Preparation method of pyroxasulfone

Abstract

The invention belongs to the technical field of herbicides, and particularly relates to a preparation method of pyroxasulfone. According to the method, an intermediate is mixed with a solvent, a catalyst and an oxidizing agent, pyroxasulfone can be prepared through oxidation, and the catalyst is any one or a mixture of two of magnesium oxide and tetramethylpiperidone. The pyroxasulfone preparation method has the beneficial effects that the yield of pyroxasulfone can be more than or equal to 95% through catalytic oxidation reaction including the solvent, the catalyst and the oxidizing agent; the catalyst has the advantages of economy and high efficiency, and certainly cannot cause heavy metal harm.

Description

Technical Field

[0001] The invention belongs to the technical field of herbicides, and in particular relates to a preparation method of pyraclostrobin. Background Art

[0002] Sulfonepyraclostrobin refers to a new type of isoxazole selective herbicide, which is suitable for the pre-emergence control of grass and broad-leaved weeds in corn, soybean, wheat fields, etc.

[0003] The overall preparation method of sulfonepyraclostrobin generally starts from 1-methyl-3-trifluoromethyl-5-hydroxy-1H-pyrazole, and sequentially undergoes condensation and oxidation reactions to obtain the final sulfonepyraclostrobin product.

[0004] In the above oxidation reaction, the oxidation object is sulfide, which is mixed with a solvent, a catalyst and an oxidant, and under certain conditions, it can be oxidized to obtain sulfonepyraclostrobin.

[0005] For example, a Chinese invention patent application with application publication number CN118307533A and application publication date 2024.07.09 discloses a method for preparing sulfonepyraclostrobin, comprising the following steps: (1) reacting N-methyl-3-trifluoromethyl-5-hydroxypyrazole, sodium sulfate and a difluoromethylating agent to obtain an intermediate; (2) mixing the intermediate, a first solvent, an alkali solution and a formaldehyde solution to carry out a hydroxymethylation reaction to obtain hydroxypyrazole methanol; (3) carrying out a condensation reaction of hydroxypyrazole methanol, a phase transfer catalyst and isoxazole thiourea salt to obtain a sulfide; (4) mixing the sulfide, a second solvent, a catalyst and hydrogen peroxide to carry out an oxidation reaction to obtain sulfonepyraclostrobin.

[0006] The preparation method in the invention patent application has the following advantages: improved yield, avoidance of the use of halogenated hydrocarbons, and reduced generation of pollutants.

[0007] However, in the preparation method, the catalyst used in step (4) is sodium tungstate or ammonium molybdate, both of which are expensive. In addition, tungsten is a heavy metal, which is difficult to treat in the subsequent wastewater treatment process. Summary of the invention

[0008] The invention provides a method for preparing sulfonepyraclostrobin, and the technical problem to be solved is: how to make the step of oxidizing sulfide to sulfonepyraclostrobin more economical and environmentally friendly.

[0009] The technical solution adopted by the present invention to solve the above problem is: a method for preparing sulfonepyraclostrobin, wherein an intermediate is mixed with a solvent, a catalyst and an oxidant, and then oxidized to obtain sulfonepyraclostrobin, wherein the structural formula of the intermediate is , The catalyst is any one of magnesium oxide and tetramethyl piperidone or a mixture of the two.

[0010] A further preferred technical solution is that the solvent is any one or a mixture of C1-C6 alcohol, carboxylic acid, ester, nitriles, C1-C4 alkane amide, and water; and the oxidant is any one or a mixture of hydrogen peroxide, ozone, and persulfate.

[0011] A further preferred technical solution is that: the amount of the solvent is 2-10 times the weight of the intermediate; the amount of the catalyst is 0.01-10% of the weight of the intermediate; and the molar amount of the oxidant is 1-5 times the molar amount of the intermediate.

[0012] A further preferred technical solution is that the concentration of the hydrogen peroxide is 5-60wt%.

[0013] A further preferred technical solution is that the reaction temperature for oxidizing to obtain sulfonepyraclostrobin is 20-75°C, and the pH of the reaction system is 3-10.

[0014] In the prior art, the oxidation reaction of sulfonepyraclostrobin obtained from the above intermediates is catalyzed by tungstate because tungstate contains tungsten ions, which are strong oxidants that can accept electrons and promote the oxidation reaction of the substrate under appropriate conditions, corresponding to the Lewis acid reaction mechanism.

[0015] In the present application, magnesium oxide and / or tetramethyl piperidone can also catalyze the above oxidation reaction because: First, magnesium hydroxide formed by the oxidation of magnesium oxide itself contains magnesium ions, and tetramethylpiperidinone formed by the oxidation of tetramethylpiperidin oxide is itself a tetramethylpiperidin free radical; Second, according to Lewis acid theory, the above-mentioned magnesium ions and tetramethylpiperidine free radicals are both Lewis acids and can accept electrons, so they can also catalyze the above-mentioned oxidation reaction.

[0016] The specific catalytic process is as follows: The catalyst is denoted as M, which first reacts with H2O2, ozone, etc. to form an M-OOH complex, and then obtains [MO]· and ·OH groups through the homolytic cleavage of the -O-OH bond. Finally, the sulfide is rapidly oxidized by the ·OH group to obtain sulfoxide or sulfone, and the yield of sulfoxide and sulfone can be adjusted by controlling the ratio of the oxidant to the substrate.

[0017] In other words, whether it is tungstate, magnesium oxide, or tetramethyl piperidone, its main role in the reaction of oxidizing sulfide to prepare sulfone is to promote the hydrolysis of hydrogen peroxide.

[0018] Wherein, the structural formula of the above-mentioned tetramethyl piperidine oxide is .

[0019] The beneficial effects of the present invention include at least the following three points.

[0020] First, the catalytic oxidation reaction including the above-mentioned solvent, catalyst and oxidant can make the yield of sulfonepyraclostrobin ≥ 95%.

[0021] Second, the catalyst is economical and highly efficient, and of course it is unlikely to cause heavy metal hazards.

[0022] Third, the overall operating conditions of the catalytic oxidation reaction are mild, easy to operate and highly practical. DETAILED DESCRIPTION

[0023] The following descriptions are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention.

[0024] Example 1 A method for preparing sulfonepyraclostrobin comprises the following steps: an intermediate is mixed with a solvent, a catalyst and an oxidant, and then oxidized to obtain sulfonepyraclostrobin, wherein the catalyst is magnesium oxide.

[0025] Among them, the structural formula of sulfonepyraclostrobin is .

[0026] The solvent is acetonitrile and water, the oxidant is hydrogen peroxide, and finally aqueous isopropanol is used to promote the precipitation and crystallization of pyraclostrobin.

[0027] The catalytic oxidation reaction is specifically carried out as follows.

[0028] S1. Add 200 g of acetonitrile, 40 g of the intermediate, 40 g of water and 0.2 g of magnesium oxide into a reaction flask.

[0029] S2. After stirring for 0.5 hours, check the pH and control the pH to be 8-9. If the pH is not within the above range, adjust it by adding acid or alkali.

[0030] S3, heating the mixture to 45°C and keeping it warm, during which time 30 wt% aqueous hydrogen peroxide solution (38 g in total) was added dropwise for 2 hours. After the addition was completed, the mixture was kept warm for another 4 hours.

[0031] S4. Remove water and acetonitrile by distillation under reduced pressure, control the temperature to 60°C, add aqueous isopropanol after desolventizing, and carry out heating dissolution, cooling, crystallization, filtration and drying operations in sequence to obtain the final sulfonepyraclostrobin product, weighing 35.7 g.

[0032] Example 2 A method for preparing sulfonepyraclostrobin comprises the following steps: an intermediate is mixed with a solvent, a catalyst and an oxidant, and then oxidized to obtain sulfonepyraclostrobin, wherein the catalyst is tetramethyl piperidone.

[0033] The solvent is methanol and water, the oxidant is hydrogen peroxide, and finally aqueous isopropanol is used to promote the precipitation and crystallization of pyraclostrobin.

[0034] The catalytic oxidation reaction is specifically carried out as follows.

[0035] S1. Add 250 g of methanol, 40 g of the intermediate, 60 g of water and 1.0 g of tetramethylpiperidone into a reaction flask.

[0036] S2. After stirring for 0.5 hours, check the pH and control the pH to be 8-9. If the pH is not within the above range, adjust it by adding acid or alkali.

[0037] S3, heating the mixture to 45°C and keeping it warm, during which time 30 wt% aqueous hydrogen peroxide solution (38 g in total) was added dropwise for 2 hours. After the addition was completed, the mixture was kept warm for another 4 hours.

[0038] S4. Remove water and methanol by distillation under reduced pressure, control the temperature at 60°C, add aqueous isopropanol after desolventizing, and perform heating and dissolving, cooling, crystallization, filtering, and drying operations in sequence to obtain the final sulfonepyraclostrobin product, weighing 35.8 g.

[0039] Example 3 A method for preparing sulfonepyraclostrobin comprises the following steps: an intermediate is mixed with a solvent, a catalyst and an oxidant, and then oxidized to obtain sulfonepyraclostrobin, wherein the catalyst is magnesium oxide and tetramethyl piperidone.

[0040] The solvent is acetic acid and water, the oxidant is hydrogen peroxide, and finally aqueous isopropanol is used to promote the precipitation and crystallization of pyraclostrobin.

[0041] The catalytic oxidation reaction is specifically carried out as follows.

[0042] S1. Add 250 g of acetic acid, 40 g of the intermediate, 50 g of water, and 0.8 g of magnesium oxide and tetramethylpiperidone in total into a reaction flask.

[0043] S2. After stirring for 0.5 hours, check the pH and control the pH to be 8-9. If the pH is not within the above range, adjust it by adding acid or alkali.

[0044] S3, heating the mixture to 45°C and keeping it warm, during which time 30 wt% aqueous hydrogen peroxide solution was added dropwise, a total of 30 g, for 2 hours. After the addition was completed, the mixture was kept warm for another 4 hours.

[0045] S4. Remove water and acetic acid by distillation under reduced pressure, control the temperature to 60°C, add aqueous isopropanol after desolventizing, and carry out heating dissolution, cooling, crystallization, filtration and drying operations in sequence to obtain the final sulfonepyraclostrobin product, weighing 36.0 g.

[0046] Example 4 A method for preparing sulfonepyraclostrobin comprises the following steps: an intermediate is mixed with a solvent, a catalyst and an oxidant, and then oxidized to obtain sulfonepyraclostrobin, wherein the catalyst is magnesium oxide and tetramethyl piperidone.

[0047] The solvent is acetic acid and water, the oxidant is ozone, and finally aqueous isopropanol is used to promote the precipitation and crystallization of pyraclostrobin.

[0048] The catalytic oxidation reaction is specifically carried out as follows.

[0049] S1. Add 250 g of acetic acid, 40 g of the intermediate, 50 g of water, and 0.8 g of magnesium oxide and tetramethylpiperidone in total into a reaction flask.

[0050] S2. After stirring for 0.5 hours, check the pH and control the pH to be 8-9. If the pH is not within the above range, adjust it by adding acid or alkali.

[0051] S3, heating the above mixture to 45°C and keeping it warm, during which ozone gas is introduced, and ensuring that the molar amount of ozone is 4 times the molar amount of the intermediate. After all the ozone is introduced, the reaction is kept warm for 4 hours.

[0052] S4. Remove water and acetic acid by distillation under reduced pressure, control the temperature to 60°C, add aqueous isopropanol after desolventizing, and carry out heating dissolution, cooling, crystallization, filtration and drying operations in sequence to obtain the final sulfonepyraclostrobin product, weighing 35.9 g.

[0053] Example 5 A method for preparing sulfonepyraclostrobin comprises the following steps: an intermediate is mixed with a solvent, a catalyst and an oxidant, and then oxidized to obtain sulfonepyraclostrobin, wherein the catalyst is magnesium oxide and tetramethyl piperidone.

[0054] The solvent is acetic acid and water, the oxidant is sodium persulfate, and finally aqueous isopropyl alcohol is used to promote the precipitation and crystallization of pyraclostrobin.

[0055] The catalytic oxidation reaction is specifically carried out as follows.

[0056] S1. Add 250 g of acetic acid, 40 g of the intermediate, 50 g of water, and 0.8 g of magnesium oxide and tetramethylpiperidone in total into a reaction flask.

[0057] S2. After stirring for 0.5 hours, check the pH and control the pH to be 8-9. If the pH is not within the above range, adjust it by adding acid or alkali.

[0058] S3, heating the mixture to 45°C and keeping it warm, adding 15wt% sodium persulfate aqueous solution, and ensuring that the molar amount of sodium persulfate is 4 times the molar amount of the intermediate, and after the addition is completed, continue to keep the temperature and react for 4 hours.

[0059] S4. Remove water and acetic acid by distillation under reduced pressure, control the temperature to 60°C, add aqueous isopropanol after desolventizing, and carry out heating dissolution, cooling, crystallization, filtration and drying operations in sequence to obtain the final sulfonepyraclostrobin product, weighing 35.9 g.

[0060] Comparative Example 1 The catalytic oxidation reaction in this comparative example is different from that in Example 1 in the following respects: 0.2 g of magnesium oxide was replaced with 0.3 g of magnesium hydroxide.

[0061] Comparative Example 2 The catalytic oxidation reaction in this comparative example is different from that in Example 2 in only one respect: 1.0 g of tetramethylpiperidinone was replaced with 1.0 g of tetramethylpiperidinoxide.

[0062] Comparative Example 3 The catalytic oxidation reaction in this comparative example is different from that in Example 1 in the following respects: Eliminating 0.2 g of magnesium oxide corresponds to an addition ratio of 0%.

[0063] Comparative Example 4 The catalytic oxidation reaction in this comparative example is different from that in Example 1 in the following respects: Replace 0.2 g of magnesium oxide with 8 g of magnesium oxide, corresponding to an addition ratio of 20%.

[0064] Comparison results of content and yield The following table shows the comparative results of the content and yield of sulfonepyraclostrobin in 5 examples and 4 comparative examples of the present invention. Sulfonepyraclostrobin weight (g) content(%) Yield (%) Example 1 35.7 98.5 95.0 Example 2 35.8 98.7 95.5 Example 3 36.0 98.5 95.8 Example 4 35.9 98.3 95.4 Example 5 35.9 98.5 95.7 Comparative Example 1 35.7 98.6 95.1 Comparative Example 2 35.9 98.2 95.4 Comparative Example 3 35.1 95.4 90.7 Comparative Example 4 34.8 96.8 91.0

[0065] Data analysis The catalytic oxidation reactions in the first and fifth embodiments all have a yield of ≥95%.

[0066] Second, in Comparative Examples 1 and 2, magnesium oxide and tetramethyl piperidine ketone oxide were used, and similar yields were finally achieved, which proved the catalytic mechanism of magnesium oxide and tetramethyl piperidine ketone.

[0067] Third, in Comparative Example 3, the catalyst was not used, resulting in a relatively low yield of sulfonepyraclostrobin within the same reaction time, which proves the necessity of a range of catalyst dosage.

[0068] Fourth, in Comparative Example 4, excessive use of the catalyst actually reduced the yield of sulfonepyraclostrobin, during which harmful side reactions may have occurred, or a large amount of waste may have been caused when the product was collected. This also proves the necessity of the above-mentioned dosage range of the catalyst from another aspect.

[0069] The above describes the embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various modifications can be made within the knowledge of ordinary technicians in the technical field without departing from the purpose of the present invention. These are all non-creative modifications and are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing sulfonepyraclostrobin, characterized in that: The intermediate is mixed with a solvent, a catalyst and an oxidant, and then oxidized to obtain sulfonepyraclostrobin, wherein the structural formula of the intermediate is ， The catalyst is any one of magnesium oxide and tetramethyl piperidone or a mixture of the two.

2. The method for preparing sulfonepyraclostrobin according to claim 1, characterized in that: The solvent is any one of C1-C6 alcohol, carboxylic acid, ester, nitriles, C1-C4 alkane amide, and water or a mixture thereof; the oxidant is any one of hydrogen peroxide, ozone, and persulfate or a mixture thereof.

3. The method for preparing sulfonepyraclostrobin according to claim 1, characterized in that: The amount of the solvent used is 2-10 times the weight of the intermediate; the amount of the catalyst used is 0.01-10% of the weight of the intermediate; the molar amount of the oxidant is 1-5 times the molar amount of the intermediate.

4. The method for preparing sulfonepyraclostrobin according to claim 2, characterized in that: The concentration of the hydrogen peroxide is 5-60wt%.

5. The method for preparing sulfonepyraclostrobin according to claim 1, characterized in that: The reaction temperature for oxidizing to obtain sulfonepyraclostrobin is 20-75°C, and the pH of the reaction system is 3-10.

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