Journal of Fluorine Chemistry最新文献

Continuous fluorination presents a promising technology due to its potential for simple operation, process safety, and scale-up capabilities. However, when the metal fluoride was used as a fluorine source, the continuous fluorination process was hampered by solubility problem. In this work, we developed a water-assisted continuous flow operation for nucleophilic fluorination facilitated by KF. The effects of water on solubilization and activation step were revealed by the density functional theory (DFT) study. The continuous fluorination was successfully carried out in the tubular reactor, and the desired yield was obtained. The mass transfer performance in the tubular reactor was revealed by computational fluid dynamics (CFD) simulations. Besides, the kinetic study of the reaction in flow was also presented. Furthermore, the comparison with other two reported methods revealed the superiority of the continuous fluorination.

Knowing that fibre reinforced polymers are sensitive to moisture through their interphases, carbon and flax fibres sized with Bisphenol A diglycidyl ether were fluorinated under a N₂/F₂ atmosphere. Because of differences in reactivity of gaseous F₂ between fibres and sizing, only the latter has been fluorinated, resulting in a covalent grafting of fluorine atoms onto the fibres, that has been evidenced by Infrared spectroscopy, and X-Ray Photoelectron Spectroscopy. Fluorinated fibres exhibit enhanced mechanical properties, as highlighted by tensile tests. Hybrid and non-hybrid composite materials were then fabricated with vacuum infusion process, using non-fluorinated and fluorinated carbon and flax fibres. Their hydrothermal behaviour and mechanical properties were investigated, in order to study the impact of both hybridisation and fibre fluorination on the composite properties. A better water resistance was observed for polymer materials reinforced with fluorinated fibres, whereas their mechanical properties were slightly lower than polymers reinforced with non-fluorinated fibres.

Difluorocarbene has served as a versatile intermediate in organic synthesis. The transformation of difluorocarbene into thiocarbonyl fluoride, which was discovered by us previously, can be developed as a synthetic tool for the cyclization of vicinal X-H substituted amines to provide various five-membered heterocycles. However, aryl amines are required to be used and difluoromethylation of the NH bond or a newly generated S-H bond cannot be suppressed. Herein we describe the use of thiocarbonyl fluoride generated in situ as a thiocarbonyl source for the cyclization of vicinal X-H substituted alkyl amines (X = N, O, S) to provide imidazolidine-2-thiones, oxazolidine-2-thiones and thiazolidine-2-thiones. The use of alkyl amines constructs different heterocycles with those obtained from aryl amines. The free NH bond remains intact without being difluoromethylated.

Fluorinated polyacrylate copolymers containing various amounts of 1H,1H,2H,2H-perfluorooctyl methacrylate (FA) were synthesized via a miniemulsion polymerization process. The characteristics of latex particles and films were investigated using transmission electron microscopy, dynamic light scattering, attenuated total reflectance Fourier transform infrared spectroscopy, ¹H and ¹⁹F nuclear magnetic resonance spectroscopy, atomic force microscopy, energy dispersive spectroscopy, water contact angle measurements, and thermogravimetric analysis. The results showed that particle size increased almost linearly with FA content, and the surface hydrophobicity of the films increased with FA content up to 14.6 wt% and then plateaued. As the FA content increased, the surface roughness of the films initially increased and then decreased. The thermal stability of fluorinated polyacrylate was significantly enhanced when a high amount of FA was incorporated into the polymer chains. The fluorinated acrylic copolymer coating also exhibited a significant drag reduction effect, with the maximum drag reduction ratio reaching 12% at a water flow velocity of 0.8 m/s.

The morphology and size of LiYF₄:Yb,Er nanoparticles were controlled using an automatic nanomaterial synthesizer by changing the reaction time at high temperature. It was found that the nanoparticles underwent a growth and change process from small to large and then to small, and then remained at a basically stable size, reflecting the different growth stages of the nanoparticles, such as nucleation, growth, phase transition, and internal Ostwald ripening, etc. XRD analyses showed that LiF nanocrystals were first formed during the reaction process, and then all the products were converted into LiYF₄ nanocrystals. Under the excitation of a 980 nm laser, the LiYF₄:Yb,Er nanoparticles showed regular downconversion and upconversion luminescence properties, which was basically consistent with the regularity of nanocrystal growth. The experimental results showed that the upconversion luminescence and downconversion luminescence intensities of nanocrystals increasd rapidly when the synthesis time was between 0 and 50 min, and they increased slowly after the synthesis time exceeded 50 min.

The reaction of partially fluorinated epoxides with strong, hindered bases in the presence of electrophiles resulted in functionalization of the epoxy ring. For example, the reaction of hexafluoroisobutene epoxide with LDA and trimethyl- or triethychlorosilanes at low temperature led to the formation of the corresponding epoxy silanes. In the case of the E- and Z-epoxides of 1,1,1,3,3,3-hexafluorobutene-2, the deprotonation step can be successfully carried out using i-PrMgCl^.LiCl (Turbo Grignard reagent), and the reaction with chlorosilanes can be carried out at ambient temperature, which significantly simplifies the synthetic protocol. The process was found to be stereospecific, proceeding with complete retention of configuration of the epoxide ring and giving access to pure E- or Z-isomers of the corresponding epoxy silanes. Using this protocol, the corresponding epoxy silanes were also prepared from the epoxides of E-3,3,3,1-tetrafluoropropene-1 and 3,3,3-trifluoropropene-1.

The new silanes were demonstrated to be convenient reagents for the transfer of a fluorinated epoxy moiety to carbonyl compounds under fluoride anion catalysis. This process was shown to proceed with complete retention of the geometry of the epoxy ring.

In this communication, we explore a unique molecule that exhibits a substantial interaction between a CF₂H group and a CF group.  In medicinal chemistry, CF₂H groups are known as weak hydrogen bond donors, and CF groups as weak H-bond acceptors.  Seldom are they paired up together in an array such that their unique properties can be examined.  In this case, we establish that along with an attractive hydrogen bonding interaction, an n → σ* component anchors the interactions. A unique combination of steric and hyperconjugative effects ‘switches’ the interaction away from previously reported dominant tetrel-type bonding in the case of a CH₂F and CF interation towards an unusualy complex hybrid interaction.  Crystallographic, computational, and spectroscopic studies illuminate the problem.

We herein descript a metal-free and highly regioselective [3 + 2] cycloaddition reaction between diazo compounds and internal alkynes, accessing to a series of trifluoromethylated pyrazoles. Using different combination of starting materails, both regioisomers can be obtained under this protocal. The developed cycloaddition reaction provides a valuable tool for future medicinal chemistry research on highly substituted trifluoromethyl pyrazoles.

An efficient direct azo-coupling reaction of trifluoromethyl N-acylhydrazones/N-aryl hydrazones with aryldiazonium tetrafluoroborates was developed for the synthesis of various trifluoromethyl formazans. This protocol has the advantages of mild reaction condition, broad substrate scope and easy operation, which extends the application of trifluoromethyl N-acylhydrazones/N-aryl hydrazones as versatile trifluoromethyl building blocks in organic synthesis.

A series of ω-substituted alkanoic acids functionalized with 1-aryl-3-trifluoromethylpyrazol-4-yl group was synthesized via two-step protocol using in situ generated CF₃-nitrile imines and cyclic enones as key building blocks. The first 1,3-dipolar cycloaddition step proceeded in a fully selective manner either in solutions or under solvent-free mechanochemical activation. Treatment of the first formed cycloadducts derived from 2-cyclopentenone or 2-cyclohexenone with DDQ afforded corresponding bicyclic pyrazoles formed via dehydrogenative oxidation pathway, whereas MnO₂-mediated deacylative aromatization led to desired propionic or butyric acid derivatives, respectively. In contrast, oxidation of model 2-cycloheptenone-derived (3 + 2)-cycloadduct yielded bicyclic analogue irrespectively to the applied conditions.