Preparation of fluorinated graphene to study its gas sensitivity

In this paper, fluorinated graphene was prepared from graphite fluoride by an improved Hummers method. The fluorinated graphene was characterized using an X-ray diffractometer (XRD), transmission electron microscope (TEM), atomic force microscope (AFM) and X-ray photoelectron spectrometer (XPS). Moreover, a gas sensitivity test was carried out. The results show that the fluorinated graphene is composed of about 5 layers prepared by utilising the improved Hummers method. The content of fluorine in fluorinated graphene decreased, mainly due to the fracture of C–F bonds. Fluorinated graphene showed gas sensitivity to ethanol, ammonia, methane and formaldehyde gases. The sensitivity of fluorinated graphene to ammonia is the highest and is 3.5 times the sensitivity of graphene to ammonia. The doping of fluorine atoms was conducive to improving the gas sensitivity of fluorinated graphene.

In this paper, fluorinated graphene was prepared from graphite fluoride by an improved Hummers method. Moreover, the gas sensitivity of fluorinated graphene has been researched.     

Direct synthesis of sulfenamides,sulfinamides, and sulfonamides from thiols and amines

Needless to say that organosulfur compounds with sulfur–nitrogen bonds have found various applications in diverse fields such as pharmaceuticals, agrochemicals, polymers, and so forth. Three major groups of such compounds are sulfenamides, sulfinamides, and sulfonamides which have been widely applied as building blocks in medical chemistry. Owing to their significant role in drug design and discovery programs, the search for and development of efficient, environmentally friendly, and economic processes for the preparation of the title compounds is of great importance in the pharmaceutical industry. Recently, oxidative coupling of thiols and amines, two readily available low-cost commodity chemicals, has emerged as a highly useful method for synthesizing structurally diverse sulfenamides, sulfinamides, and sulfonamides in a single step. Since this strategy does not require additional pre-functionalization and de-functionalization steps, it considerably streamlines synthetic routes and substantially reduces waste generation. This review will focus on recent advances and achievements in this attractive research arena.

This review provides a concise overview of the synthesis of biologically and synthetically valuable sulfenamide, sulfinamide, and sulfonamide derivatives through the direct oxidative coupling of readily available low-cost thiols and amines.     

Vicinal halo-trifluoromethylation of alkenes

Both trifluoromethyl and halide groups are widely found in medicinally and pharmaceutically important compounds and, moreover, organohalides are commonly used as versatile intermediates in synthetic organic chemistry. Due to their prevalence and easy accessibility, alkene halo-trifluoromethylation provides a convenient way to install these valuable functionalities in complex targets. In this review, we summarize recent advances and achievements in this fast-growing research field. For clarity, the reactions were classified according to the type of halogen atom.

Both trifluoromethyl and halide groups are widely found in medicinally and pharmaceutically important compounds and, moreover, organohalides are commonly used as versatile intermediates in synthetic organic chemistry.     

Decarboxylative cross-coupling reactions for P(O)–C bond formation

Phosphorus-containing compounds are one of the most important classes of organic compounds, which have wide applications in organic chemistry, medicinal chemistry, agricultural chemistry, and materials chemistry. In particular, organophosphorus compounds bearing a P(O)–C bond have attracted significant attention in recent decades due to their widespread biological and pharmacological activities. In this review, we will highlight the most important developments in the construction of P(O)–C bonds through decarboxylative C–P cross-coupling reactions. The literature has been surveyed from 2011 to May 2018.

Phosphorus-containing compounds are one of the most important classes of organic compounds, which have wide applications in organic chemistry, medicinal chemistry, agricultural chemistry, and materials chemistry.     

Arylhydrazines: novel and versatile electrophilic partners in cross-coupling reactions

Arylhydrazines are extremely valuable compounds in organic chemistry that are widely used for the synthesis of a variety of biologically active molecules such as indoles, indazoles, pyrazoles, aryltriazoles, β-lactams and quinazolines. These compounds have also been widely utilized as arylation agents in oxidative cross-coupling reactions. In this review, we will highlight the most important explorations and developments in the carbon–carbon and carbon–heteroatom (nitrogen, phosphorus, sulfur, and selenium) cross-coupling of arylhydrazines. The literature has been surveyed from 2001 to June 2018.

Arylhydrazines are extremely valuable compounds in organic chemistry that are widely used for the synthesis of a variety of biologically active molecules such as indoles, indazoles, pyrazoles, aryltriazoles, β-lactams and quinazolines.     

Brønsted acid-promoted hydroamination of unsaturated hydrazones: access to biologically important 5-arylpyrazolines

A novel and efficient Brønsted acid-promoted hydroamination of hydrazone-tethered olefins has been developed. A variety of pyrazolines have been easily obtained in good to excellent yields with high chemo- and regioselectivity under simple and mild conditions. This method represents a straightforward, facile, and practical approach toward biologically important 5-arylpyrazolines, which are difficult to access by previously reported radical hydroamination of β,γ-unsaturated hydrazones.

An efficient, chemo- and regioselective Brønsted acid-promoted hydroamination reaction of hydrazone-tethered olefins towards 5-arylpyrazolines was developed.     

Synthesis of α,β-unsaturated esters of perfluoropolyalkylethers (PFPAEs) based on hexafluoropropylene oxide units for photopolymerization

α,β-unsaturated esters are usually synthesized for polymer applications. However, the addition of maleate (cis-configuration) to a fluorinated moiety is challenging due to its potential isomerization during esterification. Various synthetic routes were attempted and led to very low conversion or side-products. The immiscibility of both reagents combined with an easy isomerization or attack on the double bond were potential explanations. In this paper, the synthesis of maleates oligo(hexafluoropropylene oxide) is reported by Steglich esterification and the reaction conditions are discussed depending on the molecular weight of the fluorinated moieties. After UV-curing, hydrophobic polymers were obtained by copolymerization with vinyl ethers by electron acceptor–donor systems.

Hydrophobic macromonomers synthesized by Steglich esterification to generate UV-curable materials.     

Intermolecular difunctionalization of alkenes: synthesis of β-hydroxy sulfides

Direct difunctionalization of carbon–carbon double bonds is one of the most powerful tools available for concomitant introduction of two functional groups into olefinic substrates. In this context, vicinal hydroxysulfenylation of unactivated alkenes has emerged as a novel and straightforward strategy for the fabrication of β-hydroxy sulfides, which are extremely valuable starting materials in constructing various natural products, pharmaceuticals, and fine chemicals. The aim of this review is to summarize the most representative and important reports on the preparation of β-hydroxy sulfides through intermolecular hydroxysulfenylation of the corresponding alkenes with special emphasis on the mechanistic features of the reactions.

This review provides a concise overview of the synthesis of biologically and synthetically important β-hydroxy sulfides through the direct hydroxysulfenylation of the respective alkenes.     

Conformational transition of a non-associative fluorinated amphiphile in aqueous solution. II. Conformational transition vs. supramolecular assembly

Unlike many known amphiphiles, the fluorinated amphiphilic dendrimer studied in this work demonstrated a concentration-dependent conformational transition rather than micellization or assembly. Hydrophobic and hydrophilic interactions with water were suggested as the most probable driving force of this transition. This assumption was consistent with the observed ¹⁹F chemical shift changes of the dendrimer compared to a known micelle-forming fluorinated amphiphile. Since water is an important factor in the process, trends of the concentration-dependent changes in water proton transverse relaxation rate served as an indicator of structural changes and/or supramolecular assembly. The conformational transition process was also confirmed by ion-mobility mass-spectrometry. We suggested that structural features, namely, steric hindrances, prevented the micellization/assembly of the dendrimer of this study. This conclusion might inform the approach to develop novel unconventional amphiphiles.

Conformational transition in non-associative fluorinated dendrimer—a way to novel unconventional amphiphiles.     

Exfoliated fluorinated carbons with a low and stable friction coefficient

Exfoliation appears as a promising way to decrease the friction coefficient of carbon materials. Although there is massive defluorination during exfoliation, the friction coefficient is not increased and an exfoliated structure facilitates the formation of a homogeneous and stable tribofilm. The weakening of the interparticle interactions due to the exfoliation process is the main explanation for the excellent tribological properties. Three representative examples are studied to evidence the efficiency of the thermal shock to prepare solid lubricants or additives for lubricating oils, high temperature graphite fluorides, fluorinated carbon nanofibers and fluorinated nanodiscs. An opened (graphite fluoride) or defect structure (nanofibers) allows the gases formed during the exfoliation to be evolved; the exfoliation is then successful regardless of the C–F bonding. Exfoliation and defluorination occur simultaneously resulting in samples with a low F/C atomic ratio. On the contrary for the case of fluorinated nanodiscs, the exfoliation fails because of cracks and edges as well as the low diameter of the discs.

Exfoliation appears as a promising way to decrease the friction coefficient of carbon materials.     

The electrochemical performance of fluorinated ketjenblack as a cathode for lithium/fluorinated carbon batteries

The inferior rate capacity of lithium/fluorinated carbon (Li/CF_x) batteries limits their application in the field, requiring large discharge current and high power density. Herein, we report a novel type of fluorinated carbon with superior performance through gas-phase fluorination of ketjenblack. The investigation shows that the F/C ratio of the fluorinated ketjenblack (FKB) increases with the fluorination temperature, whereas the discharge voltage decreases due to the lowered content of semi-ionic C–F bonds. Accordingly, a suitable fluorination temperature of 520 °C was selected, under which the product exhibits the largest specific capacity of 924.6 mA h g⁻¹ with discharge potential exceeding 3.1 V (vs. Li/Li⁺) and the highest energy density of 2544 W h kg⁻¹ with power density of 27 493 W kg⁻¹. This energy density is higher than the theoretical energy density of commercial fluorinated graphite (2180 W h kg⁻¹). In addition, the sample delivers good rate capability demonstrated by a specific capacity retention ratio of 79.5% even at a current density of 20C. Therefore, the FKB material may have very promising practical applications in lithium primary batteries.

Fluorinated kejtenblack as the cathode of Li/CF_x batteries exhibits excellent energy density and power density with high rate capability.     

Synthesis,characterization, aggregation-induced emission,solvatochromism and mechanochromism of fluorinated benzothiadiazole bonded to tetraphenylethenes

Compounds consisting of unsubstituted, monofluoro and difluoro substituted benzothiadiazole bonded to two tetraphenylethenes were successfully prepared by palladium catalyzed Suzuki–Miyaura cross-coupling reaction of their corresponding co-monomers. All compounds exhibited aggregation-induced emission characteristics when the water fraction was higher than 60% in the THF/water mixtures. The emission maximum for the three compounds was blue-shifted when the water content reached 90% compared to that in THF solution. The intensity of emission maximum of difluorinated benzothiadiazole linked with two tetraphenylethenes was 2.5 times higher in 90% water compared to those in THF solution. Surprisingly, two liquid crystal phases with two distinct emission colors were observed only for the compound containing difluorinated benzothiadiazole bonded to two tetraphenylethene. All compounds showed remarkable solvatochromic properties in selected solvents with different polarities. The powder XRD results and mechanochromism of the compounds suggested that the solid state structures can change from one form to another by grinding, fuming or annealing processes.

Fluorinated benzothiadiazole bonded to two tetraphenylethenes were synthesized. The compounds exhibited remarkable aggregation-induced emission, solvatochromism and mechanochromism.     

Recent developments in decarboxylative cross-coupling reactions between carboxylic acids and N–H compounds

Carboxylic acids and their derivatives are ubiquitous compounds in organic chemistry, and are widely commercially available in a large structural variety. Recently, carboxylic acids have been frequently used as non-toxic and environmentally benign alternatives to traditional organohalide coupling partners in various carbon–carbon and carbon–heteroatom cross-coupling reactions. Along this line, several methods have been reported for the synthesis of nitrogen-containing organic compounds through decarboxylative cross-coupling reactions between carboxylic acids and N–H compounds. This review focuses on recent advances and discoveries on these reactions with special attention on the mechanistic aspects of the reactions.

Carboxylic acids and their derivatives are ubiquitous compounds in organic chemistry, and are widely commercially available in a large structural variety.     

Fe-mediated synthesis of N-aryl amides from nitroarenes and acyl chlorides

Amides are prevalent in nature and valuable functional compounds in agrochemical, pharmaceutical, and materials industries. In this work, we developed a selective and mild method for the synthesis of N-aryl amides. Starting from commercially available nitroarenes and acyl halides, N-aryl amides with good yields can be obtained in water. Especially in the process of transformation, Fe dust is the only reductant and additive, and the reaction can be easily performed on a large scale.

Amides are prevalent in nature and valuable functional compounds in agrochemical, pharmaceutical, and materials industries.     

Fluorine-functionalized ionic liquids with high oxygen solubility

Eight fluorine-functionalized ionic liquids were synthesized and the oxygen solubility was compared to commercial ionic liquids without the extra fluorinated chain. The concentration of dissolved oxygen increased with the fluorine content of the alkyl chain, which can be attached either to the cation or the anion. This approach maintains the freedom to design an ionic liquid for a specific application, while at the same time the oxygen solubility is increased.

Oxygen solubility in ionic liquids is improved by increasing the number of fluorine atoms in the alkyl side chains.     

Fluorinated Iron(ii) clathrochelate units in metalorganic based copolymers: improved porosity,iodine uptake,and dye adsorption properties

We report the synthesis of metalorganic copolymers made from the palladium catalyzed Sonogashira cross-coupling reaction between various iron(ii) clathrochelate building blocks with diethynyl–triptycene and fluorene derivatives. The target copolymers CCP1–5 were isolated in excellent yield and characterized by various instrumental analysis techniques. Interestingly, investigation of the copolymers'' porosity properties discloses BET surface areas up to 337 m² g⁻¹ for the target compounds bearing fluorinated iron(ii) clathrochelate units CCP2,5. Moreover, the fluorinated copolymers display an outstanding uptake capacity of iodine with a maximum adsorption of 200 wt%. The target metalorganic copolymers CCP1–5 reveal very good adsorption of organic dyes, namely, methyl blue and methylene blue, from aqueous media.

We report the synthesis of metalorganic copolymers made from the palladium catalyzed Sonogashira cross-coupling reaction between various iron(ii) clathrochelate building blocks with diethynyl–triptycene and fluorene derivatives.     

Evolution of the phases and the polishing performance of ceria-based compounds synthesized by a facile calcination method

Ceria-based compounds with additions of La and F (CLF compounds) were prepared by using industrial-grade fluorinated lanthanum cerium carbonate as a precursor via a facile calcination method. The evolution of phase structures of the compounds during preparation and the relationship between the structure and the polishing performance were investigated. The compounds consist of three phases: CeO₂, LaOF, and LaF₃. The phase component could be controlled by tuning the calcination process. A higher degree of fluorination and a higher calcination temperature led to the formation of more LaOF and less LaF₃ phases. The LaOF phase performs a higher stock removal rate. The best polishing efficiency was achieved with LaOF phase ratio around 18%. Intermetallic LaF₃ is a low-hardness phase and is easily crushed during polishing, which lowers the removal rate and shortens the useful life of the polishing powder.

Ceria-based compounds with additions of La and F (CLF compounds) were prepared by using industrial-grade fluorinated lanthanum cerium carbonate as a precursor via a facile calcination method.     

2,3-Dimethoxy-2,3-dimethyl-1,4-dioxane as a useful precursor to 2,3-dimethylene-1,4-dioxane for [4+2] cycloaddition reaction

2,3-Dimethoxy-2,3-dimethyl-1,4-dioxane readily prepared from biacetyl serves as a stable precursor to 2,3-dimethylene-1,4-dioxane which undergoes a [4+2] cycloaddition reaction with dienophiles to give functionalized cyclohexene derivatives. The cycloaddition adducts obtained by the present procedure are transformed into potentially useful intermediates for biologically important materials.

2,3-Dimethoxy-2,3-dimethyl-1,4-dioxane serves as a stable precursor to 2,3-dimethylene-1,4-dioxane which undergoes a cycloaddition with dienophiles. The adducts are transformed into useful intermediates for biologically important materials.     

Advancements in the synthesis of fused tetracyclic quinoline derivatives

Fused tetracyclic systems containing a quinoline nucleus represent an important class of heterocyclic bioactive natural products and pharmaceuticals because of their significant and wide-spectrum biological properties. Several of these compounds have been obtained with diverse pharmacological and biological activities, such as antiplasmodial, antifungal, antibacterial, potent antiparasitic, antiproliferative, anti-tumor and anti-inflammatory activities. This information will be beneficial for medicinal chemists in the field of drug discovery to design and synthesize new fused tetracyclic quinolines as potent therapeutical agents. This review article provides a comprehensive report regarding the methods developed for the synthesis of fused tetracyclic quinolines reported so far (till October 2019). The article includes synthesis by one-pot domino reaction, microwave synthesis using a catalyst, using ionic liquids, photocatalytic synthesis (UV radiation), Pfitzinger reaction, I₂-catalyzed cyclization reaction, Wittig reaction, cascade reaction, imino Diels–Alder reaction, Friedel–Crafts reaction, CDC reaction, solvent-free reactions and using small chiral organic molecules as catalysts. To the best of our knowledge, this is the first review focused on the synthesis of fused tetracyclic quinolines along with mechanistic aspects.

Fused tetracyclic systems containing a quinoline nucleus represent an important class of heterocyclic bioactive natural products and pharmaceuticals because of their significant and wide-spectrum biological properties.