A novel method of copper-catalyzed cyclization of 1-aryl-1-cycloalcohols and 1,3-dicarbonyl compounds has been developed, affording various cycloalkane-fused dihydrofurans in moderate to excellent yields. This transformation proceeds under mild conditions and with a good tolerance of functional groups. The mechanistic investigation revealed that the reaction involved radical intermediates.

Axially chiral biaryl skeletons are ubiquitous stuctural motifs that are widely represented in pharmaceuticals and natural products, and have been widely used as privileged chiral ligands/catalysts in asymmetric synthesis. Therefore, the asymmetric construction of these compounds has received tremendous attention. However, the established strategies are mainly limited to the construction of biaryls containing hexatomic aromatics, and the approaches towards atropisomers featuring pentatomic heteroaromatics connected through C-C or C-N bond have emerged gradually only until recently. The main hurdle is basically due to the increased distance of substituents ortho to the axis, which is responsible for lower barriers to rotation, thus rendering the asymmetric synthesis more challenging. This review summarizes recent advances on the enantioselective synthesis of atropisomers featuring pentatomic heteroaromatics.

Carbazole and its derivatives are widely used in the field of medicine and photoelectric materials. A kind of stable cyclic hypervalent iodine reagents containing carbazole group was developed, which belong to benziodoxole compounds. In the presence of Cu(I) catalyst, these reagents reacted with aromatic substrates to give N-aryl carbazole derivatives. The reaction conditions are mild and suitable for a variety of electron-rich arenes. And a radical mechanism was proposed.

A phosphine-mediated Staudinger/Aza-Michael addition of azides with trifluoromethyl substituted α,β-unsaturated ketones was developed, giving hydroamination products in medium to good yields (up to 96%). The hydroamination products could be prepared on gram scale and a wide range of substrates are tolerated under the optimized reaction conditions (30 examples). ³¹P NMR experiments indicate that this reaction was initiated by Staudinger reaction of azide with phosphine.

A nickel-catalyzed Negishi coupling of cyclobutanone oxime esters with aryl zinc reagents has been developed, in which nickel serves both as an initiator for imine radicals and a catalyst for the coupling of aryl zinc reagents with oxime esters. The protocol can avoid the use of poisonous cyanide and has broad substrate scope as well as good functional group compatibility. Therefore, this method provides an attractive strategy for the synthesis of valuable nitriles. Preliminary mechanistic studies indicate that a radical pathway is involved in the product formation.

A highly chemo-, regio-, and stereo-selective cobalt-catalyzed dehydrogenative silylation of vinylarenes was described. The imidazoline iminopyridine cobalt complex could promote this reaction effectively and improve the chemoselectivity dramatically. This protocol used earth-abundant transition metal, readily available alkenes and hydrosilanes to construct valuable vinylsilanes. The reaction could be carried out in gramscale and the proposed mechanism was also described.

The C=C double bond cleavage of NH₂-functionalized enaminones has been realized at room temperature to provide various N-sulfonyl amidines by reacting with sulfonyl azides. The reactions take place with good substrate tolerance in the presence of 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) without any metal or oxidant reagent. The ¹⁵N-labelling experiment on enaminone indicates that the sulfonyl azide component donates solely the sulfonamide fragment, and the reaction mechanism involving a key decomposition of the in situ generated 1,2,3-triazoline intermediate is convictively supported.

Trifluoromethylation using Togni reagents usually releases one equivalent of iodobenzoats as wasteful byproducts. A visible-light-mediated, atom-and step-economical hydrotrifluoromethylation of aromatic alkynes and remote benzoyl-oxylation of α-C(sp³)-H bond of ether with Togni reagent as a bifunctional reagent by means of hydrogen atom transfer strategy was disclosed. The combination of two organic transformations into one reaction not only brings 100% atom economy but also addresses the challenge of stereoselective hydrotrifluoromethylation of aromatic alkynes. This unprecedented protocol offers an important access to a wide range of highly functionalized CF₃-containing alkenes with great potential for post-modification.

A novel palladium(0)-catalyzed dearomative spirocyclization reaction of bromophenols has been developed for building a series of spirocyclic architectures containing a quaternary carbon center via[2+2+1] strategy. This method employs inexpensive bromophenols and easily accessible alkynes. It exhibits a broad substrate scope in good yields. Notably, this transformation can be realized with high regioselectivity (>19:1 rr) when using unsymmetrical alkynes, which greatly expands the research scope of phenol dearomatization.

Organosilicon compounds play an important role in pharmaceutical chemistry, material science and organic synthesis. Transition-metal-catalyzed direct silylation of C-H bond, as one of the most concise and efficient methods for the synthesis of organosilanes, has developed rapidly in recent years. In this paper, the recent advance in transition-metal-catalyzed silylation of C-H bonds since 2015 is mainly reviewed.

3-(5-Oxazolyl)indole-type natural products such as pimprinine and streptochlorin, widely exist in marine microorganism, because of their diverse biological activity, 3-(5-oxazolyl)indoles show good research and development potential in the field of medicine and pesticide. Numerous studies have been performed to synthesize 3-(5-oxazolyl)indole-type natural products, in which the construction of indole ring and oxazole ring is the most important part. In this paper, the reported natural products with 3-(5-oxazolyl)indole skeleton structure and their biological activities are summarized, and the synthetic methods for 3-(5-oxazolyl)indole skeleton and some of their mechanism are also reviewed. The application prospect of 3-(5-oxazol-yl)indole as a dominant active structure in the future was discussed.

The development of efficient methods for the preparation of unnatural amino acids has long been an important goal since their widely application in synthetic and medicinal chemistry. The asymmetric α-functionalization of nucleophilic metalated azomethine ylides, which could be in situ-generated from readily-available aldimine esters, has been recogonized as a powerful strategy to synthesize unnatural amino acids. Over the past 20 years, tranistion metal-catalyzed asymmetric construction of unnatural amino acids using azomethine ylides have been extensively studied. In this review, the progress on metallated azomethine ylides invovled aymmetric transformation for the synthesis of unnatural amino acids is summarized according to eletrophilic reagents.

Pyrazole, an important class of nitrogen-containing five-member hetrocyclic compounds, widely exists in natural products, bio-active molecules and drugs, and it is also a valuable intermediate in organic synthesis. The synthesis of polysubstituted pyrazoles has attracted much attention and developed rapidly in recent years. Herein, the recent research progress in the construction of polysubstituted pyrazoles is summarized.

Chiral aryl alcohols are prevalent in a broad range of biologically active compounds, pharmaceutical agents and natural products. They also constitute a broad class of optically active building blocks for the synthesis of important chiral compounds. In recent years, organoboron reagents are widely used in organic synthesis as they possess advantages of ready availability, low toxicity, good air and moisture stability as well as high functional group compatibility. Since the first report of rhodium-catalyzed asymmetric addition of aryl boronic acids to aryl aldehydes in 1998 by Miyaura, the use of organoboron reagents in asymmetric addition to various carbonyl compounds under various transition-metal catalyses has been intensively investigated. Over the past two decades, transition metal-catalyzed asymmetric addition of organoboron reagents to aldehydes and ketones has proved as one of the most direct and powerful methods for accessing versatile optically active alcohols. The development and progress of a wide range of chiral ligands for Rh, Ru, Pd, Ir, Cu, Ni and Co catalysis for asymmetric addition of organoboron reagents to aldehydes and ketones are summarized, and the achievements in enantioselective synthesis of chiral aryl alcohols and their applications in the synthesis of related biocative products are described. Among them, rhodium and ruthenium-catalyzed enantioselective additions have received considerable attention. In the cases of activated carbonyl compounds such as α-aryl ketoesters and α-diaryl diketones, excellent results can be attained in terms of both yield and enantioselectivity. However, it remains a daunting challenge for highly enantioselective addition to simple unactivated aldehydes and ketones owing to the difficulty in overcoming stereo differentiation. Future efforts in the community would focus on developing new effective transition-metal catalysts in addressing these issues by promoting efficient transformation and controlling excellent enantioselectivity.

The phosphine-catalyzed[3+2] annulation of γ-methyl allenoates with 2-arylidene-1H-indene-1,3(2H)-diones is reported. In the reaction, a series of highly functionalized spiro[4.4]dec-6-ene skeletons were obtained in moderate to good yields and high diastereoselectivities. It should be noted that the perfect α-regioselective annulation adducts were obtained with simple PPh₃ catalyst.

Asymmetric hydroformylation is one of the most important reactions for preparation of chiral aldehydes from alkenes. Recently, significant progress has been made in this field and a series of new ligands have been developed. Asymmetric hydroformylation of several important alkenes has been achieved, offering efficient and concise methods for the synthesis of chiral aldehydes. In this review, the achievements of asymmetric hydroformylation of typical alkenes and the development of ligands for asymmetric hydroformylation are summarized.

The multifunctional fluorescent probes can detect a plurality of anions and cations or other small molecules. These probes can greatly improve the detection efficiency and reduce the analysis cost with respect to the mono-analyte fluorescent probes. Thus, they have attracted much attention in recent years. According to their molecular structural characteristics, the reported multifunctional fluorescent probes are divided into three types as organic small molecules, polymers and metal-organic complexes. The new progress on their molecular design, synthesis and detecting application is reviewed on the viewpoint of sensing objects and performances. The developing potential of multifunctional fluorescent probes is envisioned also, and the probes capable of simultaneously identifying multiple analytes in the same system should be highlighted in the future

Aspirin (ASP), the first synthetic drug, is widely used as a non steroidal anti-inflammatory drug. It displays a variety of biological activities, such as anti-thrombosis, anti-inflammatory, anti-tumor, etc. A lot of works about the synthesis and related activity evaluation of its derivatives were reported. There are four kinds of derivatization methods:skeleton derivatization, prodrug derivatization, twin derivatization and metal coordination derivatization. According to the different modification sites, skeleton derivatization could be further divided into C(1)-COOH site modification, C(1)-COOH site and C(2)-OAc site simultaneous modification, C(2)-OAc site modification and benzene ring modification. NO-ASP is the main method to prepare antithrombotic derivatives, and metal coordination modification is the main synthesis scheme of anticancer derivatives. The structure modification and bioactivity research of aspirin in recent twenty years and the synthetic routes of 353 aspirin derivatives and the pharmacological activities of some derivatives are described, which provides a reference for the further development of aspirin derivatives.

Quinoxalin-2(1H)-ones are very important N-heterocyclic moieties found in natural products and pharmaceuticals, and exhibit an amazingly wide spectrum of biological properties. Numerous efforts have been devoted to the development of efficient approaches for the C-H bond activation and functionalization of quinoxalin-2(1H)-ones in recent years, including alkylation, benzylation, acylation, arylation,amination, amidation, phosphonation, and fluoroalkylation. The recent advances in this area are summarized and their reaction mechanisms are discussed.

Scientists have found more and more sulfur compounds in food with the development of science and technology, high-precision analytical methods and equipment. In 2015, Flavor and Extract Manufactures Association of the United State published 2816 safe flavors, and there are more than 388 sulfur-containing compounds, accounting for more than 13%. The main smell of sulfur-containing flavors is food, especially the non-staple food and dishes. It is mainly used as food flavor, flower flavor and fruity flavor. Due to the increase of sulfur-containing perfume and flavors demand, its production scale is increasing, the research on synthesis methods is also deepening, and the green and efficient construction methods are also constantly reported. In this review, the recent progress in the construction of sulfide, thiol, thioester and polysulfide perfume & flavors is summarized.

Alkaline-earth metals continue to receive growing interest, as they are used as low-cost and non-toxic alternatives to transition-metals in various organic transformations. As ionic character and bond lengths increase along the row in the order Mg²⁺2+2+2+, bond energies decrease along the same row, the corresponding metal hydrides are apt to the formation of insoluble metal hydrides[AeH₂]_∞ (Ae=Mg, Ca, Sr, Ba) through Schlenk equilibrium in solution. Recently, a series of alkaline-earth metal hydrides stabilized by suitable ligands were discovered and characterized, and stoichiometric and catalytic reactions with small molecules were studied as well. In this paper, the recent progress in molecular alkaline-earth metal hydrides is reviewed.

Maleimide, a common motif in a variety of natural alkaloids, has been extensively investigated due to its noteworthy biological activities and optical properties. Additionally, it can be transformed into many important heterocyclic frameworks such as succinimides, pyrrolidines, and 2-pyrrolidones. Thus, a great deal of attention has been focused on the development of new synthetic routes to access polyfunctionalized maleimides. In this article, the recent research progress in functionalization of double bond is reviewed based on maleimides according to Michael addition, oxidative coupling and cycloaddition reaction.

Heterocyclic compounds are widely applied in medicine, fine chemical engineering and the related industrial fields. Consequently, the development of efficient strategies for heterocycle constructions continues to be of great appeal in organic synthesis. In recent years, the I₂-catalyzed direct C-H bond functionalizations have emerged as one of the most efficient synthetic protocols to construct diverse heterocycles. In this review, the recent advances in I₂-catalyzed C-H bond functionalizations by the types of C-C and C-N/O/S bond formations are summarized, and an outlook of this research filed is given.

Benzofulvenes were widely found in natural products and bioactive molecules, and also served as important building blocks in material science and transition-metal chemistry. Great efforts have been devoted to the efficient synthesis of these interesting molecules, and rapid advancement has been made in the past two decades. According to the types of the initiation of the reaction, these methods can roughly be classified into five categories:thermal or photochemical cyclization of enyne-al-lenes or enediynes, transition metal-catalyzed sequential cyclization reaction, electrophilic or nucleophilic attack initiated cyclization, radical initiated cyclization and acid promoted cyclization. This review describes the important synthetic methods of benzofulvenes according to their reaction types.

As interesting synthetic targets, dimeric cyclotryptamine alkaloids bearing sterically hindered vicinal all-carbon quaternary stereocenters have attracted significant attention from the synthetic community. Stereocontrolled synthesis of the congested all-carbon quaternary stereocenters in these alkaloids presents a formidable challenge. This review summarizes the synthetic efforts towards dimeric cyclotryptamine alkaloids in the last twelve years.

Synthesis of complex molecules via multicomponent reactions (MCRs) in a one-pot reaction manner has emerged as an important means to realize the value-added conversion of cheap and easily available renewable bio-based platform molecules. The diversity and multi-functionality of these biomass-derived molecules provide a fascinating platform for establishing MCRs, and in many cases, the developed MCRs would not be attained from less functionalized substrates. This review introduces some typical examples for the conversion of biomass-derived platform compounds to high value-added products through MCRs. It mainly summarizes the MCRs developed by using polyols, dicarboxylic acids, levulinic acid and furfural derivatives as one of the starting substrates. At the end of this review, a perspective of this direction is also given.

N-O bond cleavage is one of the most efficient and powerful strategies to introduce N-or O-functional groups into molecules in organic synthesis. Copper catalyst, as the abundant in earth and inexpensive advantages has been widely used to construct C-N and C-O bond. Furthermore, N-O bond cleavage has been successfully applied in the total synthesis of natural products and pharmaceuticals. The new development of copper-catalyzed N-O bond cleavage and its application in the total synthesis of natural products and pharmaceuticals in recent years have been summarized.

Indolines, an important class of heterocycles with a wide range of biological properties, are a key structural motif in numerous natural products and biologically active compounds. As a result, efficient methods for indolines synthesis have been the subject of extensive studies. In this review, recent studies on the synthesis of various functionalized indolines using unactivated alkenes are described. It involves radical addition/cyclization reaction in the presence of oxidizing agent, which is usually carried out under neutral reaction conditions using readily available oxidizing agents and different transition metals or under metal-free as catalysts.

α-Amino acids are the units of proteins, which not only widely occur in many biological important compounds and natural products, but also are useful as organic catalysts or ligands for asymmetric synthesis. Among them, glycines are particularly useful building blocks in organic synthesis. Direct C(sp³)-H bond functionalization of glycine derivatives provided an attractive synthesis strategy for the construction of a variety of α-substituted α-amino acids. The recent progress in the α-C(sp³)-H bond activation of glycine derivatives, with various reagents to form carbon-carbon and carbon-heteroatom bond, and oxidative coupling/cyclization reaction involving glycine derivatives is reviewed.

Treatment of PhSbCl₂ with 2 equiv. of (2,6-Cl₂C₆H₃)(2-LiC₆H₄)NLi, which was generated in situ by the interaction of (2,6-Cl₂C₆H₃)(2-BrC₆H₄)NH with 2 equiv. of BuⁿLi, followed by quenching with water, afforded the diamine-stibine compound ((o-(N-(2,6-Cl₂C₆H₃)NH)C₆H₄)₂SbPh (denoted as H₂(^dcpN₂Sb)). H₂(^dcpN₂Sb) undergoes amine-elimination reaction with[Fe(N(SiMe₃)₂)₂]₂ (0.5 euiqv.) to afford an iron(Ⅱ) complex[(κ³-N,N,Sb-^dcpN₂Sb)Fe(THF)] (1) bearing an unique tridentate bisamido-stibine ligand. Solution magnetic susceptibility measurements (μ_eff=4.7(2) μ_B in C₆D₆) reveal a high spin (S=2) electronic structure for 1. Complex 1 represents the first high-spin iron(Ⅱ) complex with organic stibine ligation, and features a long Fe-Sb bond distance of 0.2792(1) nm. Density functional theory (DFT) calculations indicate weak σ interaction betwen the high-spin iron(Ⅱ) center and the antimony atom due to ineffective orbital overlap. Complex 1 can react with organic azides RN₃ to furnish the high-spin (S=2) iron(Ⅱ) complexes that bear tridentate bisamido-stibonium imine ligands[(κ³-N,N,N-^dcpN₂SbN^R)Fe(py)] (R=dcp (2,6-Cl₂C₆H₃), 2; R=Dipp (2,6-ⁱPr₂C₆H₃), 3). These compexes are among the rare metal complexes with stibonium imine ligation. The average Sb-N distance of 0.194 nm in the imine moieties is found comparable to those of the Sb-N bonds in the reported stibonium imine compounds Mes₃SbNCOCl₃ (0.199 nm) and 2-MeC₆H₄)₃SbNSO₂CF₃ (0.196 nm). The reactions of 1 with diazo compounds (R¹R²)CN₂ afford the high-spin iron(Ⅱ) complexes featuring tridentate bisamido-stibonium ylide ligands[(κ³-N,N,C-^dcpN₂SbC^R1,R2)Fe(PMe₃)] (R¹=H, R²=CO₂Bu^t, 4; R¹=Ph, R²=CO₂Et, 5). The average Sb-C distance of 0.206 nm in the ylide moieties is found comparable to those of the Sb-C bonds in the reported stibonium ylide compounds (around 0.20 nm). H₂(^dcpN₂Sb) and 1~5 have been characterized by elemental analysis, ¹H NMR, solution magnetic susceptibility measurements and single-crystal X-ray diffraction studies.

Acetohydroxyacid synthase (AHAS) was one of important herbicidal targets. However, the issue of weed resistance to commercial AHAS inhibitors has become one of the largest obstacles for their application. Therefore, there is a high demand to design new anti-resistance AHAS inhibitors. Herein, based on the reported low resistance AHAS inhibitors, a series of pyrimidyl-salicylates with "double oxygen bridge" utilized the "conformation flexibility analysis" strategy were designed. All the synthesized compounds were characterized by ¹H NMR, ¹³C NMR and HRMS. The bioactivity results showed that most of the derivatives displayed good inhibitory activities against P197L mutant. Especially, 2-((4,6-dimethoxypyrimidin-2-yl)oxy)-6-(2-fluoro-4-nitrophenoxy)-4-methylbenzoic acid (6l) was identified as the most potent anti-resistance AHAS inhibitor. In addition, some compounds showed good weed control for resistant Descurainia sophia (P197L AHAS). Most importantly, 2-((4,6-dimethoxypyrimidin-2-yl)oxy)-6-(2-fluorophenoxy)-4-methylbenzoic acid (6b) showed 80% herbicidal activities against sensitive and resistant Descurainia sophia at the dosage of 150 g ai/ha. These results indicated that this type of compounds worth of the further investigation.

Flavonoid glycoside is commonly found in natural plants, possesses diverse bioactivities and potential medicinal values, and its synthesis methods are worthy to be studied. The synthesis of flavonoid glycosides covering the literatures from 2014 to 2018 is reviewed. The flavonoid glycoside synthesis includes two major methods of chemosynthesis and biosynthesis. Chemosynthesis includes total synthesis and semi-synthesis. The total synthesis has two classical methods of the Baker- Venkataraman (BK-VK) reaction and the Algar-Flynn-Oyamada (AFO) reaction. The semi-synthesis is usually starting from natural flavonoid, such as rutin, quercetin, kaempferol, naringenin and so on. Moreover, the chemosynthesis of flavonoid O-glucoside has three prime methods, Koening-Knorr method, phase transfer catalysis method, and glycosyl trichloroacetimidate method. As for the chemosynthesis of flavonoid C-glycoside, its glycosidic linkage is mainly completed via the O→C rearrangement reaction. Currently, the glycosyltransferase and glycosynthase are usually employed in the enzyme-catalyzed biosynthesis of flavonoid glycosides.

Tremendous advance has been achieved for the transition-metal free coupling reactions induced by light these years, providing important strategies for the construction of C-N/S/P bonds, which was used frequently in the preparation of pharmaceutical drugs, agricultural products or materials and so on. In this review, the recent advance for the photo-induced coupling reactions for the construction of C-N/S/P bonds under transition-metal free conditions is reviewed.

Transition-metal-catalyzed Suzuki-Miyaura cross-coupling is one of the most powerful transformations for C-C biaryl bond formation at present. With the increasing demand for green chemistry, water as solvent for the Suzuki-Miyaura cross-coupling reactions has been of widespread interest. The literature in recent years on the Suzuki-Miyaura cross-coupling reactions by heterogeneous or homogeneous catalysis in water is reviewed, and their perspectives for further developments are also presented.

Compounds bearing difluoromethylthio (SCF₂H) and monofluoromethylthio (SCFH₂) groups are potentially important targets in the pharmaceutical and agrochemical fields due to their unique physical and chemical properties. The traditional methods of synthesizing these two kinds of compounds are difluoromethylation and monofluoromethylation of sulfhydryl substrates. However, the limitation of sulfhydryl substrates also limited the application and development of such compounds. Thus, it is still highly desirable to develop new methods for difluoromethylthiolation and monofluoromethylthiolation as well as new types of difluoromethylthiolation and monofluoromethylthiolation reagents. The recent development of direct difluoromethylthiolation and monofluoromethylthiolation reactions is summarized, and the related mechanism are also discussed.

A series of 1,3,4-thiadiazolo[3,2-a]pyrimidinone mesoionic derivatives were designed and synthesized with triflumezopyrim as the leading compound, and their structures were characterized by ¹H NMR, ¹³C NMR, ¹⁹F NMR and HRMS. The preliminary biological activities indicated that the target compounds showed certain insecticidal activities at 100 μg/mL, of which the lethality rates of 2-((4-chlorobenzyl)thio)-8-((2-chlorothiazol-5-yl)methyl)-5-oxo-6-(3-(trifluoromethyl)phen-yl)-5H-[1,3,4]-thiadiazolo[3,2-a]pyrimidin-8-ium-7-olate (8b) and 2-(((2-chlorothiazol-5-yl)methyl)thio)-8-((2-chlorothiazol-5-yl)methyl)-5-oxo-6-(3-(trifluoromethyl)phenyl)-5H-[1,3,4]thiadiazolo-[3,2-a]pyrimidin-8-ium-7-olate (8d) against white-backed planthopper (WBPH) were 70%. Some compounds showed good antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas oryzae pv. oryzicola (Xoc) and Xanthomonas citri pv. citri (Xcc) at 50 μg/mL, and the inhi-bitory rates of 2-((2-(trifluoromethyl)benzyl)thio)-8-((2-chlorothiazol-5-yl)methyl)-5-oxo-6-(3-(trifluoromethyl)phenyl)-5H-[1,3,4]thiadiazolo[3,2-a]pyrimidin-8-ium-7-olate (8h) to Xoo and Xoc were 70.91% and 53.34%, respectively, which were better than thiodiazole copper (47.76% and 23.25%) and bismerthiazol (66.97% and 17.24%). The inhibition rate of 2-((3-(tri-fluoromethyl)benzyl)thio)-8-((2-chlorothiazol-5-yl)methyl)-5-oxo-6-(3-(trifluoromethyl)phenyl)-5H-[1,3,4]thiadiazolo[3,2-a]-pyrimidin-8-ium-7-olate (8e) to Xcc was 68.97%, which was better than thiediazole copper (35.85%) and bismerthiazol (37.53%)

As one of the most important transformations in organic synthesis, deoxygenation reduction of sulfoxides to thioethers has attracted wide attention in researches and applications. With the development of organicmetallic chemistry, many mild and practical methods have been developed to reduce sulfoxides. In this review, based on the types of the reducing agents, the research progress on the deoxygenation reduction of sulfoxides to thiothers in recent 20 years is summarized. In addition, the advantages and disadvantages of these reduction systems, some reaction mechanisms and the prospects of research in this field are discussed.

Recently, the direct sulfenylation of C——H bond for C——S formation under transition metal-free conditions has rapidly advanced and is employed for eco-friendly synthesis of sulfenylated natural or bioactive compounds with various sulfenylating reagents. In particular, the sulfenylation of indoles is considered to be the most important because it can lead to a new class of molecules displaying a broad spectrum of biological and pharmaceutical activities. The recent five-year progress in direct C——H bond sulfenylation of indoles under transition metal-free conditions is discussed and their mechanisms in detail are described.

Water is a medium for reaction in living organisms, which is safe, cheap and easy to obtain, and visible light is a clean and renewable natural resource. Exploring the controllable free radical reaction under the illumination condition in water and developing a simple, green and efficient synthesis method not only conform to the current green chemistry theme, but also have an important scientific significance in theory and practical application. The classification and review of visible light catalysis in aqueous phase have been carried out in recent years, and the corresponding mechanisms are discussed.