Journal of Fluorine Chemistry最新文献

An asymmetric dearomative cyclopropanation of benzofuran has been accomplished by a novel catalytic method that relies on using trifluoromethyl N-triftosylhydrazones as carbene sources in the presence of a chiral rhodium catalyst. This reaction produces chiral trifluoromethyl-tethered 2,3-disubstituted benzofuran cyclopropane, which carries versatile pharmacophores 2,3-dihydrobenzofuran and trifluoromethyl-substituted quaternary carbon centers. Notably, this process offers distinct advantages over other existing approaches due to being step-economic and eliminating green-gas N₂ as a harmless coproduct. DFT calculations explain the reason behind the high enantioselectivity during this cyclopropanation reaction.

Fluorinated molecules often show superior bioactivity or ADME (absorption, distribution, metabolism, and excretion) properties compared to their non-fluorinated analogues. In fact, 20–30 % of newly approved drugs and the majority of recently approved agrochemicals are organofluorine compounds. Unsurprisingly, there is great interest in the development of new and/or improved processes for fluorine incorporation. Pd-catalyzed arylfluorination of alkenes is a novel, emerging fluorination method, which simultaneously introduces a fluorine atom and an aryl group into an alkene framework. The aim of the current work was studying, improving, and extending a literature arylfluorination protocol, which originally utilized N-allylated sulfonamide substrates.

The use of metal catalysts to modulate the generation and reactivity of carbenes has offered a powerful tool for construction of functional molecules. The design and synthesis of relevant transition-metal difluorocarbene complexes have benefited the development and interpretation of transition-metal catalyzed difluorocarbene transfer reactions. Although many achievements have been made in difluorocarbene chemistry, it is still a challenging task to make use of transition-metal difluorocarbenes in synthetic chemistry. To aid interested readers in better understanding the reactivity of transition-metal difluorocarbene species and designing catalytic methods for transfer of difluorocarbene intermediates, we summarize the advances of group VIII metal difluorocarbene complexes. Details include the preparation and properties of these complexes as well as their involvement in organic synthesis.

Novel simple approach was elaborated for the preparation of 3,3-difluoropyrrolidine hydrochloride starting from commercially available technical 2,2-dichlorotrifluoro-1-iodoethane. Its radical addition to ethylene afforded the corresponding iodide that was transformed into the primary amine. The last one was heated with sodium hydrosulfide to form previously unknown 3,3-difluoropyrrolidine-2-thione which was converted into the target product in high yield. The whole transformation does not require the use of toxic, flammable, explosive and hazardous reagents as well as column chromatography purification. Alternative syntheses have been proposed for the intermediate and target compounds.

Small molecule multi-target drugs substituted with fluorine atom/s or fluorine-containing group/s continue to attract considerable interest in medicinal chemistry due to their advantages in the treatment of multifactorial diseases. In this study, fluorine-containing alkyl and benzenesulfonyl chloride building blocks were reacted with 2,4-dihydroxyacetophenone 1a or 2-hydroxy-4-methoxyacetophenone 1b to afford the corresponding sulfonic ester derivatives 2a–f and 2g–j, respectively. Detailed crystallographic characterization was performed on a representative compound from each series. The compounds were evaluated through enzymatic assays in vitro for potential to inhibit biochemical targets linked to type 2 diabetes mellitus. Compound 1a and its 4-(4-fluorophenyl)sulfonyl derivative 2d exhibited strong and significant inhibitory effect in vitro against α-glucosidase (IC₅₀ = 0.97 ± 0.02 μM and 0.81 ± 0.07 μM, respectively) and α-amylase (IC₅₀ = 6.89 ± 0.04 μM and 4.87 ± 0.02 μM, respectively) compared to acarbose (IC₅₀ = 8.60 ± 0.20 μM and 1.96 ± 0.03 μM, respectively). The presence of a 4-fluorophenylsulfonyl moiety resulted in moderate inhibitory activity for 2d (IC₅₀ = 27.05 ± 0.01 μM) against protein tyrosine phosphatase 1 beta (PTP1B) compared to the PTP1B inhibitor, suramin (IC₅₀ = 4.63 ± 0.003 μM). The test compounds exhibited strong to moderate nitric oxide radical scavenging activity in vitro against ascorbic acid (IC₅₀ = 5.53 ± 0.03 μM) with IC₅₀ values in the range 0.05–19.30 μM. Compounds 1a and 2d did not inhibit superoxide dismutase (SOD) activity. Molecular docking revealed the involvement of hydrophobic, hydrophilic and electrostatic interactions with amino acid residues in the active site of the test enzymes.

Polyfluorinated diaminotetraoxacalixarenes and diaminobicyclooxacalixarene were obtained in good yield by reduction of the corresponding dinitrooxacalixarenes with sodium dithionite. Fluorinated tetraoxacalix[4]arenes with nitro and amino groups located in the inner rim of the macrocycle exists in the solution as an equilibrium mixture of two conformers. For diaminotetraoxacalixarenes the conformational equilibrium is shifted towards conformers having a 1,3-alternate structure. The ESI-MS method shows the possibility of complexing fluorinated diaminotetraoxacalixarenes and diaminobicyclooxacalixarenes with metal cations.

Palladium-catalyzed allylic substitution reaction of ethyl tetrafluorocyclopentenyl carbonate or tetrafluorocyclopentenyl methanesulfonate with carbon, nitrogen, and oxygen nucleophiles was systematically investigated. As a result, malonate-derived enolates as a carbon nucleophile, primary and secondary amines as a nitrogen nucleophile, and phenoxide derivatives as an oxygen nucleophile participated all in the reaction very well to furnish the corresponding allylated malonates, allylic amines, and allyl aryl ethers in high yields, respectively. DFT calculations of the reaction mechanism indicate that the direction of nucleophile's attack in the case of carbon nucleophiles, unlike other nucleophiles, is considerably off from the ideal direction, and thus the distance of the newly formed carbon-carbon bond is also considerably longer than the commonly accepted one. It was found then that the activation energies for reactions with carbon nucleophiles were considerably larger than those for reactions with nitrogen or oxygen nucleophiles, and hence the reaction with carbon nucleophiles is less likely proceed.

Deoxygenative perfluoroalkylthiolation reactions of readily available carboxylic acid derivatives have been developed using a series of 2-(perfluoroalkylthio)benzothiazolium (BT-SR_F) reagents as convenient sources of perfluoroalkylthiolate anions. This method avoids pre-activation of the substrates and delivers rarely reported perfluoroalkyl thioesters featuring SR_F groups up to C₆F₁₃. A survey of carboxylic acid substrates with the pentafluoroethylthiolating reagent BT-SC₂F₅ also revealed the generality of the approach as a method for accessing underexplored fluorinated compounds.

An aza-Wittig reaction of in situ generated difluoroalkyl diazo analog, (β-diazo-α,α-difluoroethyl)phosphonates, with aldehyde under mild conditions has been developed to afford difluoromethylphosphonate-containing arylidene hydrazones up to 99 % yields. The reaction was carried out under mild conditions with a broad substrate scope and was suitable for scale-up application. This reaction provides an efficient method for the facile construction of a series of difluoromethylphosphonate-containing arylidene hydrazones and is also a useful supplement to the transformation of (β-diazo-α,α-difluoroethyl)phosphonates.