This review summarizes studies on halogen bonding of fluorine-containing alkyl and aryl iodides in China. From 1987 to 1993, Chen et al. found that there existed donor-acceptor interaction between fluorinated organic (di)iodides, as Lewis acids, and organic Lewis bases such as amines and ethers, which represented early important advances for the research on the non-covalent force currently called as halogen bonding. From 2001 to now, several groups have used halogen bonding as driving force to conduct researches on crystal engineering. In this catogery, Zhu et al. investigated the one-dimensional self-assembly between perfluoro-α,?-diioodalkanes and amines, ethers, and hexamethylphosphamide. Jin et al. studied the complexation between fluorinated aryl iodides and various N-heterocycles, whereas Zhang and Li et al. constructed supramolecular double and quadruple helices from one or two molecular components. Jin et al. conducted extensive studies on C—I…p halogen bonding and its applications in crystal engineering. Wang and Wan et al. utilized halogen bonding to induce trianglular aromatic molecules to co-assemble into two-dimensional honeycomb arrays on surface, whereas Wang et al. utilized halogen bond to induce mono-layer and layer-by-layer self-assembly of two polymers or organic molecules. Zhao and Li et al. developed the applications of halogen bonding in solution-phase multi-site molecular recognition of foldamer receptors for ICF₂-incorporated tri-armed guests. Hu, Gong, Liao et al. utilized halogen bonding to improve the material properties of a variety of organic aromatic molecules. Several groups have also used halogen bonding to increase the selectivity of a number of organic reactions. Representative examples are described, which highlight the utility of halogen bonding.

Diaryliodonium salts with fluorines have potential bioactivity. Vicinal trifluoromethanesulfonate substituted diaryliodonium salts were synthesized for the purpose of studying their anti-bacterial properties aganist Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtilis). Firstly, their chemical structures were characterized by ¹H NMR, ¹³C NMR, ¹⁹F NMR and mass spectra. The minimum inhibitory concentration (MIC) of these compounds was tested by the micro-broth dilution method. The most active 2-((3-fluorophenyl)(((trifluoromethyl)sulfonyl)oxy)-l3-iodanyl)- phenyl trifluoromethanesulfonate (1) containing fluorine group gave the promising results for Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtilis) (MIC values of 16, 4 and 4 μg·mL^-1), which is significantly lower than the commercial antibacterial agent of isothiazolinones. Scanning electron microscope (SEM) analysis sugggested that the compound led to the death of bacteria. Cytotoxicity tests showed that the compound 1 as well as isothiazolinones had a slight effect on the growth of Hela cells in vitro conditions.

Aldol reaction of hydroxyacetone is an all-purpose route to construct the 1,2-diol building blocks for the synthesis of multifarious natural products and biological active molecules. In this work, a new series of trifluoromethylated-imidazoline organocatalysts have been designed and synthesized. It is found that the trifluoromethylated chiral organocatalyst (2R,4S)-4-benzyl-1,2-dimethyl-2-(trifluoromethyl) imidazolidine (1a) has proved to be very efficient for the direct asymmetric aldol reaction of α-hydroxyketones with aldehydes to build the syn-1,2-diol building blocks. Among the synthesized syn-aldol products, a good yield (up to 96%) and high stereoselectivity (up to dr＝15:1, 99% ee) could be obtained. The F—H bonding derived from trifluoromethyl group was proposed to play an important role in the stabilization of the transition state.

Organic fluorine chemistry has attracted considerable attention due to its unique character in the field of materials science, catalytic chemistry, medicine, fine chemicals and biochemistry, which majorly focus on the construction and cleavage of carbon-fluorine bonds. The transition metals are introduced to allow new possibilities for activating carbon-fluorine bonds and are gradually becoming an alternative way to synthesize numerous complex organics containing fluorine. In this review, the recent works on the theoretical mechanistic study for transition metals mediated carbon-fluorine bonds activation and cleavage are summarized. Meanwhile, the general modes of carbon-fluorine bonds activation have been concluded systematically, including the oxidative addition of carbon-fluorine bonds to transition metals, transition-metal-activated nucleophilic substitution, S_N2 type activation of carbon(sp³)-fluorine bonds and β-fluorine elimination, etc. The theoretical calculation shows that the reaction could be proceed by an oxidation addition mode, when the zero-valent nickel catalyst with strong reducibility is employed. However, if a zero-valent platinum catalyst is used, oxidation addition only occurs at extra activated carbon-fluorine bonds. In the reduction of polyfluorinated aromatic hydrocarbons by hydrogenated metal species, aromatic nucleophilic substitution between hydride and polyfluorinated aromatic hydrocarbons could occur to realize the activation of carbon-fluoride bonds. For carbon(sp³)-fluorine bonds, if “hard” Lewis base such as lithium or magnesium salt is employed, the carbon(sp³)-fluorine bonds can be activated via bimolecular nucleophilic substitution (S_N2). In addition, β-fluoride elimination is also frequently proposed in transition metal-catalyzed C—F functionalizations.

Herein, a nucleophilic fluorination reaction to construct fluorine-containing β-ketoesters and β-ketoamides is reported. The reaction uses PhI(OAc)₂ as oxidant and 3HF·Et₃N as fluorinating reagent. It can effectively build a series of fluorochemical compounds containing quaternary carbon center under room temperature reaction conditions for 30 min. Compared with the traditional electrophilic fluorination reaction, this method has the advantages of no metal participation, short reaction time, simple reaction conditions and high reaction yield.

An iron(Ⅲ)-porphyrin-catalyzed cyclization of ketones with dimethyl sulfoxide (DMSO) and ammonium acetate for the synthesis of unsymmetrical and symmetrical pyridines by employing DMSO as C₄ or C₆ source has been developed. Various aryl ketone derivatives react readily with DMSO, producing the pyridines in yields of 30%～85%. This method uses non-noble metals and proceeds under mild reaction conditions with operational simplicity, which thus allows the expedient assembly of pyridines from readily available ketones. Based on the preliminary experiments, a plausible mechanism of this transformation is disclosed.

(-)-Peduncularine is the principal alkaloid isolated from Tasmanian shrub Aristotelia peduncularis. Due to its unusual 6-azabicyclo[3.2.1]octane core, the indole alkaloid was received numerous attention from the synthetic community and several innovative synthetic strategies have been developed. In this minireview, the synthetic efforts of peduncularine are summarized as inspiration for future development of medicinally interesting derivatives.

A novel palladium-catalyzed intramolecular fluoroarylation of alkenes has been developed, in which ArIF₂ was employed as fluorine source as well as I(Ⅲ) reagent to activate olefin, to deliver the fluoroarylation products from 4-aryl- 1-olefins in moderate to good yields. The current transformation presents a convenient method to provide fluorotetralins and fluorochromanes under mild conditions from alkenes tethered arenes.

3,3-Bis(difluoroamino)-1,5-dinitratopentane was used as energetic plasticizer with improving energy properties and low glass transition temperature. To obtain more new difluoroamino energetic compounds with similar sturctures, a series of 3,3-bis(difluoroamino)-1,5-substituted-pentane derivatives were designed as candidates of novel energetic plasticizers. The heats of formation (HOFs), electronic structure, energy property and thermal stability were studied using density functional theory (DFT) method. The difluoroamino groups can increase energy gaps of electronic structure, density and detonation properties among the title compounds. Especially, 1,3,3,5-tetra(difluoroamino)pentane (S₃) has given outstanding values of potential energetic plasticizer. Its crystal density (1.91 g/cm³), detonation velocity (9.01 km/s), detonation pressure (37.31 GPa) and impact sensitivity (h₅₀ 29.83 cm) are very close to those of cyclotetramethylenetetranitramine (HMX). Furthermore, S₃ can be synthesized via some mature processes in five steps.

Fluorine-containing organic compounds have been widely applied in various fields, such as pharmacy, agrochemicals, materials science, etc. Trifluoromethyl, difluoromethyl and perfluoroalkyl groups represent the typical fluorine-containing functional groups. Hence, the development of highly efficient methods for introducing fluoroalkyl groups is of primary importance. In recent years, the reactions based on fluoroalkyl radicals have been developed into competent methods for introducing fluoroalkyl groups. On the other hand, the synthesis of the chiral molecules containing fluoroalkyl groups has attracted considerable attentions. However, attributed to the high reactivity of the fluoroalkyl radicals, the control of the reaction selectivity is difficult. Particularly, so far there have been only limited reports on the enantiocontrol of the reaction in this regard and the corresponding review of the field still lacks. This review summarizes the research on the asymmetric synthesis based on fluoroalkyl radical reactions developed over the past 20 years. The review introduces the selectivities, scope and mechanism of various reactions. It is divided into three different parts according to the type of the reaction: (1) asymmetric fluoroalkylation of enol/enamine intermediate through fluoroalkyl radical, (2) asymmetric difunctionalization of olefin through fluoroalkyl radical, (3) stereoselective 1,2-shift of vinylboronate complexes through fluoroalkyl radical.

The sulfinatodehalogenation reaction is a common method of introducing a fluoroalkyl group. In this paper, the reaction of α-trifluoromethylbenzyl bromide under sulfinatodehalogenation conditions was investigated. It was found that the product was an sodium alkyl sulfate (ArCH(CF₃)OSO₃Na) instead of an sodium alkyl sulfinate (ArCH(CF₃)SO₂Na) which was normal produced. α-Trifluoromethylbenzyl bromide did not react with the olefin after its generation of a radical intermediate under sulfinatodehalogenation conditions even though an olefin was presented. Instead, the reaction directly gave an alkyl sulfinate, and then oxidized by air to provide a product as an alkyl sulfate.

Trifluoromethylthiolation/oxidation of styrenes with easiy-handling AgSCF₃ used as the trifluoromethylthiolating reagent has been described, which furnished a series of α-trifluoromethylthio acetophenons. A variety of substituted styrene could be bifunctionalized via radical process in a mixed solvent of dimethyl sulfoxide (DMSO) and CHCl₃, with potassium persulfate used as the oxidant under mild conditions. A simple and efficent method for the facile construction of various α-trifluoromethylthio acetophenons is thus demonstrated.

Fluorination on conjugated components is one of popular strategies to modify organic optoelectronic materials. Following the research of a benzodithiophene/benzothiadiazole ADA-type optoelectronic molecule, two benzothiadiazole (BT) units were fluorinated with different numbers and positions, and the change in basic properties and performances for field-effect transistors and organic solar cells was investigated. It was found that when the F-substitution number increases, the molecule enhances thermal stability, decreases solubility, lowers HOMO and LUMO energy levels, but almost does not alter light absorption range. Furthermore, investigations on organic field-effect transistors found the molecular hole mobility reduces with only one F-substituent at outer position of BT units, while increases up to 0.27 cm²·V^-1·s^-1 with two F substituents on BT units. However, when these materials are applied in organic solar cells, the fluorinated ones enhance open-circuit voltage, but deteriorate active layer morphology, finally leading to decrease in short-circuit current and device efficiency.

Recently, the preparation of fluorinated compounds through difunctionalization strategies has become a hot research area in fluorine chemistry. In this work, a copper-catalyzed hydroxytrifluoromethylthiolation of arylpropynones for the synthesis of the corresponding trifluoromethylthiolated enols was developed. The copper salt and solvent are crucial to the yields of this reaction. Under optimized reaction conditions, a series of trifluoromethylthiolated enols were obtained in moderate to good yields.

Recent years the great progress in transition metal-catalyzed direct aromatic C—H oxidation has been witnessed, which has been utilized in the preparation of various phenolic compounds. These transformations employ inter alia palladium, copper, ruthenium, iridium, etc. as the transition metal catalysts, and hypervalent iodine, persulfate, or oxygen as the oxidants. There have been several reviews in which the C—H oxidations with specific transition metal or oxidant was discussed. This review focuses specifically on transition metal-catalyzed aromatic C—H oxidations with ortho-, meta-, or para-selectivity, and rationalizes the possible generation mechanism of regio-selectivities, which might be controlled by the directing group via chelation-assistance, the ligand, or intrinsic properties of the substrate. The discussion section indicated the existing problems of transition metal-catalyzed aromatic C—H oxidations, as well as the possible limiting factors for the development and application of this strategy.

The addition reaction of perfluoroalkanesulfenic acids, in-situ formed from imines, to alkynes and allenes were investigated. A series of perfluoroalkyl alkenyl sulfoxides were synthesized. Markovnikov adducts were obtained in good to excellent yields from the reactions of aryl or alkyl-substituted alkynes with perfluoroalkanesulfenic acids under mild conditions. However, the reaction of terminal alkynes containing an electron-withdrawing group afforded Michael-type adducts in good yields. The addition reaction of electron-rich allenes took place at the double bond with less steric hindrance, while the double bond connecting an electron-withdrawing group was the prior reaction site in the case of electron-deficient allenes.

Aryl trifluoromethyl ketone is a very important intermediate in the organic synthesis. Much attention has been attracted from researchers, due to its potential bioactivity. In this paper, the recent progress in the synthesis of aryl trifluoromethyl ketone is reviewed, including the oxidant of α-trifluoromethyl alcohols, trifluoromethylation of carboxylic acid derivatives, trifluoroacetylation of organometallic reagents, electron-rich aromatics, aryl halides and aryl diazonium salts, and the reaction mechanisms are also discussed.

Transition-metal catalyzed allylic substitution reaction is an important approach for constructing carbon-carbon bond and carbon-heteroatom bond. Due to its cheapness, easy access, and wide applicability in organic synthesis, nickel has attracted intense attention. Over the past 50 years, nickel-catalyzed allylic substitution reactions have been extensively studied. The progresses on nickel-catalyzed allylic substitution reactions and their applications in organic synthesis are summarized according to bond formation and nucleophilic reagent.

A simple and versatile metal-free protocol for the synthesis of perfluoroalkyated fluorene derivatives bearing phosphonate group is achieved. The reactions proceeded via one-pot three-component condensation of indenones, fluorinated alkynylphosphonates and malononitrile under mild conditions. This protocol is highly regioselective, operationally facile and applicable to a variety of indenones in good to excellent yields.

Transition metal-free and metal-catalyzed reactions using aryl(trifluoroethyl)iodonium salts as the trifluoroethylation reagents are summarized in this review. A large number of different types of N-, O-, S-, and C-nucleophiles were readily trifluoroethylated in these reactions under mild conditions. The results revealed that aryl(trifluoroethyl)iodonium salts possess much higher electrophilic reactivity than the other CH₂CF₃ sources. Especially, aryl(trifluoroethyl)iodonium bis(trifluoromethanesulfonyl)amides are stable and slightly soluble in water, which were successfully applied in the aqueous trifluoroethylation of amino acid derivatives and peptides. The utilization of aryl(trifluoroethyl)iodonium salts for aromatic trifluoroethylation has promisingly solved the problems that arise from the other reagents. These achievements have also demonstrated the synthetic possibilities of direct trifluoroethylation using aryl(trifluoroethyl)iodonium salts under transition-metal catalysis.

An efficient protocol for facile access to trifluoromethylated tetrahydrofuran and tetrahydropyran has been developed under visible light irradiation conditions via radical 1,2-alkoxyl-trifluoromethylation of unactivated alkene. It features the use of readily commercially available and operatively simple trifluoromethanesulfonyl chloride as a trifluoro- methyl radical source, thus making the protocol potentially appealing for practical preparation.

The traditional methods for synthesizing Z-olefins generally require the use of high-energy reagents. These methods are usually controlled by kinetics. The reaction conditions are harsh and low atom economic. During the process of separation, Z-olefins are easy to convert to the thermodynamically more stable E-olefins. With the continuous development of organic photochemistry and photocatalysis technology, more and more synthetic challenges have been solved by photocatalysis. Herein, various types of visible light-promoted photocatalytic isomerization of olefins are reviewed.

A readily prepared chiral pyrrolylphosphinite has been found highly efficient for Rh(I) catalyzed asymmetric hydroformylation of 1,1-disubstituted olefins. Chiral linear aldehydes have been synthesized with high productivity (turnover number (TON) up to 8900), excellent regioselectivity, and good to high chemo- and enantio-selectivites (71%～86% ee). The reaction features ready catalyst preparation and wide functional group tolerance, thus will be of practical value in the use of asymmetric hydroformylation (AHF) for the synthesis of chiral α-alkyl-β-formylpropanoate analogues.

A nickel-catalyzed direct difluoromethylation of (hetero)aryl bromides with bromodifluoromethane (BrCF₂H) is described. This reaction features high efficiency, broad substrate scope and high functional group tolerance, providing a cost-efficient and straightforward route for applications in medicinal chemistry. Preliminary mechanistic studies reveal that a nickel-based, reductive cross-coupling catalytic cycle is involved in the reaction.

Trifluoromethylated triazoles and tetrazoles have emerged as increasingly important heterocycles in pharmaceuticals, agrochemicals, catalysis, and materials. As a consequence, great attention has been paid to the efficient synthesis of these valuable CF₃-containing molecules. Herein, the advances in the past decade towards the synthesis of CF₃-substituted triazoles and tetrazoles are summarized. The remarkable progress in the utilization of versatile CF₃-functionalized building blocks including CF₃-containing alkynes, CF₃-containing carbonyl compounds, CF₃-containing pyrones and trifluorodiazoethane (CF₃CHN₂) is demonstrated accordingly.

As a type of important carbocyclic compounds, indenes and spiroindenes are not only widely found in natural products but extensively employed as synthetic building blocks in materials, pharmaceuticals, and asymmetric synthesis. An efficient and rapid synthesis of indenes and spiroindenes via the annulation of benzylic alcohols (or aryl-substituted cycloalkanols) with alkynes in the presence of TiCl₄ or AlCl₃ was desclosed. This reaction is normally completed within 30 min at room temperature and compatible with a variety of substituted alkynes. Two new C—C bonds are constructed during the reaction. Cycloalkanols such as cyclobutanol, cyclohexanol, cycloheptanol, cyclooctanol, and cyclododecanol are suitable substrates to afford a set of valuable spiroindenes. This method is featured with simple operation, short reaction time, and mild reaction conditions.

The formation of sterically hindered C—C bond represents a great challenge in modern synthetic organic chemistry. A particularly challenging issue is the construction of all-carbon quaternary stereocenters. Herein, a ceric ammonium nitrate (CAN)-mediated intramolecular oxidative cross-coupling of silyl ethers for direct construction of valuable polycyclic scaffolds is described. The reaction enables sterically congested vicinal all-carbon quaternary and tertiary stereocenters to be installed diastereoselectively. The developed method provides a concise and efficient approach for ligation of two different segments through a compact C—C bond formation, which has potential applications in the synthesis of complex molecules as well as sterically congested natural products.

Aminoclay (AC), as a kind of layered silicates with positive charges, shows high dispersity in water and has been widely applied in the fabrication of intelligent hybrid hydrogel. Herein, heptakis-[6-deoxy-6-(2-sulfanylethanesulfonic acid)]-β-cyclodextrin (SCD), a kind of negatively charged cyclodextrin, was employed to construct the supramolecular hydrogel with aminoclay through the static electronic interactions, and the resultant SCD-AC hydrogel was fully characterized by means of X-ray powder diffraction (XRD), scanning electronic microscopy (SEM), fourier transform infrared spectroscopy (FT-IR), zeta potential, rheological test, etc. Significantly, the SCD-AC hydrogel can efficiently absorb not only I₃^- ion in aqueous solution but also I₂ molecule in organic solvent, giving a high adsorption capacity up to 90% with 10 min.