- Low-temperature NMR spectra of fluoride-acetic acid hydrogen-bonded complexes in aprotic polar environment
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Using low-temperature NMR (1H, 19F) technique in the slow exchange regime, the solutions containing tetrabutylammonium (TBA) acetate and HF have been studied in an aprotic freon mixture, CDF3/CDF 2Cl, exhibiting a dielectric permittivity, which increases strongly by lowering the temperature. Two different hydrogen bonded anionic clusters, a 1:1 cluster of the type AcOδ-?H?F -1+δ+ ([AcOHF]-) and a 2:1 cluster of the type AcOH?F-?HOAc ([(AcOH)2F]-) have been detected in equilibrium with each other, both forming ion pairs with the TBA countercation. [AcOHF]- exhibits an extremely strong hydrogen bond, with a proton shared between partially negatively charged oxygen and fluorine atoms. The NMR chemical shifts and scalar spin-spin coupling constants, 1J(FH), have been measured in the temperature range between 110 and 160 K, where separate NMR signals are observed for both species. In addition, H/D isotope effects on the 19F NMR chemical shielding have been measured for both clusters. In contrast to the related complexes [(FH) nF]- (n=1-4) studied previously, the NMR parameters of [AcOHF]- and of [(AcOH)2F]- depend strongly on temperature. This effect is associated with the increasing polarity of the solvent with decreasing temperatures, established earlier, which displaces the proton from fluorine to oxygen. As a motive power of this conversion, preferential solvation of the compact fluoride ion as compared to acetate is proposed.
- Golubev, Nikolai S.,Tolstoy, Peter M.,Smirnov, Sergei N.,Denisov, Gleb S.,Limbach, Hans-Heinrich
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Read Online
- Convenient Procedures for the Preparation of Lipophilic Quaternary Onium Fluorides, Hydrogendifluorides and Dihydrogentrifluorides via Ion Exchange in Two-Phase Systems
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A series of lipophilic quaternary onium fluorides 2, hydrogendifluorides 3, and dihydrogentrifluorides 4 are easily synthesized in almost quantitative yields from the corresponding quaternary hydrogen sulfates by exchange with the appropriate anion in an organic aqueous two-phase system; alternatively quaternary salts 4 can be prepared from onium chlorides 5 or bromides 6 under the same conditions.
- Landini, Dario,Molinari, Henriette,Penso, Michele,Rampoldi, Alessandro
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Read Online
- Boron-Containing Organic Diradicaloids: Dynamically Modulating Singlet Diradical Character by Lewis Acid-Base Coordination
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Organic diradicaloids have unique open-shell structures and properties and promising applications in organic electronics and spintronics. Incorporation of heteroatoms is an effective strategy to alter the electronic structures of organic diradicaloids. However, B-containing organic diradicaloids are very challenging due to their high reactivities, which are caused by not only diradical nature but also the B atom. In this article, we report a new kind of organic diradicaloids containing boron atoms. Our strategy is to incorporate planarized triarylboranes to antiaromatic polycyclic hydrocarbons (PHs). We synthesized two isomeric B-containing PHs composed of indenofluorene π-skeletons and two dioxa-bridged triphenylborane moieties. As proved by theoretical and experimental results, both of them have excellent ambient stability and open-shell singlet diradical structures, as well as intriguing magnetic and optoelectronic properties, such as thermally accessible triplet species, reversible multiredox ability, and narrow energy gaps. Notably, they possess sufficient Lewis acidity, which has never been observed for organic diradicaloids. In addition, they can coordinate with Lewis bases to form Lewis adducts, achieving unprecedented dynamic modulations of (anti)aromaticity and thus diradical character of organic diradicaloids.
- Dou, Chuandong,Guo, Jiaxiang,Wang, Yue,Yang, Yue
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supporting information
p. 18272 - 18279
(2021/11/12)
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- Unraveling the cation and anion effects and kinetics for ionic liquid catalyzed direct synthesis of methyl acrylate under mild conditions
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The direct synthesis of methyl acrylate (MA) from methyl acetate and trioxane at 350-380 °C is regarded as a supplementary route for the industrial propylene oxidation process; however, it suffers from rapid catalyst deactivation. Herein, a novel ionic liquid catalyzed mild liquid-phase system was developed for the direct synthesis of MA from methyl acetate and trioxane, where N,O-bis(trimethylsilyl)acetamide (BSA) was used as a probase for α-deprotonation and enol silyl etherification of methyl acetate. The trioxane decomposition to formaldehyde and methyl acetate enolization to 1-methoxy-1-trimethylsilyloxyethene proceeded with the catalysis of [Cation]Cl/MClx (M = Cu+, Fe3+, Zn2+ and Al3+) and [Cation]F, respectively. The cations and anions were observed to have significant effects on the yield and selectivity of MA, owing to the steric hindrance, acid site category and strength confirmed by pyridine probing FT-IR characterization. As a result, up to 60.2% yield with 94.6% selectivity of MA could be achieved when [N3,3,3,3]F and [N3,3,3,3]Cl/AlCl3 with 67 mol% AlCl3 were used in the presence of BSA at 25 °C. Kinetic studies indicated that the trioxane decomposition with the activation barrier of 41.2 ± 0.3 kJ mol-1 was the rate-determining step.
- Wang, Gang,Li, Zengxi,Li, Chunshan,Zhang, Suojiang
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p. 7913 - 7923
(2020/12/01)
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- Syntheses and anion binding capabilities of bis(diarylboryl) ferrocenes and related systems
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Isomeric diborylated ferrocenes featuring 1,1′-, 1,2-, and 1,3-substitution patterns have been targeted via a combination of electrophilic aromatic substitution and directed ortho-lithiation protocols. While none of these systems are competent for the Lewis acid chelation of fluoride, related systems featuring a mixed B/Si acceptor set capture 1 equiv of fluoride via a Si-F-B bridging motif.
- Kelly, Michael J.,Broomsgrove, Alexander E.J.,Morgan, Ian R.,Siewert, Inke,Fitzpatrick, Philip,Smart, Jessica,Vidovic, Dragoslav,Aldridge, Simon
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p. 2674 - 2684
(2013/06/26)
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- A naked eye detection of fluoride with urea receptors which have both an azo group and a nitrophenyl group as a signaling group
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Anion recognition via hydrogen-bonding interactions could be monitored with changes in UV-vis absorption spectra and in some cases easily monitored with naked eye. Urea receptors 1 and 2 connected with both an azo group and a nitrophenyl group as a signaling group for color change proved to be an efficient naked eye receptor for the fluoride ion. The anion recognition phenomena of the receptors 1 and 2 via hydrogen-bonding interactions were investigated through UV-vis absorption and 1H NMR spectra.
- Dang, Nhat Tuan,Park, Jin Joo,Jang, Soonmin,Kang, Jongmin
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body text
p. 1204 - 1208
(2010/09/10)
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- Encapsulated binding sites - Synthetically simple receptors for the binding and transport of HCl
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We report a receptor with an encapsulated amine/amide binding site, which binds HCl with high affinity in organic media - the rate of HCl transport through an apolar phase is controlled by the degree of encapsulation of the HCl binding site.
- Winstanley, Keith J.,Allen, Sarah J.,Smith, David K.
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scheme or table
p. 4299 - 4301
(2011/03/19)
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- Methods and Agents for Preparing 18F-Radiolabeled Fluorinating Agents
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The present invention is directed to a method for preparing an anhydrous 18F-radiolabeled fluorinating agent by a nucleophilic reaction of a hydrated 18F-radiolabeled fluoride ion source with an unsaturated carrier compound; treating the 18F-radiolabeled carrier compound to produce a non-aqueous mixture of the 18F-radiolabeled carrier compound in a solvent; and reacting the 18F-radiolabeled carrier compound with a nucleophilic composition in a nucleophilic reaction to produce an anhydrous 18F-radiolabeled fluorinating agent. The present invention is also directed to an anhydrous 18F-radiolabeled fluorinating agent comprising the formula [QnM]x+(18F?)x. Additionally, the present invention is directed to an 18F-radiolabeled fluorinated radiopharmaceutical or an 18F-radiolabeled fluorinated radiotracer prepared by reacting the anhydrous 18F-radiolabeled fluorinating agent with a drug intermediate. The present invention is further directed to methods for treating a disease or imaging a subject using an 18F-radiolabeled fluorinated radiopharmaceutical or an 18F-radiolabeled fluorinated radiotracer.
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(2008/06/13)
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- Fluoride relay: A new concept for the rapid preparation of anhydrous nucleophilic fluoride salts from KF
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Fluoride relay is used to generate exceptionally nucleophilic fluoride reagents from KF on a time scale commensurate with radiotracer synthesis. The Royal Society of Chemistry.
- Sun, Haoran,DiMagno, Stephen G.
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p. 528 - 529
(2007/10/03)
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- Room-temperature nucleophilic aromatic fluorination: Experimental and theoretical studies
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(Chemical Equation Presented) Taming the reagent: The use of anhydrous tetrabutylammonium fluoride (TBAFanh) in nucleophilic aromatic substitution reactions, including variants of the selective halogen-exchange and fluorodenitration processes (see scheme), was investigated. It was shown that TBAFanh permits these reactions to be performed under surprisingly mild conditions if it is used in relatively nonpolar media.
- Sun, Haoran,DiMagno, Stephen G.
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p. 2720 - 2725
(2007/10/03)
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- Anhydrous flouride salts and reagents and methods for their production
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Anhydrous organic fluoride salts and reagents prepared by a method comprising the nucleophilic substitution of a fluorinated aromatic or fluorinated unsaturated organic compound with a salt having the formula: [QnM]x+Ax?in an inert polar, aprotic solvent; wherein M is an atom capable of supporting a formal positive charge, the n groups Q are independently varied organic moieties, n is an integer such that the [QnM] carries at least one formal positive charge, x is an integer defining the number of formal positive charge(s), +, carried by the [QnM], A? is an anionic nucleophile capable of substituting for F in the fluorinated compound and F represents fluorine or a radioisotope thereof.
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Page/Page column 5
(2008/06/13)
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- Highly sensitive sensory materials for fluoride ions based on the dithieno[3,2-b:2′,3′-d]phosphole system
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The newly developed functionalization of an unsubstituted dithieno[3,2-b:2′,3′-d]phosphole at the 5,5′-positions gives access to bis(pinacoleboryl) species that can be utilized as sensory materials for fluoride ions. The fluoride-triggered response of the air- and moisture-stable boryl-functionalized dithienophosphole oxide manifests itself in the generation of a new fluorescence emission that can be detected at very low analyte concentrations (ppm) or even with the naked eye upon irradiation with UV light (366 nm).
- Neumann, Toni,Dienes, Yvonne,Baumgartner, Thomas
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p. 495 - 497
(2007/10/03)
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- Anhydrous tetrabutylammonium fluoride
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Tetrabutylammonium fluoride (TBAF) is prepared at low temperature by nucleophilic aromatic substitution of hexafluorobenzene with tetrabutylammonium cyanide. Adventitious water is scavenged during this synthesis by the generated hexacyanobenzene, which readily adds water under basic conditions. Contrary to expectations, TBAF is stable to Hofmann elimination in polar aprotic solvents under anhydrous conditions. Added hydroxylic solvents are shown to catalyze the decomposition of TBAF and to catalyze proton exchange with DMSO. The synthetic utility of this salt is described briefly. Copyright
- Sun, Haoran,DiMagno, Stephen G.
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p. 2050 - 2051
(2007/10/03)
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- Homocoupling of aryl halides promoted by tetrabutylammonium fluoride
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The palladium-catalysed homocoupling of aryl halides takes place in the presence of anhydrous, in situ generated, tetrabutylammonium fluoride (TBAF).
- Albanese, Domenico,Landini, Dario,Penso, Michele,Petricci, Silvia
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p. 199 - 200
(2007/10/03)
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- Vitamin D analogues having a halogen-or azido- substituted side chain
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A compound of formula I STR1 wherein R stands for a straight or branched, saturated or unsaturated alkyl group containing from 4 to 12 carbon atoms optionally substituted with a hydroxy group, and possibly containing a ring structure, and in which at least one of the carbon atoms not bearing hydroxyl group is substituted with one or more halogen atoms or an azido group; and prodrugs of I in which one or more of the hydroxy groups are masked as groups which can be reconverted to hydroxy groups in vivo, in pure form or in mixtures. The compounds show antiinflammatory and immunomodulating effects as well as strong activity in inducing differentiation and inhibiting undesirable proliferation of certain cells. The compounds are prepared by oxidizing 1(S),3(R)-bis-(tert-butyldimethylsilyloxy)-20(S)formyl-9,10-seco-pregna-5(E),7(E),10(19)-triene, reducing the resulting product; alkylating the reduction product and then subjecting the alkylated product to triplet-sensitized photoisomerization.
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- Vitamin D analogues
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Vitamin D analogues of the formula: STR1 wherein X is hydrogen or hydroxy; R1 and R2 are each hydrogen or C1 -C6 hydrocarbyl or R1 and R2 together with the starred carbon form a C3 -C8 carbocyclic ring; Q is a single bond or a C1 -C8 hydrocarbylene diradical; and m is 0, 1 or 2. One of the m carbons designated by ° may be optionally substituted with deuterium, fluorine or C1 -C2 alkyl. R1, R2 and/or Q may also be substituted with deuterium or fluorine. The analogues show, for example, anti-inflammatory and immunomodulating effects.
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- Vitamin D analogues
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The invention relates to compounds of formula I STR1 in which formula X is hydrogen or hydroxy; Y is oxygen, sulphur, or oxidized sulfur (S(O) or S(O2)); R1 and R2, which may be the same or different, stand for hydrogen or C1 -C6 hydrocarbyl, or R1 and R2, taken together with the carbon atom (starred in formula I) bearing the group X, form a C3 -C8 carbocyclic ring; Q is a C1 -C8 hydrocarbylene diradical. R3 is hydrogen or C1 -C6 hydrocarbyl. R1, R2 and/or Q, may be optionally substituted with one or more deuterium or fluorine atoms; n is 0 or 1. The present compounds show antiinflammatory and immunomodulating effects as well as a strong activity in inducing cell differentiation and inhibiting undesirable proliferation of certain cancer and skin cells.
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- Kristallstruktur und Schwingungsspektren von 2*2(C2H5)2O
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The dark blue title compound has been prepared by reaction of 2- and F-, both dissolved as ion pairs with + in anhydrous CH2Cl2, and recrystallization from acetone/diethylether.Structure determination by single crystal X-ray diffractometry at 150 K reveals crystallization in the cubic system, space group Pnn with a = 19.873(3) Angstroem, V = 7742.4 Angstroem3, Z=6.The *O(C2H5)2>2- entity consists of an axially elongated F8-cubane frame around the Re2 unit, which is coordinated at one side by an ether molecule (Re-O distance2.64(4) Angstroem) and displaced from the center towards the ether.The Re-Re quadruple bond (2.188(3) Angstroem) is the shortest of the four octahalogenodirhenates(III).In contrast to its Cl, Br and I homologues no disorder of the Re2 units is observed.The Re-F distances of 1.92(3) and 1.96(3) Angstroem are equal within the standard error, and the Re-Re-F angles are 99.9(4) deg and 102.6(4) deg, respectively.The UV-Vis spectrum of 2 shows only the δ-δ* transition at 558 nm (ε=771 cm2/mmol).At 10 K this band exhibits a weak vibrational fine structure with an averaged progression of 209 cm-1.The Raman spectrum is dominated by ν(Re-Re) at 317.5 cm-1 with up to five overtones, the IR spectrum by ν(Re-F) at 560 cm-1.Additional bands for the solvated compound at 525 and 306 cm-1 are assigned to ν(Re-O) and ν(Re-Re), respectively.The 19F NMR spectrum in aceton-d6 shows a singlet at -135.06 ppm; in the presence of ether an additional weak signal arises at -134.15 ppm versus external CFCl3.
- Henkel, G.,Peters, G.,Preetz, W.,Skowronek, J.
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p. 469 - 475
(2007/10/02)
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- Synthesis of Quaternary Ammonium Fluoride Salts by a Solid-Liquid Halogen Exchange Process in Protic Solvents
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Both hydrophilic and lipophilic quaternary ammomium fluoride compounds are prepared by direct exchange of the corresponding halides with solid potasium fluoride containing an optimized amount of water (4.0 mol percent).The procedure is most effective when methanol is applied as a solvent.A variety of quaternary ammonium fluorides were prepared in 75-97percent yield.
- Dermeik, Salman,Sasson, Yoel
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p. 4827 - 4829
(2007/10/02)
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- Silyl Nitronates in Organic Synthesis. Silylation of Secondary Nitro Compounds. Preparation of Nitroso Compounds and α,β-Unsaturated Aldehydes
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Secondary nitro compounds can be silylated by triethylamine and chlorotrimethylsilane in acetonitrile as solvent.The silyl nitronates add to olefins forming 3,3-disubstituted isoxazolidines, which can be rearranged to tertiary nitroso compounds.Addition of the secondary nitronates to acrylonitrile and subsequent treatment with fluoride ion leads to β,β-unsaturated aldehydes.
- Mukerji, Somir K.,Torssell, Kurt B. G.
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p. 643 - 648
(2007/10/02)
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- Radikale durch Oxidation von λ5-Phosphorin-Derivaten
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λ5-Phosphorins 1 with exocyclic OCH3-substituents are oxidized electrolytically or by oxidants first to the less stable cation radicals 2 and then by CH3+-splitting into the very stable neutral radicals 3. λ5-Phosphorins with F or N(CH3)2 at the P-atom give immediately the neutral radicals 7 and 13, resp.In the presence of fluorine ions 1,1-difluoro-λ5-phosphorin 5a is oxidized to the cation radical 6a which by water affords the neutral radical 7a.The small αP of the ESR spectra prove that the cation- and the neutral radicals are cyclohexadienyl radicals.The P-atom is not involved in the delocalization of the unpaired electron.By synthesis of the C-2/6 or C-4 13C-labelled 2,4,6-tri-tert-butyl-1,1-dimethoxy-λ5-phosphorin (1c), the 13C-coupling constants of the generated radicals (2c and 3c) could be measured and compared with those of known iso- and heterocyclic cyclohexadienyl radicals.
- Dimroth, Karl,Heide, Wilfried
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p. 3004 - 3018
(2007/10/02)
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- Fluoride ion catalyzed alkylation of purines, pyrimidines, nucleosides and nucleotides using alky halides.
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Alkyl halides react rapidly with purines and pyrimidines in the presence of fluoride ion. Alkylation of thymidine leads to novel dimeric nucleoside derivatives bridged through N3. Alkylation of thymidine mono and dinucleotides leads to alkylation at the base (N3) as well as diester and triester formation at the phosphate.
- Ogilvie,Beaucage,Gillen,Entwistle,Quilliam
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p. 1695 - 1708,1696, 1703
(2007/10/05)
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