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Fluoroacetate is a toxic compound whose environmental accumulation may represent an important contamination problem, its elimination is therefore a challenging issue. Fluoroacetate dehalogenase catalyzes its degradation through a two step process initiated by an SN2 reaction in which the aspartate residue performs a nucleophilic attack on the carbon bonded to the fluorine; the second step is hydrolysis that releases the product as glycolate. In this paper, we present a study based on density functional theory calculations of the SN2 initiation reaction modeled through the interaction between the substrate and the propionate anion as the nucleophile. Results are analyzed within the framework of the reaction force and using the reaction electronic flux to identify and characterize the electronic activity that drives the reaction. Our results reveal that the selective protonation of the substrate catalyzes the reaction by decreasing the resistance of the structural and electronic reorganization needed to reach the transition state. Finally, the reaction energy is modulated by the degree of stabilization of the fluoride anion formed after the SN2 reaction. In this way, a site-induced partial protonation acts as a chemical switch in a key process that determines the output of the reaction. [ABSTRACT FROM AUTHOR]

A comprehensive understanding of protein function demands correlating structure and dynamic changes. Using time-resolved serial synchrotron crystallography, we visualized half-of-the-sites reactivity and correlated molecular-breathing motions in the enzyme fluoroacetate dehalogenase. Eighteen time points from 30 milliseconds to 30 seconds cover four turnover cycles of the irreversible reaction. They reveal sequential substrate binding, covalent-intermediate formation, setup of a hydrolytic water molecule, and product release. Small structural changes of the protein mold and variations in the number and placement of water molecules accompany the various chemical steps of catalysis. Triggered by enzyme-ligand interactions, these repetitive changes in the protein framework’s dynamics and entropy constitute crucial components of the catalytic machinery. [ABSTRACT FROM AUTHOR]

Abstract Monofluoroacetate (MFA) is considered one of the most toxic substances known. It is found naturally in plants, and causes sudden death syndrome in ruminants. Due to hyperacute evolution of poisoning and the absence of effective treatment, induction of resistance in animals might be the best tool to control MFA poisoning in ruminants. The objective of this study was to promote resistance in cattle against the toxic effects of MFA through its degradation by the ruminal microbiota after the administration of sodium trifluoroacetate (TFA). Ten calves were distributed into two groups: control group (n = 3) and treated group (n = 7). The calves in the treated group received 0.1 mg/kg live weight of TFA, whereas, those in the control group received water; both for 28 consecutive days. The calves were subjected to daily clinical evaluation and weekly blood biochemical determination to identify any signs of poisoning. After 28 d of administration of TFA or water, 2.0 g/kg body weight of Palicourea marcgravii leaves (containing 0.15% MFA) were administered using a stomach tube to determine the occurrence of resistance. The administration of TFA did not induce any clinical or biochemical changes in blood. The administration of P. marcgravii induced clinical changes in the calves of control group, but there was no change in the calves of the treated group. In conclusion, the administration of TFA to cattle can induce effective resistance against MFA poisoning. Highlights • Monofluoroacetate (MFA) is considered one of the most toxic substances known. • Plants containing MFA cause lethal poisoning in animals. • MFA degradation by the ruminal microbiota was induced by sodium trifluoroacetate (TFA) in calves. • The administration of TFA to cattle can induce effective resistance against MFA poisoning. [ABSTRACT FROM AUTHOR]

This work focused on the biodegradation of three structurally related fluoroacetates (FAs), mono- (MFA), di- (DFA) and trifluoroacetate (TFA), using as microbial inocula samples collected from a site with a long history of industrial contamination and activated sludge obtained from a municipal wastewater treatment plant. Biodegradation experiments were carried out under different modes of substrate supplementation, which included (i) FAs fed as sole carbon sources; (ii) FAs (only for DFA and TFA) fed in co-metabolism with sodium acetate; and (iii) mixtures of MFA with DFA or TFA. Biodegradation of the target compounds was assessed through fluoride ion release. Defluorination was obtained in the cultures fed with MFA, while DFA and TFA were recalcitrant in all tested conditions. When present in mixture, DFA was shown to inhibit biodegradation of MFA, while TFA had no effect. A total of 13 bacterial isolates obtained from MFA degrading cultures were found to degrade 20 mgL −1 of this compound, as single strains, when supplemented as a sole carbon source. Sequencing of the 16S rRNA gene indicated that among these degrading bacteria only Delftia acidovorans had been previously reported to be able to degrade MFA. This work shows that, despite their similar chemical structures, biodegradation of the three tested FAs is very distinct and draws attention to the unknown impacts that the accumulation of DFA and TFA may have in the environment as a result of their high recalcitrance. [ABSTRACT FROM AUTHOR]

In the racemic title molecular salt, C17H17F6N2O+·C2ClF2O3- (systematic name: 2-{[2,8-bis(trifluoromethyl)quinolin-4-yl](hydroxy)methyl}piperidin-1-ium chlorodifluoroacetate), the cation, which is protonated at the piperidine N atom, has the shape of the letter, L, with the piperidin-1-ium group being approximately orthogonal to the quinolinyl residue [the Cq-Cm-Cm-Na (q = quinolinyl; m = methine; a = ammonium) torsion angle is 177.79 (18)°]. An intramolecular, charge-assisted ammonium-N-H...O(hydroxyl) hydrogen bond ensures the hydroxy-O and ammonium-N atoms lie to the same side of the molecule [Oh-Cm-Cm-Na (h = hydroxyl) = -59.7 (2)°]. In the crystal, charge-assisted hydroxyl-O-H...O-(carboxylate) and ammonium-N+-H...O-(carboxylate) hydrogen bonds generate a supramolecular chain along [010]; the chain is consolidated by C-H...O interactions. Links between chains to form supramolecular layers are of the type C-Cl...π(quinolinyl-C6) and the layers thus formed stack along the a-axis direction without directional interactions between them. The analysis of the calculated Hirshfeld surface points to the dominance of F...H contacts to the surface (40.8%) with significant contributions from F...F (10.5%) and C...F (7.0%) contacts. [ABSTRACT FROM AUTHOR]

A reactivity pattern for C3-arylation of 9-MeO-phenanthrene has been established for the first time by using 2-naphthyl amines as coupling partners. A series of phenanthrene- and naphthalene-based multifunctionalized polycyclic aromatic hydrocarbons have been obtained in good to excellent yields. Alternative C10-arylation of 9-MeO-phenanthrene has also been accomplished, using 2-naphthalenol derivatives as coupling partners. Trifluoroacetic acid is found crucial for the regioselectivity. Density functional theory calculations and electrochemical analyses have been performed to rationalize the reaction mechanism. [ABSTRACT FROM AUTHOR]

The low molecular weight ( Mr ∼ 200  Da) chiral N-trifluoroacetylated α -aminoalcohols (TFAAAs) are able for gelate various organic solvents and water in very low concentrations ( ∼ 10 - 3  M). The gelation was not observed in the racemic solutions or solution of achiral TFAAA. The gelation is temperature-reversible and demonstrates the memory effect. The gel scaffold is composed of thin supramolecular elements (strings) having a helical structure. The thinnest (elementary) strings have a crystalline, highly ordered structure and braid together to form thicker elements. The sign of the helicity changes with the growing of the strings in course of the gelation process, so that the thicker strings have the opposite helicity as compared to thinner ones. We provide a theoretical description of the strings growing process. [ABSTRACT FROM AUTHOR]

Abstract: A palladium‐catalyzed cross‐coupling of α‐oxo ketene dithioacetals and bromodifluoroacetate derivatives has been developed for the synthesis of a class of CF2‐containing tetra‐substituted olefins, which has potential to extend to drug design and material application. The process is proposed to involve two single electron transfer processes accompanied by an alternative loop from palladium(0) to palladium(I), likely due to unique structural properties of ketene dithioacetals with β,β‐dialkylthiol substituents on the olefin double bond. [ABSTRACT FROM AUTHOR]

Abstract: Fluoroacetate dehalogenase is able to cleavage a carbon–fluoride bond, the strongest carbon–halogen bond in nature, in a process initiated by a SN2 reaction. The role of the enzyme machinery and particularly of the halogen pocket in the SN2 reaction is thoroughly explored by using state‐of‐the‐art computational tools. A comparison between the non‐catalyzed versus enzyme‐catalyzed reaction, as well as with a mutant of the enzyme (Tyr219Phe), is presented. The energy barrier changes are rationalized by means of reaction force analysis and the activation strain model coupled with energy decomposition analysis. The catalysis is in part caused by the reduction of structural work from bringing the reactant species towards the proper reaction orientation, and the reduction of the electrostatic repulsion between the nucleophile and the substrate, which are both negatively charged. In addition, catalysis is also driven by an important reduction of the electronic reorganization processes during the reaction, where Tyr from the halogen pocket acts as a charge acceptor from the SN2 reaction axis therefore reducing the electronic steric repulsion between the reacting parts. [ABSTRACT FROM AUTHOR]

Natural products have inspired over 60% of today’s drugs and biocides, including rodenticides, with examples such as warfarin, fluoroacetate and cholecalciferol. Fluoroacetate is a toxic component of poisonous plants found in Australia, Africa, South America and India and is thought to deter herbivores. Together with other rodenticides it has medical applications. In relation to its use for the control of unwanted introduced animals in New Zealand, research has focused on mode of action, sub-lethal effects, welfare, reducing its risk to non-target species, and fate in the environment following use in baits. Less attention has been placed on its role in nature. In this paper the natural occurrence of bioactives that have stimulated the development of rodenticides are reviewed and links between biocidal and medical applications are explored. [ABSTRACT FROM AUTHOR]

Efficient and enantioselective radical difluoroalkylation and perfluoroalkylation reactions of β-ketoesters were successfully developed through an asymmetric photoredox and nickel catalysis cascade. This protocol provides Rf-containing quaternary stereocenters in up to 67% yield and 95:5 er with ethyl iododifluoroacetate and perfluoroalkyl iodides (C3F7I and C4F9I) as radical sources under extremely mild conditions. [ABSTRACT FROM AUTHOR]

This paper firstly describes the synthesis of a series of ( Z )-4-((3-chloro-4-fluorophenyl)amino)-1,1,1-trifluorobut-3-en-2-ones ( 3a–f ) as well as 1-(1-((3-chloro-4-fluorophenyl)amino)-3,4-dihydronaphthalen-2-yl)-2,2,2-trifluoroethanone ( 3g ), from the O,N-exchange reaction of some 4-methoxy-4-alkyl(aryl)-1,1,1-trifluoroalk-3-en-2-ones ( 1 ) with 3-chloro-4-fluoroaniline ( 2 ), at 70–90% yields. Subsequently, in concentrated sulfuric acid, the enaminoketones 3 underwent a successful and regioselective intramolecular cyclocondensation reaction, which furnished a novel series of 2-alkyl(aryl)-7-chloro-6-fluoro-4-(trifluoromethyl)-quinolines ( 4 ) at 70–85% yields. To demonstrate synthetic applicability through the Sonogashira coupling reaction for obtaining quinolines with potential antimicrobial activity, the synthesis of a novel series of 2-alkyl(aryl)-6-fluoro-7-(phenylethynyl)-4-(trifluoromethyl)-quinolines ( 5 ) was performed, using quinolines 4 and phenylacetylene, via a regioselective Sonogashira coupling reaction (25–50% yield). Unfortunately, the new series of heterocycles 4 and 5 did not produce significant results against bacteria and fungi at the concentrations of 80–0.31 μg/mL. [ABSTRACT FROM AUTHOR]

A one-pot synthesis of bulky bis-pocket A3B-type meso-cyano porphyrin, 5-cyano- 10,15,20-tris(2,4,6-triphenylphenyl)porphyrin, has been accomplished via trifluoroacetic acid (TFA) catalyzed condensation of pyrrole and 2,4,6-triphenylbenzaldehyde in an acceptable yield of about 4%. DDQ served as oxidant and the cyanating agent. [ABSTRACT FROM AUTHOR]

An efficient one-pot cascade methodology for the synthesis of (ethoxycarbonyl)difluoromethyl thioethers is described. Benzyl, allyl, alkyl halides or diazonium salts as the starting materials together with thiocyanate sodium and TMS-CF 2 CO 2 Et in the presence of CsF or NaOAc afford a variety of the fluoroalkylthiolated products in moderate to good yields. [ABSTRACT FROM AUTHOR]

Seven mixed ligand complexes of lanthanide trifluoroacetates with diethylenetriamine [Ln(tfa) 2 (deta) 2 ](tfa) (Ln = Y, Dy − Lu; Htfa — trifluoroacetic acid, deta — diethylenetriamine) with mononuclear structure were synthesized and characterized by powder X-ray diffraction, IR and NMR spectroscopy, TGA, conventional elemental analysis; crystal structure of [Y(tfa) 2 (deta) 2 ](tfa) was determined by single crystal X-ray diffraction. The structure of the new type consists of mononuclear complex cations [Y(tfa) 2 (deta) 2 ] + and outer-sphere tfa − anions connected into dimeric associates by intra-dimeric H-bonds. The complexes in crystalline state demonstrate high stability to storage in air and also retain tfa − anions within the coordination sphere in solution according to the results of NMR spectroscopy. Stability of [Ln(tfa) 2 (deta) 2 ](tfa) species was explained by DFT calculations. This allows their application as precursors of rare earth fluorides illustrated by synthesis of NaYF 4 powder and thin films. [ABSTRACT FROM AUTHOR]

The reaction of N-substituted 3-oxopentanediamides with phenyliodine bis(trifluoroacetate) (PIFA) was found to give a novel class of phenyliodonio-substituted spirofurooxindole trifluoroacetates under metal-free conditions. The reaction is postulated to proceed via a cascade process involving an oxidative C-O bond formation, an oxidative C-C bond formation and a final iodination step. [ABSTRACT FROM AUTHOR]

Hexagonal phase ultrafine nanoparticles of NaY(Gd)F 4 were synthesized using chloride precursors and sodium acetate to provide liquid environment for ionic transportand as a source of sodium ions. Prepared ultrafine nanocrystals were analysed by XRD, laser Doppler electrophoresis and TEM measurements. Absence of fluoroacetic acid was confirmed by NMR of wash water obtained by dispersion centrifugation. Synthesized nanocrystals were 8.9 nm in diameter and had a hexagonal crystal structure. The method is appropriate for further experimental development, e.g. the synthesis of luminescent fluorides based on NaY(RE)F 4 system, and for possible industrial application because of its ability to prepare large amounts of nanocrystals and due to the fact that the process is affordable and environmental friendly. [ABSTRACT FROM AUTHOR]

A convenient and facile method for the direct synthesis of α,α-difluorobenzoyl lactones or cyclic ethers via the radical cyclization reaction of 2-iodo-2,2-difluoroacetophenone with unsaturated acids or alcohols was reported. [ABSTRACT FROM AUTHOR]

Diversely substituted arylsilyl triflates, as aryne precursors for aryne cycloaddition reactions, were accessed from benzodioxasilines. Catalytic reductive C H ortho- silylation of phenols with traceless acetal directing groups was exploited to prepare benzodioxasilines. Sequential addition of MeLi and then trifluoromethanesulfonic anhydride to benzodioxasilines provided arylsilyl triflates in a single pot. Notably, this approach was successfully utilized to prepare sterically hindered 1,2,3-trisubstituted arylsilyl triflates, which ultimately underwent fluoride-mediated aryne cycloaddition. [ABSTRACT FROM AUTHOR]

19F MRI is valuable for in vivo imaging due to the only trace amounts of fluorine in biological systems. Because of the low sensitivity of MRI however, designing new fluorochemicals remains a significant challenge for achieving sufficient 19F signal. Here, we describe a new class of high-signal, water-soluble fluorochemicals as 19F MRI imaging agents. A polyamide backbone is used for tuning the proteolytic stability to avoid retention within the body, which is a limitation of current state-of-the-art perfluorochemicals. We show that unstructured peptides containing alternating N-ϵ-trifluoroacetyllysine and lysine provide a degenerate 19F NMR signal. 19F MRI phantom images provide sufficient contrast at micromolar concentrations, showing promise for eventual clinical applications. Finally, the degenerate high signal characteristics were retained when conjugated to a large protein, indicating potential for in vivo targeting applications, including molecular imaging and cell tracking. [ABSTRACT FROM AUTHOR]

Exposure to asbestos is associated with the development of mesothelioma. In addition to asbestos, other fibers have been identified as risk factors for malignant and non-malignant diseases of the lungs. Among these, fluoro-edenite (FE) was found in patients from Biancavilla (Sicily, Italy) with pleural and lung disease, suggesting its role for tumor expansion. In this context, the identification of early biomarkers useful for the diagnosis of cancer is mandatory. Fibulin-3 represents an important marker for the diagnosis of mesothelioma. However, it remains to be determined whether it is directly associated with exposure to asbestos-like fibers. In the present study, peripheral blood levels of fibulin-3 from 40 asbestos-exposed workers were compared with those detected in 27 street cleaners from Biancavilla. Intriguingly, the results showed that fibulin-3 levels were higher in the group of street cleaners compared with those of the asbestos-exposed workers, suggesting that these workers used the personal protective equipment according to the current regulations. These data suggest that subjects exposed to FE should be monitored for the risk of mesothelioma. FE and volcanic particulates are probably contained within dust inhaled by street cleaners from Biancavilla during their work activities. Based on these criteria, in this study, such fibers were used to treat mesothelial cells (MeT5A) in order to verify whether fibulin-3 levels are affected by these treatments. The results showed that only treatment with FE was associated with fibulin-3 overexpression at both the transcript and protein levels. It was previously demonstrated that mesothelial cells exhibited low levels of p27 following treatment with FE. Notably, p27 downregulation is associated with stathmin upregulation in cancer, conferring an aggressive phenotype of tumor cells. This observation prompted us to perform a computational evaluation demonstrating the activation of stathmin in lung cancer in patients exposed to asbestos. Overall, it can be speculated that both fibulin-3 and stathmin overexpression may be associated with the malignant transformation of mesothelial cells following exposure to asbestos-like fibers. [ABSTRACT FROM AUTHOR]

The first example of copper-catalyzed decarboxylative atom transfer radical addition of alkynyl carboxylic acids has been developed with a readily available fluoroalkyl halide. This novel protocol has demonstrated a unique difunctionalization of nonterminal alkynes with a broad substrate scope and excellent functional-group tolerance. Mechanistic investigations revealed that the catalytic cycle was initiated by the attack of a difluoroalkyl radical to an in situ generated alkynylcopper species. [ABSTRACT FROM AUTHOR]

A nickel-catalyzed three-component reaction for the synthesis of difluoroalkylated compounds through tandem difluoroalkylation-arylation of enamides has been developed. The reaction tolerates a variety of arylboronic acids and widely available difluoroalkyl bromides, and even the relatively inert substrate chlorodifluoroacetate. The significant advantages of this protocol are the low-cost nickel catalyst, synthetic convenience, excellent functional-group compatibility and high reaction efficiency. [ABSTRACT FROM AUTHOR]

An efficient multigram-scale synthesis of methyl 2,3,4,6-tetra- O -benzyl- l - glycero -α- d - manno -heptopyranoside from methyl 2,3,4-tri- O -benzyl-α- d -mannopyranoside is reported. It involves a sequence of Swern oxidation, Grignard addition and Fleming-Tamao reactions. The resulting scaffold was used as a precursor to design a small library of clickable l -heptosides. This study shows that the use of mercuric bistrifluoroacetate is required both to accelerate and to cleanly perform the Fleming-Tamao oxidation, without side-reactions. [ABSTRACT FROM AUTHOR]

During thermolysis of metal trifluoroacetates in high boiling organic solvents the two Ba 1−x RE x F 2+x phases with cubic fluorite-type structure are formed in BaF 2 -YF 3 system. In contrast to previous reports formation of so-called ‘BaYF 5 ’ nanocrystals was not observed. Besides the X-ray diffraction analysis the samples doped with optically active Eu 3+ and Er 3+ ions were characterized with photoluminescence spectroscopy and results provided by both methods corroborates each other. Upconversion emission observed under excitation at 980 nm for the Ba 1−x Y x F 2+x phase co-doped with Yb 3+ and Er 3+ ions is strongly composition dependent. Its intensity increases with increasing of REF 3 content for 0.2 < x < 0.45, whereas the opposite trend is evident for x > 0.45 and upconversion emission is totally quenched for x > 0.6. The important outcome of the present study is that compositions other than that with x = 0.5 should be probed to fully benefit from photoluminescence potential of Ba 1−x RE x F 2+x nanofluoride phases activated with lanthanide ions. [ABSTRACT FROM AUTHOR]

Astrocytes have been promoted as a possible mechanistic target for anaesthetic hypnosis. The aim of this study was to explore this using the neocortical brain slice preparation. The methods were in two parts. Firstly, multiple general anaesthetic compounds demonstrating varying in vivo hypnotic potency were analysed for their effect on 'zero-magnesium' seizure-like event (SLE) activity in mouse neocortical slices. Subsequently, the effect of astrocyte metabolic inhibition was investigated in neocortical slices, and compared with that of the anaesthetic drugs. The rationale was that, if suppression of astrocytes was both necessary and sufficient to cause hypnosis in vivo, then inhibition of astrocytic metabolism in slices should mimic the anaesthetic effect. In vivo anaesthetic potency correlated strongly with the magnitude of reduction in SLE frequency in neocortical slices (R 37.7 %, p = 0.002). Conversely, SLE frequency and length were significantly enhanced during exposure to both fluoroacetate (23 and 20 % increase, respectively, p < 0.01) and aminoadipate (12 and 38 % increase, respectively, p < 0.01 and p < 0.05). The capacity of an anaesthetic agent to reduce SLE frequency in the neocortical slice is a good indicator of its in vivo hypnotic potency. The results do not support the hypothesis that astrocytic metabolic inhibition is a mechanism of anaesthetic hypnosis. [ABSTRACT FROM AUTHOR]

The trans-o-hydroxybenzylidene pyruvate aldolase-catalysed reactions between fluoropyruvate and many (hetero)aromatic aldehydes yield aldol adducts without subsequent dehydration. Treatment of the reaction products with hydrogen peroxide yields the corresponding syn-configured α-fluoro β-hydroxy carboxylic acids which have >98 % ee. The overall chemoenzymatic approach, in which fluoropyruvate serves as a fluoroacetate equivalent, may be exploited in the synthesis of polar building blocks and fragments with potential value in drug discovery. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to evaluate the chromaticity and color saturation of anthocyanin extraction from fruit pericarps of Ixora siamensis in a poly(vinyl alcohol) (PVA) matrix. The colored PVA matrix was exposed to UV-B irradiation for 93 days at UV intensity of 17.55 lux. Anthocyanin colorant has been extracted using methanol acidified with 0.5% trifluoroacetic acid (TFA). Different concentrations of ferulic acid (FA) (0, 1, 2, 3, 4 and 5 wt.%) have been added to the anthocyanin extractions before mixing with PVA to form a coating system. The PVA-anthocyanin-FA mixtures have been coated on glass slides and kept overnight in the dark for curing before exposure to UV-B irradiation. The FA-free sample undergoes more color degradation compared to samples containing FA. The coating with 2% FA has the most stable color with chromaticity of 41% and color saturation of 0.88 compared to other FA containing coats. The FA-free coat exhibits 29% chromaticity and color saturation of 0.38 at the end of the experiment. [ABSTRACT FROM AUTHOR]

Numerous plant species worldwide including Palicourea marcgravii (Rubiaceae) and Tanaecium bilabiatum (Bignoniaceae) in Brazil cause acute cardiac failure (sudden death) and are known to contain monofluoroacetate (MFA). Other Bignoniaceae species including Fridericia japurensis ( Arrabidaea japurensis ) are reported to cause sudden death in livestock in the Brazilian state of Roraima and are suspected to contain MFA due to the similarity of clinical signs. In this study herbarium specimens of Fridericia japurensis and field collections suspected to be F. japurensis were analyzed for MFA, and plant material from the field collections was dosed to rabbits. No MFA was detected in the herbarium specimens authoritatively identified as F. japurensis ; however, MFA was detected in the field collections, which were identified as T. bilabiatum . Rabbits dosed orally with T. bilabiatum died acutely. Voucher toxic specimens initially described as F. japurensis were incorrectly identified, and the correct botanical name for this plant is T. bilabiatum ( Arrabidaea bilabiata ). Based on this study we conclude that there are no data to support the toxicity of F. japurensis and that the plant previously reported under this name as causing acute cardiac failure in cattle in Roraima is T. bilabiatum. This research highlights the importance of voucher specimens as part of any toxic plant investigation and corrects the literature regarding these toxic plants. [ABSTRACT FROM AUTHOR]

As a food defense measure against an extortion threat to poison infant formula with monofluoroacetate, a robust methodology for monofluoroacetate analysis in fluid milk and powdered dairy products was developed and optimized. Critical challenges posed by this situation required that the analytical methodology provide (i) high specificity, (ii) high throughput capable of analyzing thousands of samples of fluid milk per day, and (iii) trace-level detection of 1 ng/g or lower to achieve the maximum residue limit. Solid-phase extraction-purified acetone extracts of fluid milk were derivatized with aniline, and after ultrahigh-performance liquid chromatography using a Kinetex-C18 column packed with 1.3-µm shell particles, the resulting N- phenyl 2-fluoroacetamide could be determined by liquid chromatography-tandem mass spectrometry in a highly specific manner and with a limit of quantification of 0.5 ng/ml. By using 4-(4-chlorophenoxy)aniline as a derivatizing agent, the method could be extended to powdered dairy products with the same limit of quantification. Between January and July 2015, some 136,000 fluid milk samples were tested using this method. This analytical testing of fluid milk formed one element in a larger program of work by multiple agencies to ensure that consumers could continue to have confidence in the safety of New Zealand milk and dairy products. [ABSTRACT FROM AUTHOR]

Synergistetes strain MFA1 is an asaccharolytic ruminal bacterium isolated based on its ability to degrade fluoroacetate, a plant toxin. The amino acid and peptide requirements of the bacterium were investigated under different culturing conditions. The growth of strain MFA1 and its fluoroacetate degradation rate were enhanced by peptide-rich protein hydrolysates (tryptone and yeast extract) compared to casamino acid, an amino acid-rich protein hydrolysate. Complete utilization and preference for arginine, asparagine, glutamate, glycine, and histidine as free amino acids from yeast extract were observed, while the utilization of serine, threonine, and lysine in free form and peptide-bound glutamate was stimulated during growth on fluoroacetate. A predominant peptide in yeast extract preferentially utilized by strain MFA1 was partially characterized by high-liquid performance chromatography-mass spectrometry as a hepta-glutamate oligopeptide. Similar utilization profiles of amino acids were observed between the co-culture of strain MFA1 with Methanobrevibacter smithii without fluoroacetate and pure strain MFA1 culture with fluoroacetate. This suggests that growth of strain MFA1 could be enhanced by a reduction of hydrogen partial pressure as a result of hydrogen removal by a methanogen or reduction of fluoroacetate. [ABSTRACT FROM AUTHOR]

A mild, versatile and efficient method for the silver(i)-catalyzed oxidative decarboxylative gem-difluoromethylenation has been developed. The radical cascade reaction comprises the addition of an oxidatively generated difluoromethylene radical to the isonitrile functionality and subsequent homolytic aromatic substitution. It provides a novel and efficient access to the C–CF2 bond formation. [ABSTRACT FROM AUTHOR]

An unprecedented example of Pd-catalyzed difluoromethylation of aryl boronic acids with bromodifluoroacetate is described. The reaction proceeds under mild reaction conditions with hydroquinone and Fe(acac)3 as additives. Preliminary mechanistic studies reveal that a difluorocarbene pathway is involved in the reaction, which is unusual compared to the most traditional approaches. This reaction has advantages of high efficiency and excellent functional group compatibility, even toward bromide and hydroxy group, thus providing a useful protocol for drug discovery and development. [ABSTRACT FROM AUTHOR]

A convenient “one-pot” Friedel–Crafts reaction of mono -, bi - and tert -thiophenes with trifluoroacetic acid anhydride (TFAA) as an acylating agent and magnesium perchlorate dihydrate (anhydron) as catalyst affords trifluoroacetyl-substituted products in high yields. This method provides a novel approach for the synthesis of thiophene based derivatives bearing trifluoroacetyl group. The mechanism of this reaction is suggested. [ABSTRACT FROM AUTHOR]

Electrospun poly(butylene terephthalate) (PBT) fibers were prepared from trifluoroacetic acid (TFA)-based solvent. Rheological studies revealed the concentration ( ϕ , volume fraction) dependence of zero-shear viscosity ( η o ) to be η o ∼ ϕ 3.87 in the entangled solution regime, and the entanglement concentration (ϕ e ) was 7.84 vol.%. Effects of η o on the straight jet-end diameter ( d j ) and fiber diameter ( d f ) were investigated; two scaling laws existed for PBT/TFA solutions, i.e., d j ∼ η o 0.06 and d f ∼ η o 0.73 . Moreover, d f can be scaled with entanglement density and solution plateau modulus ( G N ) through d f ∼ (ϕ/ϕ e ) 2.6 ∼ G N . Results of differential scanning calorimetry and wide-angle X-ray diffraction revealed that as-spun PBT fibers were not amorphous but contained imperfect small α crystallites. During stepwise annealing, crystal perfection gradually occurred, and well-ordered, α -form crystal was developed at temperatures above 160 °C. When electrospun PBT fibers were embedded in isotactic polypropylene (iPP) matrix, fiber surface-induced crystallization readily occurred to develop a transcrsytalline layer of iPP monoclinic crystals at the interface. Similar effects were found for electrospun fibers of poly(ethylene terephthalate) (PET) and poly(trimethylene terephthalate) (PTT). The conventional method of counting iPP nuclei occurring on the fiber surface to determine fiber nucleation rate was infeasible because of the fine fiber diameter. A new approach to characterize the nucleating ability of polyester fibers with submicron diameter was developed. By measuring the intensity of depolarized light during cooling from the melt, the initial temperature ( T i ) for iPP transcrystallization was determined and compared. Based on the derived T i , the nucleating ability of electrospun fibers toward iPP followed the order PBT > PET ∼ PTT. This finding was consistent with isothermal crystallization results. Moreover, the maximum temperature for PBT fiber to induce crystallization of iPP was ca. 157 °C, which was 20 °C higher than those of PET and PTT fibers. The remarkable nucleating ability of PBT fibers was likely associated with epitaxial crystallization and the large substrate crystal dimension in the matching direction, as revealed by atomic force microscopy. [ABSTRACT FROM AUTHOR]

The article offers information on the determination of monofluoroacetate in powdered nutritional products using derivatization with 2-Nitrophenylhydrazine. Topics covered include the preparation of samples by dilution in water followed by protein precipitation, the use of reagents like acetonitrile and ethyl acetate and the method acceptance criteria such as the coefficients of determination for calibration curves.

The article discusses an example of a nickel-catalyzed monofluoromethylation of aryl boronic acids hampered by the high loading of a transition metal. It outlines the examination of a variety of phosphine and diamine ligands to improve the yield further. The presence of halo substituents in the products and the exploration of ethyl 2-bromo-2-fluoroacetate (4) as a fluoromethylator are also tackled.

A new reagent trimethylsilyl chlorodifluoroacetate (TCDA) is reported for the introduction of a -CF3 group to arenes and heteroarenes. Compared with current known reagents, TCDA shows very broad scope with respect to electron-deficient, -neutral, and -rich aryl/heteroaryl iodides as well as excellent functional group tolerance, including ester, amide, aldehyde, hydroxyl, and carboxylic acid. [ABSTRACT FROM AUTHOR]

A theoretical investigation has been performed on the mechanism, kinetics and thermochemistry of the gas phase reactions of methyl fluoroacetate CH 2 FC(O)OCH 3 (MFA) with Cl atoms. Geometry optimization and frequency calculations have been made at the MPWB1K/6-31+G(d,p) level of theory and energetic information is further refined by calculating the energy of the species using G2(MP2) theory. The rate constant for reactions of MFA with Cl atoms are reported over wide range of 250–450 K using the Canonical Transition State Theory (CTST). The atmospheric lifetime of CH 2 FC(O)OCH 3 was estimated to be around 1.21 years with respect to reaction with Cl atoms. The rate constant obtained is compared with literature values for other similar species to establish reactivity trends. It is shown that the F-atom substitution decrease the reactivity of C H bond of esters. [ABSTRACT FROM AUTHOR]

A practical method for the synthesis of gem -difluorinated compounds from organozinc reagents is described. Potassium bromodifluoroacetate serves as a source of CF 2 -fragment, which is inserted into carbon zinc bond of organozinc reagents. The intermediate difluorinated organozinc species can be protonated, brominated or coupled with allylic electrophiles. [ABSTRACT FROM AUTHOR]

A theoretical study on the mechanism of the reactions of methyl difluoroacetate (MDFA) CFHC(O)OCH with Cl atoms is presented. Two conformers relatively close in energy have been identified for MDFA. Geometry optimization and frequency calculations have been performed at the MPWB1K/6-31+G(d,p) level of theory, and energetic information is further refined by calculating the energy of the species using G2(MP2) theory. Transition states (TSs) are searched on the potential energy surface involved during the reaction channels, and each of the TSs is characterized by the presence of only one imaginary frequency. The existence of TSs on the corresponding potential energy surface is ascertained by performing intrinsic reaction coordinate calculation. Our calculations reveal that hydrogen abstraction from the -CH group is thermodynamically and kinetically more facile than that from the -CFH group. Theoretically calculated rate constants at 298 K using the canonical transition state theory are found to be in good agreement with the experimentally measured ones. The atmospheric lifetime of CFHC(O)OCH was estimated to be 16 years. The atmospheric fate and the main degradation process of alkoxy radical CFHC(O)OCHO are also discussed for the first time. Our calculation indicates that the fluorine atoms substitution has deactivating effect for the α-ester rearrangement. [ABSTRACT FROM AUTHOR]

Anecdotal reports in 2001 suggested that the European Red Fox ( Vulpes vulpes) had been deliberately released in Tasmania and thereafter an eradication programme using buried fluoroacetic acid (1080) baits was believed to be a necessary precautionary action until mid-2013. Prerequisites for the successful eradication of foxes relate to the scale of the undertaking and the ability to collect in situ data such as the distribution and abundance of the target population and measures of the efficacy of the control technique. Previously, 1080 baiting has demonstrated only limited potential as a fox eradication technique on islands when used on a scale between 685 and 2141 times smaller than Tasmania. In the absence of empirical monitoring data confirming the distribution or abundance of extant foxes, buried baiting was targeted to specific landscapes believed to be preferred by foxes. No empirical data was collected concerning the in situ effectiveness of baiting in Tasmania, yet an a priori assumption of lethal efficacy was extrapolated from four heterogeneous mainland studies to suggest that foxes would have only a 0.23 probability of surviving each bait treatment. We show that these studies were unrepresentative of Tasmanian baiting methods used and influenced by imprecise fox population surveys and misreported data. Overall, in the absence of key population monitoring and efficacy data, the 'precautionary' baiting strategy adopted did not have a realistic potential to eradicate fox incursions in Tasmania, nor is it an appropriate risk management strategy for other large offshore Australian islands. Contingency plans to counter fox incursions on offshore islands must address the currently inadequate technical capacity to reliably detect and monitor low-density fox populations, which is an essential component of successful fox eradication. [ABSTRACT FROM AUTHOR]

A mildacylation of N-alkylindoles is reportedusing sodium chlorodifluoroacetate (SCDA) to synthesize useful chlorodifluoroketones.Friedel–Crafts reactivity of carboxylate salts is unusual andis not observed in similar electron-deficient acetate salts such assodium trifluoroacetate. Mechanistic experiments indicate that thecharacteristic ability of SCDA to generate difluorocarbene is responsiblefor the reaction pathway via self-activation to form the active ester. [ABSTRACT FROM AUTHOR]

The kinetics of hydrogen atom abstraction reactions of methyl difluoroacetate (CF2HCOOCH3) by OH radical has been studied by quantum mechanical method. The geometry optimisation and frequency calculation of the titled compound was performed with density functional theory using hybrid meta density functional MPWB1K with 6-31+G(d,p) basis set. Transition states have been determined and intrinsic reaction coordinate (IRC) calculation has been performed to ascertain that the transition from reactants to products was smooth through the corresponding transition state. Energy values are refined by making single point energy calculation at G3B3 level of theory and an energy level diagram is constructed. The standard enthalpies of formation of reactants and other species formed during the reaction were calculated using isodesmic method. The rate constants are calculated using canonical transition state theory and the overall rate constant is determined to be 1.35×10−13cm3molecule−1s−1at 298 K and 1 atmospheric pressure. Tunnelling has been taken into account in the determination of the rate constant because it plays a critical role at low temperature especially when transfer of hydrogen takes place. The calculated value is found to be in good agreement with the experimentally determined value of 1.48×10−13cm3molecule−1s−1. [ABSTRACT FROM PUBLISHER]

The development of efficient methods for accessing fluorinated functional groups is desirable. Herein, we report a twostep method that utilizes catalytic copper for the decarboxylative trifluoromethylation of propargyl bromodifluoroacetates is described. This protocol affords a mixture of propargyl trifluoromethanes and trifluoromethyl allenes. [ABSTRACT FROM AUTHOR]

A practicaland unified strategy has been described for the preparationof mono- and difluoromethylated phenanthridine derivatives using avisible-light-promoted alkylation and decarboxylation sequence frombiphenyl isocyanides with ethyl bromofluoroacetate (EBFA) or ethylbromodifluoroacetate (EBDFA). These reactions could be carried outat room temperature in good to excellent chemical yields. Both stepwiseand one-pot procedures have been developed, which makes this strategymore attractive. [ABSTRACT FROM AUTHOR]

Glia account for 90% of human brain cells and have a significant role in brain homeostasis. Thus, specific in vivo imaging markers of glial metabolism are potentially valuable. In the brain, 2-fluoroacetate is selectively taken up by glial cells and becomes metabolically trapped in the tricarboxylic acid cycle. Recent work in rodent brain injury models demonstrated elevated lesion uptake of 2-[18F]fluoroacetate ([18F]FACE), suggesting possible use for specifically imaging glial metabolism. To assess this hypothesis, we evaluated [18F]FACE kinetics in rodent models of cerebral hypoxia-ischemia at 3 and 24 hours post insult. Lesion uptake was significantly higher at 30 minutes post injection (P<0.05). An image-based method for input function estimation using cardiac blood was validated. Analysis of whole blood showed no significant metabolites and plasma activity concentrations of ∼50% that of whole blood. Kinetic models describing [18F]FACE uptake were developed and quantitatively compared. Elevated [18F]FACE uptake was found to be driven primarily by K1/k2 rather than k3, but changes in the latter were detectable. The two-tissue irreversible uptake model (2T3k) was found to be necessary and sufficient for modeling [18F]FACE uptake. We conclude that kinetic modeling of [18F]FACE uptake represents a potentially useful tool for interrogation of glial metabolism. [ABSTRACT FROM AUTHOR]

The thermal behaviors of FeF3 cathode in 1 mol dm−3 LiPF6/methyl difluoroacetate (MFA) electrolyte are quantitatively investigated by differential scanning calorimetry. MFA-based electrolyte shows great thermal stability without heat generation up to 500 °C. The cycled electrodes are studied and find to become more thermally stable after lithiation. Furthermore, the lithiated electrode shows a superior thermal stability in the electrolyte compared to the delithiated electrode. Although the heat generated by the mixtures of cycled electrodes and MFA-based electrolyte is larger, the lithiated and delithiated electrodes coexisted with MFA-based electrolyte are about 140 and 230 °C higher than that of EC + DMC-based electrolyte, respectively. Therefore, the safety of FeF3 battery is enhanced by using MFA-based electrolyte instead of EC + DMC-based electrolyte. [ABSTRACT FROM AUTHOR]

Abstract: We have corrected (Tetrahedron 2013, 69, 5859–5866) the structures of diterpenoid alkaloids reported in the Journal of Natural Products 2012, 75, 1145–1159. Our follow-up experiments compel us to present further revisions and clarifications on the diterpenoid alkaloids: (1) The naturally occurring forms of carmichaelines B, C, and D in Shi's paper (Journal of Natural Products 2012, 75, 1145–1159) are neither quaternary ammonium hydroxides 2–4 nor the initially revised trifluoroacetates. They are indeed the vakognavine-type C20-diterpenoid alkaloids 11–13. (2) The samples' concentration is the critical factor to the signals' intensity for F3CCOO− in the alkaloid trifluoroacetates. Incorporation of TFA into the corresponding salts resulted in signals' enhancement due to the closeness of δ values (∼116 ppm, ∼159 ppm) of free TFA and those of F3CCOO−. After removal of free TFA, the carbon signals of CF3COO− could become weaker, but their chemical shifts remained almost unchanged. The possible reason might be the ionization of TFA in acetone. (3) The NMR data cannot distinguish TFA from trifluoroacetates (e.g., F3CCOONa and C19-diterpenoid alkaloid trifluoroacetates), indicating that the signal at around δ −76 cannot be used to exclude the existence of trifluoroacetates. In addition to the NMR and CSI-MS data, 1H–15N HMBC technique was also used to distinguish the free alkaloids from their trifluoroacetates. (4) The X-ray crystallographic analysis of compound 20 confirmed that the ‘new alkaloid’ (-b) in the Shi's paper is indeed the known compound aconifine trifluoroacetate. (5) Collectively, Shi's paper mixed-up the free alkaloids with their salts and the concepts of structure and conformation. Naming different structures with A-b and A-c is also confusing. [Copyright &y& Elsevier]