- Synthesis of 2 - fluoro phenol compounds
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The present invention provides a method for synthetizing a 2-fluoro phenol compound shown in a formula IV. The phenol compound shown in the formula I is prepared into a 2-pyridine oxygroup arene compound shown in a formula II through an Ullmann reaction, the 2-pyridine oxygroup arene compound shown in the formula II is mixed with a palladium catalyst, a fluorinating reagent, an additive and an organic solvent, the mixture is stirred under the temperature of 30-160 DEG C to perform a fluorination reaction to obtain an ortho-position fluoridated 2-pyridine oxygroup arene compound shown in a formula III, and the ortho-position fluoridated 2-pyridine oxygroup arene compound shown in the formula III is prepared into the 2-fluoro phenol compound shown in the formula IV through the action of alkali. The method provided by the present invention has the advantages of mild reaction conditions, simplicity in operations, good substrate adaptability, high fluorination selectivity and the like. The 2-fluoro phenol compound is shown in the figure below.
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- Design of chemical shift-switching 19F magnetic resonance imaging probe for specific detection of human monoamine oxidase A
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Monoamine oxidase (MAO) A is a flavoenzyme that catalyzes the oxidation of biologically important monoamines and is thought to be associated with psychiatric disorders. Here, we report a strategy for rationally designing a 19F magnetic resonanc
- Yamaguchi, Koya,Ueki, Ryosuke,Nonaka, Hiroshi,Sugihara, Fuminori,Matsuda, Tetsuya,Sando, Shinsuke
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supporting information; experimental part
p. 14208 - 14211
(2011/10/31)
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- The element effect and nucleophilicity in nucleophilic aromatic photosubstitution (SNAR*). Local atom effects as mechanistic probes of very fast reactions
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(Chemical Equation Presented) Photoreactions of 4-nitroanisole and the 2-halo-4-nitroanisoles (halogen = F, Cl, Br, and I) with the nucleophiles hydroxide ion and pyridine have been investigated quantitatively to extend the findings recently communicated for cyanide ion. The halonitroanisoles on excitation form triplet π,π* states, which undergo substitution of the halogen by nucleophiles. Chemical yields of photoproducts, Stern-Volmer kinetic plots, triplet lifetimes, and triplet yields are reported for the five compounds with the three nucleophiles. Following a standard kinetic treatment, 73 rate constants are determined for elementary reactions of the triplets including quenching and various nucleophilic addition processes. The photoadditions are roughly 14 orders of magnitude faster than thermal counterparts. Rate constants for attack at the fluorine-bearing carbon of triplet 2-fluoro-4-nitroanisole are 2.9 × 109, 1.3 × 109, and 6.3 × 108 M-1 s-1 for cyanide ion, hydroxide ion, and pyridine, respectively. The relative rates for attack at the halogen-bearing carbons for F/Cl/Br/I are 27:1.9:1.9:1 (cyanide ion), 29:2.6:2.4:1 (hydroxide ion), and 39:3.9: 3.5:1 (pyridine), respectively. The relative nucleophilicities vary somewhat with the attack site; they are about 5:2:1 for cyanide ion, hydroxide ion, and pyridine for attack at the halogen-bearing carbons. The trend of the element effect opposes that of aliphatic substitution and elimination but is similar in size and parallel to that of thermal nucleophilic aromatic substitution. Relative nucleophilicities in the photoreactions are also similar to those of comparable but vastly slower thermal reactions. The findings imply that the efficiency-determining step of the halogen photosubstitution is simple formation of a σ-complex through electron-paired bonding within the triplet manifold.
- Wubbels, Gene G.,Brown, Toby R.,Babcock, Travis A.,Johnson, Kandra M.
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p. 1925 - 1934
(2008/09/19)
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- Elemental fluorine. Part 20. Direct fluorination of deactivated aromatic systems using microreactor techniques
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Continuous flow microreactor technology has been used for the direct fluorination of a range of deactivated di- and tri-substituted aromatic systems.
- Chambers, Richard D.,Fox, Mark A.,Sandford, Graham,Trmcic, Jelena,Goeta, Andres
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- Elemental fluorine Part 12. Fluorination of 1,4-disubstituted aromatic compounds
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Direct fluorination of a series of 1,4-disubstituted benzene derivatives in acid reaction media at convenient temperature leads, in many cases, to selectively fluorinated aromatic products in preparatively useful conversions and yields.
- Chambers, Richard D.,Hutchinson, John,Sparrowhawk, Matthew E.,Sandford, Graham,Moilliet, John S.,Thomson, Julie
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p. 169 - 173
(2007/10/03)
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- Hydroxylation of Nitroarenes with Alkyl Hydroperoxide Anions via Vicarious Nucleophilic Substitution of Hydrogen
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Rhone-Poulenc Polska Ltd., ul. Grzybowska 80/82, 00-844 Warszawa, Poland Garbo- and heterocyclic nitroarenes react with anions of tert-butyl and cumyl hydroperoxides in the presence of strong bases to form substituted o- and p-nitrophenols. The reaction usually proceeds in high yields and is of practical value as a method of synthesis and manufacturing of nitrophenols. Orientation of the hydroxylation can be controlled to a substantial extent by selection of the proper conditions. Basic mechanistic features of this process were clarified.
- Makosza, Mieczyslaw,Sienkiewicz, Krzysztof
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p. 4199 - 4208
(2007/10/03)
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- Electrophilic Fluorination Using Elemental Fluorine
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Electrophilic fluorination by elemental fluorine is promoted by the use of protonic acids; formic and sulfuric acids are especially effective.
- Chambers, Richard D.,Skinner, Christopher J.,Thomson, Julie,Hutchinson, John
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- Power and structure-variable fluorinating agents. The N-fluoropyridinium salt system
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The usefulness of the N-fluoropyridinium salt system as a source of fluorinating agents was examined by using substituted or unsubstituted N-fluoropyridinium triflates 1-11, N-fluoropyridinium salts possessing other counteranions 1a-d and 3a, and the counteranion-bound salts, N-fluoropyridinium-2-sulfonates 12 and 13. Electrophilic fluorinating power was found to vary remarkably according to the electronic nature of the ring substituents. This power increased as the electron density of positive nitrogen sites decreased, and this was correlated to the pKa values of the corresponding pyridines. By virtue of this variation, it was possible to fluorinate a wide range of nucleophilic substrates differing in reactivity. It is thus possible to fluorinate aromatics, carbanions, active methylene compounds, enol alkyl or silyl ethers, vinyl acetates, ketene silyl acetals, and olefins through the proper use of salts pentachloro 6 through 2,4,6-trimethyl 2, their power decreasing in this order. All the reactions could be explained on the basis of a one-electron-transfer mechanism. N-Fluoropyridinium salts showed high chemoselectivity in fluorination, the extent depending on the reactive moiety. In consideration of these Findings, selective 9α-fluorination of steroids was carried out by reacting 1 with tris(trimethylsilyl ether) 73 of a triketo steroid. Regio- or stereoselectivity in fluorination was determined by a N-fluoropyridinium salt structure. Steric bulkiness of the N-F surroundings hindered the ortho fluorination of phenols and aniline derivatives, while the capacity for hydrogen bonding on the part of the counteranions prompted this process, and the counteranion-bound salts 12 and 13 underwent this fluorination exclusively or almost so. Both bulky N-fluoropyridinium triflates 2 and 7 preferentially attacked the 6-position of the conjugated vinyl ester of a steroid from the unhindered β-direction to give a thermally unstable 6β-fluoro isomer. On the basis of these results, N-fluoropyridinium salts may be concluded to constitute a system that can serve as a source of the most ideal fluorinating agents for conducting desired selective fluorination through fluorinating capacity or structural alteration.
- Umemoto, Teruo,Fukami, Shinji,Tomizawa, Ginjiro,Harasawa, Kikuko,Kawada, Kosuke,Tomita, Kyoichi
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p. 8563 - 8575
(2007/10/02)
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- Hydroxylation of Nitroarenes with Alkyl Hydroperoxide Anions via Vicarious Nucleophilic Substitution of Hydrogen
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tert-Butyl and cumyl hydroperoxides in strongly basic media react with a variety of nitroarenes to produce o- and/or p-nitrophenols.The reaction proceeds via an addition-base-induced β-elimination pathway analogous to that of vicarious nucleophilic substitution.
- Makosza, Mieczyslaw,Sienkiewicz, Krzysztof
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p. 4979 - 4981
(2007/10/02)
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- Formation of 4-Halo-4-nitrocyclohexa-2,5-dienones on Nitration of p-Halophenols and p-Halophenyl Acetates.
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Nitration of p-chloro-, p-fluoro-, and p-bromo-phenol or the corresponding p-halophenyl acetates at -40 deg C and below gives the 4-halo-4-nitrocyclohexa-2,5-dienones in addition to the 4-halo-2-nitrophenols.The dienones isomerize to the nitrophenols at temperatures between -40 deg C and 0 deg C.Nitration of 4-chloro-2-methylphenol or its acetate gives both 4-chloro-2-methyl-4-nitrocyclohexa-2,5-dienone and 4-chloro-6-methyl-6-nitrocyclohexa-2,4-dienone. 4-Chloro-3-methylphenol and its acetate give 4-chloro-3-methyl-4-nitrocyclohexa-2,5-dienone.
- Clewley, Robin G.,Cross, Gordon G.,Fischer, Alfred,Henderson, George N.
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p. 1299 - 1310
(2007/10/02)
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- Certain 3,5-disubstituted-2-pyridyloxy-fluorophenoxy-alkanoic acids, derivatives thereof and herbicidal properties
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Certain novel fluorophenoxy compounds, principally aryloxyfluorophenoxyalkanoic acids and derivatives thereof, are described. More specifically, these novel compounds bear 1 to 4 fluorine substituents on the phenyl ring. These novel compounds exhibit surprising preemergent and postemergent activity when used according to the method of the invention in the control of grassy weeds.
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- A Novel Electrophilic Fluorination of Activated Aromatic Rings Using Acetyl Hypofluorite, Suitable also for Introducing (18)F into Benzene Nuclei
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Acetyl hypofluorite (1) is a new compound that serves as a novel electrophilic fluorinating agent.It is special in the sense that, while it is very reactive, it is still a milder reagent than other fluoroxy compounds such as CF3OF or CF3COOF.It is synthesized directly from elemental fluorine and is used without any isolation or purification.The hypofluorite 1 reacts efficiently and selectively with activated aromatic rings,particularly phenol and aniline derivatives after suitable protection of the hydroxyl and the amino groups.The net result of the reaction is partly according to classical aromatic electrophilic substitution.Unlike such a substitution, however, the electrophilic fluorine atom of 1 substitutes mainly an ortho hydrogen and only occasionally small amounts of p-fluoro derivatives are found.Evidence supports the mechanism for this aromatic fluorination as being mainly an addition-elimination one.In many cases the electrophilic aromatic fluorinations can replace the classical 60-year-old Balz-Schiemann method, which until today is probably the most used procedure.Since aromatic fluorination with 1 is a very fast reaction and since 1 is produced directly from elemental fluorine, this is probably one of the best ways for introduction of the short-living radioisotope (18)F into activated aromatic rings.This will greatly encourage the synthesis of compounds suitable for use in the rapidly developing field of positron emitting transaxial tomography, which in itself depends on the efficient and easy supply of compounds possessing positron emitting isotopes.
- Lerman, Ori,Yitzhak, Tor,Hebel, David,Rozen, Shlomo
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p. 806 - 813
(2007/10/02)
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- Etude des complexes du cobalt (II) transporteurs d'oxygene: Nouvelle synthese du fluoro-3 hydroxy-2 benzaldehyde
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Synthetic chelates of cobalt (II) derived from Schiff bases have remarkable behavior of reversibly absorbing and releasing molecular oxygene.Among these, bis (3-fluorosalicylaldehydeethylenediimide) Co (II) (fluomine: Formula A, X=F) is most interesting in allowing to isolate pure oxygen from air, because it absorbs with extreme rapidity 4.43percent of its weight of oxygen.Fluomine is easily prepared from 3-fluorosalicylaldehyde (3FSA), ethylenediamine and cobalt (II) chloride; but substances such as 3-substituted salicylaldehydes have proven to be extremely difficult to prepare in other than small laboratory quantities from the corresponding ortho-substituted phenol.Many author have prepared 3-fluorosalicylaldehyde, as described in patents, but often these syntheses are very long and the yields are generally less than 20percent.We now describe a new synthesis from o-fluorophenol.Nitration of o-fluorophenol with liquid nitrogen dioxide is convenient: - on the one hand, ortho-substitution to the hydroxyl group, is easy, -on the other hand, the para substituted by-product, is reinserted in the course of the synthesis, so that it is possible to minimize loss of the starting phenol, an expensive product. o-Fluorophenol 1 in solution in pentane, at about 0 deg C, is treated with liquid nitrogen dioxide (slight excess).The reaction is rapid and leads to 2-fluoro 6-nitrophenol 2 which remains in solution, and 2-fluoro 4-nitrophenol 7 which cristallizes rapidly (approximatively 50percent of each one). 2-Fluoro 6-nitrophenol 2 is converted into the anisole 3, the NO2 group of which is catalytically reduced by hydrogen into 3-fluoro 2-methoxy-aminobenzene 4.This amine 4 is diazotized, and treated with formaldoxime to lead to 3-fluoro 2-methoxybenzaldehyde 5 (Eb12 = 82 deg C). 3FSA is finally obtained by heating under reflux anisole 5 and a solution of hydrobromic acid (48percent). 2-Fluoro 4-nitrophenol 7 is converted in five steps into 3-fluoro 2-methoxyaminobenzene 4 by the same reactions as these used for its isomer.Finally the total yield of amine 4 from o-fluorophenol is 73percent, and 3FSA is obtained in 25percent yield.No primary amines are required during the isolation, so that no possible contamination of the final product is possible and therefore the fluomine prepared therefrom is not contaminated and deactivated.
- Aymes, Daniel J.,Paris, Michel R.
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p. 175 - 178
(2007/10/02)
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- Tetrahydrocarbazoles and their use
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There are disclosed novel 3-amino(and substituted amino)-hydroxy (and dihydroxy)-1,2,3,4-tetrahydrocarbazoles having positive inotropic activity and methods and compositions for the use thereof in treating the failing heart in mammals afflicted with conge
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