- Computational and Experimental Studies of Regioselective SNAr Halide Exchange (Halex) Reactions of Pentachloropyridine
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The Halex reaction of pentachloropyridine with fluoride ion was studied experimentally and computationally with a modified ab initio G3MP2B3 method. The G3 procedure was altered, as the anionic transition state optimizations failed due to the lack of diffuse functions in the small 6-31G? basis set. Experimental Halex regioselectivities were consistent with kinetic control at the 4-position. The reverse Halex reaction of fluoropyridines with chloride sources was demonstrated using precipitation of LiF in DMSO as a driving force. Reverse Halex regioselectivity at the 4-position was predicted by computations and was consistent with kinetic control. Scrambling of halide ions between chlorofluoropyridines was catalyzed by n-Bu4PCl, and the products of these reactions were shown to result from a combination of kinetic and thermodynamic control. Comparison of the C-F and C-Cl homolytic bond dissociation energies suggests that an important thermodynamic factor which controls regioselectivity in this system is the weak C2-Cl bond. The differences between ΔH° values of chlorofluoropyridines can be explained by a combination of three factors: (1) the number of fluorine atoms in the molecule, (2) the number of fluorine atoms at the C2 and C6 positions, and (3) the number of pairs of fluorine atoms which are ortho to one another.
- Froese, Robert D.J.,Whiteker, Gregory T.,Peterson, Thomas H.,Arriola, Daniel J.,Renga, James M.,Shearer, Justin W.
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- Preparation method of 4-aminopyridine compound
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The invention discloses a preparation method of a 4-aminopyridine compound. The preparation method comprises the following steps: adding a 4-amino- 3-chloropyridine compound or a 4-amino-3, 5-dichloropyridine compound, potassium phosphate and a catalyst into a solvent, and reacting at 0-10 MPa and 0-100 DEG C for 4-12 hours. According to the preparation method of the 4-aminopyridine compound, therelated raw materials are easy to obtain or self-make, the cost is low, the preparation method is simple, the reaction efficiency is high, the raw material cost is low, and byproducts have economic value; meanwhile, the reaction involved in the invention has good universality and tolerance to functional groups.
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Paragraph 0021-0023
(2021/02/06)
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- A kind of boron-containing compounds and their use in catalytic fluorination reaction (by machine translation)
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The invention relates to the field of fine chemical engineering, in particular to boron-containing compounds and application thereof in catalytic fluorination reaction. The boron-containing compoundsprovided by the invention are used as a catalyst and can be fluorinated by further mild reaction. Compared with the prior art, the boron-containing compounds have the advantages of mild conditions andhigh efficiency of the fluorination reaction, novel catalysis principle, simplicity and convenience in operation, less pollution, low solvent cost and suitability for industrial production.
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Paragraph 0042-0045
(2019/05/28)
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- Novel method for continuous production of fluroxypyr intermediate 3,5-dichloro-2,4,6-trifluoropyridine
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The invention discloses a novel method for continuous production of fluroxypyr intermediate 3,5-dichloro-2,4,6-trifluoropyridine. The method comprises the steps as follows: N-stage reactors are used,compound pentachloropyridine and a catalyst are added to each stage of reactor, and hydrogen fluoride is introduced into the first-stage reactor after heating, melting and dehydration; unreacted hydrogen fluoride and produced hydrogen chloride tail gas in each stage of reactor are introduced into a condenser in each stage for condensing, the uncondensed tail gas is introduced into the next stage of reactor, the tail gas of the last stage of reactor is condensed by two condensers, hydrogen fluoride is separated, discharged, absorbed by a tail gas recovery device and used as by-product hydrochloric acid, and hydrogen fluoride condensed and recovered by the condenser in each stage is returned to each stage of reactor. With adoption of the synthesis method, hydrogen fluoride use rate is high,purity of by-product hydrochloric acid is high, and the content of hydrogen fluoride is lower than 1%; the method has the advantages of being high in product yield and reaction selectivity, solvent-free, low in production cost, simple in process, green and environmentally friendly, and is very suitable for industrial production.
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Paragraph 0040-0043; 0052
(2018/05/30)
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- Medicament intermediate and preparation method of fluroxypyr 1-methylheptyl ester
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The invention discloses a medicament intermediate and a preparation method of fluroxypyr 1-methylheptyl ester, and relates to the field of organic synthesis. The preparation method of the medicament intermediate has the advantages that a molecular sieve is added, a fluoridation reaction and next amination reaction of pentachloropyridine can be realized through one-pot reaction, complex separation steps are saved, product loss caused by the separation process is avoided, and the key medicament intermediate for preparing herbicide can be prepared at high yield. The preparation method is easy to operate, is low in equipment demand, contributes to lowering production cost, and is suitable for large-scale industrial production. The preparation method is characterized in that low-cost and readily-available pentachloropyridine is taken as an initial raw material, the fluoridation reaction and next amination reaction are implemented by adopting the one-pot method to obtain key medicament intermediate; on the basis of the medicament intermediate, a hydroxylation reaction and a condensation reaction are implemented to obtain efficient high-yield fluroxypyr 1-methylheptyl ester. The preparation method is reasonable in route design, is simple in steps, is convenient to operate, is low in cost, is low in pollution, and is suitable for industrial large-scale production.
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Paragraph 0042-0046; 0048-0052; 0054-0058
(2017/11/18)
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- A 3,5-dichloro -2, 4, 6-trifluoro-pyridine preparation method (by machine translation)
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The invention discloses a 3, the 5 [...] two chloro -2, 4, 6-tri-fluoro pyridine preparation method, which belongs to the technical field of fine chemicals. Said method is the anhydrous potassium fluoride and 1,3 the [...] dimethyl -2 the imidazolone [...] uniformly mixed, after the distillation under reduced pressure, by adding pentachlorophenolate pyridine, in 80-120 °C lower substitution reaction, after filtering the reaction liquid, to obtain filtrate and filter residue; wash the filter residue solvent used, and after filtering, washing liquid obtained, and then the filtrate after the merger and cleaning liquid, by the rectified to obtain 3, the 5 [...] two chloro -2, 4, 6-tri-fluoro-pyridine. The invention has the advantages of low production cost, product purity and high yield. (by machine translation)
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Paragraph 0059; 0063
(2016/12/22)
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- Method for preparing fluroxypyr
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The invention discloses a method for preparing fluroxypyr, and belongs to the technical field of fine chemical engineering. The method comprises the steps of carrying out fluorination, carrying out amination, carrying out hydroxylation, carrying out stock solution extraction, carrying out condensation, carrying out hydrolysis and carrying out byproduct conversion. Byproducts and unreacted raw materials in a reaction process are used again through the steps of carrying out stock solution extraction and carrying out byproduct conversion, so that the utilization ratio of the raw materials is increased, the production cost and environmental treatment cost are reduced, and thus the method is applicable to large-scale production.
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Paragraph 0027; 0028; 0029
(2017/02/17)
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- Selective mono-and diamination of polyfluorinated benzenes and pyridines with liquid ammonia
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Amination of pentafluoropyridine, 2,3,5,6-tetrafluoropyridine, 4-chlorotetrafluoropyridine, 3,5-dichlorotrifluoropyridine, octafluorotoluene, α,α,α,2,3,5,6-heptafluorotoluene, decafluoro-m-xylene, decafluorobiphenyl, hexafluorobenzene, and pentafluorobenzene with liquid ammonia was investigated. Bis-aminodefluorination temperatures for the majority of substrates were shown to exceed significantly the corresponding temperatures of monoaminodefluorination. The optimal conditions for selective preparation of mono-and diaminopolyfluoro(het)arenes were elucidated. An efficient method for isolation of particular polyfluorophenylenediamines from product mixtures formed in nonselective reactions of pentafluorobenzene and hexafluorobenzene with aqueous ammonia based on complexation with a crown ether is proposed.
- Vaganova,Kusov,Rodionov,Shundrina,Malykhin
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p. 2239 - 2246
(2008/09/20)
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- Solvents for use in fluorination reactions
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A method of fluorinating an organic compound comprising reacting an organic compound with a fluorinating agent characterized in that a perfluorocarbon compound is present in the reaction medium. The perfluorocarbon compound may replace an amount of a solvent which would otherwise be required for the reaction to proceed efficiently. The perfluorocarbon compound is readily recoverable after reaction and may be re-used in subsequent reactions. Additives to the reaction medium, such as 18-crown-6, may increase the amoun of solvent which may be replaced. The method is beneficial where solvent consumption would otherwise be large, or where solvent recovery would otherwise be difficult.
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- Perfluorocarbon fluids as solvent replacements
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Perfluoroperhydrophenanthrene 1 may be used as a 'bulking agent' to minimise the problem of solvent recovery in halogen exchange ('Halex') reactions for the preparation of octafluorocyclopentene 8, and chlorofluoro-pyridine, -pyrimidine and -benzene derivatives. New 'one-pot' procedures for the syntheses of hexafluorobut-2-yne 3, octafluorobut-2-ene 11 and hexafluorocyclobutene 7 are described.
- Chambers, Richard D.,Edwards, Andrew R.
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p. 3623 - 3627
(2007/10/03)
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- POLYHALOAROMATIC EQUILIBRATIONS
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Chromium oxide is a good catalyst for scrambling halogens among polyhaloaromatic compounds.Chloropentafluorobenzene and bromopentafluorobenzene disproportionate to hexafluorobenzene and the respective tetrafluorodihalobenzenes.Pentachloro- and pentafluoropyridines produce pyridines with intermediate numbers of both types of halogens.Cyano, trifluoromethyl and a single hydrogen can be present on the aromatic rings without interfering with the chemistry.
- Weigert, F. J.
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- Hydrogenolysis/dehydrohalogenation process
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A process for the hydrogenolysis and/or dehydrohalogenation of fluorohalocarbons and/or fluorohalohydrocarbons by reacting the fluorohalocarbons and/or fluorohalohydrocarbons with a source of hydrogen in the presence of a catalyst, the improvement comprising utilizing a rhenium-containing catalyst, which may, optionally, contain at least one Group VIII metal and may, optionally, be supported.
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- Method of preparation of 3,5-dichloro-2,4,6-trifluoropyridine
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The preparation of 3,5-dichloro-2,4,6-trifluoropyridine from pentachloropyridine and potassium fluoride was found to proceed in high yield and at a rapid rate with little tar formation when the reaction is conducted under essentially anhydrous conditions in N-methylpyrrolidone solvent at temperatures below 170° C. High yields of this intermediate for herbicides are obtained.
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