- Halex reactions of aromatic compounds catalysed by 2-azaallenium, carbophosphazenium, aminophosphonium and diphosphazenium salts: A comparative study
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An increasing number of biologically active compounds in the pharma and agro-chemical sector contain carbon fluorine bonds. One of the most common methods to introduce fluorine into intermediates is the well-investigated halogen-exchange reaction, in which chloro- and bromoaromatics activated towards nucleophilic substitution, react with a fluoride source to yield the corresponding fluoroarenes. In general, the reaction is supported by phase-transfer catalysts. The use of a new class of very active phase-transfer catalysts gives the possibility of substituting even halogens with weak activation giving a convenient access to interesting compounds that are not available so far and opening up new synthetic routes in Halex chemistry. Our new classes of catalysts, CNC+ (1a), PNC+ (2a) and several different approaches presented by other groups are described and experimental results discussed.
- Pleschke, Axel,Marhold,Schneider,Kolomeitsev,R?schenthaler
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- Preparation method of 3,5-difluorochlorobenzene
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The invention discloses a preparation method of 3,5-difluorochlorobenzene, and relates to the field of organic synthesis technology. The preparation method comprises the following steps: using 2,4-difluoroaniline as a raw material, introducing chlorine into a meta-position of a benzene ring of fluorine under the limit of an amino group, and then removing amino from the benzene ring to obtain 3,5-difluorochlorobenzene. In the whole preparation process, high temperature and high pressure reaction are avoided, reaction conditions are mild, and intermediates are not required to be separated and purified, and can be directly used in reaction in a next step, so that not only can the treatment cost of the intermediates be reduced, but also the loss of yield of the intermediates caused in the purification process can be reduced, and the conversion percent of the intermediates in amino removal reaction is increased. The molar yield of the product, 3,5-difluorochlorobenzene, produced by using the method can be up to 80% and more and the purity can be up to 99.5% or more, so that the yield and purity of the product are ensured on the basis of reducing the cost of preparation, and the product, 3,5-difluorochlorobenzene, is used as a drug intermediate for preparation of drug.
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Paragraph 0017; 0018; 0019; 0020; 0021; 0022
(2017/08/31)
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- Process for preparing ring-fluorinated aromatics
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The present invention relates to an improved process for preparing ring-fluorinated aromatics of the general formula (I) by a halogen exchange reaction (halex reaction) of a plurality of halogen substituents in one stage in the presence of a catalyst.
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Page/Page column 5
(2008/06/13)
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- Method for producing tetrakis ( fluoroaryl) borate-magnesium compound
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Fluoroaryl magnesium halide is reacted with a boron compound so that a molar ratio of the fluoroaryl magnesium halide to the boron compound is not less than 3.0 and not more than 3.7, so as to produce a tetrakis (fluoroaryl) borate·magnesium compound. With this method, there occurs no hydrogen fluoride which corrodes a producing apparatus and requires troublesome waste water treatment.
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- Catalyst comprising an amidophosphonium salt for halex reactions
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Catalyst for halogen-fluorine exchange reactions on aromatics, consisting essentially of a mixture of one or more compounds of the component a) plus at least one compound of the components b), c) and/or d), wherein a) is an amidophosphonium salt of the formula (I) STR1 where A1, A2, A3, A4, A5, A6, A7, A8 are, independently of one another, identical or different and are each a straight-chain or branched alkyl or alkenyl having from 1 to 12 carbon atoms, cycloalkyl having from 4 to 8 carbon atoms, an aryl having from 6 to 12 carbon atoms, an aralkyl having from 7 to 12 carbon atoms, or A1 A2, A3 A4, A5 A6, A7 A8 are, independently of one another, identical or different and are in each case connected to one another either directly or via O or N--A9 to form a ring having from 3 to 7 ring atoms, A9 is an alkyl having from 1 to 4 carbon atoms and B? is a monovalent acid anion or the equivalent of a polyvalent acid anion, b) a quaternary ammonium salt, c) a quaternary phosphonium salt, and d) a crown ether or a polyether of the formula (IV):
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- AROMATIC FLUORINE CHEMISTRY. PART 4. PREPARATION OF 2,6-DIFLUOROANILINE
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The preparation of 2,6-difluoroaniline from 1,3,5-trichlorobenzene is described. 1-Chloro-3,5-difluorobenzene prepared via KF exchange on 1,3,5-trichlorobenzene is dichlorinated and nitrated in a single reactor to a mixture of trichlorodifluoronitrobenzenes.The latter are reduced to ca. 4:1 mixture of 2,6-difluoroaniline and 2,4-difluoroaniline.
- Pews, R. G.,Gall, J. A.
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p. 307 - 316
(2007/10/02)
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- Process and intermediates for the preparation of 2,6-difluoroaniline
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1-Chloro-3,5-difluorobenzene is chlorinated to give 4,6-difluoro-1,2,3-trichlorobenzene which in turn is nitrated and reduced to the corresponding novel aniline, 2,6-difluoro-3,4,5-trichloroaniline. Further reduction of this aniline provides 2,6-difluoroaniline with high selectivity.
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