Synthetic method of 3-difluoromethyl-1-methylpyrazole-4-ethyl formate

Abstract

The invention discloses a synthetic method of 3-difluoromethyl-1-methylpyrazole-4-ethyl formate, which comprises the following steps of: taking 5-difluoromethyl-1-methylpyrazole-4-ethyl formate and dimethyl carbonate as raw materials, and reacting at the temperature of between 20 and 30 DEG C to obtain 3-difluoromethyl-1-methylpyrazole-4-ethyl formate; 3-difluoromethyl-1-methylpyrazole-4-ethyl formate is synthesized under the action of a porous organic polymer catalyst immobilized with lewis acid, the porous organic polymer catalyst immobilized with lewis acid comprises a porous organic polymer, and lewis acid is immobilized on the porous organic polymer. In the synthesis method, under the action of the porous organic polymer catalyst immobilized with Lewis acid, not only can a higher reaction conversion rate be obtained at normal temperature, but also a large amount of side reactions caused by high temperature can be effectively avoided, so that the content of impurities can be remarkably reduced; the method has the advantages of simple operation, good catalyst activity, mild reaction conditions, few side reactions, fast reaction rate, high yield and the like, is suitable for industrial application, and has good market prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of compound intermediate synthesis and relates to a method for synthesizing ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate. Background Art

[0002] 3-Difluoromethyl-1-methyl-1H-pyrazole-4-carboxylic acid is an important pesticide intermediate. The succinate dehydrogenase inhibitor (SDHI) fungicides synthesized with 3-difluoromethyl-1-methyl-1H-pyrazole-4-carboxylic acid as an intermediate mainly include five types: fluopyram, benzovinflumizone, bixafen, fluazifopyram, and pyraclostrobin. In recent years, these pesticides have been in great demand in the market and have great commercial value.

[0003] As a key intermediate in the preparation of 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid, ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate is currently a hot topic of research. There are two main industrial synthetic routes: one is the ethyl difluoroacetoacetate route, which uses ethyl difluoroacetoacetate as a raw material, reacts with triethyl orthoformate to produce an intermediate, and then reacts with methylhydrazine to obtain ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate; the other is the acyl fluoride route, which uses difluoroacetyl fluoride as a raw material, reacts with ethyl N,N-dimethylacrylate to produce an intermediate, and then reacts with methylhydrazine to obtain ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate. However, the above two types of synthetic routes have a common problem, that is, when the intermediate is cyclized with methylhydrazine to obtain 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester, 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester (referred to as "isomer") will inevitably be produced, and the isomer content is relatively high, more than 10%. At the same time, the above isomer can only be removed as an impurity during the post-treatment process, thereby affecting the overall yield of the synthesis.

[0004] In addition, the prior art reports a method in which 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester (isomer) is used as a raw material and rearranged with trimethyl phosphate under the catalysis of phosphoric acid or sulfonic acid to obtain 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester. However, this method has the problems of high reaction temperature, long reaction time, many side reactions, low conversion rate, etc., and the reaction solution is dark in color, which makes post-processing difficult.

[0005] In addition, the prior art reports a method of using 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester (isomer) as a raw material, reacting with dimethyl sulfate and dimethylformamide, and rearranging to obtain 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester. However, this method also has the problems of high reaction temperature, slow reaction rate, low conversion rate, etc. At the same time, there are also problems such as high toxicity of dimethyl sulfate and difficulty in recovering dimethylformamide. The synthesis cost is high and it is not suitable for industrial production.

[0006] Therefore, obtaining a method for synthesizing 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester with simple process, convenient operation, low cost, low reaction temperature, fast reaction rate and high yield is of great significance for promoting the industrial production and widespread use of succinate dehydrogenase inhibitor (SDHI) fungicides. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for synthesizing ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate, which has the advantages of simple process, convenient operation, low cost, low reaction temperature, fast reaction rate and high yield.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A method for synthesizing 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester comprises taking 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester and dimethyl carbonate as raw materials, and synthesizing 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester under the action of a porous organic polymer catalyst carrying a Lewis acid; the porous organic polymer catalyst carrying a Lewis acid comprises a porous organic polymer, and the Lewis acid is carried on the porous organic polymer.

[0010] The above-mentioned synthesis method is further improved, and the porous organic polymer catalyst carrying Lewis acid is prepared by the following method: Lewis acid, porous organic polymer and organic solvent are mixed, stirred, heated for reaction, filtered, washed and dried to obtain the porous organic polymer catalyst carrying Lewis acid.

[0011] The above synthesis method is further improved in that the mass ratio of the Lewis acid to the porous organic polymer is 0.5-1.0:1.0.

[0012] The above synthesis method is further improved, wherein the Lewis acid is one of aluminum trichloride, ferric trichloride and tin tetrachloride.

[0013] The above synthesis method is further improved in that the porous organic polymer is a conjugated microporous phthalocyanine polymer.

[0014] The above synthesis method is further improved, wherein the organic solvent is one of toluene, xylene and chlorobenzene.

[0015] The above-mentioned synthesis method is further improved in that the stirring time is 0.5h to 2h; the reaction is carried out at a temperature of 80°C to 110°C; the reaction time is 1h to 4h; the drying is carried out under vacuum conditions; and the drying time is 2h to 5h.

[0016] The above-mentioned synthesis method is further improved. When 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester and dimethyl carbonate are used as raw materials, 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester is synthesized under the action of a porous organic polymer catalyst with a Lewis acid immobilized thereon, the method comprises the following steps: 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester, dimethyl carbonate and the porous organic polymer catalyst with a Lewis acid immobilized thereon are mixed to carry out a synthesis reaction, and then filtered to remove dimethyl carbonate to obtain 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester.

[0017] The above synthesis method is further improved in that the mass ratio of the porous organic polymer catalyst supporting Lewis acid to the 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester is 0.03-0.1:1.

[0018] The above synthesis method is further improved, wherein the molar ratio of the 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester to the dimethyl carbonate is 1.0:3.0-5.0.

[0019] The above synthesis method is further improved in that the synthesis reaction is carried out at a temperature of 25°C to 80°C; and the synthesis reaction time is 1h to 4h.

[0020] The above synthesis method is further improved, and after the filtration is completed, it also includes: using the porous organic polymer catalyst with immobilized Lewis acid obtained after the filtration to synthesize ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] (1) In view of the shortcomings of the existing synthesis methods, the present invention creatively provides a method for synthesizing 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester, wherein 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester and dimethyl carbonate are used as raw materials, and 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester is synthesized under the action of a porous organic polymer catalyst supported by a Lewis acid, wherein the porous organic polymer catalyst supported by a Lewis acid is a porous organic polymer and a Lewis acid supported on the porous organic polymer. In the porous organic polymer catalyst of the immobilized Lewis acid adopted in the present invention, the porous organic polymer is used as a carrier, and the π electrons on the aromatic ring thereof can form a stable coordination structure with the Lewis acid. At the same time, the porous organic polymer has an excellent specific surface area, so that the catalyst has good catalytic efficiency and chemical stability. Therefore, when the porous organic polymer catalyst of the immobilized Lewis acid is used for catalytic synthesis of 3-difluoromethyl-1-methylpyrazole-4-ethyl carboxylate, dimethyl carbonate is more likely to alkylate 5-difluoromethyl-1-methylpyrazole-4-ethyl carboxylate to form an unstable pyrazolium cation, and then rearrange to obtain stable 3-difluoromethyl-1-methylpyrazole-4-ethyl carboxylate, thereby reducing the reaction temperature and shortening the reaction time. Not only can a higher reaction conversion rate be obtained at room temperature, but also a large number of side reactions caused by high temperature can be effectively avoided, thereby significantly reducing the impurity content. The reaction formula is as follows:

[0023]

[0024] (2) In the present invention, dimethyl carbonate is used as both a reaction raw material and a solvent. After the reaction is completed, the reaction solution is filtered to remove the catalyst, and then the dimethyl carbonate is removed to obtain the target product, which simplifies the operation process and realizes the recovery and reuse of the catalyst. In addition, it can also avoid the production cost of solvent separation and recovery due to the additional use of reaction solvent. The synthesis method of 3-difluoromethyl-1-methylpyrazole-4-ethyl carboxylate of the present invention has the advantages of simple operation, good catalyst activity, mild reaction conditions, few side reactions, fast reaction rate, high yield, etc., is suitable for industrial application, and has a good market prospect.

[0025] (3) In the present invention, the effective components in the porous organic polymer catalyst of the immobilized Lewis acid are stable, and the catalyst after filtration can be recycled for many times, thereby improving the utilization efficiency of the catalyst, reducing the use cost, and promoting its industrial application.

[0026] (4) In the present invention, by optimizing the mass ratio of Lewis acid to porous organic polymer to 0.5 to 1.0:1.0, the catalyst has excellent stability and catalytic performance. In particular, when the mass ratio is too high, the coordination structure of the catalyst is easily unstable, which in turn easily causes the catalyst to be deactivated; and when the mass ratio is too low, the catalyst activity is easily reduced, affecting the catalytic effect. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0028] In the following examples of the present invention, unless otherwise specified, the materials and instruments used are commercially available, the equipment used is conventional equipment, and the data obtained are the average values ​​of more than three repeated experiments.

[0029] Example 1

[0030] A method for synthesizing ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate comprises the following steps:

[0031] In a three-necked flask (250 mL) equipped with a mechanical stirrer, a condenser and a thermometer, 52.0 g of 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester (98%, 0.25 mol), 68.2 g of dimethyl carbonate (99%, 0.75 mol) and 1.6 g of a porous organic polymer catalyst of a Lewis acid immobilized (aluminum chloride-immobilized porous organic polymer) were added, stirring was started, the mixture was reacted at 80° C. for 1 h, cooled to room temperature, filtered, the catalyst was separated, and dimethyl carbonate was removed by distillation under reduced pressure to obtain 50.6 g of light yellow solid 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester with a content of 99.2%, of which 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester (isomer) had a content of 0.3%, and the yield was 98.4% (based on 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester).

[0032] In this embodiment, the Lewis acid-supported porous organic polymer catalyst (aluminum chloride-supported porous organic polymer) is prepared by the following method:

[0033] In a three-necked flask (100 mL) equipped with a mechanical stirrer, a condenser, and a thermometer, 37.2 g of toluene (99%, 0.4 mol), 2.7 g of anhydrous aluminum chloride (99%, 0.02 mol) and 5.4 g of a conjugated microporous phthalocyanine polymer (CoPP-FePc-CMP, commercially available) were added, stirred for 0.5 h, mixed evenly, heated to 80°C, and kept warm for 1 h. After the insulation was completed, the mixture was cooled to room temperature and filtered. The resulting precipitate was washed with toluene and water, respectively, and dried under vacuum conditions for 2 h to obtain 7.2 g of a porous organic polymer catalyst supported on Lewis acid (aluminum chloride supported porous organic polymer).

[0034] Example 2

[0035] A method for synthesizing ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate comprises the following steps:

[0036] In a three-necked flask (250 mL) equipped with a mechanical stirrer, a condenser and a thermometer, 52.0 g of 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester (98%, 0.25 mol), 113.7 g of dimethyl carbonate (99%, 1.25 mol) and 5.2 g of a porous organic polymer catalyst supported on a Lewis acid (porous organic polymer supported on ferric chloride) were added, stirring was started, the mixture was reacted at 25° C. for 4 h, cooled to room temperature, filtered, the catalyst was separated, and dimethyl carbonate was removed by distillation under reduced pressure to obtain 50.8 g of light yellow solid 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester, with a content of 99.5%, of which the content of 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester (isomer) was 0.2%, and the yield was 99.1% (based on 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester).

[0037] In this embodiment, the Lewis acid-supported porous organic polymer catalyst (iron trichloride-supported porous organic polymer) is prepared by the following method:

[0038] In a three-necked flask (100 mL) equipped with a mechanical stirrer, a condenser, and a thermometer, 42.9 g of xylene (99%, 0.4 mol), 3.3 g of anhydrous ferric chloride (98%, 0.02 mol) and 3.3 g of a conjugated microporous phthalocyanine polymer (CoPP-FePc-CMP) were added, stirred for 2 h, mixed evenly, heated to 110°C, and kept warm for 2 h. After the insulation was completed, the mixture was cooled to room temperature and filtered. The precipitate was washed with xylene and water, respectively, and dried under vacuum conditions for 5 h to obtain 36.0 g of a porous organic polymer catalyst supported on Lewis acid (porous organic polymer supported on ferric chloride).

[0039] Example 3

[0040] A method for synthesizing ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate comprises the following steps: adding 52.0 g of 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester (98%, 0.25 mol), 90.9 g of dimethyl carbonate (99%, 1.0 mol) and 2.6 g of a porous organic polymer catalyst supported on Lewis acid (porous organic polymer supported on tin tetrachloride), start stirring, react at 60°C for 2 h, cool to room temperature, filter, separate the catalyst, and remove dimethyl carbonate by distillation under reduced pressure to obtain 50.4 g of light yellow solid 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester with a content of 99.3%, of which the content of 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester (isomer) is 0.5%, and the yield is 98.1% (based on 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester).

[0041] In this embodiment, the Lewis acid-supported porous organic polymer catalyst (aluminum chloride-supported porous organic polymer) is prepared by the following method:

[0042] In a three-necked flask (100 mL) equipped with a mechanical stirrer, a condenser and a thermometer, 37.2 g of toluene (99%, 0.4 mol), 5.3 g of anhydrous tin tetrachloride (99%, 0.02 mol) and 5.3 g of a conjugated microporous phthalocyanine polymer (CoPP-FePc-CMP) were added, stirred for 1 h, mixed evenly, heated to 90°C, and kept warm for 4 h. After the insulation was completed, the mixture was cooled to room temperature, filtered, and the precipitate was washed with toluene and water, respectively, and dried under vacuum conditions for 3 h to obtain 10.1 g of a porous organic polymer catalyst supported on Lewis acid (porous organic polymer supported on tin tetrachloride).

[0043] Example 4

[0044] A method for synthesizing ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate comprises the following steps:

[0045] In a three-necked flask (250 mL) equipped with a mechanical stirrer, a condenser and a thermometer, 52.01 g of 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester (98%, 0.25 mol), 68.2 g of dimethyl carbonate (99%, 0.75 mol) and 1.6 g of a porous organic polymer catalyst of a Lewis acid immobilized (aluminum chloride-immobilized porous organic polymer) were added, stirring was started, the mixture was reacted at 80° C. for 1 h, cooled to room temperature, filtered, the catalyst was separated, and dimethyl carbonate was removed by distillation under reduced pressure to obtain 50.7 g of light yellow solid 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester, with a content of 99.2%, of which the content of 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester (isomer) was 0.3%, and the yield was 98.6% (based on 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester).

[0046] In this embodiment, the Lewis acid-supported porous organic polymer catalyst (aluminum chloride-supported porous organic polymer) is prepared by the following method:

[0047] In a three-necked flask (100 mL) equipped with a mechanical stirrer, a condenser, and a thermometer, add 45.5 g of chlorobenzene (99%, 0.4 mol), 2.7 g of anhydrous aluminum chloride (99%, 0.02 mol) and 5.4 g of a conjugated microporous phthalocyanine polymer (CoPP-FePc-CMP), stir for 0.5 h, mix evenly, heat to 100 ° C, keep warm for 1 h, cool to room temperature after the insulation is completed, filter, wash the precipitate with chlorobenzene and water, respectively, and dry under vacuum conditions for 5 h to obtain 7.5 g of a porous organic polymer catalyst supported on Lewis acid (aluminum chloride supported porous organic polymer).

[0048] Comparative Example 1

[0049] A method for synthesizing ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate comprises the following steps:

[0050] In a three-necked flask (250mL) equipped with mechanical stirring, condenser tube and thermometer, 52.0g 5-difluoromethyl-1-methylpyrazole-4-ethyl formate (98%, 0.25mol) and 68.2g dimethyl carbonate (99%, 0.75mol) were added, stirring was turned on, and the reaction was carried out at 80°C for 4h, cooled to room temperature, filtered, and dimethyl carbonate was removed by vacuum distillation to obtain 51.3g of light yellow liquid, wherein the content of 3-difluoromethyl-1-methylpyrazole-4-ethyl formate was 3.2%, the content of 5-difluoromethyl-1-methylpyrazole-4-ethyl formate (isomer) was 95.9%, and the yield was 3.2% (based on 5-difluoromethyl-1-methylpyrazole-4-ethyl formate). In Comparative Example 1, the fundamental reason for the low yield is that when the porous organic polymer catalyst of the immobilized Lewis acid is not added, it is difficult to promote the effective conduct of the reaction.

[0051] Comparative Example 2

[0052] A method for synthesizing ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate is substantially the same as that of Example 4, except that in Comparative Example 2, aluminum trichloride is used instead of the porous organic polymer catalyst supporting Lewis acid.

[0053] After testing, the content of 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester in the obtained product is 5.8%, the content of 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester (isomer) is 92.5%, and the product yield is 5.7% (calculated as 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester). It can be concluded that when only aluminum chloride is used as a catalyst, the reaction speed is slow, the conversion rate of 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester is low, and the yield is low.

[0054] It can be seen from the above results that, compared with the conventional method, the synthesis method of ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate of the present invention, under the action of a porous organic polymer catalyst of a Lewis acid immobilized on the surface, can not only obtain a higher reaction conversion rate at room temperature, but also effectively avoid a large number of side reactions caused by high temperature, thereby significantly reducing the impurity content. It has the advantages of simple operation, good catalyst activity, mild reaction conditions, few side reactions, fast reaction rate, high yield, etc., is suitable for industrial application, and has good market prospects.

[0055] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for synthesizing ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate, characterized in that: 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester and dimethyl carbonate are used as raw materials to synthesize 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester under the action of a porous organic polymer catalyst carrying a Lewis acid; the porous organic polymer catalyst carrying a Lewis acid comprises a porous organic polymer, and the Lewis acid is carried on the porous organic polymer.

2. The synthesis method according to claim 1, characterized in that The porous organic polymer catalyst supporting Lewis acid is prepared by the following method: mixing Lewis acid, porous organic polymer and organic solvent, stirring, heating for reaction, filtering, washing and drying to obtain the porous organic polymer catalyst supporting Lewis acid.

3. The synthesis method according to claim 2, characterized in that The mass ratio of the Lewis acid to the porous organic polymer is 0.5-1.0:1.

0.

4. The synthesis method according to claim 3, characterized in that The Lewis acid is one of aluminum trichloride, ferric trichloride and tin tetrachloride; the porous organic polymer is a conjugated microporous phthalocyanine polymer; and the organic solvent is one of toluene, xylene and chlorobenzene.

5. The synthesis method according to claim 2, characterized in that The stirring time is 0.5h to 2h; the reaction is carried out at a temperature of 80°C to 110°C; the reaction time is 1h to 4h; the drying is carried out under vacuum conditions; and the drying time is 2h to 5h.

6. The synthesis method according to any one of claims 1 to 5, characterized in that The method uses 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester and dimethyl carbonate as raw materials and synthesizes 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester under the action of a porous organic polymer catalyst supporting a Lewis acid. The method comprises the following steps: mixing 5-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester, dimethyl carbonate and the porous organic polymer catalyst supporting a Lewis acid for a synthetic reaction, filtering, removing dimethyl carbonate, and obtaining 3-difluoromethyl-1-methylpyrazole-4-carboxylic acid ethyl ester.

7. The synthesis method according to claim 6, characterized in that The mass ratio of the porous organic polymer catalyst supporting Lewis acid to the ethyl 5-difluoromethyl-1-methylpyrazole-4-carboxylate is 0.03 to 0.1:

1.

8. The synthesis method according to claim 7, characterized in that The molar ratio of the ethyl 5-difluoromethyl-1-methylpyrazole-4-carboxylate to the dimethyl carbonate is 1.0:3.0-5.

0.

9. The synthesis method according to claim 8, characterized in that The synthesis reaction is carried out at a temperature of 25° C. to 80° C.; the synthesis reaction time is 1 h to 4 h.

10. The synthesis method according to claim 6, characterized in that: After the filtration is completed, the method further comprises: using the porous organic polymer catalyst with immobilized Lewis acid obtained after the filtration to synthesize ethyl 3-difluoromethyl-1-methylpyrazole-4-carboxylate.

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