CN111440160A - A kind of preparation method of oxaflutole and application thereof - Google Patents

Abstract

The invention discloses a preparation method and application of topramezone, which comprises the following steps: the 3- [ 3-bromo-methyl-6- (methylsulfonyl) phenyl is prepared by a first reaction process by using 2-methylbenzaldehyde, a bromination reagent, a catalyst, hydroxylamine hydrochloride, alkali, ethylene gas, a sulfonylation reagent and a preset solvent as reaction raw materials]-4, 5-dihydroisoxazole; taking diethyl malonate, triethyl formate, nickel sulfate, monobasic saturated carboxylic acid, methyl hydrazine, hydrocarbon solvent, ethanol solution and hydrochloric acid as reaction raw materials to prepare 1-methyl-5-hydroxypyrazole through a second reaction process; with 3- [ 3-bromo-methyl-6- (methylsulfonyl) phenyl]-4, 5-dihydroisoxazole, 1-methyl-5-hydroxypyrazole, triethylamine, potassium carbonate, palladium chloride, triphenylphosphine, 1, 4-dioxane, water, saturated NaHCO₃Solutions andthe topramezone is prepared by taking the hydrochloric acid solution as a reaction raw material through a third reaction process, so that the problem that the sulfur-containing intermediate can disperse odor and the raw material is difficult to obtain in the existing process is solved.

Description

A kind of preparation method of oxaflutole and application thereof

technical field

The invention relates to the technical field of chemical synthesis, in particular to a preparation method of oxaflutole and application thereof.

Background technique

The trade names of oxaflutole include Convey, Impact, Clio, Baowei, etc. It is a new type of high-efficiency herbicide developed by BASF in Germany. Oxaflutole is the first active ingredient in pyrazolinone compounds, which can be absorbed by roots, young stems, and leaves, and transmitted to the top and base in the plant to the meristematic tissue, by inhibiting the biosynthesis of plastoquinone. 4-Hydroxyphenylpyruvate dioxidase (4-HPPD), which indirectly affects carotenoid synthesis, interferes with chloroplast synthesis and function, and eventually leads to severe bleaching (due to the degradation of chlorophyll). Among the corn field post-emergence stem and leaf treatment herbicides currently on the market, oxaflutole is the safest corn field herbicide, safe for all growing periods of corn, and all types of corn are available except for seed production; It is also the most complete corn field herbicide for weed control. Baowei has a general effect on very few broad-leaved grasses, but with atrazine, it is even more powerful, and there are almost no weeds that cannot be controlled; it is also the most expensive corn field herbicide. , but there are problems that the sulfur-containing intermediates will emit odor and the raw materials are relatively difficult to obtain in the existing production process flow. Therefore, there is an urgent need for the industrialized production of oxaflutole to propose a method for industrialized production.

SUMMARY OF THE INVENTION

In order to solve the problems in the prior art that the sulfur-containing intermediate will emit odor and the raw materials are difficult to obtain in the production process of oxaflutole, a preparation method and application of oxaflutole are provided.

A method for preparing oxaflutole, comprising the steps:

Using 2-methylbenzaldehyde, bromination reagent, catalyst, hydroxylamine hydrochloride, alkali, ethylene gas, sulfonylation reagent and preset solvent as reaction raw materials, 3-[3-bromo-methyl- 6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole;

Using diethyl malonate, triethyl formate, nickel sulfate, monobasic saturated carboxylic acid, methyl hydrazine, hydrocarbon solvent, ethanol solution and hydrochloric acid as reaction raw materials through the second reaction process to prepare 1-methyl-5 -Hydroxypyrazole;

With 3-[3-bromo-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole, 1-methyl-5-hydroxypyrazole, triethylamine, potassium carbonate , palladium chloride, triphenylphosphorus, 1,4-dioxane, water, saturated NaHCO ₃ solution and hydrochloric acid solution as reaction raw materials through the third reaction process to obtain oxaflutole.

Wherein, the first reaction process refers to:

2-methylbenzaldehyde and bromination reagent are mixed in the preset solvent, and the catalyst is added under the preset constant temperature to carry out bromination reaction to obtain 2-bromo-6-methylbenzaldehyde;

2-bromo-6-methylbenzaldehyde, preset solvent, hydroxylamine hydrochloride and alkali are subjected to condensation reaction, then ethylene gas and the catalyst are introduced and chlorinated and finally cyclized to obtain 3-[2-methyl-6- bromo-phenyl]-4,5-dihydroisoxazole;

To 3-[2-methyl-6-bromo-phenyl]-4,5-dihydroisoxazole, add the sulfonylation reagent, the preset solvent and the catalyst, at a preset constant temperature Preparation of 3-[2-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole;

To 3-[2-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole were added the catalyst, the brominating reagent and the preset solvent to prepare In 3-[3-bromo-2-methyl-6-(methylsulfonyl) phenyl]-4,5-dihydroisoxazole.

Wherein, the bromination reagent is at least one of Br ₂ , BrCl, NBS and HBr, and the catalyst is acetic acid, acetic anhydride, iodobenzene, aluminum trichloride, FeCl ₃ , cuprous chloride and iodide At least one of copper, the alkali is butyllithium, LDA, sodium hydroxide, potassium hydroxide, sodium tert-butoxide, potassium tert-butoxide, lithium tert-butoxide, potassium carbonate, cesium carbonate, lithium hydroxide, At least one of triethylamine, diisopropylamine, DBU, sodium methoxide and sodium ethoxide, the sulfonylation reagent is at least one of methanesulfonyl chloride, methanesulfonic acid and methanesulfonic anhydride, the pre- Let the solvent be at least one of dichloromethane, dichloroethane, chloroform, chlorobenzene, toluene, xylene, tetrahydrofuran, methyl acetate, ethyl acetate, methanol, ethanol and isopropanol, and the preset constant temperature The temperature range is 30 ~ 60 ℃.

Wherein, the second reaction process refers to:

Diethyl malonate and triethyl orthoformate are mixed with the hydrocarbon solvent in a reaction vessel, and under the action of nickel sulfate and the monobasic saturated carboxylic acid, diethyl ethoxymethylene malonate is prepared ;

Condensation and cyclization of diethyl ethoxymethylenemalonate and methyl hydrazine in an ethanol solution at a preset low temperature to obtain ethyl 1-methyl-5-hydroxypyrazole-4-carboxylate liquid;

Hydrochloric acid is added to the prepared ethyl 1-methyl-5-hydroxypyrazole-4-carboxylate reaction solution for reflux reaction to prepare 1-methyl-5-hydroxypyrazole.

Wherein, the hydrocarbon solvent is at least one of xylene and toluene.

Among them, the monobasic saturated carboxylic acid is a saturated monobasic carboxylic acid having 1 to 5 carbon atoms, and is preferably acetic acid.

Among them, the substance ratio of triethyl orthoformate: diethyl malonate: monobasic saturated carboxylic acid: nickel sulfate: hydrochloric acid: methyl hydrazine is equal to 3:1:0.1:0.0001:0.24:0.55.

Wherein, the third reaction refers to:

3-[3-Bromo-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole, 1-methyl-5-hydroxypyrazole, triethylamine, potassium carbonate , Palladium chloride and triphenylphosphorus are mixed by preset ratio and added into autoclave, then add 1,4-dioxane as solvent to obtain mixed solution;

After purging the mixed solution with nitrogen and carbon monoxide, wait for the completion of the reaction under pressure and heating conditions;

After the completion of the reaction, distillation under reduced pressure was carried out, water was added and the insolubles were removed by suction filtration to obtain an aqueous filtrate;

The aqueous filtrate is extracted, adjusted to pH, and extracted and separated again to obtain an organic phase;

The oxadiafen product is obtained after the organic phase is distilled under reduced pressure and recrystallized from solid methanol.

Among them, 3-[3-bromo-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole: 1-methyl-5-hydroxypyrazole: triethylamine: carbonic acid The substance ratio of potassium:palladium chloride:triphenylphosphorus was 1:1:2:2:0.05:0.1.

The present invention also provides an application of oxaflutole, which includes the above-mentioned preparation method of oxaflutole, and also includes the application of oxaflutole in controlling grass weeds and some broad-leaved weeds in corn fields.

In the prior art, the present invention proposes a new synthetic route of 3-[3-bromo-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole, avoiding the existing In the technology, the sulfur-containing intermediates will emit odor, and by improving the synthesis route of 1-methyl-5-hydroxypyrazole, the yield of 1-methyl-5-hydroxypyrazole is improved to solve the problem that the raw materials are not easy to prepare. taken the problem, and by combining 3-[3-bromo-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole and 1-methyl-5-hydroxypyrazole through Catalytic carbonylation to obtain fenflufen, thereby achieving the purpose of reducing the technological difficulty of production, and fenflufen has a very good control effect on grass weeds and some broad-leaved weeds in corn fields, and has a very good control effect. good application prospects.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

Fig. 1 is a kind of fenoxazone preparation method of the present invention and the synthetic process flow schematic diagram of its application.

Fig. 2 is a kind of preparation method of oxaflutole of the present invention and the preparation of its application 3-[3-bromo-2-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxanil Schematic diagram of the synthetic process flow of azoles.

Fig. 3 is a kind of preparation method of oxaflutole according to the present invention and a schematic structural diagram of the synthetic process flow for preparing 1-methyl-5-hydroxypyrazole by application thereof.

Fig. 4 is a kind of preparation method of oxaflutole of the present invention and the synthetic process flow diagram of the application of the method for preparing oxaflutole.

Fig. 5 is a chemical equation of the preparation method of oxaflutole of the present invention and its application.

Detailed ways

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, and are intended to explain the present invention and should not be construed as limiting the present invention.

In the description of the present invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", The orientations or positional relationships indicated by "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than An indication or implication that the referred device or element must have a particular orientation, be constructed and operate in a particular orientation, is not to be construed as a limitation of the invention. In addition, in the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

Please refer to FIG. 1 to FIG. 5, the present invention provides a technical solution:

Specific embodiment 1:

S101 uses 2-methylbenzaldehyde, bromination reagent, catalyst, hydroxylamine hydrochloride, alkali, ethylene gas, sulfonylation reagent and preset solvent as reaction raw materials through the first reaction process to prepare 3-[3-bromo-methyl -6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole;

S201 2-methylbenzaldehyde and bromination reagent are mixed in the preset solvent, and under the condition of preset constant temperature, the catalyst is added to carry out bromination reaction to obtain 2-bromo-6-methylbenzaldehyde;

Preparation of 2-bromo-6-methylbenzaldehyde:

The reaction vessel is protected by nitrogen filling, and 200mL of ethyl acetate, 0.2mol 2-methylbenzaldehyde, 0.005mol ferric chloride are added successively, because the reaction is an exothermic reaction, preferably a condenser can be added on the reaction vessel, preferably The temperature of the reaction vessel was controlled to 45°C, a mixture of 0.25mol NBS and 100mL of ethyl acetate was added dropwise within 2h, and then the temperature was controlled to 45°C to the extent that the 2-methylbenzaldehyde content was less than 1%, the pH was adjusted to 7, and the After liquid separation, precipitation and rectification, 2-bromo-6-methylbenzaldehyde with a content of more than 98% and a yield of 80% is obtained.

S202 performs a condensation reaction with 2-bromo-6-methylbenzaldehyde, a preset solvent, hydroxylamine hydrochloride and a base, then feeds ethylene gas and the catalyst and chlorinates the final cyclization to obtain 3-[2-methyl-6 -Bromo-phenyl]-4,5-dihydroisoxazole;

Preparation of 3-[2-Methyl-6-bromo-phenyl]-4,5-dihydroisoxazole:

In the reaction vessel under nitrogen protection, 200 mL of THF, 0.2 mol of 2-bromo-6-methylbenzaldehyde, and 0.3 mol of hydroxylamine hydrochloride were sequentially added, and 20% aqueous solution of sodium hydroxide (0.4 mol) was added dropwise at 30° C. for 1 h. The inner dropwise addition is completed; keep the temperature at 30 ° C for 5 hours until the content of 2-bromo-6-methylbenzaldehyde in the total material is less than 1%, adjust the pH to 7, add solvent extraction, liquid separation, and desolubilization to obtain a product content > 98% , the yield is 76% oxime intermediate

Then, 200 mL of THF, 0.2 mol of oxime intermediate, 0.25 mol of NCS and 0.005 mol of ferric chloride were successively added to the reaction vessel under nitrogen protection, the pressure of ethylene gas was controlled to be 1.0 MPa, and the reaction was carried out at 60 °C for 5 h to the oxime intermediate in the total material. The content is less than 1%, after adjusting the pH of the total material to 7, adding solvent extraction, liquid separation, and desolubilization to obtain 3-[2-methyl-6-bromo-phenyl]- 4,5-Dihydroisoxazole.

S203 Add the sulfonylation reagent, the preset solvent and the catalyst to 3-[2-methyl-6-bromo-phenyl]-4,5-dihydroisoxazole, and at a preset constant temperature 3-[2-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole was obtained under the following method;

Preparation of 3-[2-Methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole:

In a reaction vessel equipped with a condenser under nitrogen protection, 200 mL of DMF, 0.2 mol of 3-[2-methyl-6-bromo-phenyl]-4,5-dihydroisoxazole, 0.05 mol of chlorinated chloride were added in sequence. Copper, 0.25mol methanesulfonyl chloride (dissolved in 50mL THF) was added dropwise under stirring at 0°C, the dropping was completed within 2h (maintain the temperature not exceeding 5°C), and the temperature was kept at this temperature for 10h until the 3-[2-methyl group in the total material The content of -6-bromo-phenyl]-4,5-dihydroisoxazole is less than 1%. After adjusting the pH of the total material to 7, adding a solvent for extraction, liquid separation and desolubilization to obtain a content > 97% and a yield of 75% 3-[2-Methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole.

S204 Add the catalyst, the bromination reagent and the preset solvent to 3-[2-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole to obtain 3-[3-Bromo-2-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole was obtained.

Preparation of 3-[3-Bromo-2-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole:

In a reaction vessel equipped with a condenser under nitrogen protection, 200 mL of THF, 0.2 mol of 3-[2-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole, 0.05 mol ferric chloride, a mixture of 0.25mol NBS and 100 mL THF was added dropwise at 50 °C, the mixture was added dropwise within 2 h, and the mixture was stirred at 65 °C to react to 3-[2-methyl-6-(methyl) in the total material. The content of phenylsulfonyl)phenyl]-4,5-dihydroisoxazole is less than 1%. After adjusting the pH of the total material to 7, adding a solvent for extraction, liquid separation and desolubilization to obtain the product 3-[3-bromo-2- Methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole, crude product content > 80%, recrystallization from ethanol to obtain 3- [3-Bromo-2-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole.

S102 uses diethyl malonate, triethyl formate, nickel sulfate, monobasic saturated carboxylic acid, methyl hydrazine, hydrocarbon solvent, ethanol solution and hydrochloric acid as reaction raw materials through the second reaction process to prepare 1-methyl- 5-Hydroxypyrazole;

S301 diethyl malonate and triethyl orthoformate are mixed with the hydrocarbon solvent in a reaction vessel, and under the action of nickel sulfate and the monobasic saturated carboxylic acid, diethyl ethoxymethylene malonate is prepared ester;

Preparation of diethyl ethoxymethylenemalonate:

In a reaction vessel equipped with a condenser under nitrogen protection, add 0.1 mol of diethyl malonate, 0.3 mol of triethyl orthoformate, 15 ml of absolute ethanol, 0.1 mol of acetic acid, and 0.0001 mol of nickel sulfate, and heat under stirring. , when the reactant was heated to 130～135 ℃, kept for 30 minutes, then warmed up to 148～158 ℃ and reacted for three hours, after the reaction mixture was cooled to room temperature, vacuum distillation was used to carry out pumping under 4KPa pressure, and received 130～135 ℃/0.67KPa fraction, namely obtains ethoxymethylene diethyl malonate.

S302 Condenses and cyclizes diethyl ethoxymethylenemalonate and methyl hydrazine in an ethanol solution at a preset low temperature to obtain ethyl 1-methyl-5-hydroxypyrazole-4-carboxylate The reaction solution;

S303 Add hydrochloric acid to the prepared ethyl 1-methyl-5-hydroxypyrazole-4-carboxylate reaction solution for reflux reaction to prepare 1-methyl-5-hydroxypyrazole.

Preparation of 1-methyl-5-hydroxypyrazole:

In a reaction vessel equipped with a condenser under nitrogen protection, 0.05 mol of diethyl ethoxymethylene malonate and 15 ml of anhydrous ethanol were added, and 0.055 mol of methyl ester was added dropwise while stirring at a temperature below 0 °C. Hydrazine was added dropwise within 2 h, the reaction mixture was stirred at room temperature for 1 h, then heated to reflux until the cyclization reaction was completed, cooled to room temperature to form a suspension, concentrated hydrochloric acid was added to the suspension, and heated to reflux again until hydrolysis The decarboxylation reaction was complete, and finally the solvent and water were removed under reduced pressure. After drying, 20 ml of isopropanol was added to the residue, concentrated under reduced pressure, and azeotropically dehydrated. After the residue was cooled, the yield was obtained by filtration and vacuum drying. >88.5%, content >97% of 1-methyl-5-hydroxypyrazole.

S103 starts with 3-[3-bromo-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole, 1-methyl-5-hydroxypyrazole, triethylamine, carbonic acid Potassium, palladium chloride, triphenylphosphorus, 1,4-dioxane, water, saturated NaHCO ₃ solution and hydrochloric acid solution are used as reaction raw materials to obtain oxaflutole through the third reaction process.

S401 3-[3-bromo-methyl-6-(methylsulfonyl)phenyl]-4,5-dihydroisoxazole, 1-methyl-5-hydroxypyrazole, triethylamine, carbonic acid Potassium, palladium chloride and triphenylphosphorus are mixed in a preset ratio and added to the autoclave, and then 1,4-dioxane is added as a solvent to obtain a mixed solution;

S402, after purging the mixed solution with nitrogen and carbon monoxide, wait for the completion of the reaction under pressure heating conditions;

S403 after the reaction is completed, carry out underpressure distillation, add water and remove insolubles by suction filtration, to obtain an aqueous filtrate;

The aqueous phase filtrate described in S404 obtains an organic phase after extraction, adjusting pH, and extracting and separating again;

In S405, the organic phase is distilled under reduced pressure and recrystallized from solid methanol to obtain the oxaflutole product.

To prepare oxaflutole:

In a reaction vessel under nitrogen protection and equipped with a condenser, 1 mol of 1-methyl-5-hydroxypyrazole, 1 mol of 3-[3-bromo-2-methyl-6-(methylsulfonyl) phenyl]-4,5-dihydroisoxazole, 2mol triethylamine, 2mol potassium carbonate, 0.05mol palladium chloride, 0.1mol triphenylphosphorus, and then 1,4-dioxane was added as a solvent, respectively After purging three times with nitrogen and carbon monoxide, pressurize with carbon monoxide to 1MPa, and heat up to 130 ° C, and react for 10 hours until the raw material content is less than 0.1%, then dioxane is distilled off under reduced pressure, and water is added, suction filtration Remove insolubles, add dichloromethane to the obtained filtrate for extraction, the obtained aqueous phase is adjusted to pH 3, and then add dichloromethane to extract and separate the liquid to obtain an organic phase, and add saturated NaHCO ₃ solution, after stirring, dropwise add hydrochloric acid to adjust When the pH reaches 6, extraction and liquid separation are carried out, and dichloromethane is distilled off under reduced pressure from the organic phase to obtain a yellow solid, which is recrystallized from solid methanol to obtain oxaflutole with a yield of >70% and a content of >88.4%.

The present invention also proposes an application of oxaflutole, which includes the above-mentioned preparation method of oxaflutole, and also includes the application of oxaflutole in controlling grass weeds and some broad-leaved weeds in corn fields. Field grass weeds and some broad-leaved weeds have very good control effects and have good application prospects.

The above disclosure is only a preferred embodiment of the present invention, and of course, it cannot limit the scope of rights of the present invention. Those of ordinary skill in the art can understand that all or part of the process for realizing the above-mentioned embodiment can be realized according to the rights of the present invention. The equivalent changes required to be made still belong to the scope covered by the invention.

Claims (10)

1. A preparation method of topramezone is characterized by comprising the following steps:

preparing 3- [ 3-bromo-methyl-6- (methylsulfonyl) phenyl ] -4, 5-dihydro isoxazole by using 2-methylbenzaldehyde, a bromination reagent, a catalyst, hydroxylamine hydrochloride, alkali, ethylene gas, a sulfonylation reagent and a preset solvent as reaction raw materials through a first reaction process;

taking diethyl malonate, triethyl formate, nickel sulfate, monobasic saturated carboxylic acid, methyl hydrazine, hydrocarbon solvent, ethanol solution and hydrochloric acid as reaction raw materials to prepare 1-methyl-5-hydroxypyrazole through a second reaction process;

with 3- [ 3-bromo-methyl-6- (methylsulfonyl) phenyl]-4, 5-dihydroisoxazole, 1-methyl-5-hydroxypyrazole, triethylamine, potassium carbonate, palladium chloride, triphenylphosphine, 1, 4-dioxane, water, saturated NaHCO₃The solution and the hydrochloric acid solution are used as reaction raw materials to prepare the topramezone through a third reaction process.

2. The process for preparing topramezone according to claim 1, wherein the first reaction process is:

mixing the 2-methyl benzaldehyde and a bromination reagent in the preset solvent, and adding the catalyst under the condition of a preset constant temperature to perform bromination reaction to prepare 2-bromo-6-methyl benzaldehyde;

carrying out condensation reaction on 2-bromo-6-methylbenzaldehyde, a preset solvent, hydroxylamine hydrochloride and alkali, then introducing ethylene gas and the catalyst, and chloridizing to finally cyclize to obtain 3- [ 2-methyl-6-bromo-phenyl ] -4, 5-dihydro-isoxazole;

adding the sulfonylation reagent, the preset solvent and the catalyst into 3- [ 2-methyl-6-bromo-phenyl ] -4, 5-dihydro isoxazole to prepare 3- [ 2-methyl-6- (methylsulfonyl) phenyl ] -4, 5-dihydro isoxazole at a preset constant temperature;

adding the catalyst, the brominating reagent and the predetermined solvent to 3- [ 2-methyl-6- (methylsulfonyl) phenyl ] -4, 5-dihydroisoxazole to produce 3- [ 3-bromo-2-methyl-6- (methylsulfonyl) phenyl ] -4, 5-dihydroisoxazole.

3. The process for preparing topramezone according to claim 2, wherein the brominating reagent is Br₂At least one of BrCl, NBS and HBr, wherein the catalyst is acetic acid, acetic anhydride, iodobenzene, aluminum trichloride, FeCl₃The base is at least one of butyl lithium, L DA, sodium hydroxide, potassium hydroxide, sodium tert-butoxide, potassium tert-butoxide, lithium tert-butoxide, potassium carbonate, cesium carbonate, lithium hydroxide, triethylamine, diisopropylamine, DBU, sodium methoxide and sodium ethoxide, the sulfonylation reagent is at least one of methanesulfonyl chloride, methanesulfonic acid and methanesulfonic anhydride, the preset solvent is at least one of dichloromethane, dichloroethane, chloroform, chlorobenzene, toluene, xylene, tetrahydrofuran, methyl acetate, ethyl acetate, methanol, ethanol and isopropanol, and the preset constant temperature range is 30-60 ℃.

4. The process for preparing topramezone according to claim 1, wherein the second reaction process is:

mixing diethyl malonate and triethyl orthoformate with the hydrocarbon solvent in a reaction vessel, and preparing diethyl ethoxymethylidynemalonate under the action of nickel sulfate and the monobasic saturated carboxylic acid;

condensing and cyclizing diethyl ethoxymethylidynemalonate and methylhydrazine in an ethanol solution under the condition of preset low temperature to prepare 1-methyl-5-hydroxypyrazole-4-ethyl carboxylate reaction liquid;

hydrochloric acid is added into the prepared 1-methyl-5-hydroxypyrazole-4-ethyl carboxylate reaction liquid for reflux reaction to prepare 1-methyl-5-hydroxypyrazole.

5. The process for preparing topramezone according to claim 4, wherein the hydrocarbon solvent is at least one of xylene and toluene.

6. The process for preparing topramezone according to claim 4, wherein the saturated monocarboxylic acid is a saturated monocarboxylic acid having 1 to 5 carbon atoms.

7. The process for preparing topramezone according to claim 5, wherein the weight ratio of triethyl orthoformate: diethyl malonate: saturated monocarboxylic acids: nickel sulfate: hydrochloric acid: the mass ratio of methylhydrazine equal to 3: 1: 0.1: 0.0001: 0.24: 0.55.

8. the process for preparing topramezone according to claim 1, wherein the third reaction is:

mixing 3- [ 3-bromo-methyl-6- (methylsulfonyl) phenyl ] -4, 5-dihydroisoxazole, 1-methyl-5-hydroxypyrazole, triethylamine, potassium carbonate, palladium chloride and triphenylphosphine according to a preset proportion, adding the mixture into an autoclave, and adding 1, 4-dioxane serving as a solvent to prepare a mixed solution;

after the mixed solution is purged by nitrogen and carbon monoxide, waiting for the reaction to be finished under the pressure and heating condition;

after the reaction is finished, carrying out reduced pressure distillation, adding water, and carrying out suction filtration to remove insoluble substances to obtain water-phase filtrate;

extracting the water phase filtrate, adjusting the pH value, extracting again and separating liquid to obtain an organic phase;

and carrying out reduced pressure distillation and solid methanol recrystallization on the organic phase to obtain the topramezone product.

9. The process for preparing topramezone according to claim 8, wherein the ratio of 3- [ 3-bromo-methyl-6- (methylsulfonyl) phenyl ] -4, 5-dihydroisoxazole: 1-methyl-5-hydroxypyrazole: triethylamine: potassium carbonate: palladium chloride: the mass ratio of triphenylphosphine was 1: 1: 2: 2: 0.05: 0.1.

10. an application of topramezone, which comprises the preparation method of topramezone according to any one of claims 1 to 9, and is characterized by further comprising the application of topramezone in preventing and removing grassy weeds and part of broadleaf weeds in corn fields.

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