A kind of synthetic method of 3,4,5-trifluorobromobenzene

Abstract

The present invention relates to the technical field of chemical synthesis, and more particularly to a method for synthesizing 3,4,5-trifluorobromobenzene. The present invention uses tetrachlorophthalic anhydride as a raw material, first performs a fluorination reaction with potassium fluoride, then obtains 3,4,5-trifluorobenzoic acid through hydrogenation, hydrolysis, and decarboxylation, then replaces with ammonia, then performs Hofmann amide degradation, and finally performs a diazotization reaction (Himan reaction) to obtain the target product 3,4,5-trifluorobromobenzene, with a yield of 84%. The synthetic route has the advantages of mild reaction, easy operation, safety and environmental protection, and convenience for large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a method for synthesizing 3,4,5-trifluorobromobenzene. Background Art

[0002] 3,4,5-Trifluorobromobenzene, a colorless to light yellow liquid, is an important pesticide intermediate, mainly used to synthesize the succinate dehydrogenase inhibitor fungicide fluopyraclostrobin, and is also an important liquid crystal intermediate, used to produce the fourth-generation TFT color liquid crystal material. It is also an intermediate for olefin polymerization catalysts. It has a wide range of applications, a large demand, and is growing year by year, and has important economic value. Its chemical structure is as follows:

[0003]

[0004] At present, there are several methods for synthesizing 3,4,5-trifluorobromobenzene:

[0005] 1. Using 2,3,4-trifluoroaniline as raw material, bromine is first used to obtain 2,3,4-trifluoro-6-bromoaniline, and then diazotization deamination is performed to obtain 3,4,5-trifluorobromobenzene. For example, patent CN103601613A uses bromine, which is highly toxic and corrosive. The diazotization deamination process also requires the use of hypophosphorous acid and copper catalyst, which will produce phosphorus-containing heavy metal wastewater, which has high environmental protection disposal costs and is not conducive to the occupational health protection of operators.

[0006]

[0007] 2. Using 2,3,4-trifluoroaniline as raw material, 1,2,3-trifluorobenzene is obtained by diazotization deamination, and then reacted with bromine to obtain 3,4,5-trifluorobromobenzene. For example, in patent CN105439810A, the diazotization deamination process is consistent with patent CN103601613A. Bromine is used in combination with hydrogen peroxide during the bromination process, which only reduces the amount of bromine used, but does not avoid the use of bromine. The process defects described in patent CN103601613A still exist.

[0008]

[0009] 3. Take 1,2,3-trifluorobenzene as the starting material, first disperse it in an organic solvent and then mix it with a sodium bromide aqueous solution containing a buffer salt, then drop a sodium hypochlorite aqueous solution to obtain a crude 3,4,5-trifluorobromobenzene, and then melt crystallize to obtain a finished 3,4,5-trifluorobromobenzene. For example, patent CN108947763A, the unit consumption of the buffer salt sodium dihydrogen phosphate in this patent is as high as 0.6, and the disposal cost of high-phosphorus wastewater is high.

[0010]

[0011] 4. Yin Kai published a paper titled "New Synthesis Process of 3,4,5-Trifluorobromobenzene" in "World Pesticides" Vol. 42, No. 4, 2020, pp. 54-56. The paper reported that 3,4,5-trifluorobromobenzene can be synthesized from 1,2,3-trichlorobenzene as the starting material through fluorination and bromination in two steps. This process still produces high-phosphorus wastewater, and the by-products potassium chloride and sodium chloride are of low purity and need to be disposed of as waste salt. Therefore, the environmental protection cost of this process is extremely high, the market competitiveness is not strong, and the industrial feasibility is low.

[0012]

[0013] In summary, as an important fine chemical, the current preparation process of 3,4,5-trifluorobromobenzene has serious problems and hidden dangers. Developing a new process for 3,4,5-trifluorobromobenzene with industrial production value is an urgent issue that needs to be solved. Summary of the invention

[0014] In order to solve the above problems, the present invention provides a method for synthesizing 3,4,5-trifluorobromobenzene, and provides a new method for synthesizing 3,4,5-trifluorobromobenzene.

[0015] In order to achieve the above object, the present invention provides the following technical solutions:

[0016] The present invention provides a method for synthesizing 3,4,5-trifluorobromobenzene, comprising the following steps:

[0017] 1) mixing tetrachlorophthalic anhydride with potassium fluoride, sulfolane and a catalyst to obtain a mixture, stirring the mixture for reaction, and separating to obtain tetrafluorophthalic anhydride;

[0018] 2) mixing the tetrafluorophthalic anhydride obtained in step 1) with acetic anhydride and a hydrogenation catalyst to obtain a product to be hydrogenated, introducing hydrogen gas to carry out a hydrogenation reaction, and obtaining trifluorophthalic anhydride;

[0019] 3) mixing the trifluorophthalic anhydride obtained in step 2) with water and manganese dioxide and subjecting the mixture to a thermal reaction to obtain a thermal reaction product, and separating the product to obtain 3,4,5-trifluorobenzoic acid;

[0020] 4) mixing the 3,4,5-trifluorobenzoic acid obtained in step 3) with benzonitrile, introducing ammonia gas to react, and drying, filtering and purifying the obtained reactant to obtain 3,4,5-trifluorobenzamide;

[0021] 5) mixing the 3,4,5-trifluorobenzamide obtained in step 4) with liquid alkali and sodium hypochlorite solution and then performing a heat-insulating reaction, adding the obtained reaction solution dropwise into water and performing a heat-insulating reaction for 1 hour, and then filtering, washing with water and drying in sequence to obtain 3,4,5-trifluoroaniline;

[0022] 6) The 3,4,5-trifluoroaniline obtained in step 5) is mixed with acetonitrile, hydrogen bromide solution and sodium nitrite solution, and the mixture is kept warm for reaction for 0.5 h, and then mixed with copper bromide and stirred overnight to obtain 3,4,5-trifluorobromobenzene.

[0023] Preferably, in step 1), the mass ratio of tetrachlorophthalic anhydride to potassium fluoride and sulfolane is 286:58:600;

[0024] The mass percentage of the catalyst in the mixture is 5%, and the catalyst includes benzyltriethylammonium bromide and / or dodecyltrimethylammonium bromide.

[0025] Preferably, the stirring reaction conditions in step 1) include: temperature of 210° C. and time of 12 h;

[0026] The separation method comprises: filtering the obtained stirred reactant, mixing the filtrate with chloroform, washing with ice water, separating an organic layer, drying the organic layer, filtering and distilling off the solvent to obtain tetrafluorophthalic anhydride;

[0027] The ice water washing was performed 3 times, using 400 ml each time;

[0028] The mass ratio of chloroform to tetrachlorophthalic anhydride is 600:286.

[0029] Preferably, in step 2), the mass ratio of tetrafluorophthalic anhydride to acetic anhydride is 210:500;

[0030] The mass percentage of the hydrogenation catalyst in the hydrogenated product is 10%, and the hydrogenation catalyst comprises palladium carbon and / or Raney nickel;

[0031] The conditions of the hydrogenation reaction include: pressure of 0.5 MPa and time of 2 h.

[0032] Preferably, in step 3), the mass ratio of trifluorophthalic anhydride to water and manganese dioxide is 190:500:10; the mixing temperature is 15°C;

[0033] The temperature of the thermal reaction is 90-100° C. and the time is 4-5 hours.

[0034] Preferably, the method for separating and obtaining 3,4,5-trifluorobenzoic acid in step 3) comprises: adjusting the pH value of the hot reactant to 12.0, filtering, and obtaining a filtrate;

[0035] The pH value of the obtained filtrate is adjusted to 1.0-2.0, extracted with chloroform, and the chloroform is evaporated to obtain 3,4,5-trifluorobenzoic acid.

[0036] Preferably, in step 4), the mass ratio of 3,4,5-trifluorobenzoic acid to benzonitrile is 160:1000;

[0037] The temperature of the ammonia gas introduced is maintained at 150-155° C., and the introduction time is 5.5-7 hours.

[0038] Preferably, in step 5), the mass ratio of 3,4,5-trifluorobenzamide to liquid caustic soda and sodium hypochlorite solution is 140:290:490;

[0039] The mass percentage of the sodium hypochlorite solution is 12%;

[0040] The insulation reaction time is 1 to 2 hours, and the temperature is 0°C;

[0041] The temperature of the water is 75° C., and the mass ratio of the 3,4,5-trifluorobenzamide to water is 140:500.

[0042] Preferably, in step 6), the mass ratio of 3,4,5-trifluoroaniline to the volume of acetonitrile, the mass of hydrogen bromide solution, and the mass ratio of sodium nitrite solution is 100 g: 300 ml: 210 g: 160 g;

[0043] The mass percentage of the hydrogen bromide solution is 40%, and the mass percentage of the sodium nitrite solution is 30%;

[0044] The mass ratio of the 3,4,5-trifluoroaniline to copper bromide is 100:0.5.

[0045] Preferably, in step 6), the stirred overnight product is obtained by stirring overnight, and the stirred overnight product is quenched in ice water, adjusted to alkalinity, and then extracted, dried, filtered and concentrated in sequence to obtain 3,4,5-trifluorobromobenzene.

[0046] The invention uses tetrachlorophthalic anhydride as a raw material, first performs a fluorination reaction with potassium fluoride, then performs hydrogenation, hydrolysis and decarboxylation to obtain 3,4,5-trifluorobenzoic acid, then performs substitution with ammonia, then performs Hofmann amide degradation, and finally performs a diazotization reaction (Himan reaction) to obtain the target product 3,4,5-trifluorobromobenzene, with a yield of 84%. The synthetic route has the advantages of mild reaction, easy operation, safety, environmental protection and convenience for large-scale production.

[0047] The route is as follows:

[0048] DETAILED DESCRIPTION

[0049] The present invention provides a method for synthesizing 3,4,5-trifluorobromobenzene, comprising the following steps:

[0050] 1) mixing tetrachlorophthalic anhydride with potassium fluoride, sulfolane and a catalyst to obtain a mixture, stirring the mixture for reaction, and separating to obtain tetrafluorophthalic anhydride;

[0051] 2) mixing the tetrafluorophthalic anhydride obtained in step 1) with acetic anhydride and a hydrogenation catalyst to obtain a product to be hydrogenated, introducing hydrogen gas to carry out a hydrogenation reaction, and obtaining trifluorophthalic anhydride;

[0052] 3) mixing the trifluorophthalic anhydride obtained in step 2) with water and manganese dioxide and subjecting the mixture to a thermal reaction to obtain a thermal reaction product, and separating the product to obtain 3,4,5-trifluorobenzoic acid;

[0053] 4) mixing the 3,4,5-trifluorobenzoic acid obtained in step 3) with benzonitrile, introducing ammonia gas to react, and drying, filtering and purifying the obtained reactant to obtain 3,4,5-trifluorobenzamide;

[0054] 5) mixing the 3,4,5-trifluorobenzamide obtained in step 4) with liquid alkali and sodium hypochlorite solution and then performing a heat-insulating reaction, adding the obtained reaction solution dropwise into water and performing a heat-insulating reaction for 1 hour, and then filtering, washing with water and drying in sequence to obtain 3,4,5-trifluoroaniline;

[0055] 6) The 3,4,5-trifluoroaniline obtained in step 5) is mixed with acetonitrile, hydrogen bromide solution and sodium nitrite solution, and the mixture is kept warm for reaction for 0.5 h, and then mixed with copper bromide and stirred overnight to obtain 3,4,5-trifluorobromobenzene.

[0056] The invention mixes tetrachlorophthalic anhydride with potassium fluoride, sulfolane and a catalyst to obtain a mixture, stirs the mixture for reaction and separates the tetrafluorophthalic anhydride.

[0057] In the present invention, the mass ratio of tetrachlorophthalic anhydride to potassium fluoride and cyclopentane is preferably 286:58:600; the mass percentage of the catalyst in the mixture is 5%, and the catalyst includes benzyltriethylammonium bromide and / or dodecyltrimethylammonium bromide. In the present invention, the conditions of the stirring reaction preferably include: temperature of 210°C and time of 12h. In the present invention, the separation method preferably includes: filtering the obtained stirring reactant, mixing the filtrate with chloroform, washing with ice water, separating the organic layer, drying the organic layer, filtering and distilling off the solvent to obtain tetrafluorophthalic anhydride. In the present invention, the number of ice water washing is preferably 3 times, and 400 ml is preferably used each time. In the present invention, the mass ratio of chloroform to tetrachlorophthalic anhydride is preferably 600:286.

[0058] The present invention mixes the obtained tetrafluorophthalic anhydride with acetic anhydride and a hydrogenation catalyst to obtain a product to be hydrogenated, and introduces hydrogen to carry out a hydrogenation reaction to obtain trifluorophthalic anhydride. In the present invention, the mass ratio of the tetrafluorophthalic anhydride to the acetic anhydride is preferably 210:500. In the present invention, the mass percentage of the hydrogenation catalyst in the product to be hydrogenated preferably accounts for 1-10% of the substrate, more preferably 2%. The hydrogenation catalyst preferably includes palladium carbon and / or Raney nickel. In the present invention, the conditions of the hydrogenation reaction preferably include: a pressure of 0.5MPa and a time of 2h.

[0059] The present invention mixes the obtained trifluorophthalic anhydride with water and manganese dioxide and then conducts a thermal reaction to obtain a thermal reactant, and separates and obtains 3,4,5-trifluorobenzoic acid. In the present invention, the mass ratio of trifluorophthalic anhydride to water and manganese dioxide is preferably 190:500:10; the mixing temperature is preferably 15°C. In the present invention, the temperature of the thermal reaction is preferably 90-100°C, and the time is preferably 4-5h. In the present invention, the method for separating and obtaining 3,4,5-trifluorobenzoic acid preferably includes: adjusting the pH value of the thermal reactant to 12.0, filtering, and obtaining a filtrate. The present invention preferably adjusts the pH value of the obtained filtrate to 1.0-2.0, extracts with chloroform, and evaporates the chloroform to obtain 3,4,5-trifluorobenzoic acid.

[0060] The present invention mixes the obtained 3,4,5-trifluorobenzoic acid with benzonitrile, introduces ammonia gas and reacts, dries, filters and purifies the obtained reactant to obtain 3,4,5-trifluorobenzamide. In the present invention, the mass ratio of the 3,4,5-trifluorobenzoic acid to benzonitrile is preferably 160:1000. In the present invention, the temperature of the introduced ammonia gas is preferably maintained at 150-155° C., and the introduction time is preferably 5.5-7 hours.

[0061] The present invention mixes the obtained 3,4,5-trifluorobenzamide with liquid caustic soda and sodium hypochlorite solution and then performs heat preservation reaction, drops the obtained reaction solution into water and perform heat preservation reaction for 1 hour, and then successively filters, washes with water and dries to obtain 3,4,5-trifluoroaniline. In the present invention, the mass ratio of the 3,4,5-trifluorobenzamide to the liquid caustic soda and sodium hypochlorite solution is preferably 140:290:490. In the present invention, the mass percentage of the sodium hypochlorite solution is preferably 12%. In the present invention, the heat preservation reaction time is preferably 1 to 2 hours, and the temperature is preferably 0°C. In the present invention, the temperature of the water is preferably 75°C, and the mass ratio of the 3,4,5-trifluorobenzamide to water is preferably 140:500.

[0062] The present invention mixes the obtained 3,4,5-trifluoroaniline with acetonitrile, hydrogen bromide solution, and sodium nitrite solution, and heats for reaction for 0.5h, and then mixes with copper bromide and stirs overnight to obtain 3,4,5-trifluorobromobenzene. In the present invention, the mass ratio of the mass of the 3,4,5-trifluoroaniline to the volume of acetonitrile, the mass of the hydrogen bromide solution, and the mass ratio of the sodium nitrite solution is preferably 100g:300ml:210g:160g. In the present invention, the mass percentage of the hydrogen bromide solution is preferably 40%, and the mass percentage of the sodium nitrite solution is preferably 30%. In the present invention, the mass ratio of the 3,4,5-trifluoroaniline to copper bromide is preferably 100:0.5. In the present invention, the stirring overnight obtains a stirred overnight product, and the stirred overnight product is preferably quenched in ice water, adjusted to alkalinity, and then extracted, dried, filtered and concentrated in sequence to obtain 3,4,5-trifluorobromobenzene.

[0063] In order to further illustrate the present invention, the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0064] Example 1

[0065] A method for synthesizing 3,4,5-trifluorobromobenzene, comprising the following steps:

[0066] Step 1: 286g (1 mole) of tetrachlorophthalic anhydride and 58g of potassium fluoride are dissolved in 600g of sulfolane, and 5% of the total system mass percentage of benzyltriethylammonium bromide is added as a catalyst, heated to 210°C, stirred at 100rpm for 12 hours, cooled to room temperature after the reaction, filtered, 600g of chloroform is added to the filtrate, and then ice water is added to wash 3 times (400ml*3), the organic layer is separated, 8.0g of sodium sulfate is added to dry, filtered, and the solvent is evaporated at 40°C to obtain 210.0g of tetrafluorophthalic anhydride, with a yield of 95.4%, which is directly put into the next step reaction.

[0067] Step 2: Add the product of step 1 to 500g of acetic anhydride, add Raney nickel 5.0 as a catalyst, introduce hydrogen at a pressure of about 0.5MPa, and react for 2 hours. After the reaction is completed, filter to remove the catalyst, and distill the filtrate under reduced pressure at 50°C to remove acetic anhydride to obtain 190.0g of trifluorophthalic anhydride (yield: 98.5%), and directly proceed to the next step of reaction.

[0068] Step 3: At 15°C, add 500g of water to the product of step 2, add 10.0g of MnO2 catalyst, heat and stir for 4 hours, gas is released, and after the reaction is completed, adjust the pH value to 12.0 with a 40% by mass percentage NaOH aqueous solution, filter, adjust the pH value of the filtrate to 1 with a 20% by mass percentage hydrochloric acid, add 500g of chloroform for extraction, and evaporate the chloroform to obtain 160.0g of 3,4,5-trifluorobenzoic acid, with a yield of 91.8%.

[0069] Step 4: Add 1000g of benzonitrile to the product of step 3, mix well, heat to 150°C, maintain the temperature and pass ammonia for 7 hours, stop the ventilation and cool to room temperature. Add 300ml of water for water washing and liquid separation. Add 5.0g of anhydrous sodium sulfate to the organic phase for drying and filtering. Finally, control the temperature to 80-90°C and evaporate the solvent under reduced pressure to obtain 140.0g of 3,4,5-trifluorobenzamide, with a yield of 88.0%.

[0070] Step 5: Add the product of step 4 to 290g of liquid alkali, cool to 0°C, add 490g of 12% sodium hypochlorite aqueous solution at 0°C, keep the temperature at 0°C, and react for 2 hours after the addition is completed. Slowly drop the reaction solution into 500ml of 75°C water, and react for 1 hour. Cool to room temperature, filter under reduced pressure, wash the filter cake with water, and dry it to obtain 100.0g of 3,4,5-trifluoroaniline, with a yield of 85.0%.

[0071] Step 6: Add the product of step 5 to 300ml of acetonitrile, stir, slowly add 210g of 40% hydrogen bromide solution, cool to 0°C, slowly drop 160g of 30% sodium nitrite solution, keep warm for 0.5 hours, then slowly add 0.5g of copper bromide, and stir overnight at room temperature. After the reaction is completed, slowly pour the system into 300ml of ice water to quench, add 60.0g of sodium carbonate in batches to neutralize to alkalinity, and then extract three times with 400ml of dichloromethane. The combined organic phase is dried over anhydrous sodium sulfate, filtered, vacuum concentrated to remove dichloromethane, and then subjected to vacuum distillation to obtain the product 3,4,5-trifluorobromobenzene 120.0g yield: 84%.

[0072] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for synthesizing 3,4,5-trifluorobromobenzene, characterized in that: The synthetic route is as follows: The following steps are involved: 1) mixing tetrachlorophthalic anhydride with potassium fluoride, sulfolane and a catalyst to obtain a mixture, stirring the mixture for reaction, and separating to obtain tetrafluorophthalic anhydride; the catalyst is benzyltriethylammonium bromide; 2) mixing the tetrafluorophthalic anhydride obtained in step 1) with acetic anhydride and a hydrogenation catalyst to obtain a product to be hydrogenated, introducing hydrogen gas to carry out a hydrogenation reaction to obtain trifluorophthalic anhydride; the hydrogenation catalyst is Raney nickel; 3) mixing the trifluorophthalic anhydride obtained in step 2) with water and manganese dioxide, and heating and stirring the mixture to obtain a thermal reaction product, and separating the mixture to obtain 3,4,5-trifluorobenzoic acid; 4) mixing the 3,4,5-trifluorobenzoic acid obtained in step 3) with benzonitrile, introducing ammonia gas to react, and drying, filtering and purifying the obtained reactant to obtain 3,4,5-trifluorobenzamide; 5) mixing the 3,4,5-trifluorobenzamide obtained in step 4) with liquid alkali and sodium hypochlorite solution and then performing a heat-insulating reaction, adding the obtained reaction solution dropwise into water and performing a heat-insulating reaction for 1 hour, and then filtering, washing with water and drying in sequence to obtain 3,4,5-trifluoroaniline; 6) The 3,4,5-trifluoroaniline obtained in step 5) is mixed with acetonitrile, hydrogen bromide solution and sodium nitrite solution, and the mixture is kept warm for reaction for 0.5 h, and then mixed with copper bromide and stirred overnight to obtain 3,4,5-trifluorobromobenzene.

2. The synthesis method according to claim 1, characterized in that In the step 1), the mass ratio of tetrachlorophthalic anhydride to potassium fluoride and sulfolane is 286:58:600; The mass percentage of the catalyst in the mixture is 5%.

3. The synthesis method according to claim 1, characterized in that The stirring reaction conditions in step 1) include: temperature of 210° C. and time of 12 h; The separation method comprises: filtering the obtained stirred reactant, mixing the filtrate with chloroform, washing with ice water, separating an organic layer, drying the organic layer, filtering and distilling off the solvent to obtain tetrafluorophthalic anhydride; The ice water washing was performed 3 times, using 400 ml each time; The mass ratio of chloroform to tetrachlorophthalic anhydride is 600:

286.

4. The synthesis method according to claim 1, characterized in that In the step 2), the mass ratio of tetrafluorophthalic anhydride to acetic anhydride is 210:500; The mass percentage of the hydrogenation catalyst in the hydrogenated material is 10%; The conditions of the hydrogenation reaction include: pressure of 0.5 MPa and time of 2 h.

5. The synthesis method according to claim 1, characterized in that In step 3), the mass ratio of trifluorophthalic anhydride to water and manganese dioxide is 190:500:10; the mixing temperature is 15° C.; The temperature of the thermal reaction is 90-100° C. and the time is 4-5 hours.

6. The synthesis method according to claim 1, characterized in that The method for separating and obtaining 3,4,5-trifluorobenzoic acid in step 3) comprises: adjusting the pH value of the hot reactant to 12.0, filtering, and obtaining a filtrate; The pH value of the obtained filtrate is adjusted to 1.0-2.0, extracted with chloroform, and the chloroform is evaporated to obtain 3,4,5-trifluorobenzoic acid.

7. The synthesis method according to claim 1, characterized in that In the step 4), the mass ratio of 3,4,5-trifluorobenzoic acid to benzonitrile is 160:1000; The temperature of the ammonia gas introduced is maintained at 150-155° C., and the introduction time is 5.5-7 hours.

8. The synthesis method according to claim 1, characterized in that In the step 5), the mass ratio of 3,4,5-trifluorobenzamide to liquid caustic soda and sodium hypochlorite solution is 140:290:490; The mass percentage of the sodium hypochlorite solution is 12%; The insulation reaction time is 1 to 2 hours, and the temperature is 0°C; The temperature of the water is 75° C., and the mass ratio of the 3,4,5-trifluorobenzamide to water is 140:

500.

9. The synthesis method according to claim 1, characterized in that In step 6), the mass ratio of 3,4,5-trifluoroaniline to the volume of acetonitrile, the mass of hydrogen bromide solution, and the mass ratio of sodium nitrite solution is 100 g: 300 ml: 210 g: 160 g; The mass percentage of the hydrogen bromide solution is 40%, and the mass percentage of the sodium nitrite solution is 30%; The mass ratio of the 3,4,5-trifluoroaniline to copper bromide is 100:0.

5.

10. The synthesis method according to claim 1, characterized in that The step 6) is stirred overnight to obtain a stirred overnight product, which is quenched in ice water, adjusted to alkalinity, and then extracted, dried, filtered and concentrated in sequence to obtain 3,4,5-trifluorobromobenzene.

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