dimensional liquid chromatography has been developed rapidly. Recently, to achieve the chiral separation with two dimensional liquid chromatoraphy, the development of the ultrafast liquid chromatography has caused considerable attention. The development of ultrafast liquid chromatography and two-dimensional liquid chromatography also caters to the development of high-throughput organic synthesis technology. In this review the recent progress in the chiral separation by the ultrafast and two-dimensional liquid chromatography is summarized. This review focuses on the progress in the techniques of the chiral packing materials for ultrafast chromatography, the chiral separation strategy and its application in complex samples. Finally, the application perspective of ultra-fast and two-dimensional liquid phase in high-throughput organic synthesis techniques is prospected.

C—H oxidation represents one of the most important reactions in organic chemistry. In particular, asymmetric C—H oxidation, which can directly convert simple alkanes into chiral alcohols, ketones, aldehydes and so on, provides more economic and efficient access to the synthesis of complex molecules. Although increasing efforts have been devoted to this area, asymmetric C—H oxidation is still far away from the goal due to the inert nature of C—H and the subtle stereo-difference of C—H bonds. The factors that dictate the selectivity of asymmetric C—H oxidation, mechanism of the C—H oxidation catalyzed by enzyme and some successful examples achieved by biomimetic metal complexes bearing various ligands are reviewed.

A metal-free, BCl₃ mediated borylative cyclization of 2-(1-alkynyl)-2-alken-1-ones leading to synthetic valuable multi-functionalized naphthalene boronates in one step was developed. The boronate functionality present in the product provides many opportunities for derivatization. The salient features of this reaction include moderate to good yields, gram-scale synthesis and diverse synthetic transformations. In the meantime, the new synthetic applications of 2-(1-alkynyl)-2-alken-1-ones have been developed.

A Brønsted acid-catalyzed substitution reaction of 2-indolylmethanols with tryptophols has been established, which afforded a series of 2,2'-bisindolylmethanes in high yields (up to 98% yield) with chemoselectivity. This protocol not only provides an efficient method for constructing biologically important 2,2'-bisindolylmethane frameworks, but also has realized a substitution reaction of 2-indolylmethanols, which will enrich the chemical property of 2-indolylmethanols. Moreover, this approach has utilized the C(2)-nucleophilicity of tryptophols, which provided a good example for controlling the chemoselectivity in tryptophol-involved reactions.

Calixarenes, pillararenes and their analogues are composed of hydroxy-or alkoxy-substituted aromatic rings bridged by methylene or methenyl groups, which can be collectively called as macrocyclic arenes. Macrocyclic arenes have attracted much attention and increasing interests because of their unique structures, easily synthesis and derivatization, electron-rich cavities and wide applications in supramolecular chemistry, and they have also become one of the most significant and studied synthetic macrocyclic hosts during the last decades. Recently, with the rapid development of macrocycles and supramolecular chemistry, various types of novel macrocyclic arenes except the classic macrocyclic arenes such as calixarenes and pillararenes have been reported. The construction and functionalization of novel macrocyclic arenes have become the new focus and hot topic of macrocyclic and supramolecular chemistry. The recent advances in the synthesis and properties of novel macrocyclic arenes are summarized. It is expected that this review will be helpful to the research of macrocyclic arenes and promote the development of macrocyclic arene chemistry.

Two isomers of azulene and indacenodithiophene (IDT)-based compounds 1 and 2 were designed and synthesized, according to the different connections of azulene unit with IDT through its electron-rich five-membered ring and the electron-deficient seven-membered ring, respectively. The UV-Vis spectra, electrochemical properties and proton-responsive properties of 1 and 2 were studied. Compounds 1 and 2 show obviously different physicochemical properties and device performance of organic field-effect transistors (OFET). Both compounds 1 and 2 have reversible proton response characteristics. The end absorption peaks of these two compounds are between 400 and 600 nm before protonation. With the addition of trifluoroacetic acid (TFA), the absorption peaks are red shifted to 550~850 nm. When they are protonated fully (TFA volume ratio is about 1%), they are red shifted about 200 and 177 nm, respectively. The color of compounds 1 and 2 in dichloromethane solution before protonation is red after the adequate protonation. It turned to blue and returned to its original color after the addition of triethylamine. OFET thin film devices of 1 and 2 showed an order of magnitude difference, with hole mobilities of 4.14×10^-3 and 1.05×10^-5 cm²·V^-1·s^-1, respectively. The different connections of IDT and azulene units through the electronic rich five-membered ring and the electronic deficient seven-membered ring of azulene greatly affect the materials’ device performance as well as their physicochemical properties, providing valuable insights for developing azulene-based novel organic functional molecules.

1,2-Diols have important applications in pesticides, chiral medicines and fine chemicals. A Pd(II)-catalyzed 1,2-diacetoxylation method using readily available acetic acid as the oxygen source and oxygen as the oxidant was developed. For the 1,2-diacetoxylation of conjugated dienes, the reaction proceeds with high 1,2-regioselectivity. This protocol has good substrate scope for conjugated dienes possessing aryl-, ester-and carbonyl groups. The catalytic products can be transformed to 1,2-diols through simple alcoholysis or hydrolysis, therefore it is an efficient method for the synthesis of 1,2-diols.