阅读说明：本技术 一种3,5-二氟苯酚的合成方法 (Synthetic method of 3, 5-difluorophenol ) 是由 袁其亮 鹿威威 陈建 王超 竺坚飞 陈寅镐 于 2020-11-26 设计创作，主要内容包括：本发明公开了一种3,5-二氟苯酚的合成方法,属于化学合成技术领域。2,4,6-三氟苯甲酸在溶剂中,在碱作用下,经一锅反应得到3,5-二氟苯酚盐,调酸游离后得到3,5-二氟苯酚,该法具有原料价廉易得、合成步骤短、操作简单、反应条件温和、合成收率高、产品质量好、适合工业化生产等优点。2,4,6-三氟苯甲酸以价廉易得的五氯苯腈为原料,首先经氟化反应得到2,4,6-三氟-3,5-二氯苯腈,再经水解反应得到2,4,6-三氟-3,5-二氯苯甲酸,最后经选择性脱氯反应合成,实现了原料2,4,6-三氟苯甲酸的简单、廉价、高效制备,提升合成工艺的工业化应用价值。(The invention discloses a method for synthesizing 3, 5-difluorophenol, and belongs to the technical field of chemical synthesis. The 2,4, 6-trifluoro-benzoic acid is reacted in solvent in one pot under the action of alkali to obtain 3, 5-difluoro-phenol salt, and the 3, 5-difluoro-phenol is obtained after acid adjustment and dissociation. The 2,4, 6-trifluorobenzoic acid is prepared by taking cheap and easily-obtained pentachlorobenzonitrile as a raw material, firstly obtaining 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile through a fluorination reaction, then obtaining 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid through a hydrolysis reaction, and finally synthesizing through a selective dechlorination reaction, so that the simple, cheap and efficient preparation of the raw material 2,4, 6-trifluorobenzoic acid is realized, and the industrial application value of the synthesis process is improved.)

1. A method for synthesizing 3, 5-difluorophenol is characterized by comprising the following steps: 2,4, 6-trifluoro-benzoic acid is reacted in a solvent under the action of alkali in one pot to obtain 3, 5-difluoro phenol salt, and the 3, 5-difluoro phenol is obtained after the acid is regulated and dissociated.

2. The method for synthesizing 3, 5-difluorophenol according to claim 1, characterized in that: the alkali is selected from one or more of the following: the ratio of the amounts of lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, rubidium bicarbonate, cesium bicarbonate, lithium phosphate, sodium phosphate, potassium phosphate, rubidium phosphate, cesium phosphate, lithium hydrogen phosphate, sodium hydrogen phosphate, potassium hydrogen phosphate, rubidium hydrogen phosphate, and cesium hydrogen phosphate to the amounts of 2,4, 6-trifluorobenzoic acid in the alkali to 2,4, 6-trifluorobenzoic acid is 1-10: 1.

3. The method for synthesizing 3, 5-difluorophenol according to claim 1, characterized in that: the solvent is selected from one or more of the following: aromatic hydrocarbon solvent, ether solvent and water, wherein the dosage of the solvent is 1-15 times of the mass of the 2,4, 6-trifluorobenzoic acid.

4. The method for synthesizing 3, 5-difluorophenol according to claim 3, characterized in that: the aromatic hydrocarbon solvent is selected from one or more of the following solvents: benzene, toluene, ethylbenzene, xylene, trimethylbenzene, chlorobenzene, dichlorobenzene.

5. The method for synthesizing 3, 5-difluorophenol according to claim 3, characterized in that: the ether solvent is represented by the following general formula: R-O-R ', wherein R and R' are respectively and independently selected from C1-C10 linear chain, branched chain or cyclic alkyl, C1-C10 linear chain, branched chain or cyclic alkoxy alkyl, and are selected from one or more of the following: diethyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, methyl isopropyl ether, ethyl isopropyl ether, n-propyl ether, isopropyl ether, methyl n-butyl ether, ethyl n-butyl ether, methyl isobutyl ether, ethyl isobutyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, dimethoxymethane, diethoxymethane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, 1-dimethoxypropane, 1-diethoxypropane, 2-dimethoxypropane, 2-diethoxypropane, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 4-dioxane, cyclopentyl methyl ether, cyclohexyl methyl ether.

6. The method for synthesizing 3, 5-difluorophenol according to claim 1, characterized in that: the reaction temperature is 50-200 deg.C^oC。

7. The method for synthesizing 3, 5-difluorophenol according to claim 1, characterized in that: the 2,4, 6-trifluoro-benzoic acid is prepared by the following method: 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid is subjected to selective dechlorination reaction to obtain the 2,4, 6-trifluorobenzoic acid.

8. The method for synthesizing 3, 5-difluorophenol according to claim 7, wherein: the selective dechlorination reaction is a catalytic hydrodechlorination reaction.

9. The method for synthesizing 3, 5-difluorophenol according to claim 8, wherein: the catalyst is selected from one or more of the following components: the catalyst is palladium, platinum, rhodium, ruthenium, nickel and cobalt, and the dosage of the catalyst is 0.00001-0.3 time of the mass of 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid.

10. The method for synthesizing 3, 5-difluorophenol according to claim 8, wherein: in the catalytic hydrodechlorination reaction, the solvent is selected from one or more of the following solvents: the solvent comprises an alcohol solvent, an ester solvent, an ether solvent and water, wherein the dosage of the solvent is 1-20 times of the mass of 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid.

11. The method of claim 10, wherein the synthesis of 3, 5-difluorophenol comprises: the alcohol solvent is represented by the following general formula: r (OH)_nWherein R is C1-C10 linear chain, branched chain or cyclic alkyl, C1-C10 linear chain, branched chain or cyclic alkoxy alkyl, and n = 1-3.

12. The method of claim 10, wherein the synthesis of 3, 5-difluorophenol comprises: the ester solvent is represented by the following general formula: R-CO₂-R', wherein R is a linear, branched or cyclic alkyl group of C1 to C10, a linear, branched or cyclic alkoxy group of C1 to C10, a linear, branched or cyclic alkoxyalkyl group of C1 to C10; r' is C1-C10 linear chain, branched chain or cyclic alkyl, C1-C10 linear chain or branched chain alkoxy alkyl.

13. The method of claim 10, wherein the synthesis of 3, 5-difluorophenol comprises: the ether solvent is represented by the following general formula: R-O-R ', wherein R and R' are respectively and independently selected from linear, branched or cyclic alkyl of C1-C10 and linear, branched or cyclic alkoxy alkyl of C1-C10.

14. The method for synthesizing 3, 5-difluorophenol according to claim 8, wherein: the catalytic hydrogenation dechlorination reaction has the hydrogenation pressure of 0.001-3.0 MPa.

15. The method for synthesizing 3, 5-difluorophenol according to claim 8, wherein: the catalytic hydrogenation dechlorination reaction is carried out at the reaction temperature of 0-100 DEG C^oC。

16. The method for synthesizing 3, 5-difluorophenol according to claim 7, wherein: the 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid is prepared by the following method: 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile is subjected to hydrolysis reaction to obtain the 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid.

17. The method of claim 16, wherein the step of synthesizing 3, 5-difluorophenol comprises the steps of: the hydrolysis reaction is carried out in a sulfuric acid aqueous solution with the mass concentration of 20-90%, and the dosage of the sulfuric acid aqueous solution is 1-15 times of the mass of 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile.

18. The method of claim 16, wherein the step of synthesizing 3, 5-difluorophenol comprises the steps of: the hydrolysis reaction temperature is 100-200%^oC。

19. The method of claim 16, wherein the step of synthesizing 3, 5-difluorophenol comprises the steps of: the 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile is prepared by the following method: reacting pentachlorobenzonitrile with a fluorinating agent in a polar aprotic solvent to obtain the 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile.

20. The method of claim 19, wherein the synthesis of 3, 5-difluorophenol comprises: the polar aprotic solvent is selected from one or more of the following: the solvent is N, N-dimethylformamide, N-dimethylacetamide, N-diethylformamide, N-diethylacetamide, N-methylpyrrolidone, 1, 3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, dimethyl sulfone, sulfolane, nitrobenzene, benzonitrile, 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile, and the amount of the solvent is 1-15 times of the mass of pentachlorobenzonitrile.

21. The method of claim 19, wherein the synthesis of 3, 5-difluorophenol comprises: the fluorinating agent is selected from one or more of the following: the ratio of the amount of lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride and cesium fluoride to the amount of pentachlorobenzonitrile is 3-6: 1.

22. The method of claim 19, wherein the synthesis of 3, 5-difluorophenol comprises: the fluorination reaction temperature is 100-250 deg.C^oC。

The technical field is as follows:

the invention belongs to the technical field of chemical synthesis, and particularly relates to a synthesis method of 3, 5-difluorophenol.

Background art:

3, 5-difluorophenol is a very important fluorine-containing fine chemical, has wide application in the fields of medicines, pesticides, new materials and the like, and is a key intermediate for synthesizing Tegoprazan for treating gastroesophageal reflux disease and erosive esophagitis.

There are three main methods for synthesizing 3, 5-difluorophenol.

(1) 3, 5-difluoroaniline is used as a raw material, and diazo reaction and hydrolysis reaction are carried out to synthesize 3, 5-difluorophenol:

this method is a conventional method for synthesizing phenolic compounds. The method has the disadvantages that the raw material 3, 5-difluoroaniline is expensive and not easy to obtain, the diazo/hydrolysis reaction has certain safety risk, the wastewater amount in the synthesis process is large, the method is not environment-friendly, and the yield is not ideal.

(2) 3, 5-difluorobromobenzene is used as a raw material, and 3, 5-difluorophenol is synthesized through lithiation/boronization and oxidation reactions:

the method has the advantages that raw materials and reagents are expensive and not easy to obtain, lithiation/boronization reaction needs to be carried out at low temperature, reaction conditions are harsh, and reagents such as butyl lithium, hydrogen peroxide and the like have certain potential safety hazards in use, so that the industrial application value is low.

(3) 3, 5-difluorobromobenzene is used as a raw material, and 3, 5-difluorophenol is synthesized through etherification and hydrolysis reactions:

the raw materials used in the method are expensive and not easy to obtain, cuprous halide is used as a catalyst and bidentate ligands such as nitrogen, phosphorus and the like in the etherification reaction, the synthesis cost is high, a large amount of acidic wastewater is generated in the hydrolysis reaction, and the method is not environment-friendly.

The invention content is as follows:

the invention aims to provide a synthetic method of 3, 5-difluorophenol, which has the advantages of cheap and easily obtained raw materials, short synthetic steps, simple operation, mild reaction conditions, high synthetic yield, good product quality and suitability for industrial production.

The technical scheme adopted by the invention is as follows:

a method for synthesizing 3, 5-difluorophenol is characterized by comprising the following steps: 2,4, 6-trifluoro-benzoic acid (I) is reacted in a solvent under the action of alkali in a one-pot way to obtain 3, 5-difluorophenol salt, and 3, 5-difluorophenol (II) is obtained after the acid is regulated and dissociated.

The synthetic route adopted by the invention can be represented by the following reaction formula:

the invention further provides that:

the reaction process of synthesizing 3, 5-difluorophenol from 2,4, 6-trifluorobenzoic acid under alkaline condition has two reaction stages, one is hydroxylation reaction stage, and the other is decarboxylation reaction stage, and can be represented by the following reaction formula:

the hydroxylation reaction stage and the decarboxylation reaction stage do not have the requirement of a sequence, and can be subjected to the decarboxylation reaction first and then the hydroxylation reaction, or the hydroxylation reaction first and then the decarboxylation reaction, or both of the hydroxylation reaction and the decarboxylation reaction. When hydroxylation reaction is carried out firstly and then decarboxylation reaction is carried out, an intermediate A or an intermediate B or a mixture of the intermediate A and the intermediate B is generated firstly in the reaction process, and then decarboxylation reaction is carried out to obtain 3, 5-difluorophenate; when decarboxylation reaction and hydroxylation reaction are carried out firstly, an intermediate C is generated in the reaction process, and then hydroxylation reaction is carried out to obtain 3, 5-difluorophenate; when the hydroxylation reaction and the decarboxylation reaction are carried out simultaneously, an intermediate A, an intermediate B, an intermediate C and 3, 5-difluorophenate exist simultaneously in the reaction process, and the proportion of the intermediate A, the intermediate B, the intermediate C and the 3, 5-difluorophenate is different due to different reaction conditions, reaction processes and the like; when the reaction conditions are more severe, the reaction can directly generate the 3, 5-difluorophenol salt from the 2,4, 6-trifluorobenzoate without an intermediate stage; and (3) carrying out acid adjustment and ionization on the generated 3, 5-difluorophenol salt to obtain 3, 5-difluorophenol. In the reaction process, the intermediate A, the intermediate B and the intermediate C in the reaction liquid are separated and purified by adopting a proper separation method, the separated intermediate A, the separated intermediate B, the separated intermediate C or a mixture consisting of the intermediate A, the intermediate B and the intermediate C in any proportion is subjected to a second-stage reaction under an alkaline condition, and 3, 5-difluorophenylphenol can be obtained similarly, but a step-by-step reaction mode is adopted, so that the separation and purification operation is increased, the operation process is complicated, the additional purification cost and operation loss are increased, the synthesis cost is increased, and therefore, the method is not a preferred mode, and the preferred reaction mode is: the 3, 5-difluorophenate is obtained by adopting a one-pot reaction method without separation and purification operations in the process.

The alkali can be inorganic alkali or organic alkali, the preferable alkali is inorganic alkali and is selected from one or more of hydroxides, carbonates, bicarbonates, phosphates and hydrogen phosphates of alkali metals and alkaline earth metals, the more preferable alkali is alkali hydroxides, carbonates, bicarbonates, phosphates and hydrogen phosphates, and is selected from one or more of the following: lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, lithium hydrogencarbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, rubidium hydrogencarbonate, cesium hydrogencarbonate, lithium phosphate, sodium phosphate, potassium phosphate, rubidium phosphate, cesium phosphate, lithium hydrogenphosphate, sodium hydrogenphosphate, potassium hydrogenphosphate, rubidium hydrogenphosphate, and cesium hydrogenphosphate. The ratio of the amount of the base to the amount of 2,4, 6-trifluorobenzoic acid is (1-10): 1.

The solvent can be alkane solvent, chloroalkane solvent, aromatic solvent, alcohol solvent, ester solvent, ketone solvent, ether solvent, polar aprotic solvent, water and the like, and can be single solvent or homogeneous or heterogeneous mixed solvent consisting of two or more solvents. Preferred solvents are chloroalkane solvents, aromatic solvents, ether solvents, polar aprotic solvents and water. Representative chloroalkane solvents are: methylene chloride, chloroform, carbon tetrachloride, 1, 1-dichloroethane, 1, 2-dichloroethane, 1,1, 1-trichloroethane, and the like. Representative aromatic hydrocarbon solvents are: benzene, toluene, ethylbenzene, xylene, trimethylbenzene, chlorobenzene, dichlorobenzene, and the like. The ether solvent is represented by the following general formula: R-O-R ', wherein R and R' are respectively and independently selected from C1-C10 linear chain, branched chain or cyclic alkyl, C1-C10 linear chain, branched chain or cyclic alkoxy alkyl, and representative ether solvents are: diethyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, methyl isopropyl ether, ethyl isopropyl ether, n-propyl ether, isopropyl ether, methyl n-butyl ether, ethyl n-butyl ether, methyl isobutyl ether, ethyl isobutyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, dimethoxymethane, diethoxymethane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, 1-dimethoxypropane, 1-diethoxypropane, 2-dimethoxypropane, 2-diethoxypropane, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 4-dioxane, cyclopentyl methyl ether, cyclohexyl methyl ether, and the like. Representative polar aprotic solvents are: n, N-dimethylformamide, N-diethylformamide, N-dimethylacetamide, N-diethylacetamide, dimethylsulfoxide, dimethylsulfone, N-methylpyrrolidone, 1, 3-dimethyl-2-imidazolidinone, sulfolane, and the like. More preferred solvents are selected from one or more of the following: aromatic hydrocarbon solvent, ether solvent and water. The dosage of the solvent is 1-15 times of the mass of the 2,4, 6-trifluorobenzoic acid.

The reaction can be smoothly carried out under a certain temperature condition, the reaction speed is slow due to the excessively low reaction temperature, the synthesis efficiency is not favorably improved, the side reaction is aggravated due to the excessively high reaction temperature, the reaction yield and the product quality are reduced, and the preferable reaction temperature is 50-200 ℃. When the boiling point of the solvent is lower than the reaction temperature, the reaction temperature can be raised to the required temperature by means of a closed reaction system, so as to obtain a better reaction result.

The acid adjustment and dissociation refer to a process of reacting 3, 5-difluorophenate with protonic acid to obtain 3, 5-difluorophenol. The protonic acid can be organic protonic acid, such as formic acid, acetic acid, propionic acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzoic acid, benzenesulfonic acid, phenylacetic acid and the like, and can also be inorganic protonic acid, such as hydrochloric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid and the like. When the protonic acid is polybasic acid, the acidic salt thereof can also be used as an acid-adjusting free reagent, such as hydrosulfate, dihydrogen phosphate and the like. The protonic acid is used in an amount sufficient to completely neutralize 3, 5-difluorophenol salt and to sufficiently dissociate 3, 5-difluorophenol.

The 2,4, 6-trifluoro-benzoic acid is prepared by the following method: 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid is subjected to selective dechlorination reaction to obtain the 2,4, 6-trifluorobenzoic acid. The alternative dechlorination reaction comprises the following steps: catalytic hydrodechlorination, metal reductive dechlorination, metal hydride or borohydride dechlorination, organometallic alkylation and the like. The preferable dechlorination reaction is catalytic hydrodechlorination reaction, and the following steps are further set:

the catalyst is selected from one or more of the following: the palladium, platinum, rhodium, ruthenium, nickel and cobalt can be in the form of elementary metal, and can also be in the form of corresponding compounds, such as oxide, hydroxide, halide, organic acid salt and the like. In order to increase the specific surface area of the catalyst and increase the catalytic activity, the catalyst can be dispersed on a carrier, such as palladium carbon, platinum carbon and the like, and can also be prepared into a microporous catalyst, such as sponge nickel, sponge cobalt and the like. The dosage of the catalyst is 0.00001-0.3 time of the mass of the 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid.

The optional solvent includes alkane solvent, aromatic solvent, alcohol solvent, ester solvent, and ketoneSolvents, ether solvents, water, etc., and preferred solvents are alcohol solvents, ester solvents, ketone solvents, ether solvents, and water. The alcohol solvent can be monohydric alcohol solvent or polyhydric alcohol solvent, and is represented by the following general formula: r (OH)_nWherein R is a C1-C10 linear, branched or cyclic alkyl group, a C1-C10 linear, branched or cyclic alkoxyalkyl group, and n is 1-3, and representative alcohol solvents are: methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, n-pentanol, n-hexanol, cyclopentanol, cyclohexanol, ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-cyclohexanediol, glycerol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and the like. The ester solvent is represented by the following general formula: R-CO₂-R', wherein R is a linear, branched or cyclic alkyl group of C1 to C10, a linear, branched or cyclic alkoxy group of C1 to C10, a linear, branched or cyclic alkoxyalkyl group of C1 to C10; r' is C1-C10 linear chain, branched chain or cyclic alkyl, C1-C10 linear chain or branched chain alkoxy alkyl; representative ester solvents are: methyl formate, ethyl formate, n-propyl formate, isopropyl formate, n-butyl formate, cyclohexyl formate, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, cyclohexyl acetate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl methoxyacetate, ethyl methoxyacetate, and the like. The ketone solvent is represented by the following general formula: R-CO-R ', wherein R and R' are respectively and independently selected from linear, branched or cyclic alkyl of C1-C10, linear, branched or cyclic alkoxyalkyl of C1-C10, and representative ketone solvents are: acetone, butanone, 2-pentanone, 3-pentanone, methyl isopropyl ketone, 2-hexanone, 3-hexanone, methyl isobutyl ketone, and the like. The ether solvent is represented by the following general formula: R-O-R ', wherein R and R' are respectively and independently selected from C1-C10 linear chain, branched chain or cyclic alkyl, C1-C10 linear chain, branched chain or cyclic alkoxy alkyl, and representative ether solvents are: diethyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, methyl isopropyl ether, ethyl isopropyl ether, n-propyl ether, isopropyl ether, methyl n-butyl ether, ethyl n-butyl ether, methyl isobutyl ether, ethyl isobutyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, dimethoxymethane, diethyl etherOxymethane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, 1-dimethoxypropane, 1-diethoxypropane, 2-dimethoxypropane, 2-diethoxypropane, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 4-dioxane, cyclopentyl methyl ether, cyclohexyl methyl ether, and the like. The solvent can be a single solvent, or a homogeneous or heterogeneous mixed solvent consisting of two or more solvents, and the dosage of the solvent is 1-20 times of the mass of the 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid.

Hydrogen chloride is generated in the reaction process, and in order to avoid adverse effects of the generated hydrogen chloride on reaction equipment and a catalyst, a proper amount of acid binding agent can be added in the reaction process to neutralize the hydrogen chloride generated in the reaction. Of course, if a reaction apparatus having corrosion resistance is selected and an acid-resistant catalyst is selected, the reaction can be carried out without using an acid-binding agent. The acid-binding agent may be organic amine compound such as alkyl tertiary amine, pyridine and its derivatives, or oxide, hydroxide, carbonate, phosphate of alkali metal and alkaline earth metal. The alkyl tertiary amine acid-binding agent can be represented by the following general formula: RR 'R' N, wherein R, R 'and R' are each independently selected from C1-C10 linear, branched or cyclic alkyl. The preferable acid-binding agent is selected from one or more of the following: lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, magnesium hydroxide, calcium hydroxide, magnesium oxide, calcium oxide, lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, magnesium carbonate, calcium carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, rubidium bicarbonate, cesium bicarbonate, magnesium bicarbonate, calcium bicarbonate, lithium phosphate, sodium phosphate, potassium phosphate, rubidium phosphate, cesium phosphate, magnesium phosphate, calcium phosphate, dilithium hydrogen phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, rubidium hydrogen phosphate, dicesium hydrogen phosphate, magnesium hydrogen phosphate, calcium hydrogen phosphate, trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, dimethylethylamine, dimethyl-n-propylamine, dimethyl-iso-propylamine, dimethyl-n-butylamine, diethyl-methylamine, diethyl-n-propylamine, diethyl-isopropylamine, di-n-propylmethylamine, di-N-propylethylamine, di-N-propylisopropylamine, di-N-propyln-butylamine, diisopropylmethylamine, diisopropylethylamine, diisopropyl-N-propylamine, diisopropyl-N-butylamine, di-N-butylmethylamine, di-N-butylethylamine, di-N-butyl-N-propylamine, di-N-butylisopropylamine, triethylenediamine, N-methylmorpholine, N-dimethylpiperazine, pyridine, 4-dimethylaminopyridine. The dosage of the acid-binding agent is determined according to the molecular structure and the acid-binding capacity of the acid-binding agent, and the hydrogen chloride generated by neutralization reaction is used as a standard.

The reaction needs to be carried out in the presence of hydrogen, and because the hydrogen partial pressure in the reaction system cannot be directly measured in the reaction process, the hydrogen partial pressure is usually replaced by the hydrogenation pressure, and the content of the hydrogen in the reaction system is represented. The hydrogenation pressure refers to the sum of the partial pressures of various gases in the reaction kettle under certain hydrogenation conditions, such as a certain feeding ratio and reaction temperature, and includes the sum of the partial pressure of hydrogen, the partial pressure of raw material vapor, the partial pressure of solvent vapor and the like under the conditions. Under fixed conditions, the hydrogenation pressure can indirectly represent the partial pressure of hydrogen in the reaction vessel. The hydrogenation pressure has a significant influence on the hydrogenation reduction rate and the type of hydrogenation equipment. The hydrogenation pressure is low, the hydrogenation speed is slow, but the requirement on hydrogenation equipment is low; the hydrogenation pressure is high, the hydrogenation speed is high, but the requirements on hydrogenation equipment and safe operation are increased. The preferable hydrogenation pressure is 0.001 to 3.0 MPa.

The hydrogenation reaction temperature is related to the reaction solvent, the type and amount of the catalyst, the hydrogenation pressure and the like, and the preferable reaction temperature is 0-100 ℃.

The 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid is prepared by the following method: 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile is subjected to hydrolysis reaction to obtain the 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid. The hydrolysis reaction is preferably carried out in a sulfuric acid aqueous solution, the mass percentage of sulfuric acid in the sulfuric acid aqueous solution is 20% -90%, the use amount of the sulfuric acid aqueous solution is 1-15 times of the mass of 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile, and the hydrolysis reaction temperature is 100-200 ℃.

The 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile can be prepared by the following method: reacting pentachlorobenzonitrile with a fluorinating agent in a polar aprotic solvent to obtain 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile, which is further set as follows:

the polar aprotic solvent is selected from one or more of the following: n, N-dimethylformamide, N-dimethylacetamide, N-diethylformamide, N-diethylacetamide, N-methylpyrrolidone, 1, 3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, dimethyl sulfone, sulfolane, nitrobenzene, benzonitrile, 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile. The reaction product 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile is liquid at normal temperature, has a boiling point of about 230 ℃ and stable chemical properties within the boiling point range, and can also be used as a reaction solvent. The dosage of the solvent is 1-15 times of the mass of the pentachlorobenzonitrile.

The fluorinating agent is alkali metal fluoride salt, and is selected from one or more of the following: lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride and cesium fluoride, and by combining the factors of fluorinating agent activity, cost and the like, the preferable fluorinating agent is one or two of the following: sodium fluoride and potassium fluoride. The mass ratio of the fluorinating agent to the pentachlorobenzonitrile is (3-6): 1.

In the process of fluorination reaction, a proper amount of single or composite catalyst is added, so that the fluorination reaction rate can be improved, and the fluorination reaction temperature can be reduced. The types of catalysts that can be selected are mainly: quaternary ammonium salt catalysts such as tetramethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium fluoride, benzyltriethylammonium chloride, cetyltrimethylammonium chloride, etc.; quaternary phosphonium salt catalysts such as triphenylmethylphosphonium bromide, triphenylethylphosphonium bromide, tetraphenylphosphonium bromide, etc.; crown ether catalysts such as 18-crown ether-6, 15-crown ether-5 and the like, wherein the dosage of the catalysts is 0-0.3 time of the mass of pentachlorobenzonitrile.

The fluorination reaction system has different reactivity and thus different fluorination reaction temperatures. If the reaction temperature is too low, the fluorination reaction speed is slow, the synthesis efficiency is not favorably improved, if the reaction temperature is too high, side reactions are increased, and the preferred fluorination reaction temperature is 100-250 ℃.

Compared with the prior art, the invention has the beneficial effects that:

(1) the novel route of synthesizing 3, 5-difluorophenol by taking 2,4, 6-trifluorobenzoic acid as a raw material through one-pot reaction under the action of alkali is developed, and the method has the advantages of cheap and easily-obtained raw materials, short synthesis step, simplicity in operation, mild reaction conditions, high synthesis yield, good product quality, suitability for industrial production and the like;

(2) the 2,4, 6-trifluorobenzoic acid is synthesized by taking cheap and easily available pentachlorobenzonitrile as a raw material through three reaction steps of fluorination, dechlorination and hydrolysis, so that the simple, cheap and efficient preparation of the raw material 2,4, 6-trifluorobenzoic acid is realized, and the industrial application value of the synthesis process is improved.

The present invention will be further described with reference to the following embodiments. The following embodiments are only for the purpose of facilitating understanding of the present invention and do not limit the present invention. The present invention is not intended to be limited to the specific embodiments, and all the features mentioned in the description may be combined with each other to constitute a new embodiment as long as the features do not conflict with each other.

The specific implementation mode is as follows:

example one

Adding 300 g of water, 300 g of dimethylbenzene and 113 g of sodium carbonate into a 1L pressure-resistant reaction kettle, stirring at room temperature, adding 75 g of 2,4, 6-trifluorobenzoic acid, sealing the reaction kettle, heating to 160-165 ℃, stirring for reacting for 10 hours, and stopping reaction. And cooling the reaction system to room temperature, taking out reaction liquid, adjusting the pH value to 1-2 by using concentrated hydrochloric acid, standing for layering, separating out an organic phase, extracting a water phase by using dimethylbenzene, combining the organic phases, drying, concentrating and rectifying to obtain 51.81 g of 3, 5-difluorophenol, wherein the yield is 93.5%, and the purity is 99.7%.

Example two

Adding 480 g of water and 110 g of sodium hydroxide into a 1L pressure-resistant reaction kettle, stirring at room temperature, adding 160 g of 2,4, 6-trifluorobenzoic acid, sealing the reaction kettle, heating to 150-155 ℃, stirring for reacting for 15 hours, and stopping reaction. Cooling the reaction system to room temperature, taking out the reaction liquid, stirring at room temperature, adjusting the pH value to be strongly acidic by using 10% hydrochloric acid, extracting by using trichloromethane, combining organic phases, drying, concentrating and rectifying to obtain 111.46 g of 3, 5-difluorophenol, wherein the yield is 94.3%, and the purity is 99.6%.

EXAMPLE III

Adding 210 g of water, 280 g of toluene and 110 g of potassium hydroxide into a 1L pressure-resistant reaction kettle, stirring at room temperature, adding 70 g of 2,4, 6-trifluorobenzoic acid, sealing the reaction kettle, heating to 80-85 ℃, stirring for reacting for 30 hours, heating to 140-145 ℃, continuing to react for 10 hours, and stopping the reaction. And cooling the reaction system to room temperature, taking out reaction liquid, regulating the pH value to 1-2 by using 50% sulfuric acid solution, standing for layering, separating out an organic phase, extracting a water phase by using toluene, combining the organic phases, drying, concentrating and rectifying to obtain 49.38 g of 3, 5-difluorophenol, wherein the yield is 95.5%, and the purity is 99.8%.

Example four

Adding 470 g of water and 165 g of potassium carbonate into a 1L pressure-resistant reaction kettle, stirring at room temperature, adding 105 g of 2,4, 6-trifluorobenzoic acid, sealing the reaction kettle, heating to 140-145 ℃, continuing to react for 15 hours, and stopping reaction. And cooling the reaction system to room temperature, taking out reaction liquid, adjusting the pH value to 1-2 by using concentrated sulfuric acid, extracting by using toluene, combining organic phases, drying, concentrating and rectifying to obtain 73.69 g of 3, 5-difluorophenol, wherein the yield is 95.0%, and the purity is 99.7%.

EXAMPLE five

Adding 585 g of water and 80 g of lithium hydroxide into a pressure-resistant reaction kettle of 1 liter, stirring at room temperature, adding 65 g of 2,4, 6-trifluoro-benzoic acid, sealing the reaction kettle, heating to 90-95 ℃, stirring for reaction for 25 hours, heating to 130-135 ℃, continuing to react for 12 hours, and stopping reaction. And cooling the reaction system to room temperature, taking out reaction liquid, adjusting the pH value to 1-2 by using 30% hydrobromic acid solution, extracting by using dichloromethane, combining organic phases, drying, concentrating and rectifying to obtain 45.70 g of 3, 5-difluorophenol, wherein the yield is 95.2%, and the purity is 99.7%.

EXAMPLE six

Adding 640 g of water and 127 g of sodium hydroxide into a 1L pressure-resistant reaction kettle, stirring at room temperature, adding 80 g of 2,4, 6-trifluorobenzoic acid, sealing the reaction kettle, heating to 170-175 ℃, stirring for reacting for 6 hours, and stopping reaction. And cooling the reaction system to room temperature, taking out the reaction solution, stirring at room temperature, adjusting the pH value to 1-2 by using 15% hydrochloric acid, extracting by using ethyl acetate, combining organic phases, drying, concentrating and rectifying to obtain 55.32 g of 3, 5-difluorophenol, wherein the yield is 93.6% and the purity is 99.5%.

EXAMPLE seven

Adding 500 g of 2-methyltetrahydrofuran and 127.5 g of potassium hydroxide into a 1L pressure-resistant reaction kettle, stirring at room temperature, adding 100 g of 2,4, 6-trifluorobenzoic acid, sealing the reaction kettle, heating to 130-135 ℃, stirring for reacting for 20 hours, and stopping reaction. Cooling the reaction system to room temperature, taking out the reaction liquid, adding 300 g of water, stirring at room temperature, adjusting the pH value to 1-2 by using 15% sulfuric acid, standing for layering, separating out an organic phase, extracting a water phase by using 2-methyltetrahydrofuran, combining the organic phases, drying, concentrating and rectifying to obtain 69.89 g of 3, 5-difluorophenol, wherein the yield is 94.6%, and the purity is 99.7%.

Example eight

Adding 450 g of water, 135 g of methyl tert-butyl ether and 190 g of potassium phosphate into a 1L pressure-resistant reaction kettle, stirring at room temperature, adding 45 g of 2,4, 6-trifluorobenzoic acid, sealing the reaction kettle, heating to 100-105 ℃, stirring for reaction for 20 hours, heating to 120-125 ℃, continuing the reaction for 15 hours, and stopping the reaction. And cooling the reaction system to room temperature, taking out the reaction liquid, adjusting the pH value to 1-2 by using a concentrated hydrobromic acid solution, standing for layering, separating out an organic phase, extracting a water phase by using methyl tert-butyl ether, combining the organic phases, drying, concentrating and rectifying to obtain 31.95 g of 3, 5-difluorophenol, wherein the yield is 96.1%, and the purity is 99.6%.

Example nine

Adding 540 g of water and 112 g of sodium hydroxide into a 1L pressure-resistant reaction kettle, stirring at room temperature, adding 90 g of 2,4, 6-trifluorobenzoic acid, sealing the reaction kettle, heating to 120-125 ℃, stirring for reaction for 22 hours, and stopping reaction. And cooling the reaction system to room temperature, taking out reaction liquid, adjusting the pH value to 1-2 by using concentrated hydrochloric acid, extracting by using dichloroethane, combining organic phases, drying, concentrating and rectifying to obtain 63.36 g of 3, 5-difluorophenol, wherein the yield is 95.3 percent and the purity is 99.8 percent.

Example ten

Adding 275 g of water, 330 g of tetrahydrofuran and 105 g of potassium hydroxide into a 1L pressure-resistant reaction kettle, stirring at room temperature, adding 55 g of 2,4, 6-trifluorobenzoic acid, sealing the reaction kettle, heating to 110-115 ℃, stirring for reacting for 35 hours, and stopping the reaction. And cooling the reaction system to room temperature, taking out reaction liquid, adjusting the pH value to 1-2 by using 40% sulfuric acid solution, extracting by using isopropyl ether, combining organic phases, drying, concentrating and rectifying to obtain 38.27 g of 3, 5-difluorophenol, wherein the yield is 94.2%, and the purity is 99.9%.

EXAMPLE eleven

Adding 520 g of water and 133 g of sodium hydroxide into a 1L pressure-resistant reaction kettle, stirring at room temperature, adding 130 g of 2,4, 6-trifluorobenzoic acid, sealing the reaction kettle, heating to 130-135 ℃, stirring for reacting for 18 hours, and stopping reaction. And cooling the reaction system to room temperature, taking out reaction liquid, adjusting the pH value to 1-2 by using 30% sulfuric acid solution, extracting by using toluene, combining organic phases, drying, concentrating and rectifying to obtain 92.01 g of 3, 5-difluorophenol, wherein the yield is 95.8% and the purity is 99.6%.

Example twelve

Adding 150 g of 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid and 600 g of water into a 1L pressure-resistant reaction kettle, stirring at room temperature, adding 105 g of potassium hydroxide and 4.5 g of 5% wet palladium carbon, sealing the reaction kettle, replacing gas with nitrogen for 3 times, replacing gas with hydrogen for 5 times, controlling the internal pressure of the kettle to be 0.2-0.3 MPa by hydrogen, heating to 60-65 ℃, preserving heat, reacting for 15 hours, and stopping reaction. And cooling the reaction system to room temperature, removing the pressure in the kettle, filtering the reaction solution, adjusting the pH of the filtrate to 1-2 by using concentrated hydrochloric acid, filtering, rinsing and drying the filter cake to obtain 104.37 g of 2,4, 6-trifluoro-benzoic acid, wherein the yield is 96.8 percent, and the purity is 99.2 percent.

EXAMPLE thirteen

Adding 60 g of 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid, 480 g of ethanol, 90 g of triethylamine and 3 g of 5% wet platinum carbon into a 1L pressure-resistant reaction kettle, sealing the reaction kettle, replacing gas with nitrogen for 3 times, replacing gas with hydrogen for 5 times, controlling the internal pressure of the kettle to be 0.5-0.6 MPa with hydrogen, starting stirring, heating to 50-55 ℃, preserving heat, reacting for 20 hours, and stopping reaction. Cooling the reaction system to room temperature, removing the pressure in the kettle, adding 150 g of water, uniformly stirring, filtering, adjusting the pH of the filtrate to 1-2 by using 50% sulfuric acid solution, filtering, rinsing and drying the filter cake to obtain 41.62 g of 2,4, 6-trifluorobenzoic acid, wherein the yield is 96.5%, and the purity is 99.1%.

Example fourteen

Adding 130 g of 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid and 500 g of water into a 1L pressure-resistant reaction kettle, stirring at room temperature, adding 225 g of 30% sodium hydroxide solution and 13 g of spongy nickel, sealing the reaction kettle, replacing gas with nitrogen for 3 times, replacing gas with hydrogen for 5 times, controlling the internal pressure of the kettle to be 1.0-1.1 MPa by hydrogen, heating to 40-45 ℃, preserving heat, reacting for 18 hours, and stopping reaction. The pressure of the reaction system is relieved, the reaction liquid is filtered, the pH of the filtrate is adjusted to be strong acid by 15 percent hydrochloric acid, the filtrate is filtered, and the filter cake is rinsed and dried to obtain 90.74 g of 2,4, 6-trifluoro-benzoic acid, the yield is 97.1 percent, and the purity is 99.3 percent.

Example fifteen

Adding 65 g of 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid, 325 g of water, 260 g of methanol, 45 g of magnesium carbonate and 0.35 g of 5% dry palladium carbon into a 1L pressure-resistant reaction kettle, sealing the reaction kettle, replacing gas with nitrogen for 3 times, replacing gas with hydrogen for 5 times, controlling the internal pressure of the kettle to be 1.2-1.3 MPa by hydrogen, starting stirring, controlling the temperature to be 30-35 ℃, preserving the temperature, reacting for 25 hours, and stopping the reaction. The pressure of the reaction system is relieved, the reaction liquid is filtered, the pH of the filtrate is adjusted to be strong acid by using 30 percent sulfuric acid, the filtrate is filtered, and a filter cake is rinsed and dried to obtain 44.75 g of 2,4, 6-trifluoro-benzoic acid, the yield is 95.8 percent, and the purity is 99.2 percent.

Example sixteen

Adding 80 g of 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid, 560 g of water, 125 g of potassium phosphate and 16 g of spongy cobalt into a 1L pressure-resistant reaction kettle, sealing the reaction kettle, replacing gas with nitrogen for 3 times, replacing gas with hydrogen for 5 times, controlling the internal pressure of the kettle to be 1.5-1.6 MPa with hydrogen, starting stirring, heating to 70-75 ℃, preserving heat, reacting for 12 hours, and stopping reaction. And cooling the reaction system to room temperature, removing the pressure in the kettle, filtering the reaction solution, adjusting the pH of the filtrate to 1-2 with concentrated sulfuric acid, filtering, rinsing and drying the filter cake to obtain 55.33 g of 2,4, 6-trifluoro-benzoic acid, wherein the yield is 96.2 percent and the purity is 99.4 percent.

Example seventeen

Adding 90 g of 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid, 540 g of water, 33 g of magnesium oxide and 0.9 g of 10% wet palladium carbon into a 1L pressure-resistant reaction kettle, sealing the reaction kettle, replacing gas with nitrogen for 3 times, replacing gas with hydrogen for 5 times, controlling the internal pressure of the kettle to be 0.8-0.9 MPa with hydrogen, starting stirring, heating to 80-85 ℃, preserving heat, reacting for 10 hours, and stopping reaction. Cooling the reaction system to room temperature, removing the pressure in the kettle, filtering the reaction solution, adjusting the pH of the filtrate to 1-2 by using 20% hydrobromic acid solution, filtering, rinsing and drying the filter cake to obtain 62.95 g of 2,4, 6-trifluoro-benzoic acid, wherein the yield is 97.3%, and the purity is 99.1%.

EXAMPLE eighteen

350 g of 65% sulfuric acid solution and 70 g of 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile are added into a 500 ml reaction bottle, stirring is started, the temperature is increased to 150-155 ℃, reaction is carried out for 15 hours under the condition of heat preservation, and the reaction is stopped. The reaction system is cooled to room temperature, filtered, and the filter cake is washed by water and dried to obtain 71.94 g of 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid, the yield is 94.8 percent, and the purity is 99.3 percent.

Example nineteen

Adding 300 g of 75% sulfuric acid solution and 100 g of 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile into a 500 ml reaction bottle, starting stirring, heating to 160-165 ℃, keeping the temperature for reaction for 10 hours, and stopping reaction. The reaction system is cooled to room temperature, filtered, and the filter cake is washed with water and dried to obtain 103.85 g of 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid with the yield of 95.8 percent and the purity of 99.1 percent.

Example twenty

320 g of 70% sulfuric acid solution and 80 g of 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile are added into a 500 ml reaction bottle, stirring is started, the temperature is increased to 155-160 ℃, reaction is carried out for 12 hours under the condition of heat preservation, and the reaction is stopped. The reaction system is cooled to room temperature, filtered, and the filter cake is washed by water and dried to obtain 82.65 g of 2,4, 6-trifluoro-3, 5-dichlorobenzoic acid, the yield is 95.3 percent, and the purity is 99.2 percent.

Example twenty one

Adding 80 g of pentachlorobenzonitrile, 240 g of N, N-dimethylformamide, 61 g of sodium fluoride, 1.6 g of tetrabutylammonium bromide and 15-crown-50.8 g into a 500 ml dry reaction bottle, starting stirring, heating to 130-140 ℃, preserving heat, reacting for 16 hours, and stopping reaction. The reaction system is subjected to reduced pressure distillation until the system is completely evaporated to dryness, and the obtained fraction is subjected to reduced pressure rectification to obtain 60.99 g of 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile, the yield is 92.9 percent, and the purity is 99.2 percent.

Example twenty two

Adding 70 g of pentachlorobenzonitrile, 280 g of sulfolane and 52 g of potassium fluoride into a 500 ml dry reaction bottle, starting stirring, heating to 170-180 ℃, preserving heat, reacting for 15 hours, and stopping reaction. The reaction system is subjected to reduced pressure distillation until the system is completely evaporated to dryness, and the obtained fraction is subjected to reduced pressure distillation to obtain 53.83 g of 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile, the yield is 93.7 percent, and the purity is 99.4 percent.

Example twenty three

Adding 55 g of pentachlorobenzonitrile, 330 g of 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile, 46.4 g of potassium fluoride and 1 g of tetraphenylphosphonium bromide into a 500 ml dry reaction bottle, starting stirring, heating to 200-210 ℃, preserving the temperature, reacting for 20 hours, and stopping the reaction. The reaction system is decompressed and distilled until the system is completely evaporated to dryness to obtain 374.24 g of 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile, 44.24 g of 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile is obtained after the solvent is deducted, the yield is 98.0 percent, and the purity is 98.8 percent.

Example twenty-four

Adding 60 g of pentachlorobenzonitrile, 300 g of dimethyl sulfoxide and 57 g of potassium fluoride into a 500 ml dry reaction bottle, starting stirring, heating to 150-160 ℃, preserving heat, reacting for 12 hours, and stopping reaction. The reaction system is distilled under reduced pressure until the system is completely evaporated to dryness, and the obtained fraction is distilled under reduced pressure to obtain 46.04 g of 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile, the yield is 93.5 percent, and the purity is 99.3 percent.