- Fluorination of 4-alkyl-substituted phenols and aromatic ethers with fluoroxy and N-F reagents: Cesium fluoroxysulfate and N-fluoro-1,4-diazonia- bicyclo[2.2.2]octane dication salts case Dedicated to Prof. Dr. Boris ?emva in honor to his great contribution to fluorine chemistry.
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4-Alkyl-substituted phenols and aromatic ethers were comparatively fluorinated with electrophilic fluorinating reagents such as cesium fluoroxysulfate (CFS), Selectfluor F-TEDA-BF4, and Accufluor NFTh in MeCN or MeOH. Reactions resulted in the formation of three types of products: 2-fluoro-4-alkyl-substituted corresponding compounds (5) as a result of ortho fluorination process, 4-alkyl-4-fluoro-cyclohexa-2,5- dienone compounds (6), resulting after an addition-elimination process, and 4-fluorosubstituted corresponding compounds (7) derived from ipso attack and release of the 4-alkyl group. The distribution of products depends on the bulkiness of alkyl groups at both positions and reaction media. The reaction in methanol proved more selective toward the formation of 2-fluoro derivatives. Tyramin and l-tyrozine were transformed with NFTh reagent in methanol to their fluorophenyl-substituted derivatives in good yield.
- Pravst, Igor,Stavber, Stojan
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p. 276 - 282
(2014/01/06)
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- Metal-Catalyzed Carbon-Fluorine Bond Formation
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One aspect of the invention relates to a metal-catalyzed conversion of aryl halides and sulfonates to the corresponding aryl fluorides. Another aspect of the invention relates to a metal-catalyzed conversion of heteroaryl halides and sulfonates to the corresponding heteroaryl fluorides. Another aspect of the invention relates to a metal-catalyzed conversion of vinyl halides and sulfonates to the corresponding vinyl fluorides. In certain embodiments, simple fluoride sources, such as AgF and CsF, are used. In certain embodiments, the transformations tolerate a wide range of functional groups, allowing for introduction of fluorine atoms into highly functionalized organic molecules.
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Page/Page column 18
(2011/02/18)
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- Fluorination of aromatic compounds with N-fluorobenzenesulfonimide under solvent-free conditions
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Reactions of N-fluorobenzenesulfonimide with methylbenzenes, phenols, and phenol ethers were studied under solvent-free conditions. The rate constant ratio for the reactions with mesitylene and durene indicates polar mechanism of the process. Solvent-free fluorination of aromatic compounds with N-fluorobenzenesulfonimide in some cases is more selective than reactions with other N-F reagents in a solvent.
- Andreev,Borodkin,Shubin
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scheme or table
p. 1468 - 1473
(2010/03/24)
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- First application of ionic liquids in electrophilic fluorination of arenes; Selectfluor (F-TEDA-BF4) for "green" fluorination
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The NF fluorinating agent F-TEDA-BF4 dication salt (Selectfluor) 1 dissolves in imidazolium-based ionic liquids [emim][OTf] 7, [emim][BF4] 8, [bmim][PF6] 9 and [bmim][BF4] 10 (assisted by sonication), providing a convenient medium for fluorination of arenes under essentially acid-free conditions in a simple set-up (no volatile solvent; simple extraction of the aromatics without aqueous work-up), from which the ionic liquid can be easily recycled and reused. Comparative studies in [emim][OTf] 7 with anisole as substrate show that 1 is superior to NFTh-BF4 (Accufluor) 2 and that the N-fluoropyridinium salt NFPy-B2F7 4 is least effective. The scope of the reaction has been surveyed. Substrate selectivity (k mesitylene: k durene = 10) measured in competitive experiments in 7 is clearly indicative of a conventional polar mechanism. Substrate selectivity measured without the ionic liquid in MeCN solvent is also indicative of a polar mechanism but exhibits lower magnitude (k mesitylene: kdurene = 6). Addition of dicyclohexano-24-crown-8 to the fluorination reaction mixture (1 and anisole) in 7 reduced the conversion but did not change the isomer distribution. AM1 minimization was used to model the complexation of 1 with this crown. With reactive aromatics optimal fluorination yields in ionic liquids (using 1 equivalent of the NF reagent) are around 50% (higher for naphthalene). A key control experiment suggests that the free base (produced upon transfer-fluorination) could complex to unreacted 1 (generating a bulky dimer complex which may be ineffective for fluorine transfer) in competition to N-protonation.
- Laali, Kenneth K.,Borodkin, Gennady I.
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p. 953 - 957
(2007/10/03)
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- α-arylation of 2-arylacetates and benzofuran-2-one with tricarbonyl(fluoroarene)chromium complexes
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In order to synthesise fragments of the natural product diazonamide A, α-arylation of 2-arylacetates 3 and benzofuran-2-one with the aid of the tricarbonyl(fluoroarene)chromium complex rac-2 was investigated. After decomplexation of the products rac-4 and
- Schley, Daniela,Radspieler, Alexander,Christoph, Guido,Liebscher, Juergen
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p. 369 - 374
(2007/10/03)
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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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- Substituent modulation of mild fluorination of aromatic molecules with caesium fluoroxysulphate
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Functionalization of mono- and di-substituted benzene derivative with CsSO4F has been modulated by substituents on the benzene ring. α-Hydroxyalkylbenzenes, with a deactivated ring, were oxidized to phenones, while fluorodealkylation was achieved in high yield when electron-donating groups were present in a para position. Electron-withdrawing substituents favoured chain fluorofunctionalization in alkylbenzenes, while ring fluorination was found exclusively in acylamino-derivatized alkylbenzenes; fluoro-addition products were formed in the case of p-alkoxy-substituted alkylbenzene derivatives.
- Stavber, Stojan,Planinsek, Zdenka,Kosir, Iztok,Zupan, Marko
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p. 409 - 412
(2007/10/02)
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