Synthesis method of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole

Abstract

The invention relates to the technical field of pesticide production, in particular to a synthesis method of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, which at least comprises the following steps: firstly, mixing trioxymethylene and 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole to prepare a solution A; the solution A and chlorosulfonic acid are mixed and then subjected to a chloromethylation reaction, 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole is obtained through aftertreatment after sampling detection is qualified, and the method is high in product yield, high in purity, low in production cost, high in production efficiency, easy to operate, capable of meeting the green and environment-friendly requirements and suitable for industrial production. The industrial production is easy to realize.

Description

Technical Field

[0001] The invention relates to the technical field of pesticide production, and in particular to a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole. Background Art

[0002] 1-Methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole is an important intermediate for the synthesis of the herbicide sulfone pyrazoline. A Chinese patent (publication number CN111574511A) discloses a method for synthesizing 1-methyl-3-trifluoromethyl-4-hydroxymethyl-5-difluoromethoxy-1-H-pyrazole by chlorination reaction using 1-methyl-3-trifluoromethyl-4-hydroxymethyl-5-difluoromethoxy-1-H-pyrazole and a chlorination agent as raw materials, but the purity of the product prepared by this method is relatively low at 90%. A Chinese patent (publication number CN114716379A) ​​discloses a method for synthesizing 1-methyl-3-trifluoromethyl-4-methyl-5-difluoromethoxy-1-H-pyrazole by halogenating 1-methyl-3-trifluoromethyl-4-halomethyl-5-difluoromethoxy-1-H-pyrazole and a halogenating agent as raw materials. The halogenating agents used in the method, such as bromine, NBS, dibromohydantoin, NCS, etc., produce a large amount of succinimide (when NBS and NCS are used) and 5,5-dimethylhydantoin (when dibromohydantoin is used), etc., which are expensive, have a high production cost, and have a low conversion rate (maximum 85%) and a low content (maximum 75%), which is not conducive to industrialization. European patent (EP11541561A1) discloses the method for synthesizing 1-methyl-3-trifluoromethyl-4-halomethyl-5-difluoromethoxy-1-H-pyrazoles as raw material with 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazoles, formaldehyde or paraformaldehyde, hydrogen halide, Lewis acid, the reaction needs to add the Lewis acid of equivalent, produces a large amount of metal waste salts, does not meet environmental protection requirements, and complicated operation is unfavorable for industrialized production. Chinese patent (publication number is CN117777122A) discloses the method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazoles as raw material with 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazoles, paraformaldehyde, sulfuric acid, thionyl chloride, the method has the shortcomings that product yield is low, formaldehyde utilization rate is low, three wastes are difficult to handle. In addition, sulfur dioxide gas will be produced during the reaction, which will pollute the environment and does not meet the requirements of green environmental protection. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, which has high product yield and high purity, low production cost, high production efficiency, simple operation, meets green environmental protection requirements, and is easy to realize industrial production.

[0004] The invention provides a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole. The method comprises at least the following steps: firstly, trioxymethylene and 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole are mixed to prepare a solution A, the solution A is mixed with chlorosulfonic acid, and then a chloromethylation reaction is carried out, and after sampling and testing, the sample is post-treated to obtain 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole.

[0005] In one embodiment, the molar ratio of 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole, trioxymethylene and chlorosulfonic acid is 1:(0.33-0.50):(1-2).

[0006] Preferably, the molar ratio of 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole, trioxymethylene and chlorosulfonic acid is 1:(0.33-0.43):(1-1.2).

[0007] In one embodiment, the chloromethylation reaction comprises:

[0008] Method a. adding chlorosulfonic acid dropwise to a batch reactor containing solution A to carry out chloromethylation reaction;

[0009] Mode b: Chlorosulfonic acid and solution A are continuously fed into the reaction device, and the reaction liquid at the outlet of the reaction device is transported to the reactor for chloromethylation reaction.

[0010] Method c. Chlorosulfonic acid and solution A are pumped into the preheated reactor at the same time, and the feeding rates of chlorosulfonic acid and solution A are controlled respectively. After the feeding is completed, chloromethylation reaction is carried out.

[0011] In one embodiment, the reaction temperature of the chloromethylation reaction is 10-100°C.

[0012] Preferably, the reaction temperature of the chloromethylation reaction is 50-90°C.

[0013] More preferably, the reaction temperature of the chloromethylation reaction is 75-90°C.

[0014] In one embodiment, the chloromethylation reaction time in the method a is 5 min to 24 h.

[0015] Preferably, the chloromethylation reaction time in the method a is 30 min to 10 h.

[0016] More preferably, the chloromethylation reaction time in the method a is 2 h to 10 h.

[0017] In one embodiment, in the method a, the temperature for dropping chlorosulfonic acid into solution A is 10 to 100° C., and the time for dropping is 1 to 10 hours.

[0018] Preferably, in the method a, the temperature for dropping chlorosulfonic acid into solution A is 30 to 60° C., and the time for dropping is 2 to 4 hours.

[0019] More preferably, in the method a, the temperature for dropping chlorosulfonic acid into solution A is 30-40° C., and the time for dropping is 2-3 h.

[0020] In one embodiment, the reaction apparatus in the mode b comprises one or more combinations of a tank reactor, a tubular reactor, and a tower reactor.

[0021] In one embodiment, the chloromethylation reaction time in the method b is 10 min to 2 h.

[0022] Preferably, the chloromethylation reaction time in the method b is 10 min to 1 h.

[0023] In one embodiment, in the method b, chlorosulfonic acid and solution A are continuously fed into the reaction device and stay there for 10 min to 2 h.

[0024] Preferably, in the method b, the chlorosulfonic acid and solution A are continuously fed into the reaction device and stay there for 10 min to 1 h.

[0025] In one embodiment, the preheating temperature in the method c is 50-80°C.

[0026] Preferably, the preheating temperature in the method c is 65-75°C.

[0027] In one embodiment, the feed rate of chlorosulfonic acid in the method c is 5 to 20 g / min.

[0028] Preferably, the feed rate of chlorosulfonic acid in the method c is 8.09 to 15.5 g / min.

[0029] In one embodiment, the feeding rate of solution A in the method c is 10 to 40 g / min.

[0030] Preferably, the feed rate of solution A in the method c is 14.46-28.61 g / min.

[0031] In one embodiment, the reaction time of the chloromethylation reaction in the method c is 0.5 to 5 hours.

[0032] Preferably, the reaction time of the chloromethylation reaction in the method c is 1 to 2 hours.

[0033] The invention optimizes the problems existing in the existing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole synthesis method, designs a method of mixing trioxymethylene and 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole and carrying out a chloromethylation reaction with chlorosulfonic acid, and effectively reduces the generation of side reactions and tar by comprehensively controlling the molar ratio of reaction raw materials and reaction conditions, and the yield can reach more than 96%, and the purity can reach more than 98%.

[0034] The synthesis method provided by the present invention can be carried out not only by an intermittent device, but also by a continuous device in combination with an intermittent device. It has flexible and extensive application scenarios, a wide range of applicability, and is easy to industrialize.

[0035] The synthesis method provided by the present invention has a simple and easy-to-control process flow, a solvent-free reaction, and no harmful gases such as sulfur dioxide are generated during the reaction, thus meeting the requirements of green environmental protection.

[0036] Beneficial Effects

[0037] 1. The present invention provides a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole. The method has high product yield, high purity, low production cost, high production efficiency, simple operation, meets green environmental protection requirements, and is easy to realize industrial production.

[0038] 2. The present invention optimizes the problems existing in the existing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole synthesis method, designs a method of mixing trioxymethylene and 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole and then conducting a chloromethylation reaction with chlorosulfonic acid, and effectively reduces side reactions and tar generation by comprehensively controlling the molar ratio of the reaction raw materials and the reaction conditions, and the yield can reach more than 96%, and the purity can reach more than 98%.

[0039] 3. The synthesis method provided by the present invention can be carried out not only by an intermittent device, but also by a continuous device in combination with an intermittent device. It has flexible and extensive application scenarios, a wide range of applicability, and is easy to industrialize.

[0040] 4. The synthesis method provided by the present invention has a simple and easy-to-control process flow, a solvent-free reaction, and no harmful gases such as sulfur dioxide are generated during the reaction, which meets the requirements of green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the IR chart (infrared ATR method) of 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole in Example 1.

[0042] Figure 2 This is the IR chart (infrared ATR method) of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole in Example 1.

[0043] Figure 3 This is the EI mass spectrum of 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole in Example 1.

[0044] Figure 4 This is the EI mass spectrum of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole in Example 1.

[0045] Figure 5 is the 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole in Example 1 1 H NMR spectra.

[0046] Figure 6 is the 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole in Example 1 1 HNMR spectrum.

[0047] Figure 7 Schematic diagram of the pipeline reactor in Examples 5, 6 and Comparative Example 3.

[0048] In the figure: 1-solution A feed port, 2-chlorosulfonic acid feed port, 3-Y-type tee, 4-jacket outlet, 5-reaction pipeline, 6-jacket inlet, 7-discharge port. DETAILED DESCRIPTION

[0049] Example 1

[0050] Embodiment 1 of the present invention provides a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, comprising the following steps:

[0051] 1-Methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole (500g, 2.267mol, 1eq) and trioxymethylene (68.02g, 0.748mol, 0.33eq) were mixed to prepare solution A, and chlorosulfonic acid (296.55g, 2.494mol, 1.1eq) was added dropwise to solution A, and the dropping temperature was controlled at 40°C for 2h. After the dropping was completed, chloromethylation reaction was carried out at 70°C for 2h. After the reaction was completed, 593.79g of colorless transparent liquid was obtained after post-treatment, and the content of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole was 98.2%, and the yield was 97.2%.

[0052] The IR spectra information of 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole and 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole are shown in Tables 1 and 2, respectively.

[0053] Table 1

[0054]

[0055] Table 2

[0056]

[0057] The IR spectrum of 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole ( Figure 1 ) and IR spectra of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole ( Figure 2 ) were compared and it was found that the stretching vibration band of the CH bond on the pyrazole ring (3161cm -1 ) disappeared, and a new CC bond stretching vibration band (1296cm -1 ) and the stretching vibration band of C-Cl bond (803cm -1 ).

[0058] The GC-MS (EI) characterization results of 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole can be found in Figure 3 ,analyze Figure 3 It can be seen that: m / z = 216.0 (M + ), 197.1([MF] + ), 166.1([M-CHF2] + ).

[0059] 1-Methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole 1 H NMR characterization results are shown in Figure 5 ,analyze Figure 5 It can be seen that:1 H NMR (400MHz, CDCl3): δ6.56 (t, J=71.4Hz, 1H), 6.18 (s, 1H), 3.80 (s, 3H).

[0060] The GC-MS (EI) characterization results of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole can be found in Figure 4 ,analyze Figure 4 It can be seen that: m / z = 264.0 (M + ), 229.1([M-Cl] + ), 179.1([M-(Cl+CHF2)] + ).

[0061] 1-Methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole 1 H NMR characterization results are shown in Figure 6 ,analyze Figure 6 It can be seen that: 1 H NMR (400MHz, CDCl3): δ6.69 (t, J=71.5Hz, 1H), 4.51 (s, 2H), 3.83 (s, 3H).

[0062] Example 2

[0063] Embodiment 2 of the present invention provides a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, comprising the following steps:

[0064] 1-Methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole (500g, 2.267mol, 1eq) and trioxymethylene (72.143g, 0.794mol, 0.35eq) were mixed to prepare solution A, and chlorosulfonic acid (323.51g, 2.721mol, 1.2eq) was added dropwise to solution A, and the dropping temperature was controlled at 30°C for 3h. After the dropping was completed, chloromethylation reaction was carried out at 75°C for 4h. After the reaction was completed, 591.95g of colorless transparent liquid was obtained after post-treatment, and the content of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole was 98.1%, and the yield was 96.8%.

[0065] Example 3

[0066] Embodiment 3 of the present invention provides a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, comprising the following steps:

[0067] 1-Methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole (1500g, 6.802mol, 1eq) and trioxymethylene (216.43g, 2.381mol, 0.35eq) were mixed to prepare solution A. Chlorosulfonic acid (930.10g, 7.822mol, 1.15eq) and solution A were simultaneously pumped into a reactor preheated to 65°C. The feeding rates of solution A and chlorosulfonic acid were controlled to be 28.61g / min and 15.5g / min, respectively. After the feeding was completed, chloromethylation reaction was carried out at 90°C for 2h. After the reaction was completed, the reaction solution was post-treated to obtain 1796.04g of a colorless transparent liquid with a content of 98.3% and a yield of 98.1%.

[0068] Example 4

[0069] Embodiment 4 of the present invention provides a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, comprising the following steps:

[0070] 1-Methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole (1500g, 6.802mol, 1eq) and trioxymethylene (234.98g, 2.58mol, 0.38eq) were mixed to prepare solution A. Chlorosulfonic acid (970.54g, 8.16mol, 1.2eq) and solution A were simultaneously pumped into a reactor preheated to 75°C. The feeding rates of solution A and chlorosulfonic acid were controlled to be 14.46g / min and 8.09g / min, respectively. After the feeding was completed, chloromethylation reaction was carried out at 90°C for 1h. After the reaction was completed, the reaction solution was post-treated to obtain 1781.43g of a colorless transparent liquid with a content of 98.5% and a yield of 97.5% for 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole.

[0071] Example 5

[0072] Embodiment 5 of the present invention provides a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, comprising the following steps:

[0073] 1-Methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole (1000 g, 4.535 mol, 1 eq) and trioxymethylene (164.90 g, 1.814 mol, 0.4 eq) were mixed to prepare solution A. Chlorosulfonic acid (593.11 g, 4.99 mol, 1.1 eq) and solution A were simultaneously pumped into a pipeline reactor (preheated to 70°C) through a Y-type tee. Figure 7), the feed rate of solution A is controlled to be 38.83 g / min, the feed rate of chlorosulfonic acid is controlled to be 19.77 g / min, and the residence time in the pipeline reactor is 30 min. The reaction liquid at the outlet of the tubular reactor is transported to a reactor and subjected to chloromethylation reaction at 70° C. for 30 min. After the reaction, the reaction liquid is post-treated to obtain 1185.27 g of a colorless transparent liquid, with a content of 99.1% of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole and a yield of 97.9%.

[0074] Among them, the pipeline reactor includes a solution A feed port 1, a chlorosulfonic acid feed port 2, a Y-type tee 3, a jacket outlet 4, a reaction pipeline 5, a jacket inlet 6, and a discharge port 7, wherein the Y-type tee 3 is connected to the reaction pipeline 5, the jacket outlet 4 and the jacket inlet 6 are respectively arranged above and below the jacket wrapped outside the reaction pipeline 5, and the Y-type tee 3 includes a solution A feed port 1 and a chlorosulfonic acid feed port 2.

[0075] The working principle is as follows: solution A and chlorosulfonic acid enter the reaction pipe 5 simultaneously through the liquid A feed port 1 and the chlorosulfonic acid feed port 2 of the Y-type tee 3, respectively, and are discharged from the discharge port 7 after staying in the reaction pipe 5 for a corresponding period of time. Cooling water enters from the jacket inlet 6 and is discharged from the jacket outlet 4 to control the temperature of the reaction liquid in the reaction pipe 5.

[0076] Example 6

[0077] Embodiment 6 of the present invention provides a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, comprising the following steps:

[0078] 1-Methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole (1000 g, 4.535 mol, 1 eq) and trioxymethylene (173.14 g, 1.91 mol, 0.42 eq) were mixed to prepare solution A. Chlorosulfonic acid (647.03 g, 5.44 mol, 1.2 eq) and solution A were simultaneously pumped into a pipeline reactor (preheated to 60°C) through a Y-type three-way pipe. Figure 7 ), the feed rate of solution A is controlled to be 19.55 g / min, the feed rate of chlorosulfonic acid is controlled to be 10.78 g / min, and the residence time in the pipeline reactor is 1 hour. The reaction liquid at the outlet of the tubular reactor is transported to a reactor and subjected to a chloromethylation reaction at 60° C. for 1 hour. After the reaction, the reaction liquid is post-treated to obtain 1175.49 g of a colorless transparent liquid, with a content of 98.7% of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole and a yield of 96.7%.

[0079] Comparative Example 1

[0080] Comparative Example 1 of the present invention provides a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, comprising the following steps:

[0081] 1-Methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole (500g, 2.267mol, 1eq) and trioxymethylene (72.14g, 0.794mol, 0.35eq) were mixed to prepare solution A, and chlorosulfonic acid (593.11g, 4.988mol, 2.2eq) was added dropwise to solution A, and the dropping temperature was controlled at 70°C for 3h. After the dropping was completed, chloromethylation reaction was carried out at 70°C for 5h. After the reaction was completed, 505.83g of colorless transparent liquid was obtained after post-treatment, and the content of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole was 96.3%, and the yield was 81.2%.

[0082] Comparative Example 2

[0083] Comparative Example 2 of the present invention provides a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, comprising the following steps:

[0084] 1-Methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole (500 g, 2.267 mol, 1 eq) and trioxymethylene (88.63 g, 0.975 mol, 0.43 eq) were mixed to form solution A. Chlorosulfonic acid (296.55 g, 2.494 mol, 1.1 eq) and solution A were simultaneously pumped into a reactor precooled to 0° C., the feeding rates of solution A and chlorosulfonic acid were controlled to be 4.91 g / min and 2.47 g / min, and chloromethylation reaction was carried out at 75° C. for 3 h after the feeding was completed. After the reaction was completed, the reaction solution was post-treated to obtain 608.8 g of colorless transparent liquid with a content of 87.6% and a yield of 88.9% for 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole.

[0085] Comparative Example 3

[0086] Comparative Example 3 of the present invention provides a method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, comprising the following steps:

[0087] 1-Methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole (500 g, 2.267 mol, 1 eq) and trioxymethylene (133.98 g, 1.474 mol, 0.65 eq) were mixed to prepare solution A. Chlorosulfonic acid (296.55 g, 2.494 mol, 1.1 eq) and solution A were simultaneously pumped into a pipeline reactor (preheated to 110°C) through a Y-type three-way pipe. Figure 7 ), the feed rate of solution A is controlled to be 21.13 g / min, the feed rate of chlorosulfonic acid is controlled to be 9.89 g / min, and the residence time in the pipeline reactor is 30 min. The reaction liquid at the outlet of the tubular reactor is transported to a reactor and subjected to chloromethylation reaction at 110° C. for 8 h. After the reaction, the reaction liquid is post-treated to obtain 484.68 g of a colorless transparent liquid, with a content of 93.2% of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole and a yield of 75.3%.

Claims

1. A method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, characterized in that: At least the following steps are included: First, trioxymethylene and 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole are mixed to prepare solution A, and solution A is mixed with chlorosulfonic acid to carry out chloromethylation reaction. After sampling and testing, 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole is obtained through post-treatment.

2. The method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole according to claim 1, characterized in that: The molar ratio of the 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole, trioxymethylene and chlorosulfonic acid is 1:(0.33-0.50):(1-2).

3. The method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole according to claim 2, characterized in that: The method of the chloromethylation reaction comprises: Method a. adding chlorosulfonic acid dropwise to a batch reactor containing solution A to carry out chloromethylation reaction; Mode b. Continuously feeding chlorosulfonic acid and solution A into the reaction device, and conveying the reaction solution at the outlet of the reaction device to the reactor for chloromethylation reaction; Method c. Chlorosulfonic acid and solution A are pumped into the preheated reactor at the same time, and the feeding rates of chlorosulfonic acid and solution A are controlled respectively. After the feeding is completed, chloromethylation reaction is carried out.

4. The method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole according to claim 3, characterized in that: The reaction temperature of the chloromethylation reaction is 10-100°C.

5. The method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole according to claim 4, characterized in that: The chloromethylation reaction time in the method a is 5 minutes to 24 hours.

6. The method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole according to claim 5, characterized in that: In the method a, the temperature for dropping chlorosulfonic acid into solution A is 10 to 100° C., and the time for dropping is 1 to 10 hours.

7. The method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole according to claim 6, characterized in that: The reaction device in the mode b comprises one or more combinations of a kettle reactor, a tubular reactor and a tower reactor.

8. The method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole according to claim 7, characterized in that: The chloromethylation reaction time in the method b is 10 min to 2 h.

9. The method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole according to claim 8, characterized in that: In the method b, chlorosulfonic acid and solution A are continuously fed into the reaction device and stay there for 10 minutes to 2 hours.

10. The method for synthesizing 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole according to claim 9, characterized in that: The reaction time of the chloromethylation reaction in the method c is 0.5 to 5 hours.

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