- Synthetic method for 2,4,6-trifluorophenol
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The invention relates to the technical field of organic synthesis, in particular to a synthetic method for 2,4,6-trifluorophenol. The synthetic method comprises the following steps of (1) sequentiallyperforming hydrogen removal reaction and reaction with
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- Catalytic defluorination of perfluorinated aromatics under oxidative conditions using N-bridged diiron phthalocyanine
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Carbon-fluorine bonds are the strongest single bonds in organic chemistry, making activation and cleavage usually associated with organometallic and reductive approaches particularly difficult. We describe here an efficient defluorination of poly- and perfluorinated aromatics under oxidative conditions catalyzed by the μ-nitrido diiron phthalocyanine complex [(Pc)Fe III(μ-N)FeIV(Pc)] under mild conditions (hydrogen peroxide as the oxidant, near-ambient temperatures). The reaction proceeds via the formation of a high-valent diiron phthalocyanine radical cation complex with fluoride axial ligands, [(Pc)(F)FeIV(μ-N)FeIV(F) (Pc+?)], which was isolated and characterized by UV-vis, EPR, 19F NMR, Fe K-edge EXAFS, XANES, and Kβ X-ray emission spectroscopy, ESI-MS, and electrochemical techniques. A wide range of per- and polyfluorinated aromatics (21 examples), including C6F6, C6F5CF3, C6F5CN, and C6F5NO2, were defluorinated with high conversions and high turnover numbers. [(Pc)FeIII(μ-N)Fe IV(Pc)] immobilized on a carbon support showed increased catalytic activity in heterogeneous defluorination in water, providing up to 4825 C-F cleavages per catalyst molecule. The μ-nitrido diiron structure is essential for the oxidative defluorination. Intramolecular competitive reactions using C6F3Cl3 and C6F3H 3 probes indicated preferential transformation of C-F bonds with respect to C-Cl and C-H bonds. On the basis of the available data, mechanistic issues of this unusual reactivity are discussed and a tentative mechanism of defluorination under oxidative conditions is proposed.
- Colomban, Cédric,Kudrik, Evgenij V.,Afanasiev, Pavel,Sorokin, Alexander B.
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supporting information
p. 11321 - 11330
(2014/11/07)
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- Kinetics and mechanisms of the photolytic and OH° radical induced oxidation of fluorinated aromatic compounds in aqueous solutions
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Laboratory experiments with H2O2/UV oxidation processes and photolysis at 253.7 nm wavelength have been carried out on dilute aqueous solutions (C0 = 0.1 to 3.0 mM) of trifluorobenzene derivatives (1,3,5-trifluorobenzene, 1,2,3 and 1,2,4-trifluorobenzene) and of α,α,α-trifluorotoluene in the presence and in the absence of dissolved oxygen. The analyses of fluoride ions content during the oxidation experiments showed that the first steps lead to the production of about 2 mol of F-/mol of trifluorobenzene decomposed and of 1 mol of F-/mol of trifluorotoluene decomposed. Kinetic studies lead to the determination of the quantum yield for the photolysis of 1,3,5-trifluorobenzene, 1,2,3 and 1,2,4-trifluorobenzene (Φ = 0.011, 0.010 and 0.015 respectively), and of trifluorotoluene (Φ = 0.015). The rate constants for the reaction of hydroxyl radicals with these molecules, determined under specific experimental conditions, were found to range from 3.7 109 to 4.9 109 M-1.s-1). GC/MS analyses carried out on extracts at different irradiation time (UV, H2O2/UV) lead to the identification of numerous by-products from trifluorobenzene and trifluorotoluene. They consist mostly in hydroxylated and dehalogenated compounds. Dimers have also been observed during photolysis. Moreover, experiments carried out under oxygen limiting conditions revealed the formation of other compounds. For each case studied, a detailed mechanism involving radical intermediates and the different reaction sequences is proposed.
- Karpel vel Leitner,Gombert,Ben Abdessalem,Dore
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p. 893 - 906
(2007/10/03)
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