Fluoride In Acetonitrile Research Articles

On the Risk of 18F-Regioisomer Formation in the Copper-Free Radiofluorination of Aryliodonium Precursors.

Aryliodonium precursors are widely applied for copper-free labeling of positron emission tomography (PET) tracers with fluorine-18. We assessed 18F-fluoroarene regioisomer formation in examples of these labeling methods. Aryliodonium ylides derived from Meldrum's acid bearing para electron-donating groups react with [18F]fluoride in acetonitrile to produce regioisomeric 18F-fluoroarenes via a competing aryne pathway. Regioisomer formation is decreased or absent in DMF. Analytically checking for the absence of the 18F-regioisomer from any particular PET tracer radiosynthesis using these or similar methods is recommended.

Catalysing electropolymerization: High-quality polythiophene films for electrochemical sensors by the utilization of fluorine based Lewis acid catalysts

Polythiophene and other conductive polymers can be obtained by electropolymerization from various solvents, of which boron trifluoride diethyl etherate (BFEE) is preferably used. In this solvent, electropolymerization can be performed at significantly lower potentials and therefore milder conditions, from which polymers with improved properties result. However, their quality cannot easily be reproduced. We discovered the mechanism behind the decreased initial oxidation potential of thiophene in BFEE and transferred it onto stable solvents by the utilization of fluorine based Lewis acid catalysts. By exemplarily utilizing zinc fluoride in acetonitrile, we found that the catalysis allows for lower oxidation potentials, higher selectivity of polymerization, and smoother film surface morphology – in a reproducible manner. The presented polythiophene films constitute a promising substrate material for the fabrication of electrochemical sensors. Films were deposited by cyclic voltammetry, chronoamperometry, and chronopotentiometry, and characterized by electrochemical impedance spectroscopy and Raman spectroscopy. Surface morphology and elemental composition were analysed with white light interferometry, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. We propose a number of alternative catalysts that can be utilized in various solvents, not just for thiophene electropolymerization, but for various other conductive polymers. The presented catalysis can therefore serve as a universal tool for the synthesis of high quality conductive polymer films for innovative and trendsetting applications.

Intercepting the Banert cascade with nucleophilic fluorine: direct access to α-fluorinated NH-1,2,3-triazoles.

The treatment of propargylic azides with silver(i) fluoride in acetonitrile was found to yield α-fluorinated NH-1,2,3-triazoles via the Banert cascade. The reaction was regioselective and the products result from an initial [3,3] rearrangement. The reaction is demonstrated on >15 examples with yields ranging from 37% to 86%.

Hydrazone derivative of 2-hydroxyquinoline-3-carbaldehyde: an efficient anionic and cationic sensor

A hydrazone (1) based on 2-hydroxyquinoline-3-carbaldehyde was synthesized and its anion and cation detection ability were studied. It could detect both fluoride in acetonitrile selectively among anions and copper ions in semiaqueous medium among cations. The addition of fluoride ion to the acetonitrile solution of the receptor produced a sharp colour change from light yellow to bluish green. The corresponding UV–vis measurements showed a red shift of the band of receptor 1 for fluoride and a blue shift of the band for copper ions. The fluorescence intensity of the receptor 1 got quenched with both fluoride and copper ions. The detection limits for both the ions are in order of micromolar level. The practical applications of fluoride detection were extended to oral care products.

An Acridone‐Based Fluorescent Chemosensor for Cationic and Anionic Species, and Its Application for Molecular Logic Operations

AbstractThe metal ion and anion recognition abilities of the newly synthesized acridone derivative having amide and ester groups were studied by UV–vis and fluorescence spectroscopies. The sensor molecule revealed selective recognition toward Ca(II), Hg(II), and fluoride in acetonitrile. Based on X‐ray crystallographic and 1H NMR analyses, intramolecular bifurcated H‐bond is formed between the acridone NH and the amide oxygens in the free receptor. Addition of Ca(II) and Hg(II) induced large fluorescence enhancements and changes in the 1H NMR shifts due to complexation, while fluoride deprotonated the sensor molecule giving rise to a new emission band. Selective sensing of Hg(II) based on absorption changes was also observed, presumably due to the tautomerization of the acridone unit upon complexation. The optical spectroscopic behavior in the presence or absence of Ca(II) and fluoride as chemical inputs provided an opportunity to construct IMP, INH, XOR, and XNOR molecular logic gates as well as a complementary IMP/INH circuit, and integrated logic functions such as a half‐subtractor (XOR/INH combination) and a magnitude comparator (XNOR/INH combination).

Synthesis of aryl and heteroaryl tetrafluoro-λ6-sulfanyl chlorides from diaryl disulfides using trichloroisocyanuric acid and potassium fluoride

A catalyst-free method for the synthesis of (Het)ArSF4Cl by using trichloroisocyanuric acid and potassium fluoride in acetonitrile is disclosed.

Benzo-15-crown-5 (2,3,5,6,8,9,11,12-octahydrobenzo[b][1,4,7,10,13]pentaoxacyclopentadecine) and dibenzo-15-crown-5 (6,7,9,10,17,18-hexahydrodibenzo[b,h][1,4,7,10,13]pentaoxacyclopentadecine as fluorescent probes for physiologically important potassium ion

Cation recognition plays a vital role in defining advanced functions of macromolecules in nature. An example of such an interaction is the action of a natural antibiotic, valinomycin, that behaves as a potassium ionophore. It encages the cation to transport it across a cell membrane and easily releases it inside the cell. Macrocyclic complexes of some crown ethers mimick alkali ion interactions with natural ionophores. We have synthesized complexes of two crown ethers namely benzo-15-crown-5 (2,3,5,6,8,9,11,12-octahydrobenzo[b][1,4,7,10,13]pentaoxacyclopentadecine) and dibenzo-15-crown-5 (6,7,9,10,17,18-hexahydrodibenzo[b,h][1,4,7,10,13]pentaoxacyclopentadecine with potassium halides (fluoride, chloride, bromide and iodide) in acetonitrile and characterized them by IR, UV, ESI-MS, 1H NMR and 13C NMR techniques. The effect of the anion on the stability of the complexes was observed by 1H NMR studies. The alkali metal ion is held to the oxygen donor atoms of the macrocyclic ring by ion-dipole interactions. The potential of the small ring oxacrown ethers, benzo-15-crown-5 and dibenzo-15-crown-5, to act as probes for potassium ions in dilute solutions (4.1 × 10−4 M) was investigated by recording the variation in the fluorescence spectra of benzo-15-crown-5 and dibenzo-15-crown-5 on complexation with potassium fluoride in acetonitrile and chloroform. The rigidity of the macrocyclic ring and proximity of fluorophore units affected the fluorescence intensity of the complexes.

Synthesis of 3-(Arylsulfonyl)-3-pyrrolines from Allenyl Sulfonamides by Silver Ion Catalysis.

Treatment of allenyl sulfonamides with catalytic amounts of silver fluoride in acetonitrile at reflux afforded the corresponding 3-sulfonyl-3-pyrrolines in excellent yields by intramolecular hydroamination via a 5- endo-trig cyclization. The starting allenyl sulfonamides were prepared by lithiation of allenic sulfones and trapping with various N-sulfonylimines.

A new synthesis of N-alkoxyaminopyridinium salts

It was found, that methyl N-alkoxy-N-chlorocarbamates interaction with 4-dimethylaminopyridine was overall manner of synthesis of 1-N-alkoxyaminopyridinium chlorides. New1-N-n-octyloxyamino-4-dimethylaminopyridinium and 1-N-benzyloxyamino-4-dimethylaminopyridinium chlorides have been synthesized by the methyl N-chloro-N-n-octyloxycarbamate and methyl N-benzyloxy-N-chlorocarbamate interaction with 4-dimethylaminopyridine in acetonitrile solution, respectively. The novel synthesis of 1-N-alkoxyaminopyridinium chlorides by reaction of N- -алкоксимочевин alkoxy-N-(1-pyridinium)ureas chlorides ammonolysis has been proposed. 1-N-Methoxyamino-4-dimethylaminopyridinium chloride and 1-N-n-butyloxyamino-4-dimethylaminopyridinium chloride have been synthesized by reaction of N-1-4-dimethylaminopyridinium-N-methoxyurea chloride and N-n-butyloxy-N-(1-4-dimethylaminopyridinium)urea chloride, respectively, with excess of ammonia in ethanol solution at room temperature during few minutes. Evidently, the carbamoyl proton elimination by ammonia causes further formation 1-N-alkoxy-4-dimethylaminopyridinium chlorides and HNCO. It is new example of decarbamoylation of N-alkoxy-N-(1-pyridinium)ureas salts. 1-N-Metoxyamino-4-dimethylaminopyridinium fluoride has been synthesized by N-1-(4-dimethylamino)pyridinium-N-methoxyurea chloride reaction with potassium fluoride in acetonitrile. Probably, in this reaction N-1-(4-dimethylamino)pyridinium-N-methoxyurea caution decarbamoylation occurs after the chloride anion exchange on fluoride anion. 1-N-Alkoxyaminopyridinium salts structures have been confirmed by data of NMR 1H spectra, NMR 13C spectra and mass-spectra

Silver-Catalyzed Cyclization of Sulfonyl Allenes to Dihydrofurans.

Treatment of α-hydroxy allenic sulfones with 10 mol % of silver fluoride in acetonitrile at ambient temperature furnished the corresponding 3-tosyl 2,5-dihydrofurans in excellent yields via a 5-endo-trig cyclization. The starting α-hydroxy allenic sulfones were prepared by lithiation of allenic sulfones and trapping with carbonyl compounds.

Anionic optical devices based on 4-(nitrostyryl)phenols for the selective detection of fluoride in acetonitrile and cyanide in water

Four compounds, 4-(4-nitrostyryl)phenol (1a), 4-(2,4-dinitrostyryl)phenol (2a), [4-(4-nitrostyryl)phenoxy]triisopropylsilane (3), and [4-(2,4-dinitrostyryl)phenoxy]triisopropylsilane (4), were synthesized and characterized. The three-dimensional molecular structures of compounds 3 and 4 were solved using X-ray crystallography. Compounds 1a and 2a were used in an acid-base strategy for the detection of fluoride and cyanide in acetonitrile. With the addition of small amounts of water the systems were able to detect only cyanide. Compounds 1a and 2a were also able to selectively detect cyanide in pure water, in the presence of a micellar concentration of cetyltrimethylammonium bromide, which is required to adjust the acidity constants of the compounds for the detection of the anion. Compounds 3 and 4 were used in a chemodosimeter approach for the selective detection of fluoride in acetonitrile. The fluoride attacks the silicon centers of 3 and 4 and through a nucleophilic substitution at the silicon (SN2@Si) their corresponding colored phenolate species are immediately released as leaving groups. This process is effective in acetonitrile for the detection of fluoride, which is a strongly nucleophilic analyte under these experimental conditions. Paper test strips were prepared, containing compounds 1a and 2a, and in tests with aqueous solutions of different anions it was verified that only CN− changes the color of the modified paper.

2-Hydroxyarylimidazole-based colorimetric and ratiometric fluoride ion sensors

Two novel 2-hydroxyarylimidazoles were developed as colorimetric and ratiometric sensors for the naked-eye detection of fluoride anions. The discriminating absorption and fluorescence responses to fluoride in acetonitrile as well as a methanol–acetonitrile solvent system were observed. The bathochromic optical changes are attributed to the deprotonated species evidenced from 1H NMR titrations. Their selectivity for fluoride over acetate was successfully established in the methanol–acetonitrile mixture. A fluorene-bridged imidazole dimer, 4a demonstrated better response for fluoride than acetate in the neat acetonitrile. Moreover, the sensor 4a exhibited a larger ratio of fluorescence intensity response (I489/I431 = 51) than 4b (I521/I448 = 18) for fluoride in acetonitrile.

A reversible and reusable selective chemosensor for fluoride detection using a phenolic OH-containing BODIPY dye by both colorimetric 'naked-eye' and fluorometric modes.

A novel BODIPY-based probe 1 was designed and synthesized as a selective fluorescent and colorimetric chemosensor for fluoride. The spectral responses of 1 to fluoride in acetonitrile were studied: an approximately 118nm red shift in absorption and 'turn-off' emission response was observed. The striking pink to indigo change in ambient light was thought to be due to the deprotonation of the phenol moiety by way of O-H · · · F hydrogen bonding interactions. Interestingly, when the nonfluorescent 1-F(-) solution treated with trifluoroacetic acid (TFA) resulted in color change from indigo to pink and a significant enhancement of fluorescence intensity (10-fold). Furthermore, the reversibility and reusability of probe 1 for the detection of F(-) ion was tested for four cycles indicating the probe 1 could be used in reversible manner.

ChemInform Abstract: Enantiospecific Total Synthesis of N‐Methylwelwitindolinone D Isonitrile.

ChemInform Abstract: Enantiospecific Total Synthesis of N‐Methylwelwitindolinone D Isonitrile.

Ratiometric sensing of fluoride and acetate anions based on a BODIPY-azaindole platform and its application to living cell imaging

A new BODIPY-azaindole based fluorescent sensor 1 was designed and synthesized as a new colorimetric and ratiometric fluorescent chemosensor for fluoride. The binding and sensing abilities of sensor 1 towards various anions were studied by absorption, emission and (1)H NMR titration spectroscopies. The spectral responses of 1 to fluoride in acetonitrile-water were studied: an approximately 69 nm red shift in absorption and ratiometric fluorescent response was observed. The striking light yellow to deep brown color change in ambient light and green to blue emission color change are thought to be due to the deprotonation of the indole moiety of the azaindole fluorophore. From the changes in the absorption, fluorescence, and (1)H NMR titration spectra, proton-transfer mechanisms were deduced. Density function theory and time-dependent density function theory calculations were conducted to rationalize the optical response of the sensor. Results were supported by confocal fluorescence imaging and MTT assay of live cells.

Enhanced nucleophilic fluorination and radiofluorination of organosilanes appended with potassium-chelating leaving groups

Here we aimed to explore the feasibility of enhancing the fluorination of organosilanes by appending potassium-chelating groups to the substrates. For this purpose, eight organosilanes were prepared in which a linear or cyclic leaving group, with putative potassium-chelating ability, was attached covalently to a congested silicon atom via an ether linkage to serve as a potential nucleophilic assisting leaving group (NALG). Organosilicon-NALGs with expected strong potassium-chelating capability enhanced reactions with potassium fluoride in acetonitrile to produce organofluorosilanes without any need to separately add phase transfer reagent. Similar rate enhancements were also observed with cyclotron-produced [18F]fluoride ion (t1/2=109.7min, β+=97%) in the presence of potassium carbonate in MeCN–0.5% H2O. This study found that metal-chelating NALG units can accelerate fluorination and radiofluorination reactions at sterically crowded silicon atoms.

Thiourea linked peracetylated glucopyranosyl–anthraquinone conjugate as reversible ON–OFF receptor for fluoride in acetonitrile

Abstract A new thiourea linked peracetylated glucopyranosyl–anthraquinone conjugate ( L ) has been synthesized and characterized. The binding properties of L have been studied with nineteen different anions. The L exhibited selective chromogenic as well as fluorescent chemosensor property toward F − by a ∼13-fold increase in the emission intensity upon binding with F − . The minimal detection limit for F − is 185 ± 5 ppb in acetonitrile. Interaction of F − led to a bathochromic shift of 80 nm in the absorption band. An INHIBIT logic gate has been proposed using the output obtained from the fluorescence studies. The structure of the species formed upon the interaction of F − with L has been established by DFT computations.

A new colorimetric and fluorescent bis(coumarin)methylene probe for fluoride ion detection based on the proton transfer signaling mode

A new turn-on fluorescent and colorimetric sensor, oxidized bis(coumarin)methane (1) for fluoride in acetonitrile was designed and synthesized. The binding ability evaluated by UV–vis and fluorescence titration experiments reveals that 1 can selectively interact with fluoride. Upon addition of fluoride to receptor 1 in acetonitrile solution, the appearance of a new absorption band around 349nm showed a color change from colorless to yellow, which can provide a way of ‘naked eye’ detection of fluorides. The spectral change of 1 is due to the anion induced deprotonation and hence an increase in charge density and rigidity of the receptor molecule. Furthermore, the binding mode with fluoride was investigated by 1H NMR titration experiments. Again, the deprotonation of oxidized bis(coumarin)methane 1 is responsible for the color change.

Inculcating total selectivity for fluoride in pyrene based chromogenic receptors: An experimental and theoretical study

Three simple Schiff base receptors 1–3 containing pyrene skeletons have been designed and synthesized. The intramolecular hydrogen bonding between aldimine N-atom and phenolic OH of these Schiff bases were found to play a crucial role towards their sensing behavior against fluoride. The receptor 3 exhibited total selectivity towards fluoride in acetonitrile. The basis of the above designing at the molecular orbital level was studied through density functional theory (DFT) and time dependent density functional theory (TD–DFT). The observed structure dependence of the binding selectivity may provide guidelines for the development of new colorimetric/fluorescent sensors for F− of further high selectivity.

Aliphatic Nucleophilic Radiofluorination

In this review we are looking at some aspects of nucleophilic aliphatic radiofluorination, notably the labelled fluoride source, design aspects, the leaving group and the solvent. It should be clear that there is more to this branch of radiolabelling than one would suspect from the frequently used standard tosylate replacement with kryptofix/[18F]fluoride in acetonitrile or DMSO. Competitive elimination can be a serious problem that can affect both yield and purification. Deprotection of sensitive groups after radiolabelling and its possible side reactions can complicate purification. The right choice of leaving group and protecting groups may be crucial. Newer developments such as the use of tertiary alcohols or ionic liquids as solvents, long-chain polyfluorinated sulphonate leaving groups facilitating fluorous solid phase extraction, or immobilisation of the precursor on a solid phase support may help to solve these problems, for example the long-standing problems with [18F]FLT, whereas older concepts such as certain cyclic reactive entities for ring opening or even an abandoned reagent as [18F]DAST should not be forgotten.