A method for synthesizing tribenuron-methyl herbicide

Abstract

The present invention discloses a method for synthesizing tribenuron-methyl herbicide, which comprises the following steps: Step 1, weigh triphosgene and dissolve it in xylene; dissolve methyl 2-(benzenesulfonylcarbamoyl)benzoate in xylene; Step 2, place the methyl 2-(benzenesulfonylcarbamoyl)benzoate solution in a reaction vessel, add the catalyst PI-Zn / MS, and gradually add the triphosgene solution dropwise thereto, while keeping the reaction vessel airtight; Step 3, gradually raise the temperature to 80-120 °C, keep the temperature for reaction for 1-2 h, then remove the solvent by rotary evaporation to obtain a crude product; Step 4, dissolve the crude product in dichloromethane, and simultaneously add 2-methyl-4-(methylamino)-6-methoxy-1,3,5-triazine, raise the temperature for reaction to obtain tribenuron-methyl herbicide. The catalyst PI-Zn / MS prepared by the present invention has high activity, which not only reduces the overall reaction temperature, but also shows higher catalytic efficiency, shortens the reaction time, and has a higher reaction yield.

Description

Technical Field

[0001] The present invention relates to the field of herbicides, and particularly to a method for synthesizing tribenuron-methyl herbicide. Background Art

[0002] Sulfonylurea herbicides are one of the mainstream herbicide varieties in the world and also one of the most important herbicide varieties, often ranking among the top two in terms of herbicide sales. Due to their characteristics such as ultra-high efficiency, low toxicity, and low cost, sulfonylurea herbicides have been rapidly and widely promoted and applied, and their development has become an important milestone in the history of pesticide development.

[0003] There are currently more than forty commercialized varieties of sulfonylurea herbicides, and there are also more than a dozen common varieties. Tribenuron-methyl is a kind of sulfonylurea herbicide and is also one of the most commonly used products in this category of herbicides. Tribenuron-methyl has high herbicidal activity, is safe for crops, and is environmentally friendly. Tribenuron-methyl is a synthetic inhibitor of branched-chain amino acids, inhibiting the biosynthesis of valine and isoleucine, thereby preventing plant cell division.

[0004] The general synthetic process of tribenuron-methyl is to use the isocyanate route. Methyl 2-(benzenesulfonamido)acetate reacts with oxalyl chloride to obtain 2-(methoxycarbonyl)-3-(phenylsulfonyl)isocyanate, or methyl 2-(benzenesulfonamido)acetate reacts with phosgene or diphosgene to obtain 2-(methoxycarbonyl)-3-(phenylsulfonyl)isocyanate; the generated 2-(methoxycarbonyl)-3-(phenylsulfonyl)isocyanate then reacts with methyl triazine to generate tribenuron-methyl. However, considering the greater danger of phosgene or diphosgene, the existing synthetic process of tribenuron-methyl selects triphosgene to replace phosgene or diphosgene. The triphosgene method is significantly superior to the phosgene or diphosgene method in terms of safety, quality, cost, etc., and thus has become the main production process in China at present.

[0005] However, the current conditions for synthesizing tribenuron-methyl using the triphosgene method require relatively high conditions, need to react in a closed system for a long time, and require a relatively high reaction temperature, which undoubtedly greatly increases the cost and operation difficulty of the synthesis process. Therefore, it is necessary to mention a more mild and efficient synthetic process for tribenuron-methyl herbicide. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a method for synthesizing tribenuron-methyl herbicide with milder conditions and more efficient reaction.

[0007] The purpose of the present invention is achieved by the following technical solutions:

[0008] A method for synthesizing tribenuron-methyl herbicide, comprising the following steps:

[0009] Step 1: Weigh triphosgene and dissolve it in xylene to form a triphosgene solution; dissolve methyl o - formylbenzenesulfonamide in xylene to form a methyl o - formylbenzenesulfonamide solution.

[0010] Step 2: At room temperature, place the methyl o - formylbenzenesulfonamide solution in a reaction vessel, add a catalyst thereto, and after thorough mixing, add the triphosgene solution dropwise thereto while keeping the reaction vessel sealed.

[0011] Step 3: After all of the triphosgene solution has been added dropwise, gradually raise the temperature to 80 - 120 °C, keep the temperature for 1 - 2 h for the reaction, remove the catalyst, and then remove the solvent by rotary evaporation to obtain a crude product.

[0012] Step 4: Dissolve the crude product in dichloromethane, add 2 - methyl - 4 - methylamino - 6 - methoxy - s - triazine thereto, raise the temperature to the reflux temperature, keep the temperature for 1 - 2 h for the reflux reaction, remove the solvent by rotary evaporation, and after washing and drying, obtain tribenuron - methyl herbicide.

[0013] Preferably, in the triphosgene solution in Step 1, the mass - to - volume ratio of triphosgene to xylene is (65 - 75) g:(100 - 200) mL.

[0014] Preferably, in the methyl o - formylbenzenesulfonamide solution in Step 1, the mass - to - volume ratio of methyl o - formylbenzenesulfonamide to xylene is (45 - 55) g:(100 - 200) mL.

[0015] Preferably, the volume ratio of the triphosgene solution to the methyl o - formylbenzenesulfonamide solution in Step 2 is 1:2 - 3.

[0016] Preferably, in Step 2, the catalyst is PI - Zn / MS, and the mass ratio of the catalyst to methyl o - formylbenzenesulfonamide in Step 1 is 1.6 - 2.8:1.

[0017] Preferably, the mass ratio of 2 - methyl - 4 - methylamino - 6 - methoxy - s - triazine in Step 4 to methyl o - formylbenzenesulfonamide in Step 1 is 22 - 30:40 - 50.

[0018] Preferably, in Step 4, the mass - to - volume ratio of the crude product to dichloromethane is 1 g:(3 - 5) mL.

[0019] Preferably, in Step 4, the reflux temperature is 40 - 45 °C.

[0020] Preferably, the preparation method of the catalyst PI - Zn / MS includes:

[0021] S1: Weigh zinc nitrate hexahydrate and absolute ethanol and add them to a beaker, and after thorough mixing, obtain an ethanol solution of zinc nitrate.

[0022] S2. Weigh isocyanatopyridine and add it to the ethanol solution. After thorough mixing, an isocyanatopyridine solution is obtained.

[0023] S3. Slowly add the ethanol solution of zinc nitrate to the isocyanatopyridine solution and continuously stir for 1 - 2 h. Then filter the reaction solution, collect the precipitate product, and place it in an oven at 70 - 80 °C for drying to obtain isocyanatopyridine zinc PI-Zn.

[0024] S4. Mix isocyanatopyridine zinc PI-Zn in nitric acid solution, then add molecular sieve to the solution. After stirring evenly at room temperature, pour it into a reaction kettle lined with polytetrafluoroethylene, seal the reaction kettle, and place it in an oven at 75 - 85 °C for heat preservation treatment for 4 - 8 h.

[0025] S5. After cooling the reaction kettle to room temperature, filter out the solid in the reaction solution, wash it with pure water until neutral, and then perform vacuum drying treatment to obtain the catalyst PI-Zn / MS.

[0026] Preferably, in S1, the mass-volume ratio of zinc nitrate hexahydrate to absolute ethanol is (0.3 - 0.6) g : (100 - 200) mL.

[0027] Preferably, in S2, the isocyanatopyridine includes 2-isocyanatopyridine or 4-isocyanatopyridine.

[0028] Preferably, in S2, the mass fraction of the ethanol solution is 70% - 90%, and the mass-volume ratio of isocyanatopyridine to the ethanol solution is (1.1 - 2.2) g : (100 - 200) mL.

[0029] Preferably, in S3, the volume ratio of the ethanol solution of zinc nitrate to the isocyanatopyridine solution is 1:1.

[0030] Preferably, in S4, the molecular sieve includes any one of Na-Y type molecular sieve, H-Y type molecular sieve, and USY type molecular sieve.

[0031] Preferably, in S4, the molar concentration of the nitric acid solution is 0.5 - 1 mol / L, and the mass-volume ratio of isocyanatopyridine zinc PI-Zn to the nitric acid solution is 1 g : (30 - 50) mL.

[0032] Preferably, in S4, the mass ratio of the molecular sieve to isocyanatopyridine zinc PI-Zn is 4.2 - 6.3:1.

[0033] The beneficial effects of the present invention are as follows:

[0034] 1. In the traditional method of synthesizing bensulfuron-methyl herbicide, n-butyl isocyanate is used as a catalyst. The catalyst is characterized in that the reaction is relatively stable, but the reaction time is too long, the reaction temperature is high (120-150°C), the reaction yield is not very high, and it is difficult to separate, which greatly increases the difficulty of using the method in existing production. The catalyst PI-Zn / MS prepared by the present invention has higher activity, not only reduces the overall reaction temperature (80-120°C), but also shows higher catalytic efficiency, shortens the reaction time, and has a higher reaction yield.

[0035] 2. The process of preparing the catalyst of the present invention is to first use a pyridine compound containing isocyanate, i.e. 2-isocyanate pyridine or 4-isocyanate pyridine, to form a complex isocyanate pyridine zinc PI-Zn with zinc nitrate; then use a molecular sieve (MS) as a carrier to effectively cross-link and load the prepared complex, thereby obtaining a molecular sieve catalyst PI-Zn / MS loaded with the isocyanate pyridine zinc complex.

[0036] 3. In the synthesis process of bensulfuron-methyl, the reaction of methyl benzenesulfonamide and triphosgene is usually not completed in one step, but methyl benzenesulfonamide will generate an intermediate product containing sulfonylurea with part of triphosgene, and the intermediate product is combined with triphosgene to generate a final product. The active ingredient of the catalyst prepared by the present invention not only contains an isocyanate group, but also contains a pyridine group complexed with a metallic zinc ion. In the process of the reaction, the presence of the isocyanate group in the catalyst can be combined with the intermediate product of the reaction as a carrier, thereby promoting the forward progress of the reaction; and the pyridine group can keep the pH of the reaction conditions alkaline, while continuously consuming the generated hydrogen chloride, and further promoting the forward progress of the reaction, so that the reaction speed is greatly improved.

[0037] 4. The catalyst carrier selected in the present invention is a Y-type molecular sieve. This type of molecular sieve carrier is stable, has a strong adsorption capacity, and has a uniform pore size distribution, so that the load of the active ingredient is more stable and the distribution is more uniform, so that the final catalyst can be easily separated from the reaction liquid, has a good catalytic effect, a high reaction yield, and can still maintain a high activity after repeated use. DETAILED DESCRIPTION

[0038] In order to more clearly illustrate the present invention and have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0039] The present invention will be further described below in conjunction with the following examples.

[0040] Example 1

[0041] A method for synthesizing tribenuron-methyl herbicide, comprising the following steps:

[0042] Step 1, Weigh trichloromethyl chloroformate and dissolve it in xylene to form a trichloromethyl chloroformate solution; wherein, the mass-volume ratio of trichloromethyl chloroformate to xylene is 70 g: 150 mL.

[0043] Dissolve methyl 2-(benzenesulfonylamino)benzoate in xylene to form a methyl 2-(benzenesulfonylamino)benzoate solution; wherein, the mass-volume ratio of methyl 2-(benzenesulfonylamino)benzoate to xylene is 50 g: 150 mL.

[0044] Step 2, Under room temperature conditions, place the methyl 2-(benzenesulfonylamino)benzoate solution in a reaction vessel, and add the catalyst PI-Zn / MS thereto. The mass ratio of the catalyst to methyl 2-(benzenesulfonylamino)benzoate in Step 1 is 2.1:1. After thorough mixing, gradually add the trichloromethyl chloroformate solution dropwise thereto. The volume ratio of the trichloromethyl chloroformate solution to the methyl 2-(benzenesulfonylamino)benzoate solution is 1:2.5. During this period, keep the reaction vessel airtight;

[0045] Step 3, After all the trichloromethyl chloroformate solution has been added dropwise, gradually raise the temperature to 100 °C, keep the temperature for reaction for 1.5 h, remove the catalyst, and then rotary evaporate to remove the solvent to obtain a crude product;

[0046] Step 4, Dissolve the crude product in dichloromethane. The mass-volume ratio of the crude product to dichloromethane is 1 g: 4 mL. At the same time, add 2-methyl-4-(methylamino)-6-(methoxy)-1,3,5-triazine. The mass ratio of 2-methyl-4-(methylamino)-6-(methoxy)-1,3,5-triazine to methyl 2-(benzenesulfonylamino)benzoate in Step 1 is 26:45. Raise the temperature to the reflux temperature of 45 °C, keep the temperature for reflux reaction for 1.5 h, rotary evaporate to remove the solvent, and after washing and drying, obtain tribenuron-methyl herbicide.

[0047] Wherein, the preparation method of the catalyst PI-Zn / MS includes:

[0048] S1. Weigh zinc nitrate hexahydrate and absolute ethanol and add them to a beaker. After thorough mixing, obtain a zinc nitrate ethanol solution; wherein, the mass-volume ratio of zinc nitrate hexahydrate to absolute ethanol is 0.4 g: 160 mL.

[0049] S2. Weigh 2-isocyanatopyridine and add it to an ethanol solution with a mass fraction of 80%. After thorough mixing, obtain an isocyanatopyridine solution; wherein, the mass-volume ratio of 2-isocyanatopyridine to the ethanol solution is 1.7 g: 160 mL.

[0050] S3, slowly adding the ethanol solution of zinc nitrate to the isocyanate pyridine solution, the volume ratio of the ethanol solution of zinc nitrate to the isocyanate pyridine solution is 1:1, stirring continuously for 1.5 hours, then filtering the reaction solution, collecting the precipitated product, and drying it in an oven at 80° C. to obtain isocyanate pyridine zinc PI-Zn;

[0051] S4, mixing pyridine zinc isocyanate PI-Zn in 0.5 mol / L nitric acid solution, the mass volume ratio of pyridine zinc isocyanate PI-Zn to nitric acid solution is 1 g: 40 mL, then adding Na-Y type molecular sieve to the solution, the mass ratio of Na-Y type molecular sieve to pyridine zinc isocyanate PI-Zn is 5.2: 1, after stirring evenly at room temperature, pouring into a reactor lined with polytetrafluoroethylene, sealing the reactor and placing it in an oven at 80°C for heat preservation for 6 hours;

[0052] S5. After cooling the reactor to room temperature, filter out the solid in the reaction solution, wash with pure water until neutral, and then perform vacuum drying to obtain the catalyst PI-Zn / MS.

[0053] Example 2

[0054] A method for synthesizing bensulfuron-methyl herbicide comprises the following steps:

[0055] Step 1, weigh triphosgene and dissolve it in xylene to form a triphosgene solution; wherein the mass volume ratio of triphosgene to xylene is 65g:100mL.

[0056] Methyl o-formate benzenesulfonamide is dissolved in xylene to form a methyl o-formate benzenesulfonamide solution; wherein the mass volume ratio of methyl o-formate benzenesulfonamide to xylene is 45 g:100 mL.

[0057] Step 2, at room temperature, placing a methyl benzenesulfonamide solution in a reaction vessel, and adding a catalyst PI-Zn / MS thereto, wherein the mass ratio of the catalyst to the methyl benzenesulfonamide in step 1 is 1.6:1, after sufficient mixing, adding the triphosgene solution dropwise thereto, wherein the volume ratio of the triphosgene solution to the methyl benzenesulfonamide solution is 1:2, and the reaction vessel is kept sealed during this period;

[0058] Step 3, after all the triphosgene solution is added dropwise, the temperature is gradually raised to 80° C., and the reaction is kept at this temperature for 1 hour. After removing the catalyst, the solvent is removed by rotary evaporation to obtain a crude product;

[0059] Step 4, dissolving the crude product in dichloromethane, the mass volume ratio of the crude product to dichloromethane is 1g:3mL, adding 2-methyl-4-methylamino-6-methoxy-s-triazine at the same time, the mass ratio of 2-methyl-4-methylamino-6-methoxy-s-triazine to methyl benzenesulfonamide in the step 1 is 22:40, heating to the reflux temperature of 40°C, keeping the reflux reaction for 1h, rotary evaporation to remove the solvent, washing and drying to obtain bensulfuron-methyl herbicide.

[0060] Wherein, the preparation method of the catalyst PI-Zn / MS comprises:

[0061] S1. Weigh zinc nitrate hexahydrate and anhydrous ethanol, add them into a beaker, and mix them thoroughly to obtain an ethanol solution of zinc nitrate; wherein the mass volume ratio of zinc nitrate hexahydrate to anhydrous ethanol is 0.3 g:100 mL.

[0062] S2. Weigh 4-isocyanate pyridine and add it to an ethanol solution with a mass fraction of 70%. After sufficient mixing, an isocyanate pyridine solution is obtained; wherein the mass volume ratio of 4-isocyanate pyridine to the ethanol solution is 1.1 g:100 mL.

[0063] S3, slowly adding the ethanol solution of zinc nitrate to the isocyanate pyridine solution, the volume ratio of the ethanol solution of zinc nitrate to the isocyanate pyridine solution is 1:1, stirring continuously for 1-2 hours, then filtering the reaction solution, collecting the precipitated product, and drying it in an oven at 70° C. to obtain isocyanate pyridine zinc PI-Zn;

[0064] S4, mixing pyridine zinc isocyanate PI-Zn in 0.5 mol / L nitric acid solution, the mass volume ratio of pyridine zinc isocyanate PI-Zn to nitric acid solution is 1 g: 30 mL, then adding HY type molecular sieve to the solution, the mass ratio of HY type molecular sieve to pyridine zinc isocyanate PI-Zn is 4.2: 1, stirring evenly at room temperature, pouring into a reactor lined with polytetrafluoroethylene, sealing the reactor and placing it in an oven at 75°C for insulation treatment for 4 hours;

[0065] S5. After cooling the reactor to room temperature, filter out the solid in the reaction solution, wash with pure water until neutral, and then perform vacuum drying to obtain the catalyst PI-Zn / MS.

[0066] Example 3

[0067] A method for synthesizing bensulfuron-methyl herbicide comprises the following steps:

[0068] Step 1, weigh triphosgene and dissolve it in xylene to form a triphosgene solution; wherein the mass volume ratio of triphosgene to xylene is 75g:200mL.

[0069] Dissolve methyl o - formylbenzenesulfonamide in xylene to form a methyl o - formylbenzenesulfonamide solution; wherein, the mass - volume ratio of methyl o - formylbenzenesulfonamide to xylene is 55 g:200 mL.

[0070] Step 2, at room temperature, place the methyl o - formylbenzenesulfonamide solution in a reaction vessel, and add the catalyst PI - Zn / MS thereto. The mass ratio of the catalyst to the methyl o - formylbenzenesulfonamide in Step 1 is 2.8:1. After thorough mixing, add the triphosgene solution dropwise thereto. The volume ratio of the triphosgene solution to the methyl o - formylbenzenesulfonamide solution is 1:3, and keep the reaction vessel airtight during this period.

[0071] Step 3, after all the triphosgene solution has been added dropwise, gradually raise the temperature to 120 °C, keep the temperature for reaction for 2 h, remove the catalyst, and then rotary evaporate to remove the solvent to obtain a crude product.

[0072] Step 4, dissolve the crude product in dichloromethane. The mass - volume ratio of the crude product to dichloromethane is 1 g:5 mL. At the same time, add 2 - methyl - 4 - methylamino - 6 - methoxy - s - triazine. The mass ratio of 2 - methyl - 4 - methylamino - 6 - methoxy - s - triazine to the methyl o - formylbenzenesulfonamide in Step 1 is 30:50. Raise the temperature to the reflux temperature of 45 °C, keep the temperature for reflux reaction for 2 h, rotary evaporate to remove the solvent, and after washing and drying, obtain the tribenuron - methyl herbicide.

[0073] Among them, the preparation method of the catalyst PI - Zn / MS includes:

[0074] S1. Weigh zinc nitrate hexahydrate and absolute ethanol and add them to a beaker. After thorough mixing, obtain an ethanol solution of zinc nitrate; wherein, the mass - volume ratio of zinc nitrate hexahydrate to absolute ethanol is 0.6 g:200 mL.

[0075] S2. Weigh 2 - isocyanatopyridine and add it to an ethanol solution with a mass fraction of 90%. After thorough mixing, obtain an isocyanatopyridine solution; wherein, the mass - volume ratio of 2 - isocyanatopyridine to the ethanol solution is 2.2 g:200 mL.

[0076] S3. Slowly add the ethanol solution of zinc nitrate to the isocyanatopyridine solution. The volume ratio of the ethanol solution of zinc nitrate to the isocyanatopyridine solution is 1:1. Continuously stir for 2 h, then filter the reaction solution, collect the precipitate product, and place it in an oven at 80 °C for drying to obtain isocyanatopyridine zinc PI - Zn.

[0077] S4, mixing pyridine zinc isocyanate PI-Zn in 1 mol / L nitric acid solution, the mass volume ratio of pyridine zinc isocyanate PI-Zn to nitric acid solution is 1g:50mL, then adding USY type molecular sieve to the solution, the mass ratio of USY type molecular sieve to pyridine zinc isocyanate PI-Zn is 6.3:1, stirring evenly at room temperature, pouring into a reactor lined with polytetrafluoroethylene, sealing the reactor and placing it in an oven at 85°C for insulation treatment for 8h;

[0078] S5. After cooling the reactor to room temperature, filter out the solid in the reaction solution, wash with pure water until neutral, and then perform vacuum drying to obtain the catalyst PI-Zn / MS.

[0079] Comparative Example 1

[0080] A method for synthesizing bensulfuron-methyl herbicide, which is different from Example 1 only in that the catalyst is different.

[0081] The catalyst of this comparative example is n-butyl isocyanate.

[0082] Comparative Example 2

[0083] A method for synthesizing bensulfuron-methyl herbicide, which is different from Example 1 only in that the catalyst, reaction temperature and reaction time are different.

[0084] The catalyst of this comparative example is n-butyl isocyanate, the reaction temperature in step 3 is increased to 135° C., and the reaction time in step 3 is increased to 2.5 h.

[0085] Comparative Example 3

[0086] A method for synthesizing bensulfuron-methyl herbicide, which is different from Example 1 only in that the catalyst is different.

[0087] The catalyst of this comparative example is Na-Y type molecular sieve.

[0088] Comparative Example 4

[0089] A method for synthesizing bensulfuron-methyl herbicide, which is different from Example 1 only in that the catalyst is different.

[0090] The catalyst of this comparative example is Zn / MS, and the preparation method is as follows:

[0091] S1. Weigh zinc nitrate hexahydrate and anhydrous ethanol, add them into a beaker, and mix them thoroughly to obtain an ethanol solution of zinc nitrate; wherein the mass volume ratio of zinc nitrate hexahydrate to anhydrous ethanol is 0.4 g:160 mL.

[0092] S2. Add the Na-Y zeolite into the ethanol solution of zinc nitrate. The mass ratio of the Na-Y zeolite to zinc nitrate is 5.2:1. After stirring evenly at room temperature, pour it into a reaction kettle lined with polytetrafluoroethylene. Seal the reaction kettle and place it in an oven at 80 °C for heat preservation treatment for 6 h;

[0093] S3. After cooling the reaction kettle to room temperature, remove the solvent under reduced pressure. Calcinate it at 400 °C for 3 h under the protection of nitrogen. Wash it three times with pure water and then perform vacuum drying treatment to obtain the catalyst Zn / MS.

[0094] Experimental example

[0095] The reaction conditions for synthesizing tribenuron-methyl herbicide in Example 1 and Comparative Examples 1-3, as well as the yields of the final products obtained and the activities of the reused catalysts were detected and compared. The results are shown in Table 1.

[0096] Table 1 Comparison of the results of synthesizing tribenuron-methyl herbicide by different methods

[0097]

[0098] It can be seen from Table 1 that in Example 1 of the present invention, under the conditions of lower temperature and shorter reaction time, the yield of the final product is as high as 99.2%; while in Comparative Example 1 using n-butyl isocyanate as the catalyst, the yield is only 87.9% under the same conditions; in Comparative Example 2 using n-butyl isocyanate as the catalyst, the yield only reaches 97.6% under suitable conditions; in Comparative Example 3 using pure molecular sieve as the catalyst, the reaction efficiency is relatively low and the yield is also relatively low; in Comparative Example 4 using the prepared Zn / MS as the catalyst, although the reaction efficiency is better than that of Comparative Example 1, it is still far lower than that of Example 1.

[0099] In addition, the present invention also conducted a detection on the reuse rate of the catalyst. Specifically, after separating the catalyst, wash it three times successively with saturated sodium bicarbonate solution and deionized water, and then dry it in an oven. Since Comparative Examples 1-2 are soluble in the reaction system and are relatively difficult to separate, no comparison is made. From the comparison results of Example 1, Comparative Example 3, and Comparative Example 4, it can be known that after being reused 5 times, the catalytic efficiency of Example 1 is still as high as 97.8%.

[0100] It can be seen from the above that the method for synthesizing tribenuron-methyl herbicide in Example 1 of the present invention has higher efficiency, lower consumption, and the catalyst can be reused multiple times, following the concept of green chemistry.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for synthesizing bensulfuron-methyl herbicide, It is characterized in that The following steps are involved: Step 1, weighing triphosgene and dissolving it in xylene to form a triphosgene solution; dissolving methyl o-formate benzenesulfonamide in xylene to form a methyl o-formate benzenesulfonamide solution; Step 2, at room temperature, placing a methyl formate benzenesulfonamide solution in a reaction vessel, adding a catalyst PI-Zn / MS thereto, and after sufficient mixing, adding a triphosgene solution dropwise thereto, while keeping the reaction vessel airtight; Step 3, after all the triphosgene solution is added dropwise, gradually raise the temperature to 80-120°C, keep the temperature for reaction for 1-2 hours, remove the catalyst, and then remove the solvent by rotary evaporation to obtain a crude product; Step 4, dissolving the crude product in dichloromethane, adding 2-methyl-4-methylamino-6-methoxy-s-triazine, heating to reflux temperature, keeping the temperature under reflux reaction for 1-2 hours, removing the solvent by rotary evaporation, washing and drying to obtain bensulfuron-methyl herbicide; The preparation method of the catalyst PI-Zn / MS comprises: S1. Weigh zinc nitrate hexahydrate and anhydrous ethanol, add them into a beaker, and mix them thoroughly to obtain an ethanol solution of zinc nitrate; S2, weighing isocyanate pyridine and adding it to the ethanol solution, and mixing thoroughly to obtain an isocyanate pyridine solution; wherein the isocyanate pyridine includes 2-isocyanate pyridine or 4-isocyanate pyridine; S3, slowly adding the ethanol solution of zinc nitrate into the isocyanate pyridine solution, stirring continuously for 1-2 hours, then filtering the reaction solution, collecting the precipitated product, and drying it in an oven at 70-80° C. to obtain isocyanate pyridine zinc PI-Zn; S4, mixing pyridinium isocyanate zinc PI-Zn in a nitric acid solution, then adding molecular sieves to the solution, stirring evenly at room temperature, pouring into a polytetrafluoroethylene-lined reactor, sealing the reactor and placing it in an oven at 75-85°C for insulation treatment for 4-8h; S5. After cooling the reactor to room temperature, filter out the solid in the reaction solution, wash with pure water until neutral, and then perform vacuum drying to obtain the catalyst PI-Zn / MS.

2. A method for synthesizing bensulfuron-methyl herbicide according to claim 1, It is characterized in that In the step 1, in the triphosgene solution, the mass volume ratio of triphosgene to xylene is (65-75) g: (100-200) mL; in the methyl phthalate benzenesulfonamide solution, the mass volume ratio of methyl phthalate benzenesulfonamide to xylene is (45-55) g: (100-200) mL.

3. A method for synthesizing bensulfuron-methyl herbicide according to claim 1, It is characterized in that The mass ratio of the catalyst in step 2 to the methyl benzenesulfonamide in step 1 is 1.6-2.8:1, and the volume ratio of the triphosgene solution to the methyl benzenesulfonamide solution is 1:2-3.

4. A method for synthesizing bensulfuron-methyl herbicide according to claim 1, It is characterized in that The mass ratio of 2-methyl-4-methylamino-6-methoxy-s-triazine in step 4 to o-methyl benzenesulfonamide in step 1 is 22 - 30:40 - 50; the mass-volume ratio of the crude product to dichloromethane is 1 g:(3 - 5) mL.

5. A method for synthesizing tribenuron-methyl herbicide according to claim 1, characterized in that in S1, the mass-volume ratio of zinc nitrate hexahydrate to absolute ethanol is (0.3 - 0.6) g:(100 - 200) mL.

6. A method for synthesizing tribenuron-methyl herbicide according to claim 1, characterized in that in S2, the mass fraction of the ethanol solution is 70% - 90%, and the mass-volume ratio of isocyanatopyridine to the ethanol solution is (1.1 - 2.2) g:(100 - 200) mL.

7. A method for synthesizing tribenuron-methyl herbicide according to claim 1, characterized in that in S3, the volume ratio of the ethanol solution of zinc nitrate to the isocyanatopyridine solution is 1:

1.

8. A method for synthesizing tribenuron-methyl herbicide according to claim 1, characterized in that in S4, the molecular sieve includes any one of Na-Y type molecular sieve, H-Y type molecular sieve, and USY type molecular sieve.

9. A method for synthesizing tribenuron-methyl herbicide according to claim 1, characterized in that in S4, the molar concentration of the nitric acid solution is 0.5 - 1 mol / L, the mass-volume ratio of isocyanatopyridine zinc PI-Zn to the nitric acid solution is 1 g:(30 - 50) mL; the mass ratio of the molecular sieve to isocyanatopyridine zinc PI-Zn is 4.2 - 6.3:1.

Images