- 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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- Constructing a catalytic cycle for c-f to c-x (x = o, s, n) bond transformation based on gold-mediated ligand nucleophilic attack
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A tricoordinated gold(I) chloride complex, tBuXantphosAuCl, supported by a sterically bulky 9,9-dimethyl-4,5-bis(di-Tert-butylphosphino)xanthene ligand (tBuXantphos) was synthesized. This complex features a remarkably longer Au?Cl bond length [2.632(1) ?] than bicoordinated linear gold complexes (2.27-2.30 ?) and tricoordinated XantphosAuCl [2.462(1) ?]. Single-crystal Xray diffraction analysis of a cocrystal of tBuXantphosAuCl and pentafluoronitrobenzene (PFNB) and UV-vis spectroscopic titration experiments revealed the existence of an anion-φ interaction between the Cl anion ligand and PFNB. Stoichiometric reaction between PFNB and tBuXantphosAuOtBu, after replacement of Cl by a more nucleophilic tBuO anion ligand, showed higher reactivity and para selectivity in the transformation of C-F to C-OtBu bond, distinctively different from that when only KOtBu was used (ortho selectivity) under the identical condition. Mechanistic studies including density functional theory calculations suggested a gold-mediated nucleophilic ligand attack of the C?F bond pathway via an SNAr process. On the basis of these results, using trimethylsilyl derivatives TMS-X (X = OMe, SEt, NEt) as the nucleophilic ligand source and the fluorine acceptor, catalytic transformation of the C-F bond of aromatic substrates to the C-X (X = O, S, N) bond was achieved with tBuXantphosAuCl as the catalyst (up to 20 turnover numbers).
- Hu, Ji-Yun,Zhang, Jing,Wang, Gao-Xiang,Sun, Hao-Ling,Zhang, Jun-Long
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supporting information
p. 2274 - 2283
(2017/01/16)
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- N-(2-ARYLETHYL) BENZYLAMINES AS ANTAGONISTS OF THE 5-HT6 RECEPTOR
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The present invention relates to the use compounds of formula I which are antagonists of the 5-HT 6 receptor, for treating a cognitive disorder selected from the group consisting of age-related cognitive decline, mild cognitive impairment and dementia
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Paragraph 0223
(2016/01/25)
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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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- Synthesis of COX-2 and FAAH inhibitors
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Methods for preparing indoles that are useful COX-2 inhibitors and intermediates useful in such methods are described.
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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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- 2,6-difluorophenol as a bioisostere of a carboxylic acid: Bioisosteric analogues of γ-aminobutyric acid
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3-(Aminomethyl)-2,6-difluorophenol (6) and 4-(aminomethyl)-2,6- difluorophenol (7) were synthesized in eight and four steps, respectively, starting from 2,6-difluorophenol, to test the potential of the 2,6- difluorophenol moiety to act as a lipophilic bio
- Qiu, Jian,Stevenson, Scott H.,O'Beirne, Michael J.,Silverman, Richard B.
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p. 329 - 332
(2007/10/03)
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- Charge control in the S(N)Ar reaction. Meta substitution with respect to the activating nitro group in 3,4-dihalogenonitrobenzenes
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The reactions of 3-fluoro-4-chloronitrobenzene and of 3,5-difluoro-4-chloronitrobenzene with thiophenoxide anion lead to predominant substitution of the chlorine atom through S(N)Ar orbital-controlled processes. However, when harder nucleophiles (methoxide anion) are used, the substitution of a fluorine atom meta with respect to the activating nitro group becomes apparent in the reaction of 3-fluoro-4-chloronitrobenzene, predominant in the reaction of 5-fluoro-4-chloro-3-methyoxynitrobenzene, and almost exclusive in the reaction of 3,5-difluoro-4-chloronitrobenzene. Kinetic measurements and theoretical calculations indicate that the observed meta substitution of a fluorine atom is a S(N)Ar charge-controlled reaction with a loosely bonded transition state.
- Cervera,Marquet,Martin
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p. 2557 - 2564
(2007/10/03)
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- The effect of fluorine substitution on the physicochemical properties and the analgesic activity of paracetamol
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The physicochemical properties and analgesic action of six fluorinated analogues of 4-hydroxyacetanilide (paracetamol) have been investigated. Fluorine substitution adjacent to the hydroxyl group increased lipophilicity and oxidation potential whilst substitution adjacent to the amide had little effect on lipophilicity but led to a greater increase in oxidation potential. Lack of coplanarity and conjugation of the amide group and aromatic ring was also apparent with the analogues that had fluorine in the 2 and 6 positions. Introduction of fluorine into the amide group of paracetamol increased the lipophilicity 4-fold and also increased the oxidation potential of paracetamol. ED50 values for analgesic activity in the phenylquinone-induced abdominal constriction test on male Swiss White mice showed that ring substitution by fluorine reduced activity, especially at the 2,6-positions. Introduction of fluorine into the amide group enhanced activity significantly. Correlation of the analgesic activity with the physicochemical properties indicated that conjugation (and planarity) of the amide group with the aromatic ring is essential for activity and that ease of oxidation may also be an important factor.
- Barnard,Storr,O'Neill,Park
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p. 736 - 744
(2007/10/02)
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