A process for the preparation of 1-(4-chlorophenyl)-3-pyrazole alcohol

Abstract

The application discloses a preparation method of 1-(4-chlorophenyl)-3-pyrazole alcohol and belongs to the technical field of organic synthesis. The method adopts heteropoly acid to catalyze air to oxidize 1-(4-chlorophenyl) pyrazole dione-3-ketone to prepare 1-(4-chlorophenyl)-3-pyrazole alcohol. After the reaction is carried out under the initial pressure of air of 2-4 MPa and the reaction temperature of 70-110 DEG C for 4.0-10.0 h, deionized water is added to the system to dissolve the catalyst and the crude product is precipitated, then the product 1-(4-chlorophenyl)-3-pyrazole alcohol is obtained through filtration, filter cake washing and drying. The filtrate is subjected to vacuum distillation to remove water and recover the catalyst and the catalyst is recycled. Compared with the traditional method, the heteropoly acid catalyst used in the application can realize high conversion rate of raw materials and high selectivity of the target product under mild reaction conditions, and the catalyst has good repeated use performance after being recovered.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a synthetic method for preparing 1-(4-chlorophenyl)-3-pyrazolol by air oxidation of 1-(4-chlorophenyl)pyrazolidine-3-one by heteropolyacid catalysis. Background Technology

[0002] 1-(4-Chlorophenyl)-3-pyrazolol is a key intermediate in the synthesis of novel insecticides (such as chlorantraniliprole) and the antiepileptic drug buvasidan, and its green synthesis technology has always been a research hotspot in the chemical industry. Currently, traditional synthesis processes mainly use chemical oxidants, such as chromium-based oxidants (e.g., Na2Cr2O7), hydrogen peroxide, and persulfate, to oxidize 1-(4-chlorophenyl)pyrazolidine-3-one. However, such methods have many drawbacks. For example, Chinese patent CN111057006B uses a copper catalyst and specific ligands in a two-step reaction, which is cumbersome and difficult to recover. Chinese patent CN103588708B uses p-chlorophenylhydrazine hydrochloride and acrylates as raw materials through cyclization and oxidation reactions, but it uses highly toxic p-chlorophenylhydrazine hydrochloride and ferric chloride, posing a risk of heavy metal pollution. Therefore, existing technologies generally suffer from environmental pollution, complex operation, and difficulty in catalyst recovery, affecting the yield and purity of 1-(4-chlorophenyl)-3-pyrazolol.

[0003] Heteropolyacid catalysts have attracted much attention in the field of green oxidation due to their tunable redox properties, structural stability, ease of preparation, and simple post-processing. Their unique cage-like structure provides abundant active sites, and catalytic performance can be precisely controlled by adjusting the constituent elements (such as phosphorus, molybdenum, vanadium, silicon, tungsten, etc.). They are suitable for various oxidation reactions and exhibit excellent catalytic activity in both homogeneous and heterogeneous systems. They also have broad substrate compatibility and can effectively reduce side reactions. Currently, there are no reports on the selective oxidation of pyrazole compounds using heteropolyacids, especially lacking research on their application in the preparation of 1-(4-chlorophenyl)pyrazolidine-3-one from 1-(4-chlorophenyl)-3-pyrazolol.

[0004] Based on this, the present invention proposes a method for preparing 1-(4-chlorophenyl)pyrazolidine-3-one by air oxidation catalyzed by heteropolyacids. Using 1-(4-chlorophenyl)pyrazolidine-3-one as a raw material, the oxidation reaction is carried out in a solvent by passing air through a solvent under the catalysis of a heteropolyacid. The vanadium atoms in the heteropolyacid can undergo a valence state change (V... 5+ With V 4+The process involves electron transfer via a reversible process, where electrons are first extracted from the raw material molecules to complete the oxidation process. The resulting product is then regenerated by oxygen in the air, forming a highly efficient catalytic cycle. Simultaneously, its cage-like structure allows for selective adsorption of substrate molecules, precisely activating specific active sites in the 1-(4-chlorophenyl)pyrazolidine-3-one molecule, thus directing the reaction. After the reaction, deionized water is added to the reaction system to dissolve the heteropolyacid and precipitate the crude product. This product is then filtered, the filter cake is washed, and dried to obtain the 1-(4-chlorophenyl)-3-pyrazolol. The filtrate is then subjected to vacuum distillation to remove water and solvent, recovering the catalyst for recycling. Compared to traditional preparation techniques, this invention not only achieves higher product purity and yield than existing technologies but also successfully overcomes the challenges of cumbersome and costly catalyst preparation. Furthermore, using air as the oxidation medium avoids the pollution problems associated with traditional chemical oxidants, significantly reducing waste emissions and aligning with the development direction of green chemistry. This opens up a new technological pathway for the large-scale production of 1-(4-chlorophenyl)-3-pyrazolol. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing 1-(4-chlorophenyl)-3-pyrazolol that is environmentally friendly, economical, and efficient. The method involves the air oxidation of 1-(4-chlorophenyl)pyrazol-3-one by heteropolyacid catalysis, replacing the traditional chromium-based oxidant and heavy metal salt catalytic process. This solves the problems of serious environmental pollution, complex operation, difficult catalyst recovery, and the need to improve product quality in the existing technology.

[0006] Based on the above, this invention relates to a method for preparing 1-(4-chlorophenyl)-3-pyrazol, characterized in that 1-(4-chlorophenyl)pyrazolidine-3-one is used as a raw material, a heteropoly acid is used as a catalyst, and air is used as an oxidant, and an oxidation reaction is carried out in a solvent. The mass ratio of 1-(4-chlorophenyl)pyrazolidine-3-one to the catalyst heteropoly acid is 50:1-200:1, the mass ratio of 1-(4-chlorophenyl)pyrazolidine-3-one to the reaction solvent is 1:3-1:8, the initial air pressure is 2-4 MPa, the reaction temperature is 70-110℃, and the reaction time is 4.0-10.0 h. After the reaction is completed, an additive is added to the reaction system. The heteropolyacid was dissolved in deionized water at a volume of 0.5-1.0 times the volume of the reaction mixture, and a crude product precipitated. This product was then filtered, the filter cake washed, and dried to obtain 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 96.5%-98.7% and a purity of 99.2%-99.6%. The filtrate (containing the dissolved heteropolyacid) was subjected to vacuum distillation to remove water and solvent, and the catalyst was recovered and recycled. After 20 cycles of recycling, the product yield remained ≥94.0% and the purity ≥99.0%. The organic solvent used in the reaction was one of methanol, ethanol, propanol, or isopropanol, and the heteropolyacid catalyst was phosphomolybdenum-vanadium heteropolyacid (H4PMo). 11VO 40 ), tungsten-vanadium heteropolyacid (H4PW) 11 VO 40 ) or silicomolybdenum-vanadium heteropolyacid (H4SiMo) 11 VO 40 One of them.

[0007] This invention solves this technical problem through the following technical solution:

[0008] Phosphorus molybdenum vanadium H4PMo 11 VO 40 Taking heteropoly acids as an example, the specific technical solution is explained as follows:

[0009] 50g of 1-(4-chlorophenyl)pyrazolidine-3-one and 0.5g of H4PMo 11 VO 40 250g of methanol was added to a pressure reactor, which was then sealed and purged with air to an initial pressure of 3MPa. The temperature was raised to 90℃ and the reaction was vigorously stirred and maintained at this temperature for 7.0h. After the reaction was completed, the mixture was cooled to room temperature, the pressure was released, the reactor was opened, and the reaction mixture was transferred to a reaction flask. 200mL of deionized water was added dropwise with stirring. The mixture was cooled to 5℃ and slowly stirred for 30min, resulting in the precipitation of a crude product. The mixture was filtered, and the filter cake was washed three times with deionized water. The resulting filter cake was then vacuum dried at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 98.7% and a purity of 99.6%. The mother liquor and washing liquid were combined, and water and methanol were removed by vacuum distillation. The catalyst was recovered and recycled. After 20 recycling cycles, the product yield was 95.3% and the purity was 99.3%.

[0010] Compared with traditional methods, the present invention is characterized by:

[0011] 1. The catalyst is green, efficient and recyclable. It uses phosphomolybdenum-vanadium heteropolyacid as the catalyst, which has no heavy metal toxicity and can be separated from the product by adding water. The recovery operation is simple and the recycling performance is stable. It solves the problems of traditional metal salt catalysts (such as ferric chloride and copper salts) being difficult to recover and easy to cause environmental pollution.

[0012] 2. The oxidation system is green and environmentally friendly, using air as an oxidant. It is widely available and inexpensive, avoiding the safety hazards of organic peroxides in traditional processes and the nitrogen-containing waste liquid generated by strong oxidants such as nitric acid. It reduces the emission of waste gas, wastewater, and solid waste from the source, which is in line with the concept of green chemistry.

[0013] 3. The reaction conditions are mild and efficient, easier to control than traditional high-temperature and high-pressure production processes, and the reaction time is short. At the same time, the product yield and purity are significantly better than existing technologies.

[0014] Example 1: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one and 0.5g of H4PMo were added.11 VO 40 250g of methanol was added to a pressure reactor, which was then sealed and purged with air to an initial pressure of 3MPa. The temperature was raised to 90℃ and the reaction was vigorously stirred and maintained at this temperature for 7.0h. After the reaction was completed, the mixture was cooled to room temperature, the pressure was released, the reactor was opened, and the reaction mixture was transferred to a reaction flask. 200mL of deionized water was added dropwise with stirring. The mixture was cooled to 5℃ and slowly stirred for 30min, resulting in the precipitation of a crude product. The mixture was filtered, and the filter cake was washed three times with deionized water. The resulting filter cake was then vacuum dried at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 98.7% and a purity of 99.6%. The mother liquor and washing liquid were combined, and water and methanol were removed by vacuum distillation. The catalyst was recovered and recycled. After 20 recycling cycles, the product yield was 95.3% and the purity was 99.3%.

[0015] Comparative Example 1: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one, 0.5g of ferric chloride, and 250g of methanol were added to a pressure reactor. After sealing the reactor, air was introduced to an initial pressure of 3MPa. The temperature was raised to 90℃ and vigorously stirred for 7.0h. After the reaction was completed, the mixture was cooled to room temperature, the pressure was released, the reactor was opened, and the reaction mixture was transferred to a reaction flask. 200mL of deionized water was added dropwise with stirring. The mixture was cooled to 5℃ and slowly stirred for 30min, resulting in the precipitation of brownish-yellow crystals (containing iron ion impurities). The mixture was filtered, and the filter cake was washed three times with deionized water. The resulting filter cake was then vacuum dried at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 85.5% and a purity of 95.2%.

[0016] Comparative Example 2: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one, 0.5g of cuprous chloride, and 250g of methanol were added to a pressure reactor. After sealing the reactor, air was introduced to an initial pressure of 3MPa. The temperature was raised to 90℃ and the reaction was vigorously stirred and maintained at this temperature for 7.0h. After the reaction was completed, the mixture was cooled to room temperature, the pressure was released, the reactor was opened, and the reaction mixture was transferred to a reaction flask. 200mL of deionized water was added dropwise with stirring. The mixture was cooled to 5℃ and slowly stirred for 30min, resulting in the precipitation of a crude product. The mixture was filtered, and the filter cake was washed three times with deionized water. The resulting filter cake was then vacuum dried at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 81.0% and a purity of 94.7%.

[0017] Comparative Example 3: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one, 18.2g of Na2Cr2O7·2H2O, and 250g of methanol were added to a pressure reactor. 10mL of concentrated sulfuric acid was added to adjust the pH to 1-2. The reactor was sealed without purging air. The temperature was raised to 90℃ and vigorously stirred for 7.0h. After the reaction, the mixture was cooled to room temperature, and the reaction mixture was transferred to a reaction flask. 300mL of deionized water was added dropwise with stirring. The pH was adjusted to neutral with 40% sodium hydroxide solution, resulting in the precipitation of a brownish-yellow solid. The mixture was filtered, and the filter cake was washed three times with deionized water. The resulting filter cake was then vacuum dried at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 82.6% and a purity of 95.1%. The mother liquor and washing liquid contained a large amount of chromium ions, which could not be directly recovered.

[0018] Comparative Example 4: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one, 47g of 30% hydrogen peroxide, and 250g of methanol were added to a pressure reactor. 3mL of dilute sulfuric acid (5% concentration) was added to adjust the pH of the system to 2-3. After sealing the reactor, no air was required. The temperature was raised to 85℃ and vigorously stirred for 7.0h. After the reaction was completed and cooled to room temperature, the reaction mixture was transferred to a reaction flask. 5% sodium sulfite solution was added dropwise until starch-potassium iodide paper did not turn blue (to remove excess hydrogen peroxide). Then, 200mL of deionized water was added dropwise with stirring. The mixture was cooled to 5℃ and slowly stirred for 30min, precipitating a crude product. The mixture was filtered, and the filter cake was washed three times with deionized water. The resulting filter cake was vacuum dried at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 89.2% and a purity of 97.1%. The mother liquor and washing liquid are combined, in which hydrogen peroxide has been completely decomposed into water and oxygen, and no oxidant can be recovered.

[0019] Comparative Example 5: 50 g of 1-(4-chlorophenyl)pyrazolidine-3-one and 250 g of methanol were added to a pressure reactor. After sealing the reactor, air was introduced to an initial pressure of 3 MPa. The temperature was raised to 90 °C and vigorously stirred for 7.0 h. After the reaction was completed, the mixture was cooled to room temperature, the pressure was released, the reactor was opened, and the reaction mixture was transferred to a reaction flask. 200 mL of deionized water was added dropwise with stirring. The mixture was cooled to 5 °C and slowly stirred for 30 min. Only a small amount of solid precipitated. The mixture was filtered, and the filter cake was washed three times with deionized water. The resulting filter cake was dried under vacuum at 60 °C for 8.0 h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 25.7% and a purity of 98.9%.

[0020] Example 2: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one and 0.25g of H4PMo were added. 11 VO 40Add 250g of ethanol to a pressure reactor, seal the reactor, and purge with air to an initial pressure of 3MPa. Heat to 90℃ and stir vigorously for 7.0h. After the reaction is complete, cool to room temperature, depressurize, open the reactor, transfer the reaction mixture to a reaction flask, add 200mL of deionized water dropwise with stirring, cool to 5℃ and stir slowly for 30min to precipitate a crude product. Filter the mixture, wash the filter cake three times with deionized water, and dry the resulting filter cake under vacuum at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 96.8% and a purity of 99.4%. Combine the mother liquor and washing liquid, and remove water and ethanol by vacuum distillation. Recover the catalyst and recycle it. After 20 cycles, the product yield is 95.2% and the purity is 99.1%.

[0021] Example 3: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one and 1g of H4PMo were added. 11 VO 40 Add 400g of methanol to a pressure reactor, seal the reactor, and purge with air to an initial pressure of 3MPa. Heat to 90℃ and stir vigorously for 7.0h. After the reaction is complete, cool to room temperature, depressurize, open the reactor, transfer the reaction mixture to a reaction flask, add 225mL of deionized water dropwise with stirring, cool to 5℃ and stir slowly for 30min to precipitate crude product. Filter the mixture, wash the filter cake three times with deionized water, and dry the filter cake under vacuum at 60℃ for 8.0h to obtain solid product 1-(4-chlorophenyl)-3-pyrazolol with a yield of 97.6% and a purity of 99.3%. Combine the mother liquor and washing liquid, and remove water and methanol by vacuum distillation. Recover the catalyst and recycle it. After 20 cycles, the product yield is 94.7% and the purity is 99.0%.

[0022] Example 4: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one and 0.625g of H4PW were added. 11 VO 40 150g of methanol was added to a pressure reactor, which was then sealed and purged with air to an initial pressure of 2.8MPa. The temperature was raised to 90℃ and the reaction was vigorously stirred and maintained at this temperature for 4.0h. After the reaction was completed, the mixture was cooled to room temperature, the pressure was released, the reactor was opened, and the reaction mixture was transferred to a reaction flask. 120mL of deionized water was added dropwise with stirring. The mixture was cooled to 5℃ and slowly stirred for 30min, resulting in the precipitation of a crude product. The mixture was filtered, and the filter cake was washed three times with deionized water. The resulting filter cake was then dried under vacuum at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 96.5% and a purity of 99.2%. The mother liquor and washing liquid were combined, and water and methanol were removed by vacuum distillation. The catalyst was recovered and recycled. After 20 recycling cycles, the product yield was 94.0% and the purity was 99.1%.

[0023] Example 5: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one and 0.333g of H4PMo were added. 11 VO 40 Add 300g of isopropanol to a pressure reactor, seal the reactor, and purge with air to an initial pressure of 3.2MPa. Heat to 70℃ and stir vigorously for 7.0h. After the reaction is complete, cool to room temperature, depressurize, open the reactor, transfer the reaction mixture to a reaction flask, add 250mL of deionized water dropwise with stirring, cool to 5℃ and stir slowly for 30min to precipitate crude product. Filter the mixture, wash the filter cake three times with deionized water, and dry the resulting filter cake under vacuum at 60℃ for 8.0h to obtain solid product 1-(4-chlorophenyl)-3-pyrazolol with a yield of 97.4% and a purity of 99.4%. Combine the mother liquor and washing liquid, and remove water and isopropanol by vacuum distillation. Recover the catalyst and recycle it. After 20 cycles, the product yield is 95.0% and the purity is 99.3%.

[0024] Example 6: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one and 0.5g of H4SiMo were added. 11 VO 40 200g of propanol was added to a pressure reactor, which was then sealed and purged with air to an initial pressure of 4.0MPa. The temperature was raised to 90℃ and the reaction was vigorously stirred and maintained at this temperature for 10.0h. After the reaction was completed, the mixture was cooled to room temperature, the pressure was released, the reactor was opened, and the reaction mixture was transferred to a reaction flask. 150mL of deionized water was added dropwise with stirring. The mixture was cooled to 5℃ and slowly stirred for 30min, resulting in the precipitation of a crude product. The mixture was filtered, and the filter cake was washed three times with deionized water. The resulting filter cake was then vacuum dried at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 97.6% and a purity of 99.2%. The mother liquor and washing liquid were combined, and water and propanol were removed by vacuum distillation. The catalyst was recovered and recycled. After 20 recycling cycles, the product yield was 94.9% and the purity was 99.0%.

[0025] Example 7: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one and 0.417g of H4PMo were added. 11 VO 40Add 250g of ethanol to a pressure reactor, seal the reactor, and purge with air to an initial pressure of 3MPa. Heat to 110℃ and stir vigorously for 5.0h. After the reaction is complete, cool to room temperature, depressurize, open the reactor, transfer the reaction mixture to a reaction flask, add 200mL of deionized water dropwise with stirring, cool to 5℃ and stir slowly for 30min to precipitate crude product. Filter the mixture, wash the filter cake three times with deionized water, and dry the resulting filter cake under vacuum at 60℃ for 8.0h to obtain solid product 1-(4-chlorophenyl)-3-pyrazolol with a yield of 96.8% and a purity of 99.5%. Combine the mother liquor and washing liquid, and remove water and ethanol by vacuum distillation. Recover the catalyst and recycle it. After 20 cycles, the product yield is 94.5% and the purity is 99.3%.

[0026] Example 8: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one and 0.625g of H4SiMo were added. 11 VO 40 350g of isopropanol was added to a pressure reactor. After sealing the reactor, air was introduced to an initial pressure of 2.0MPa. The temperature was raised to 85℃ and the reaction was vigorously stirred and maintained at this temperature for 8.0h. After the reaction was completed, the mixture was cooled to room temperature, the pressure was released, the reactor was opened, and the reaction mixture was transferred to a reaction flask. 300mL of deionized water was added dropwise with stirring. The mixture was cooled to 5℃ and slowly stirred for 30min, resulting in the precipitation of a crude product. The mixture was filtered, and the filter cake was washed three times with deionized water. The resulting filter cake was then vacuum dried at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 97.8% and a purity of 99.5%. The mother liquor and washing liquid were combined, and water and isopropanol were removed by vacuum distillation. The catalyst was recovered and recycled. After 20 recycling cycles, the product yield was 94.3% and the purity was 99.1%.

[0027] Example 9: 50g of 1-(4-chlorophenyl)pyrazolidine-3-one and 1g of H4PMo 11 VO 40 250g of isopropanol was added to a pressure reactor. After sealing the reactor, air was introduced to an initial pressure of 3MPa. The temperature was raised to 110℃ and the reaction was vigorously stirred and maintained at this temperature for 9.0h. After the reaction was completed, the mixture was cooled to room temperature, the pressure was released, the reactor was opened, and the reaction mixture was transferred to a reaction flask. 150mL of deionized water was added dropwise with stirring. The mixture was cooled to 5℃ and slowly stirred for 30min, resulting in the precipitation of a crude product. The mixture was filtered, and the filter cake was washed three times with deionized water. The resulting filter cake was then vacuum dried at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 98.0% and a purity of 99.4%. The mother liquor and washing liquid were combined, and water and isopropanol were removed by vacuum distillation. The catalyst was recovered and recycled. After 20 recycling cycles, the product yield was 94.7% and the purity was 99.3%.

[0028] Example 10: Take the H4PMo recovered from Example 1 11 VO 40 Added to the pressure reactor, based on the obtained H4PMo 11 VO 40 The mass is based on 50g of 1-(4-chlorophenyl)pyrazolidine-3-one and 0.5g of H4PMo. 11 VO 40 250g of methanol was added to a pressure reactor, which was then sealed and purged with air to an initial pressure of 3MPa. The temperature was raised to 90℃ and the reaction was vigorously stirred and maintained at this temperature for 7.0h. After the reaction was completed, the mixture was cooled to room temperature, the pressure was released, the reactor was opened, and the reaction mixture was transferred to a reaction flask. 200mL of deionized water was added dropwise with stirring. The mixture was cooled to 5℃ and slowly stirred for 30min, resulting in the precipitation of a crude product. The mixture was filtered, and the filter cake was washed three times with deionized water. The resulting filter cake was then vacuum dried at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 98.7% and a purity of 99.6%. The mother liquor and washing liquid were combined, and water and methanol were removed by vacuum distillation. The catalyst was recovered and recycled. After 20 recycling cycles, the product yield was 95.3% and the purity was 99.3%. Following the above operation, H4PMo was recovered. 11 VO 40 After five applications, the yield and purity were 98.5% and 99.5%, respectively; the recovered H4PMo 11 VO 40 After 10 applications, the yield and purity were 97.6% and 99.4%, respectively; the recovered H4PMo 11 VO 40 After 15 applications, the yield and purity were 96.9% and 99.3%, respectively; the recovered H4PMo 11 VO 40 After 20 applications, the yield and purity were 95.3% and 99.3%, respectively.

[0029] Example 11: Take the H4PMo recovered from Example 2 11 VO 40 Added to the pressure reactor, based on the obtained H4PMo 11 VO 40 The mass is based on 50g of 1-(4-chlorophenyl)pyrazolidine-3-one and 0.25g of H4PMo. 11 VO 40Add 250g of ethanol to a pressure reactor, seal the reactor, and purge with air to an initial pressure of 3MPa. Heat to 90℃ and stir vigorously for 7.0h. After the reaction is complete, cool to room temperature, depressurize, open the reactor, and transfer the reaction mixture to a reaction flask. Add 200mL of deionized water dropwise with stirring. Cool to 5℃ and stir slowly for 30min to precipitate a crude product. Filter the mixture, wash the filter cake three times with deionized water, and dry the resulting filter cake under vacuum at 60℃ for 8.0h to obtain the solid product 1-(4-chlorophenyl)-3-pyrazolol, with a yield of 96.8% and a purity of 99.4%. Combine the mother liquor and washing liquid, and distill under reduced pressure to remove water and ethanol. Recover the catalyst and recycle it. After 20 cycles, the product yield is 95.2% and the purity is 99.1%. Following the above procedure, recover the obtained H4PMo. 11 VO 40 After five applications, the yield and purity were 96.5% and 99.4%, respectively; the recovered H4PMo 11 VO 40 After 10 applications, the yield and purity were 96.0% and 99.3%, respectively; the recovered H4PMo 11 VO 40 After 15 applications, the yield and purity were 95.8% and 99.2%, respectively; the recovered H4PMo 11 VO 40 After 20 applications, the yield and purity were 95.2% and 99.1%, respectively.

[0030] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A method for preparing 1-(4-chlorophenyl)-3-pyrazol, characterized in that, An oxidation reaction was carried out in a solvent using 1-(4-chlorophenyl)pyrazolidine-3-one as the raw material, heteropoly acid as the catalyst, and air as the oxidant. The mass ratio of 1-(4-chlorophenyl)pyrazolidine-3-one to the heteropoly acid catalyst was 50:1-200:1, the mass ratio of 1-(4-chlorophenyl)pyrazolidine-3-one to the reaction solvent was 1:3-1:8, the initial air pressure was 2-4 MPa, the reaction temperature was 70-110℃, and the reaction time was 4.0-10.0 h. After the reaction is complete, deionized water with a volume of 0.5-1.0 times that of the reaction mixture is added to the reaction system to dissolve the heteropolyacid and precipitate the crude product. The product is then obtained by filtration, filter cake washing, and drying. The filtrate containing dissolved heteropolyacids after filtration is subjected to vacuum distillation to remove water and solvent, and the catalyst is recovered and recycled. The organic solvent used in the reaction is one of methanol, ethanol, propanol, or isopropanol, and the heteropolyacid catalyst is H4PMo. 11 VO 40 H4PW 11 VO 40 or H4SiMo 11 VO 40 One of them.