EP1874715A1

EP1874715A1 - Method for the production of 1,3,5-trifluoro-2,4,6-trichlorobenzene from fluorobenzene derivatives

Info

Publication number: EP1874715A1
Application number: EP06743380A
Authority: EP
Inventors: Michael Rack; Sebastian Peer Smidt; Manuel Budich; Volker Maywald; Michael Keil; Bernd Wolf
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2005-04-22
Filing date: 2006-04-21
Publication date: 2008-01-09
Also published as: CN101160278A; BRPI0610721A2; CN101160278B; WO2006111583A1; IL185855A; JP2008536895A; US20080214878A1; IL185855A0; AR056982A1; US7595426B2

Abstract

Method for the production of 1,3,5-trifluoro-2,4,6-trichlorobenzene from fluorobenzene, comprising steps A) and B): A) chlorination of fluorobenzene derivatives of formula (II), in which X = fluorine or H, Z = nitro, bromo or chloro and n = 0 or 1-4 and B) fluorination of the distillation residue and separation by distillation of the 1,3,5-trifluoro-2,4,6-trichlorobenzene thus produced.

Description

Process for the preparation of 1,3,5-trifluoro-2,4,6-trichlorobenzene from fluorobenzene derivatives

description

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):

A) chlorination of fluorobenzene derivatives of the formula II,

in which X is fluorine or hydrogen, Z is nitro, bromine or chlorine and n is zero or 1-4 and

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.

In addition, 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.

Accordingly, the method defined above was found.

The individual reactions are known per se from the literature: J. Indian Chem. Soc. Vol. 21, pp.112-14 (1944) teaches that 4-chlorofluorobenzene is first obtained from the chlorination of fluorobenzene under FeCb catalysis, and an isomeric mixture of 2,4- and 3,4-dichlorofluorobenzene in the case of excess chlorine.

The chlorination of fluorobenzene with the addition of Fe powder at 100 ⁰ C and UV-exposure results in fluoropentachlorobenzene and hexachlorobenzene as a main component. From analogous reaction with the addition of AICI ₃ , 1,2,4-trichlorofluorobenzene is obtained in 8% yield as the main component [cf. Chem. Ben, Vol. 91, pp. 2605-7 (1958). In US 6,265,627, US 6,215,032, RU 20,843,437 and Russ. J. of Appl. Chem., Vol. 73, 3, pp. 522-23 (2000) describes the fluorination of hexachlorobenzene with KF using various catalysts. According to the described method some isomer mixtures are obtained.

JP 04224535 describes the dechlorination of 1,3-dichloro-2,4,6-trifluorobenzene with hydrogen under palladium catalysis.

In Russ. J. of Org. Chem., Vol. 36, 1, p.132-33 (2000), the dehalogenation of 1,3,5-trichlorotrifluorobenzene with zinc in the presence of NiCb and bipyridine to form 1,3,5-tri fluorobenzene described.

The known methods have significant disadvantages for large-scale implementation. They go z.T. from expensive starting materials, lead to mixtures of isomers, or require the handling of hexachlorobenzene, which is classified in the European Union as POP (persient organic pollutant). The handling of hexachlorobenzene should be avoided. To avoid them requires a lot of equipment. Hexachlorobenzene-free processes usually start from more expensive starting materials. The complete avoidance of the by-product hexachlorobenzoi in the chlorination of fluorobenzenes is possible only with great technical effort.

The described syntheses are therefore out of the question for a large-scale process for economic and practical reasons.

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.

By means of the process according to the invention, 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.

In one embodiment of the process, 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.

In this case, stage A) comprises two substeps A1) and A2) and the method according to the invention is as follows:

A1) chlorination of fluorobenzene derivatives of the formula II,

in which X is fluorine or hydrogen, Z is nitro, bromine or chlorine and n is zero or 1-4,

A2) Distillative removal of volatile constituents from the reaction mixture, which chlorofluorobenzene of the formula III,

in which Y is chlorine or fluorine, contains as the main component,

B) fluorination of the distillation residue and distillative separation of the resulting 1,3,5-trifluoro-2,4,6-trichlorobenzene of the formula I.

Depending on the desired purity of the 1,3,5-trifluoro-2,4,6-trichlorobenzene, this procedure is suitable if the proportion of underchlorinated by-products after the chlorination exceeds 1, 2 or up to 5 wt .-%.

In the process according to the invention, in 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. Thus, from the process according to the invention no chlorinated hydrocarbons, which must be disposed of.

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 .

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.

The Lewis acids are usually used in amounts of 0.5 to 10 mol%.

The Lewis acid is preferably in finely divided form.

Examples of 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,

1-Chloro-2-fluoro-3-nitrobenzene, p-fluoronitrobenzene, 1-chloro-2,4-difluoro-benzene, 1-bromo-2,4-difluoro-benzene, 2,4-difluoro-1-nitrobenzene benzene, 1,3-difluoro-5-nitro-benzene, i-bromo-3,5-difluoro-benzene, 1-chloro-3,5-difluoro-benzene, 1-chloro-2,4-difluoro-5-one nitrobenzene, 2-chloro-1,3-difluoro-4-nitrobenzene. Preferred starting materials of the formula II are fluorobenzene, m-difluorobenzene, m-fluoronitrobenzene and m-chlorofluorobenzene.

If the process is carried out without the distillation step A2), 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.

The distillation in 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. In a preferred embodiment of the method, 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].

In a preferred embodiment, 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.

By azeotropic distillation, the reaction mixture can be dried in an elegant manner, preferred solvents are xylene, toluene and chlorobenzene or mixtures thereof, in particular toluene.

Advantageously, 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.

In one embodiment of the process, 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:

in which R ¹ = C ¹ -C ₄ -alkyl, R ² and R ³ together denote -CH ₂ -CH ₂ - or -CH ₂ -CH ₂ -CH ₂ - and R ⁴ = C 1 -C ₄ -alkyl. For Halexreaktionen are usually in particular the following catalysts in question: 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. Sulfate; Methyl tricaprylyl ammonium chloride; Methyl trioctyl ammonium chloride; Myristyl trimethyl ammonium bromide; Phenyl trimethyl ammonium chloride; Tetrabutyl ammonium borohydride; Tetrabutyl ammonium bromide; Tetrabutyl ammonium chloride; Tetrabutyl ammonium fluoride; Tetrabutyl ammonium hydrogen sulfate; Tetrabutyl ammonium hydroxide; Tetrabutyl ammonium iodide; Tetrabutyl ammonium perchlorate; Tetraethyl ammonium bromide; Tetraethyl ammonium chloride; Tetraethyl ammonium hydroxide; Tetrahexyl ammonium bromide; Tetrahexylammonium iodide; Tetramethyl ammonium bromide; Tetramethyl ammonium chloride; Tetramethyl ammonium fluoride; Tetramethyl ammonium hydroxide; Tetramethyl ammonium iodide; Tetraoctyl ammonium bromide; Tetrapropyl ammonium bromide; Tetrapropyl ammonium chloride; Tetrapropyl ammonium hydroxide; Tributyl methyl ammonium chloride; Triethyl benzyl ammonium chloride; Hexa-C 1 -C 6 -alkyl guanidinium chlorides and bromides.

Quaternary phosphonium salts:

benzyltriphenylphosphonium; benzyltriphenylphosphonium; Butyltriphenylphosphonium bromide; Butyltriphenylphosphoniumchlorid; Ethyltriphenylphosphonium acetate; ethyltriphenylphosphonium; ethyltriphenylphosphonium; Methyl triphenylphosphonium bromide; tetrabutylphosphonium; Tetraphenylphosphonium bromide; Tetrakisdiethylaminophosphoniumbromid;

Polyglycols and crown ethers:

18-crown-6; Aliplex DB186®; Butyl diglyme; Dibenzo-18-crown-6; Diethylene glycol dibutyl ether; diethylene glycol dimethyl ether; diglyme; Dipropyienglycoldimethylether; Monoglyme; Polyethyleneglycoldibutylether; Polyglycol BB 300®; Polyglycol DME 200®;

Polyglycol DME 250®; Polyglycol DME 500®; Polyglycol DME 1000®; Polyglycol DME 2000®; Monoethylenglycoldimethylether; tetraethylene; tetraglyme; triethylene; and triglyme.

It is also possible to use catalyst mixtures.

If the 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. In a preferred embodiment of the process, 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 trimethylamine, triethylamine, triisopropylethylamine and N-methylpiperidine, pyridine, substituted pyridines such as collidine, lutidine and 4-dimethylaminopyridine and bicyclic amines into consideration. Particularly preferred are sodium acetate, potassium acetate, sodium hydroxide and potassium hydroxide.

The bases will generally be equimolar, in excess, or optionally used as a solvent. Preferably, 3-4 molar equivalents, based on fluorochlorobenzene, are used.

If the reaction is carried out in an aqueous solvent or solvent mixture, 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.

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.

In one embodiment of the process, 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.

The process of 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.

Process examples:

Level A1) -A2)

Example 1 - Preparation of 1-fluoro-2,3,4,5,6-pentachlorobenzene

To a solution of 400 g (4.17 mol) of fluorobenzene in 21 1, 2-dichloroethane was added 53.2 g (0.417 mol) of powdered AICI ₃ . Subsequently, at 0 to 5 ⁰ C initiated 1394g of chlorine gas. After completion of the reaction, the resulting HCl was expelled at about 20 to 25 ° C with a stream of nitrogen. The reaction solution was added with vigorous stirring with 200 ml of water, then the phases are separated at 50 ⁰ C.

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. By vacuum distillation (140-145 ⁰ C, 20mbar) remaining in the sump according to GC 86.2% Fluorpentachlorben- zol, 3% fluorotetrachlorobenzenes, 3.3% pentachlorobenzene and hexachlorobenzene 2.5%. This mixture was used without further purification in the fluorination.

Example 2 - Preparation of 1,3-difluoro-2,4,5,6-tetrachlorobenzene

To a solution of 100 g (0.88 mol) of 1,3-difluorobenzene in 11 1, 2-dichloroethane was added 11.7 g (0.088 mol) of powdered AICb. Subsequently, 290 g of chlorine gas were introduced at 0 to 5 ° C. After completion of the reaction, the resulting HCl was expelled at about 20 to 25 ⁰ C with a stream of nitrogen, the solution was filtered through silica gel. According to gas chromatographic analysis, the solution contained 38.5% of dichlorodifluorobenzene, 33.6% of difluorotrichlorobenzenes, 14.5% of difluorotetrachlorobenzene and other components in the percentage range as main components. From a vacuum distillation was obtained at 0.2 mbar in the temperature range 50-90 ⁰ C 60 g of a title compound-containing fraction.

Level A)

Example 3 - Preparation of Pentachlorofluorobenzene

In a solution of 144 g (1, 5 mol) of fluorobenzene in 1080 ml of 1, 2-dichloroethane was added after addition of 10g (0.075 mol) of powdered AICI ₃ , at 5 to 15 ° C 586 g of chlorine gas. Then the solution was stirred for about 5 hrs. At 25 ° C, then heated to 65 ° C, and then was added with vigorous stirring 100ml of water. At this temperature, the phases were separated and the organic phase extracted with water. The solvent was distilled off, the residue taken up in 1300 g of NMP. The yield was calculated by gas chromatographic analysis (GC): 93.9% pentachlorofluorobenzene, 4.9% hexachlorobenzene, and 1.1% tetrachlorofluorobenzenes. The solution can be directly further reacted according to Example 6.

Stage B)

Example 4 - Preparation of 1,3,5-trichloro-2,4,6-trifluorobenzene from 1-fluoro-2,3,4,5,6-pentachlorobenzene

8.9 g of KF were suspended in 20 g of the distillation residue from Example 1 (composition GC: 85.2% fluoropentachlorobenzene, 11% fluorotetrachlorobenzenes, 3.8% hexachlorobenzene) and diluted with 50 mM DMEU. The suspension was stirred for 12 hours at 220 ^° C. in a pressure vessel. After relaxing, the contents were taken up with 100 ml of methyl tert-butyl ether (MTBE), washed with water, dried and then the solvent is distilled off in vacuo. This gave 14.6 g of an isomeric mixture containing 24% of the title compound by GC.

Example 5 - Preparation of 1, 3,5-trichloro-2,4,6-trifluorobenzene from 1,3-difluoro-2,4,5,6-tetrachlorobenzene

2.8 g of KF and 0.6 g (2.12 mmol) of (Et ₂ N) ₄ PBr were suspended in 10 g of the fraction from Example 2, the suspension was stirred for 24 hours at 18O ⁰ C in a pressure vessel. After releasing the pressure, it was taken up in 100 ml of CH 2 Cl 2, washed with water, dried and then the solvent was distilled off in vacuo. This gave 8.7 g of an isomer mixture containing 45% (GC) of the title compound.

Example 6 - Preparation of 1,3,5-trichlorotrifluorobenzene

A solution prepared analogously to Example 3 (23.2% fluoropentachlorobenzene in NMP) was admixed with 57 g (0.98 mol) of KF, 1.7 g of 1,3-dinitrobenzene and 299 g of NMP. For drying, 100 g of NMP were distilled off at 81 ° C. and 10 mbar. Subsequently, a vacuum of 540 mbar was applied and the internal temperature increased to 180 ⁰ C. Within 16 hours, the crude product-NMP mixture was distilled off. The distillate was washed twice at 70 ⁰ C with 250 g of water. There were obtained 70.9 g of a mixture of trichlorotrifluorobenzenes (75.6% of theory). The main constituent identified was 61.5% 1,3,5-trichlorotrifluorobenzene.

Example 7 - Preparation of 1,3,5-trichloro-2,4,6-trifluorobenzene from fluorochlorobenzene mixtures

74.4 g of the distillation residue from stage A1) -A2) having the composition (GC) 81.6% fluoropentachlorobenzene, 4.5% fluorotetrachlorobenzenes, 10.8% hexachlorobenzene, were mixed with 49 g of KF, 1.3 g of 1,3- Dinitrobenzene suspended in 400g NMP and 75g toluene. For azeotropic drying, the toluene was distilled off at normal pressure. Subsequently, a vacuum of 580 mbar was applied and the internal temperature increased to 190 ⁰ C. Within 14 hours, the reaction product distilled off. The distillate was taken up with MTBE, washed with water and dried. After distilling off the solvent, 23.9 g of a residue consisting of 73.6% (GC) of the title compound remained.

Example 8 - Preparation of 1,3,5-trichloro-2,4,6-trifluorobenzene from fluorochlorobenzene mixtures

In a further procedure of example 7, 100 g of a distillation residue from stage A1) -A2), with composition (GC) 86.2% fluoropentachloro benzene, 3.0% fluorotetrachlorobenzenes, 2.6% hexachlorobenzene fluorinated with 79.4 g KF. This gave 47.6 g (52.6% of theory) of the title compound, mp. 65 ° C. The purity was> 95% (determined by ¹⁹ F-NMR) ¹⁹ F-NMR (DMSO-D ₆ ): δ = -113.6 ppm (s).

Example 9 - Preparation of 1,3,5-trichloro-2,4,6-trifluorobenzene from fluorochlorobenzene mixtures

In a further procedure of example 7, 100 g of a distillation residue from stage A1) -A2) with the composition (GC) 86.2% fluoropentachlorobenzene, 3.0% fluorotetrachlorobenzenes, 2.6% hexachlorobenzene with 79.4 g of KF fluorinated in DMEU. There were obtained 30.2 g (33% of theory) of the title compound, mp. 65 ° C. The purity was> 95% ( ¹⁹ F NMR).

Example 10 - Preparation of 1, 3,5-trifluorobenzene

Palladium on carbon (10%, 410 mg), 100 g of water, 21.8 g of 1,3,5-trichloro-2,4,6-trifluorobenzene and 32.9 g of sodium acetate (4.5 equivalents) were placed in a pressure vessel. After purging with nitrogen, the pressure vessel was heated to 140 ⁰ C and pressed 12 bar hydrogen. About twelve hours was kept at 14O ⁰ C under intense stirring, a hydrogen pressure of 12 bar. After cooling to 20-25 ⁰ C, the pressure vessel was depressurized. The biphasic reaction solution was filtered, then the phases were separated. A yield of 88.2% of 1,3,5-trifluorobenzene was obtained.

Stage C)

Example 11 - Hydrodechlorination of 1,3,5-trichloro-2,4,6-trifluorobenzene

Palladium on carbon (10%, 300 mg), aqueous sodium hydroxide solution (35%, 26.5 g, 232 mmol, 3.7 equivalents), 62 g of water and 1, 3,5-trichloro-2,4,6-trifluorobenzene ( 15 g, 62 mmol) were placed in the pressure vessel. After purging with nitrogen, the pressure vessel was heated to 140 ⁰ C and 30 bar of hydrogen were injected. For 12 hours at 140 ° C, a hydrogen pressure of 30 bar was maintained. After cooling to 20-25 ° C, the pressure vessel was depressurized. The reaction solution was distilled azeotropically via a distillation bridge, the transition temperature was 99.5 C. After separation of the phases, the lower organic phase contained the title compound. After washing with water and drying, 8.05 g of 1,3,5-trifluorobenzene (98% of theory) were obtained.

Example 12 - Hydrodechlorination of trichlorotrifluorobenzene mixture

Palladium on carbon (10%, 850 mg), 130 g of water, 50 g of a mixture of trichlorotrifluorobenzenes (1,3,5: 1,2,3: 1,2,4-isomers such as 69,1%: 21,7% : 9.2%) and 60g Sodium acetate (4 equivalents) was placed in the pressure vessel. After purging with nitrogen, the pressure vessel was heated to 140 ⁰ C and 12 bar of hydrogen were injected. A hydrogen pressure of 12 bar was maintained at 140 ^° C. for six hours with intensive stirring. After cooling to 20 to 25 ° C, the pressure vessel was depressurized. The biphasic reaction solution was filtered, then the phases were separated. This gave a yield of 91.3% trifluorobenzenes.

Claims

claims

A process for the preparation of 1,3,5-trifluoro-2,4,6-trichlorobenzene from fluorobenzene comprising steps A) and B):

A) chlorination of fluorobenzene of the formula II,

in which X is fluorine or hydrogen, Z is nitro, bromine or chlorine and n is zero or 1-4, and

B) fluorination of the reaction products of step A) and distillative separation of the formed i ^ ö-trifluoro-Aβ-trichlorobenzene.

2. The method according to claim 1, characterized in that the reaction product of the process according to claim 1 in a step C hydrodechlori- tion to 1, 3,5-trifluorobenzene is subjected.

3. The method according to claim 1 or 2, which emanates from fluorobenzene of formula II, in which X is hydrogen and n is zero.

4. The method according to claim 1 or 2, which starts from 1, 3-difluorobenzene of the formula II, in which X is fluorine and n is zero.

5. The method according to any one of claims 1 to 4, characterized in that the chlorination in step A) is carried out with elemental chlorine in the presence of AICI ₃ .

6. The method according to any one of claims 1 to 5, characterized in that in step A) after the chlorination A1) of fluorobenzene of the formula II a distillation step A2) for the separation of volatile constituents from the reaction mixture, which chlorofluorobenzene of the formula III,

in which Y is chlorine or fluorine, containing as the main component is connected.

7. The method according to claim 6, characterized in that in step A2) lower chlorinated fluorobenzenes are separated by distillation and recycled.

8. The method according to any one of claims 1 to 7, characterized in that in step B) the fluorination with KF is carried out in the presence of a solvent.

9. The method according to any one of claims 1 to 8, characterized in that in step B) the fluorination is carried out in the presence of a phase transfer catalyst.

10. The method according to claim 8 or 9, characterized in that the fluorination is carried out in the presence of a reduction inhibitor.

11. The method according to any one of the preceding claims, in which the steps A) and B) are carried out as a one-pot process.

12. The method according to any one of claims 2 to 11, characterized in that in step C) the hydrodechlorination is carried out under pressure in the presence of a heterogeneous catalyst and a base.