Preparation method of metribuzin

Abstract

The invention belongs to the technical field of pesticides and chemical engineering, and particularly relates to a metribuzin preparation method which comprises the following steps: step one, in the presence of tetrahydrofuran and sodium hydroxide, adding 4-amino-6-tert-butyl-3-sulfydryl-1, 2, 4-triazine-5 (4H)-ketone and dimethyl carbonate, and under the condition of heat preservation, reacting for 1-2 hours at the temperature of 60-80 DEG C to obtain a metribuzin intermediate; carrying out a substitution reaction by mixing and stirring, and obtaining a mixed solution after the substitution reaction is completed; and 2, carrying out post-treatment on the mixed solution to obtain metribuzin. According to the invention, 4-amino-6-tert-butyl-3-sulfydryl-1, 2, 4-triazine-5 (4H)-ketone is used as a raw material, tetrahydrofuran which is a general solvent is combined, sodium hydroxide is used as a catalyst, and dimethyl carbonate is used as a methylation reagent, so that the synthetic route has the advantages of low raw material cost, few side reactions, simple and convenient post-treatment, small environmental influence and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of pesticides and chemical industry, and particularly relates to a preparation method of metribuzin. Background Art

[0002] Metribuzin (English name: Metribuzin; CAS: 21087-64-9), also known as metribuzin, methylthiocarb, and licorice, has a molecular formula of C8H14N4OS and a chemical name of 4-amino-6-(1,1-dimethylethyl)-3-methylthio-1,2,4-triazine-5-(4H)-one. In the 1970s, metribuzin was first developed by Bayer in the Federal Republic of Germany; it was officially registered in my country in 1988. Metribuzin is a typical triazine herbicide, a selective herbicide, and has the same characteristics as other triazine herbicides. The mechanism of action is: the weed roots absorb the agent, and the active ingredients flow to the upper stems and leaves with the transpiration of the plant, exerting herbicidal activity by inhibiting the photosynthesis of sensitive plants; after application, the germination of sensitive weeds is not affected, the leaves turn green after emergence, and finally die of nutrient depletion. The mixture of metribuzin with fluralin, chloranil and other pesticides has good efficacy and is mainly suitable for crops such as potatoes, carrots, sugarcane, Xanthium sibiricum, tomatoes, pineapples, etc. It can prevent and control grass and various broad-leaved weeds.

[0003] In the prior art, the commonly used synthesis methods mostly use sulfuric acid as a solvent. Patent (CN112010814 A) uses methanol methylation reagent in the presence of sulfuric acid to methylate triazone mercapto to obtain the product, and the reaction equation is as follows:

[0004] Under this process, metribuzin is precipitated in solid form, and the mother liquor contains unreacted triazinon, nitrogen methyl byproducts, methanol, triazinon sodium salt and other difficult-to-treat organic matter. Alkali needs to be added for post-treatment. This high-salt and high-COD wastewater is one of the difficulties in the metribuzin production process. It requires a long time for reflux reaction, low conversion rate, low production efficiency, and poor product quality. The wastewater produced has a strong sulfur odor. The high-COD wastewater contains a large amount of ketone and triazine organic wastes, which are difficult to biodegrade and have poor oxidizability. Other methylation agents such as dimethyl sulfate have high reaction temperatures, long times, low atomic utilization, small equipment processing capacity, and difficult purification of the byproducts, low yields, and the resulting wastewater has a strong odor and high post-treatment costs. These problems are difficult to solve.

[0005] Based on the above problems, this application document proposes a preparation method of metribuzin to improve the above problems. Summary of the invention

[0006] The present invention aims to provide a method for preparing metribuzin, which uses 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one as a raw material, combines tetrahydrofuran as a universal solvent, uses sodium hydroxide as a catalyst, and uses dimethyl carbonate as a methylating agent. The synthetic route has the advantages of low raw material cost, few side reactions, simple post-treatment, small environmental impact, etc.

[0007] The technical solution adopted by the present invention is as follows: A method for preparing metribuzin, the reaction equation is as follows:

[0008] The following steps are involved: Step 1: in the presence of tetrahydrofuran and sodium hydroxide, add 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one and dimethyl carbonate, and carry out a substitution reaction by mixing and stirring under heat preservation conditions, and after the substitution reaction is completed, a mixed solution is obtained; Step 2: post-treating the mixed solution to obtain metribuzin.

[0009] In a preferred embodiment, the post-processing method is: The mixed solution is cooled to 25°C or below, process water is added to quench the reaction, and the mixture is filtered to obtain metribuzin. The solid is dried to obtain the metribuzin. The mother liquor obtained by filtration is layered, and the organic phase is distilled and dried before direct application. The waste water is distilled under reduced pressure to recover water and precipitate salt.

[0010] In a preferred embodiment, the feed mass ratio of 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one and dimethyl carbonate is (1.3-1.6):1.

[0011] In a preferred embodiment, the feed mass ratio of 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one and sodium hydroxide is (5-10):1.

[0012] In a preferred embodiment, the feed mass ratio of 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one to tetrahydrofuran is 1:(1-4).

[0013] In a preferred embodiment, the step 1 is specifically: Add tetrahydrofuran and sodium hydroxide into a reactor, stir and add 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one, cool to 0°C to 10°C and add dimethyl carbonate dropwise, the temperature during the addition process is 10°C to 30°C, then carry out a substitution reaction under heat preservation conditions to obtain a mixed solution.

[0014] In a preferred embodiment, the dimethyl carbonate is added dropwise for 1 h to 2 h, and the substitution reaction is carried out for 1 h to 4 h.

[0015] In a preferred embodiment, the amount of process water used is 1 to 3 times the mass of dimethyl carbonate feed.

[0016] The technical effects achieved by the present invention are: The invention uses 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one as a raw material, combines tetrahydrofuran as a universal solvent, uses sodium hydroxide as a catalyst, and uses dimethyl carbonate as a methylating agent. The synthetic route has the advantages of low raw material cost, few side reactions, simple post-treatment, small environmental impact, etc., and is very suitable for industrial production. At the same time, the method has a simple preparation process, low wastewater treatment difficulty and cost, and the generated low COD wastewater can also be recycled. There is no toxic side effect in the entire production process, which further enhances the feasibility of its industrial production. DETAILED DESCRIPTION

[0017] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below.

[0018] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0019] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The phrase "in a preferred embodiment" that appears in different places in this specification does not refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0020] The present invention provides a method for preparing metribuzin, and the reaction equation is as follows:

[0021] The following steps are involved: Step 1: Add tetrahydrofuran and sodium hydroxide into a reactor, stir and add 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one, cool to 0°C to 10°C and drop dimethyl carbonate, the temperature during the dropwise addition is 10°C to 30°C, and then carry out a substitution reaction under heat preservation conditions for 1h to 4h to obtain a mixed solution; Step 2: post-treating the mixed solution, cooling the mixed solution to 25°C or below, adding process water to quench the reaction, filtering to obtain metribuzin, and drying the solid to obtain metribuzin; the mother liquor obtained by filtration is layered, and the organic phase is distilled and dried and then directly used; the waste water is distilled under reduced pressure to recover water and precipitate salt.

[0022] The amount of process water used is 1 to 3 times the mass of dimethyl carbonate feed.

[0023] Furthermore, the feed mass ratio of the 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one and dimethyl carbonate is (1.3-1.6):1; the feed mass ratio of the 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one and sodium hydroxide is (5-10):1; the feed mass ratio of the 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one and tetrahydrofuran is 1:(1-4).

[0024] In this embodiment, 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one is used as a raw material, combined with tetrahydrofuran as a universal solvent, sodium hydroxide as a catalyst, and dimethyl carbonate as a methylating agent. The synthetic route has the advantages of low raw material cost, few side reactions, simple post-treatment, and small environmental impact, and is very suitable for industrial production. In addition, the method has a simple preparation process, low difficulty and cost of wastewater treatment, and the low COD wastewater produced can also be recycled. There are no toxic side effects in the entire production process, which further enhances the feasibility of its industrial production.

[0025] It should be noted that, in the present embodiment, 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one is a triazone purchased from the market. 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one is a member of the triazone family and has the basic structural characteristics of triazone.

[0026] The following are embodiments of the present invention. Embodiment 1

[0027] 200g of tetrahydrofuran was added to a 1L four-necked bottle, 30g of 96% sodium hydroxide was added, and 200g of 97% triazone was added under stirring. When the temperature dropped to 8°C, 125g of dimethyl carbonate was added dropwise. The temperature was controlled at 15°C-20°C during the addition process. The addition lasted for 1h. After the addition was completed, the temperature was raised to 25°C. The reaction was carried out under insulation conditions for 2 hours. The residual content of triazone was detected by gas phase qualitative analysis to be 0.7%. When the temperature was lowered to 10°C in an ice-water bath, 200g of process water was added dropwise to the reaction solution. After the addition was completed, the temperature was raised to 30°C and stirred for 30min. After the stirring was completed, filtration and rinsing were performed in sequence to obtain a filter cake. The filter cake was transferred to a vacuum drying oven and dried at 60°C for 8 hours to obtain 161.8g of metribuzin.

[0028] The purity of metribuzin obtained in the experiment was 97.8%, and the yield was 77%.

[0029] Embodiment 2 300g of tetrahydrofuran was added to a 1L four-necked bottle, 35g of 96% sodium hydroxide was added, and 200g of 97% triazone was added under stirring. When the temperature dropped to 8°C, 140g of dimethyl carbonate was added dropwise. The temperature was controlled at 15°C-20°C during the addition process. The addition lasted for 1h. After the addition was completed, the temperature was raised to 25°C. The reaction was carried out under insulation conditions for 2 hours. The residual content of triazone was detected by gas phase qualitative analysis to be 0.1%. When the temperature was lowered to 10°C in an ice-water bath, 200g of process water was added dropwise to the reaction solution. After the addition was completed, the temperature was raised to 30°C and stirred for 30min. After the stirring was completed, filtration and rinsing were performed in sequence to obtain a filter cake. The filter cake was transferred to a vacuum drying oven and dried at 60°C for 8 hours to obtain 163g of metribuzin.

[0030] The purity of metribuzin obtained in the experiment was 97.2%, and the yield was 78%.

[0031] Embodiment 3 400 g of tetrahydrofuran was added to a 1L four-necked bottle, 30 g of 96% sodium hydroxide was added, and 200 g of 97% triazone was added under stirring. When the temperature dropped to 8°C, 140 g of dimethyl carbonate was added dropwise. The temperature was controlled at 15°C-20°C during the addition process. The addition lasted for 1 hour. After the addition was completed, the temperature was raised to 25°C. The reaction was carried out under insulation conditions for 2 hours. The residual content of triazone was detected to be 0.2% by gas phase qualitative analysis. When the temperature was lowered to 10°C in an ice-water bath, 200 g of process water was added dropwise to the reaction solution. After the addition was completed, the temperature was raised to 30°C and stirred for 30 minutes. After the stirring was completed, filtration and rinsing were performed in sequence to obtain a filter cake. The filter cake was transferred to a vacuum drying oven and dried at 60°C for 8 hours to obtain 163.2 g of methicillin.

[0032] The purity of metribuzin obtained in the experiment was 97.4%, and the yield was 78%.

[0033] Embodiment 4 500g of tetrahydrofuran was added to a 2L four-necked bottle, 40g of 96% sodium hydroxide was added, and 250g of 97% triazone was added under stirring. When the temperature dropped to 5°C, 150g of dimethyl carbonate was added dropwise. The temperature was controlled at 10°C-15°C during the addition process. The addition lasted for 1.5 hours. After the addition was completed, the temperature was raised to 30°C. The reaction was carried out under insulation conditions for 3 hours. The residual content of triazone was detected to be 0.35% by gas phase qualitative analysis. When the temperature was lowered to 5°C in an ice-water bath, 300g of process water was added dropwise to the reaction solution. After the addition was completed, the temperature was raised to 35°C and stirred for 45 minutes. After the stirring was completed, filtration and rinsing were performed in sequence to obtain a filter cake. The filter cake was transferred to a vacuum drying oven and dried at 65°C for 10 hours to obtain 200.5g of metribuzin.

[0034] The purity of metribuzin obtained in the experiment was 96.1%, and the yield was 75%.

[0035] Embodiment 5 600g of tetrahydrofuran was added to a 2L four-necked bottle, 50g of 96% sodium hydroxide was added, and 300g of 97% triazone was added under stirring. When the temperature dropped to 5°C, 180g of dimethyl carbonate was added dropwise. The temperature was controlled at 10°C-15°C during the addition process. The addition lasted for 1.5 hours. After the addition was completed, the temperature was raised to 30°C. The reaction was carried out under insulation conditions for 3 hours. The residual content of triazone was detected to be 0.35% by gas phase qualitative analysis. When the temperature was lowered to 5°C in an ice-water bath, 350g of process water was added dropwise to the reaction solution. After the addition was completed, the temperature was raised to 35°C and stirred for 45 minutes. After the stirring was completed, filtration and rinsing were performed in sequence to obtain a filter cake. The filter cake was transferred to a vacuum drying oven and dried at 65°C for 10 hours to obtain 233g of metribuzin.

[0036] The purity of metribuzin obtained in the experiment was 97.2%, and the yield was 76%.

[0037] In summary, the present invention provides an efficient and environmentally friendly method for synthesizing metribuzin, using 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one (i.e., triazone) as a raw material, combined with tetrahydrofuran as a universal solvent, sodium hydroxide as a catalyst, and dimethyl carbonate as a methylating agent. The synthetic route has the advantages of low raw material cost, few side reactions, simple post-treatment, and small environmental impact, and is very suitable for industrial production. In addition, the method has a simple preparation process, low difficulty and cost in wastewater treatment, and the low COD wastewater produced can also be recycled. There are no toxic side effects in the entire production process, which further enhances the feasibility of its industrial production. The method is not only suitable for laboratory-scale research, but also can be easily applied to industrial production through appropriate amplification. Through the implementation of the present invention, production costs can be effectively reduced, environmental pollution can be reduced, and production efficiency can be improved, thereby providing a new technical approach for the production of metribuzin.

[0038] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A method for preparing metribuzin, Features: The reaction equation is as follows: ； The following steps are involved: Step 1: in the presence of tetrahydrofuran and sodium hydroxide, add 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one and dimethyl carbonate, and carry out a substitution reaction by mixing and stirring under heat preservation conditions, and after the substitution reaction is completed, a mixed solution is obtained; Step 2: post-treating the mixed solution to obtain metribuzin.

2. The method for preparing metribuzin according to claim 1, Features: The post-processing method is: The mixed solution is cooled to 25°C or below, process water is added to quench the reaction, and the mixture is filtered to obtain metribuzin. The solid is dried to obtain the metribuzin. The mother liquor obtained by filtration is layered, and the organic phase is distilled and dried before direct application. The waste water is distilled under reduced pressure to recover water and precipitate salt.

3. The method for preparing metribuzin according to claim 1, Features: The feed mass ratio of 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one and dimethyl carbonate is (1.3-1.6):

1.

4. The method for preparing metribuzin according to claim 1, Features: The feed mass ratio of 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one and sodium hydroxide is (5-10):

1.

5. The method for preparing metribuzin according to claim 1, Features: The feed mass ratio of 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one to tetrahydrofuran is 1:(1-4).

6. The method for preparing metribuzin according to claim 1, Features: The step 1 is specifically as follows: Add tetrahydrofuran and sodium hydroxide into a reactor, stir and add 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one, cool to 0°C to 10°C and add dimethyl carbonate dropwise, the temperature during the addition process is 10°C to 30°C, then carry out a substitution reaction under heat preservation conditions to obtain a mixed solution.

7. The method for preparing metribuzin according to claim 6, Features: The dimethyl carbonate is added dropwise for 1 h to 2 h, and the substitution reaction is carried out for 1 h to 4 h.

8. The method for preparing metribuzin according to claim 2, Features: The usage amount of the process water is 1 to 3 times the mass of the dimethyl carbonate feed.

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