- Dehalogenation degradation method for halogenated pyridine compound
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The invention provides a dehalogenation degradation method for a halogenated pyridine compound. The halogenated pyridine compound is adopted as a raw material, alcohol is adopted as a hydrogen source, water is adopted as a solvent, reacting is carried out for 3-10 h under normal pressure at the temperature of 20 DEG C to 120 DEG C under the action of a supported catalyst, and the halogenated pyridine compound is subjected to dehalogenation degradation in situ through water phase hydrogen production. A pyridine ring of the halogenated pyridine compound at least contains an F or Cl or Br or I substituent group. The supported catalyst is composed of an active component and a carrier, the active component is composed of a mixture of transition metal and other metal, the transition metal is one of Rh, Pd, Pt and Ni, and other metal is one of Se, Ca, Ba, La and Ce. The carrier is one of activated carbon, kieselguhr, zeolite, gamma-Al2O3, AlF3 and MgO. H2 is not directly used as a reduction agent, activated hydrogen is prepared through in-situ catalysis to directly participate in reacting, the advantages of being high in reaction activity, high in selectivity, high in safety, environmentally friendly and the like are achieved, and good application prospects are achieved.
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Paragraph 0019; 0020
(2016/12/16)
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- Catalytic hydrodefluorination of fluoroaromatics with silanes as hydrogen source at a binuclear rhodium complex: Characterization of key intermediates
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Stoichiometric and catalytic hydrodefluorination reactions of fluorinated aromatic substrates on using [Rh(μ-H)(dippp)]2 (1) (dippp = 1,3-bis(diisopropylphosphino)propane) as catalyst and HSiEt3 as a hydrogen source are reported. Treatment of the hydrido complex 1 with the fluoroarenes gave the fluorido complex [Rh(μ-F)(dippp)]2 (2) and organic hydrodefluorination products. An unusual ortho-selectivity was observed in the reaction of 2,3,5,6-tetrafluoropyridine and pentafluorobenzene giving the 1,2-hydrodefluorinated products. The binuclear structure of complex 2 in the solid state was confirmed by X-ray diffraction. The fluorido complex 2 reacted with HSiEt3 and HSiiPr3 by elimination of the corresponding fluorosilanes to afford the η2-silane hydrido complexes [Rh(H)(η2-HSiEt3)(dippp)] (3) and [Rh(H)(η2-HSiiPr3)(dippp)] (4), respectively. The structures of the complexes 3 and 4 were derived from NMR data and DFT calculations. Catalytic reactions of pentafluoropyridine, 2,3,5,6-tetrafluoro- pyridine or 2,3,5,6-tetra-fluoropyridine, hexa- and pentafluorobenzene with HSiEt3 in the presence of 5 mol% of 1 afforded hydrodefluorination products with up to 19 turnovers after 48 h at 50 C. In contrast to the stoichiometric reactions, the catalytic transformations resulted predominantly in hydrodefluorinations at the para-position of the nitrogen atom in the heterocycles giving evidence for two different C-F activation pathways. Compound 3 can be considered to be an intermediate in the catalytic hydrodefluorinations of the fluoroarenes.
- Zámostná, Lada,Ahrens, Mike,Braun, Thomas
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p. 132 - 142
(2013/10/01)
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- Removal of fluorine from and introduction of fluorine into polyhalopyridines: An exercise in nucleophilic hetarenic substitution
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Starting from six industrially available fluorinated pyridines, an expedient access to all three tetrafluoropyridines (2-4), all six trifluoropyridines (5-10), and the five non-commercial difluoropyridines (11-14 and 16) was developed. The methods employed for the selective removal of fluorine from polyfluoropyridines were the reduction by metals or complex hydrides and the site-selective replacement by hydrazine followed by dehydrogenation-dediazotation or dehydrochlorination-dediazotation. To introduce an extra fluorine atom, a suitable precursor was metalated and chlorinated before being subjected to a chlorine/ fluorine displacement process.
- Bobbio, Carla,Rausis, Thierry,Schlosser, Manfred
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p. 1903 - 1910
(2007/10/03)
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- Regiochemically flexible substitutions of di-, tri-, and tetrahalopyridines: The trialkylsilyl trick
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(Chemical Equation Presented) 2,4-Difluoropyridine, 2,4-dichloropyridine, 2,4,6-trifluoropyridine, 2,4,6-trichloropyridine and 2,3,4,6-tetrafluoropyridine react with standard nucleophiles exclusively at the 4-position under halogen displacement. However, the regioselectivity can be completely reversed if a trialkylsilyl group is introduced in the 5-position of the 2,4-dihalopyridines or in the 3-position of the 2,4,6-trihalopyridines or 2,3,4,6-tetrahalopyridine. Then only the halogen most remote from the bulky silyl unit (at the 2-position in the case of the 2,4-halopyridines, at the 6-position with the other substrates) gets involved in the exchange process. After removal of the silyl protective group the nucleophile is invariably found to occupy the nitrogen-neighboring position.
- Schlosser, Manfred,Bobbio, Carla,Rausis, Thierry
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p. 2494 - 2502
(2007/10/03)
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- Rerouting nucleophilic substitution from the 4-position to the 2- or 6-position of 2,4-dihalopyridines and 2,4,6-trihalopyridines: The solution to a long-standing problem
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(Chemical Equation Presented) 2,4-Difluoro-, 2,4,6-trifluoro-, and 2,3,4,6-tetrafluoropyridine undergo nucleophilic substitution preferentially if not exclusively at the 4-position. However, after the introduction of a trialkylsilyl group at C-3 or C-5, t
- Schlosser, Manfred,Rausis, Thierry,Bobbio, Carla
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p. 127 - 129
(2007/10/03)
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- FLUORINATIONS WITH POTASSIUM TETRAFLUOROCOBALTATE(III) PART VII. FURTHER INVESTIGATIONS ON THE FLUORINATION OF PYRIDINE
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The product from the fluorination of pyridine by KCoF4 at ca. 220 deg C contains eleven fluoropyridines, two fluoro-2-azahex-enes, three azahexadienes, and two fluoro-N-methylpyrrolidines, besides an azacyclohexa-1,3-diene.Four products were isolated from fluorination of pyridine by CoF3 at ca. 150 deg C, a 2-azahexene, two N-methylpyrrolidines, and 4H-nonafluoropiperidine.
- Coe, Paul L.,Holton, Andrew G.,Tatlow, John Colin
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p. 171 - 190
(2007/10/02)
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