Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C25/00—Compounds containing at least one halogen atom bound to a six-membered aromatic ring
  • C07C25/02—Monocyclic aromatic halogenated hydrocarbons
  • C07C25/13—Monocyclic aromatic halogenated hydrocarbons containing fluorine
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/093—Preparation of halogenated hydrocarbons by replacement by halogens
  • C07C17/10—Preparation of halogenated hydrocarbons by replacement by halogens of hydrogen atoms
  • C07C17/12—Preparation of halogenated hydrocarbons by replacement by halogens of hydrogen atoms in the ring of aromatic compounds
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/093—Preparation of halogenated hydrocarbons by replacement by halogens
  • C07C17/20—Preparation of halogenated hydrocarbons by replacement by halogens of halogen atoms by other halogen atoms
  • C07C17/202—Preparation of halogenated hydrocarbons by replacement by halogens of halogen atoms by other halogen atoms two or more compounds being involved in the reaction
  • C07C17/208—Preparation of halogenated hydrocarbons by replacement by halogens of halogen atoms by other halogen atoms two or more compounds being involved in the reaction the other compound being MX
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/23—Preparation of halogenated hydrocarbons by dehalogenation

Definitions

• the present invention relates to a process for the preparation of 1, 3,5-trifluoro-2,4,6-trichlorobenzene of the formula I.
• fluorobenzene comprising steps A) and B):
• X is fluorine or hydrogen
• Z is nitro, bromine or chlorine and n is zero or 1-4
• step B fluorination of the reaction products of step A and distillative separation of the resulting 1, 3,5-trifluoro-2,4,6-trichlorobenzene of the formula I.
• the invention relates to a process for the preparation of 1,3,5-TrifluorbenzoI by hydrodechlorination of the distilled reaction product from step C) to 1, 3,5-trifluorobenzene.
• the object of the present invention was to provide an economical and industrially feasible process for preparing substantially pure trifluorotrichlorobenzenes or trifluorobenzenes, which avoids the release and handling of hexachlorobenzene.
• JP 04224535 describes the dechlorination of 1,3-dichloro-2,4,6-trifluorobenzene with hydrogen under palladium catalysis.
• the process according to the invention elegantly overcomes the disadvantages of the known processes. It starts from readily available starting materials, uses readily available reagents, and any byproducts that are generated are either recycled for re-conversion or converted to the final product during the process.
• the chlorination in stage A) can be optimized for maximum yield of chlorofluorobenzene of the formula III, without having to take account of developing proportions of hexachlorobenzene which, in addition to the chlorofluorobenzene of the formula III, are used as alternative starting material in the fluorination reaction can.
• stages A) and B) proceed without intermediate isolation of the reaction products of stage A).
• the process is preferably carried out as a one-pot reaction. If, after the chlorination, considerable amounts of underchlorinated by-products remain in the reaction solution, ie those compounds of the formula II in which Z is nitro or bromine and / or the index n is not 4, the reaction solution can be subjected to distillation (step A2 ) are subjected to the separation of the above-mentioned underchlorinated by-products.
• stage A) comprises two substeps A1) and A2) and the method according to the invention is as follows:
• X is fluorine or hydrogen
• Z is nitro, bromine or chlorine and n is zero or 1-4
• Y is chlorine or fluorine, contains as the main component
• step A1 underchlorinated products are separated off by distillation and recycled for further reaction in stage A) or A1), while the product chlorinated by fluorine-chlorine exchange hexachlorobenzene in a mixture with the main product chlorofluorobenzene Formula III remain in the distillation bottoms and are fluorinated in step B) to trichlorotrifluorobenzene of the formula I.
• the chlorination in step A), or A1) is advantageously carried out with elemental chlorine at temperatures of -10 to 50 0 C, preferably -5 to 15 ° C, more preferably +5 to 15 ° C, in the presence of Lewis acids , such as Fe, FeCl 3 , Al, AlCl 3 , SbCl 5 , SbCl 3 , BF 3 , BF 3 X OR 2 , where R is C 1 -C 4 -alkyl, TiCl 4 , SiCl 4 , SnCl 4 , ZnCl 2 , preferably FeCl 3 and AICl 3 , particularly preferably AICl 3 .
• Lewis acids such as Fe, FeCl 3 , Al, AlCl 3 , SbCl 5 , SbCl 3 , BF 3 , BF 3 X OR 2 , where R is C 1 -C 4 -alkyl, TiCl 4 , SiCl 4 , SnCl 4 , Z
• Suitable solvents are aliphatic hydrocarbons such as pentane, hexane, cyclohexane and petroleum ether, halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, 1, 2-dichloroethane, trichloroethane and chlorobenzene, inorganic acids such as sulfuric acid and phosphoric acid, organic acids such as formic acid and acetic acid, and Dimethyl sulfoxide, dimethylformamide and dimethylacetamide (DMA), N-methylpyrrolidone (NMP), dimethylethyleneurea (DMEU) and dimethylpropyleneurea (DMPU), more preferably methylene chloride, chloroform, carbon tetrachloride, 1, 2-dichloroethane and chlorobenzene. It is also possible to use mixtures of the solvents mentioned.
• halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachlor
• the Lewis acids are usually used in amounts of 0.5 to 10 mol%.
• the Lewis acid is preferably in finely divided form.
• fluorobenzene derivatives of the formula II include fluorobenzene, m-difluorobenzene, o-fluoronitrobenzene, o-chlorofluorobenzene, m-fluoronitrobenzene, m-bromofluorobenzene, m-chlorofluorobenzene, 1-chloro-3-fluoro-2-nitrobenzene and 4-chloro -2-fluoro-1-nitrobenzene,
• the separation of the solvent from the step A) by distillation is carried out after complete chlorination.
• the distillation residue containing the reaction products is treated with the solvent of stage B) and the fluorinating agent. Subsequently, residues of water can be removed by distillation, if appropriate under reduced pressure.
• step A2) depleted underchlorinated by-products; they can be fed to a further reaction in stage A) or A1), as starting material of formula II. Any resulting hexachlorobenzene remains as a high-boiling component in the distillation bottoms and is available as starting material for the subsequent fluorination.
• the reactor of stage A), or A1) i. the still as reactor for the fluorination in step B).
• the fluorination in step B) is preferably carried out by alkali metal and Erdalkalimetallfluoride at temperatures of 100 to 300 0 C, preferably 170 to 230 0 C, under anhydrous Conditions in an inert organic solvent [cf. Ref. WO 03/101926; JP 60246327; EP 163 230; US 4 500 315].
• the resulting fluorination product is distilled off during the reaction. This is preferably carried out under reduced pressure (vacuum distillation).
• the distillate has only a small proportion of isomers trifluorotrichloro-benzenes.
• Suitable alkali metal and alkaline earth metal fluorides are, for example, NaF, KF, CsF and CaF 2 in spray-dried or crystalline form. Preferred is KF.
• Suitable solvents are aliphatic hydrocarbons, aromatic hydrocarbons such as toluene, o-, m- and p-xylene, halogenated hydrocarbons such as chlorobenzene, and dimethyl sulfoxide, dimethylformamide and DMA, carboxylic acid amides, sulfolane, NMP, DMEU, DMPU, particularly preferably sulfolane, NMP, DMEU , DMPU. It is also possible to use mixtures of the solvents mentioned.
• reaction mixture can be dried in an elegant manner, preferred solvents are xylene, toluene and chlorobenzene or mixtures thereof, in particular toluene.
• the reaction takes place in the presence of substoichiometric amounts of reduction inhibitors, in particular when using DMF or NMP as solvent.
• Suitable reduction inhibitors are, for example, 1,3-dinitrobenzene, 1-chloro-3-nitrobenzene or 4-chloro-nitrobenzene.
• step B) is carried out in the presence of a catalyst.
• Catalysts for the Halex reaction are known per se [cf.: WO 03/101926], preferred are quaternary ammonium and phosphonium salts, such as those of the formulas Va, Vb and Vc:
• R 1 C 1 -C 4 -alkyl
• Benzyl tributyl ammonium bromide Benzyl tributyl ammonium chloride; Benzyl triethyl ammonium bromide; Benzyl triethyl ammonium chloride; Benzyl trimethyl ammonium chloride; Cetyl pyridinium bromide; Cetyl pyridinium chloride; Cetyl trimethyl ammonium bromide; Didecyl dimethyl ammonium chloride; Dimethyl distearyl ammonium bisulfate; Dimethyl distearyl ammonium methosulfate; Dodecyl trimethyl ammonium bromide; Dodecyl trimethyl ammonium chloride; Methyl tributyl ammonium chloride; Methyl Tributyl Ammonium Hydr.
• step B) is carried out in a water-miscible solvent
• the separation of the solvent can be carried out by addition of water, whereby the reaction product, above the melting point, as the organic phase separated from the solvent mixture.
• the product can thus be isolated by phase separation, if necessary, and subsequent washing with water from solvent residues.
• the distilled-off reaction product from stage B) is hydrodechlorinated to trifluorobenzene without further purification (stage C).
• the hydrodechlorination in step C) is usually carried out at temperatures of 50 ° C to 150 ° C, preferably 90 ° C to 120 ° C or 11O 0 C to 140 0 C 1 in water or an inert organic solvent in the presence of a base [see. JP 04224535].
• Suitable solvents are water, alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol and tert-butanol, and dimethyl sulfoxide, dimethylformamide and dimethylacetamide, carboxylic acids such as formic acid and acetic acid, preferably water and acetic acid in particular water. It is also possible to use mixtures of the solvents mentioned.
• Suitable bases are generally inorganic compounds such as alkali metal and alkaline earth metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide and calcium hydroxide, alkali metal and alkaline earth metal oxides such as lithium oxide, sodium oxide, calcium oxide and magnesium oxide, alkali metal and alkaline earth metal hydrides such as lithium hydride, sodium hydride, potassium hydride and Calcium hydride, alkali metal amides such as lithium amide, sodium amide and potassium amide, alkali metal and alkaline earth metal carbonates such as lithium carbonate, potassium carbonate and calcium carbonate and alkali metal hydrogencarbonates such as sodium bicarbonate alkali metal acetates such as sodium acetate, potassium acetate and alkali metal and alkaline earth metal alcoholates such as sodium methoxide, sodium ethoxide, potassium ethanolate, Potassium tert-butoxide and dimethoxy magnesium, also organic bases, eg tertiary amines such as tri
• the bases will generally be equimolar, in excess, or optionally used as a solvent. Preferably, 3-4 molar equivalents, based on fluorochlorobenzene, are used.
• reaction solution a pH of from 1 to 7, in particular from 4 to 6, is preferred for the reaction solution.
• the reaction can also be carried out in a buffer system.
• stage C The course of the reactions described, in particular the heterogeneous reactions, is favored by the most intensive possible mixing of the reaction solutions. This applies in particular to stage C). Usually, one or more stages Disk stirrer, propeller stirrer and / or inclined blade and / or the installation of Stromstörem in the reactor intensive mixing of the reaction solution safely.
• the combination of different types of stirrers can also prove advantageous.
• the optimal stirrer geometry depends on the dimensions of the reactors used.
• the type of gas supply is also dependent on the reactor geometry. The skilled worker is familiar with methods that ensure the finest possible distribution of gas.
• the reaction preferably takes place in the presence of a catalyst, such as transition metal catalysts, in particular Pd / C, Pt / C and Raney Ni or mixtures thereof.
• a catalyst such as transition metal catalysts, in particular Pd / C, Pt / C and Raney Ni or mixtures thereof.
• the dechlorinated reaction products are continuously distilled off during the reaction. In this embodiment, a satisfactory reaction course is achieved even without a catalyst.
• the process of the invention allows the procedure to be carried out as a one-pot reaction, i. the process steps A) to B), or A1), A2) and B) are carried out in the same reactor. Any fractions of hexachlorobenzene formed in stage A) or A1) remain in the reactor and are removed by means of fluorination in stage B) in the same reactor.
• steps A) to C) according to the invention represents an elegant and industrially feasible way to largely pure trifluorobenzenes.
• the 1,3,5-trichloro-2,4,6-trifluorobenzene and 1,3,5-trifluorobenzene obtainable by the process according to the invention is suitable as an intermediate for the preparation of dyes or active substances in the pharmaceutical or agrochemical sector.
• the organic phase contained, according to gas chromatographic analysis (GC) as main components, 43.9% fluoropentachlorobenzene, 36.2% fluorotetrachlorobenzenes, 13.4% ortrichlorobenzenes and other components in the percentage range.
• GC gas chromatographic analysis

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• 2006
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