Synthesis method of tembotrione intermediate

Abstract

The invention relates to the technical field of chemical synthesis, and particularly discloses a synthesis method of a tembotrione intermediate. The 3-chloro-2-methyl-4-methylsulfonyl acetophenone product with the yield of 95% or above and the purity of 97% or above is prepared with the vanadium-containing compound and the acid substance as the catalysts and the air as the oxidizing agent, the yield and the purity are higher than those of a sodium tungstate-hydrogen peroxide process, the reaction solvent and the catalyst can be reused, the generation amount of three wastes is small, and the method is suitable for industrial production. The process safety, the economical efficiency and the environmental protection property are obviously improved, and the method is suitable for large-scale industrial production and has very important significance on sustainable development of tembotrione pesticides.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a method for synthesizing a tembotrione intermediate. Background Art

[0002] 3-Chloro-2-methyl-4-methylsulfonyl acetophenone is a key intermediate in the synthesis of the herbicide tembotrione, and has a large market demand. At present, the main industrial synthesis methods of tembotrione are mainly divided into two types:

[0003] (1) Sodium methyl mercaptan and 2,6-dichlorotoluene are first subjected to an etherification reaction to generate intermediate 2, which is then subjected to a Friedel-Crafts reaction to generate intermediate 3. Intermediate 3 is oxidized with hydrogen peroxide to generate intermediate 4. Intermediate 4 is then subjected to haloformation, esterification, bromination, etherification, chlorination and condensation rearrangement reactions to obtain cyclosulfone. The specific synthesis route is as follows.

[0004]

[0005] (2) Using 3-chloro-2-methylaniline as the raw material, sodium nitrite and sodium methyl mercaptan are first used to synthesize intermediate 3, and then an oxidation reaction is carried out under the action of hydrogen peroxide and sodium tungstate to synthesize intermediate 4, and finally cyclosulfone is obtained through haloformation, esterification, bromination, etherification, chlorination and condensation rearrangement reactions. The synthetic route is as follows.

[0006]

[0007] Both of the above routes require the step of oxidizing intermediate 3 to generate intermediate 4. The current oxidation process uses sodium tungstate as a catalyst and hydrogen peroxide as an oxidant to react to prepare intermediate 4. Under this process, dangerous hydrogen peroxide is used as an oxidant, and the amount of hydrogen peroxide used far exceeds the theoretical amount (the molar ratio of hydrogen peroxide to intermediate 3 is 3 to 4:1), the industrial safety is poor, and the production cost is high. Therefore, it is of great significance to develop a high-efficiency synthesis method for tampronone intermediate 4 with high process safety and low production cost. Summary of the invention

[0008] Aiming at the problems of poor process safety and high production cost in the synthesis method of tembotrione intermediate in the prior art, the present invention provides a synthesis method of tembotrione intermediate.

[0009] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0010] A method for synthesizing a tembotrione intermediate comprises the following steps:

[0011] Under alcohol solvent conditions, 3-chloro-2-methyl-4-methylthioacetophenone is used as a raw material, a vanadium-containing compound and an acid substance are used as a catalyst, and air is used as an oxidant. Through an oxidation reaction, 3-chloro-2-methyl-4-methylsulfonylacetophenone is obtained; wherein the acid substance is a strong acid or a medium-strong acid.

[0012] Air or oxygen is a commonly used cheap oxidant raw material in common oxidation reactions. Therefore, the inventors tried to replace the expensive hydrogen peroxide with cheap air. However, during the experiment, it was found that it was difficult to oxidize 3-chloro-2-methyl-4-methylthioacetophenone by using air alone as an oxidant or conventional sodium tungstate as a catalyst for the oxidation reaction, resulting in an extremely low yield of the 3-chloro-2-methyl-4-methylsulfonylacetophenone product.

[0013] Compared with the prior art, the synthesis method of the tembotrione intermediate provided by the present invention adopts a vanadium-containing compound and an acid substance as a composite catalyst, and achieves the purpose of preparing the 3-chloro-2-methyl-4-methylsulfonylacetophenone intermediate by using air as an oxidant, which not only effectively reduces the production cost, but also significantly improves the safety of the process, is more conducive to large-scale industrial production and application, and is of great significance to the development of tembotrione pesticides.

[0014] Furthermore, the vanadium-containing compound is one or more of vanadium pentoxide, ammonium metavanadate, sodium metavanadate, sodium orthovanadate or ammonium orthovanadate.

[0015] Preferably, the vanadium-containing compound is vanadium pentoxide.

[0016] Furthermore, the added amount of the vanadium-containing compound is 0.1% to 1% of the mass of 3-chloro-2-methyl-4-methylthioacetophenone.

[0017] Preferably, the amount of the vanadium-containing compound added is 0.1% to 0.5% of the mass of 3-chloro-2-methyl-4-methylthioacetophenone. More preferably, the amount of the vanadium-containing compound added is 0.1% of the mass of 3-chloro-2-methyl-4-methylthioacetophenone.

[0018] Furthermore, the acid substance is one or more of concentrated sulfuric acid, concentrated phosphoric acid, concentrated nitric acid or hydrogen chloride gas.

[0019] Preferably, the acid substance is concentrated sulfuric acid.

[0020] Using concentrated sulfuric acid, concentrated phosphoric acid, concentrated nitric acid or hydrogen chloride gas as a catalyst can reduce the amount of additional water introduced into the system, facilitate the recycling of mother liquor, and reduce the generation of three wastes.

[0021] It should be noted that the concentrated sulfuric acid, concentrated phosphoric acid and concentrated nitric acid used in the present invention are all commercially available products, with the mass concentration of concentrated sulfuric acid being 98%, concentrated phosphoric acid being 85%, and concentrated nitric acid being 65% to 69%.

[0022] Furthermore, the amount of the acid substance added is 0.1% to 5% of the mass of 3-chloro-2-methyl-4-methylthioacetophenone.

[0023] Preferably, the amount of the acid substance added is 0.1% to 1% of the mass of 3-chloro-2-methyl-4-methylthioacetophenone. More preferably, the amount of the acid substance added is 0.1% of the mass of 3-chloro-2-methyl-4-methylthioacetophenone.

[0024] The invention adopts a preferred vanadium-containing compound and an acid substance as a composite catalyst, and achieves the purpose of fully oxidizing 3-chloro-2-methyl-4-methylthioacetophenone to prepare 3-chloro-2-methyl-4-methylsulfonylacetophenone by using air as an oxidant, and the amount of the catalyst used is small, thereby effectively reducing the production cost.

[0025] Furthermore, the alcohol solvent is methanol.

[0026] Furthermore, the added amount of the alcohol solvent is 1 to 8 times the mass of 3-chloro-2-methyl-4-methylthioacetophenone.

[0027] Preferably, the amount of the alcohol solvent added is 3 to 6 times the mass of 3-chloro-2-methyl-4-methylthioacetophenone, more preferably 5 times.

[0028] A preferred reaction solvent can improve the selectivity and reaction rate of the reaction, thereby increasing the yield and purity of the target product.

[0029] As a specific embodiment of the present invention, the synthesis method of the tembotrione intermediate specifically comprises the following steps:

[0030] Step a, adding 3-chloro-2-methyl-4-methylthioacetophenone, a vanadium-containing compound and an acid substance to an alcohol solvent and mixing them evenly, heating the temperature to 60° C. to 70° C., introducing air, sampling and monitoring until the content of 3-chloro-2-methyl-4-methylthioacetophenone in the system is less than 1%, cooling the temperature to -10° C. to 10° C., and performing solid-liquid separation to obtain a crude product of 3-chloro-2-methyl-4-methylsulfonylacetophenone;

[0031] Step b, adding the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone into an alcohol solvent, heating the solvent to 60°C to 70°C, cooling the solvent to -10°C to 10°C, performing solid-liquid separation, and drying to obtain a 3-chloro-2-methyl-4-methylsulfonylacetophenone product.

[0032] Furthermore, in step a, the air introduction rate is 1 mL / min to 100 mL / min.

[0033] It should be noted that in step a, the central control sampling and monitoring adopts high performance liquid chromatography, and the specific detection conditions are as follows:

[0034] Chromatographic column: C18;

[0035] Mobile phase: acetonitrile: water = 50:50;

[0036] Detection wavelength: 220nm.

[0037] Furthermore, in step b, the alcohol solvent is methanol, and its added amount is 1 to 3 times the mass of the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone (wet product).

[0038] Furthermore, in step b, the insulation time is 0.5h to 1h.

[0039] The crude 3-chloro-2-methyl-4-methylsulfonylacetophenone is added to an alcohol solvent and kept warm at a specific temperature, so that the impurities contained in the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone are fully dissolved in the alcohol solvent, and the solvent content of 3-chloro-2-methyl-4-methylsulfonylacetophenone in the alcohol solvent is reduced as much as possible, thereby improving the yield and purity of the target product.

[0040] Furthermore, in step b, activated carbon is added to the mother liquor obtained by solid-liquid separation for decolorization, and solid-liquid separation is performed. The obtained filtrate is returned to step a and reused as a reaction solvent.

[0041] The present invention uses air as an oxidant, which not only avoids the safety problem when hydrogen peroxide is used as an oxidant, but also avoids the situation that hydrogen peroxide as an oxidant will introduce additional moisture into the system. At the same time, the present invention selects concentrated sulfuric acid, concentrated phosphoric acid, concentrated nitric acid or hydrogen chloride gas as a catalyst, which also reduces the additional introduction of moisture into the system, so that the mother liquor after the solid-liquid separation product does not need to be dehydrated, and can be simply decolorized and impurity-removed before being recycled to step a for repeated use, which not only reduces the generation of the three wastes, but also realizes the recycling of the catalyst and the reaction solvent, and further reduces the production cost.

[0042] It should be noted that when the mother liquor is decolorized and impurities removed before being applied, 1% to 5% of the mass of the first batch of catalyst needs to be added to the system for each batch to ensure that the oxidation reaction proceeds fully.

[0043] Furthermore, in step b, the amount of activated carbon added is 1‰ to 5‰ of the mother liquor mass.

[0044] Furthermore, in step b, the decolorization temperature is 40°C to 60°C, and the decolorization time is 0.5h to 1h.

[0045] The synthesis process of the tembotrione intermediate provided by the invention uses air as an oxidant, and under the conditions of a specific catalyst and a reaction solvent, achieves full oxidation of 3-chloro-2-methyl-4-methylthioacetophenone, and prepares 3-chloro-2-methyl-4-methylsulfonylacetophenone with high yield and high purity, which not only effectively improves the process safety, but also significantly reduces the cost of raw materials. In addition, the mother liquor after the reaction can be recycled after simple decolorization and impurity removal, and does not need to be distilled to remove water, so the amount of three wastes generated is small, the process is more energy-saving and environmentally friendly, and is suitable for large-scale industrial production, which is of great significance to the sustainable development of the tembotrione pesticide. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0047] In order to better illustrate the present invention, further examples are given below.

[0048] The conditions for the central control detection of 3-chloro-2-methyl-4-methylthioacetophenone in the following examples and comparative examples are as follows:

[0049] Chromatographic column: C18;

[0050] Mobile phase: acetonitrile: water = 50:50;

[0051] Detection wavelength: 220nm.

[0052] Example 1

[0053] This embodiment provides a production process of tembotrione intermediate, and the specific steps are as follows:

[0054] Step a, add 214.72g (1.00mol) of 3-chloro-2-methyl-4-methylthioacetophenone into the reactor, then add 214.72g of pure methanol, 0.215g of concentrated sulfuric acid, and 0.215g of ammonium metavanadate, mix well, heat to 65°C, start to introduce air at a ventilation rate of 1mL / min, for about 25h, take samples and perform central control until the raw material content is less than 1%, after the central control is qualified, cool to -10°C, filter, and obtain a crude product of 3-chloro-2-methyl-4-methylsulfonylacetophenone;

[0055] Step b, according to the mass ratio of 1:1, the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone was added into pure methanol, the temperature was raised to 65°C, and the temperature was kept for 0.5h, the temperature was lowered to 0°C and the temperature was kept for crystallization for 0.5h, the mixture was filtered and dried to obtain 233.70g of 3-chloro-2-methyl-4-methylsulfonylacetophenone product, with a weight yield of 95.01% and a total area content of 97.12%.

[0056] 1 H NMR(Chloroform-d)δ7.60–7.85(m,2H),3.20(s,3H),2.66(s,3H),2.54(s,3H).

[0057] Example 2

[0058] This embodiment provides a production process of tembotrione intermediate, and the specific steps are as follows:

[0059] Step a, add 214.72g (1.00mol) of 3-chloro-2-methyl-4-methylthioacetophenone into the reaction kettle, then add 1720g of pure methanol, 10.75g of concentrated sulfuric acid, and 2.15g of vanadium pentoxide, mix well, heat to 60°C, start to introduce air at a ventilation rate of 100mL / min, for about 5h, take samples and control until the raw material content is less than 1%, after the control is qualified, cool to 0°C, filter, and obtain a crude product of 3-chloro-2-methyl-4-methylsulfonylacetophenone;

[0060] Step b, according to the mass ratio of 1:2, the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone was added into pure methanol, the temperature was raised to 60°C, kept warm for 1 hour, cooled to -10°C and kept warm for crystallization for 0.5 hour, filtered and dried to obtain 239.85 g of 3-chloro-2-methyl-4-methylsulfonylacetophenone product, with a weight yield of 97.50% and a total area content of 97.70%.

[0061] 1 H NMR(Chloroform-d)δ7.60–7.85(m,2H),3.20(s,3H),2.66(s,3H),2.54(s,3H).

[0062] Example 3

[0063] This embodiment provides a production process of tembotrione intermediate, and the specific steps are as follows:

[0064] Step a, add 214.72g (1.00mol) of 3-chloro-2-methyl-4-methylthioacetophenone into the reaction kettle, then add 1000g of pure methanol, 5.00g of concentrated phosphoric acid, and 0.43g of sodium orthovanadate, mix well, heat to 70°C, start to introduce air at a ventilation rate of 50mL / min, for about 10h, take samples and control until the raw material content is less than 1%, after the control is qualified, cool to 10°C, filter, and obtain a crude product of 3-chloro-2-methyl-4-methylsulfonylacetophenone;

[0065] Step b, according to the mass ratio of 1:3, the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone was added into pure methanol, the temperature was raised to 70°C, and the temperature was kept for 0.5h, the temperature was lowered to -5°C and the crystallization was kept for 1h, the crystallization was filtered and dried to obtain 238.62g of 3-chloro-2-methyl-4-methylsulfonylacetophenone product, with a weight yield of 97.00% and a total area content of 97.50%.

[0066] 1 H NMR(Chloroform-d)δ7.60–7.85(m,2H),3.20(s,3H),2.66(s,3H),2.54(s,3H).

[0067] In step b of Examples 1 to 3, activated carbon with a mass of 11‰ to 5‰ of the mother liquor is added to the mother liquor after crystallization, and the mixture is kept warm at 50°C for 0.5 to 1h, filtered, and the filtrate is a methanol solution containing the catalyst, which can be directly applied to step a. When applying, each batch of catalyst is supplemented with 1% to 5% of the amount of the first batch of catalyst.

[0068] The vanadium-containing compounds and acid substances in Examples 1 to 3 may also be replaced with other substances defined in the present invention, and the same technical effects as those in Examples 1 to 3 can be achieved.

[0069] Comparative Example 1

[0070] This comparative example provides a production process of a tembotrione intermediate, and the specific steps are as follows:

[0071] Add 90 mL of acetic acid and 21.40 g (0.10 mol) of 3-chloro-2-methyl-4-methylthioacetophenone to a 250 mL reaction bottle, stir until completely dissolved, add 1.00 g (3.41 mmol) of sodium tungstate, start to dropwise add 22.67 g (0.2 mol) of 30% hydrogen peroxide, control the temperature at 40-45°C, continue to keep warm after the addition is complete, take samples and monitor with TLC (petroleum ether: ethyl acetate = 15:1) until the raw materials react completely;

[0072] After the reaction is completed, the temperature is lowered to room temperature, the reaction solution is transferred to 100 g of ice water, filtered, and methanol twice the amount of the wet product is added. The temperature is raised to 65°C and kept warm for 0.5 h. The temperature is lowered to 0°C and crystallized for 0.5 h to obtain 3-chloro-2-methyl-4-methylsulfonylacetophenone product with a weight yield of 94.06% and a total area content of 90.32%.

[0073] Comparative Example 2

[0074] This comparative example provides a production process of a tembotrione intermediate, and the specific steps are as follows:

[0075] Add 90 mL of dichloroethane and 21.40 g (0.10 mol) of 3-chloro-2-methyl-4-methylthioacetophenone to a 250 mL reaction bottle, stir until completely dissolved, add 1.00 g (3.41 mmol) of sodium tungstate, start to drop 22.67 g (0.2 mol) of 30% hydrogen peroxide, control the temperature at 40-45°C, keep warm after the addition is complete, take samples and monitor with TLC (petroleum ether: ethyl acetate = 15:1) until the raw materials react completely;

[0076] After the reaction is completed, dichloroethane is removed by negative pressure, and the temperature is cooled to room temperature. The reaction solution is transferred to 100 g of ice water, filtered, and methanol twice the amount of the wet product is added. The temperature is raised to 65°C and kept warm for 0.5 h. The temperature is lowered to 0°C and crystallized for 0.5 h to obtain 3-chloro-2-methyl-4-methylsulfonylacetophenone product with a weight yield of 93.62% and a total area content of 92.12%.

[0077] Comparative Example 3

[0078] This comparative example provides a production process of a tembotrione intermediate, and the specific steps are as follows:

[0079] Step a, add 214.72 g (1.00 mol) of 3-chloro-2-methyl-4-methylthioacetophenone into the reactor, then add 1720 g of pure methanol, mix well, heat to 60 ° C, start to pass air, the ventilation rate is 100 mL / min, about 5 hours, the raw material content is controlled at 93.76% during sampling, cool to 0 ° C, filter, and obtain a crude product of 3-chloro-2-methyl-4-methylsulfonylacetophenone.

[0080] Step b, according to the mass ratio of 1:2, the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone was added into pure methanol, the temperature was raised to 60°C, kept warm for 1 hour, cooled to -10°C and kept warm for crystallization for 0.5 hour, filtered and dried to obtain 12.59 g of 3-chloro-2-methyl-4-methylsulfonylacetophenone product, with a weight yield of 5.12% and a total area content of 80.45%.

[0081] Comparative Example 4

[0082] This comparative example provides a production process of a tembotrione intermediate, and the specific steps are as follows:

[0083] Step a, add 214.72 g (1.00 mol) of 3-chloro-2-methyl-4-methylthioacetophenone into the reactor, then add 1720 g of pure methanol and 10.75 g of concentrated sulfuric acid, mix well, heat to 60°C, start to introduce air at a ventilation rate of 100 mL / min, for about 5 hours, take a sample to control the raw material content of 73.42%, cool to 0°C, filter, and obtain a crude product of 3-chloro-2-methyl-4-methylsulfonylacetophenone;

[0084] Step b, according to the mass ratio of 1:2, the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone was added into pure methanol, the temperature was raised to 60°C, the temperature was kept for 1 hour, the temperature was lowered to -10°C and the crystallization was kept for 0.5 hour, the crystallization was filtered and dried to obtain 35.30 g of 3-chloro-2-methyl-4-methylsulfonylacetophenone product, the weight yield was 14.35%, and the total area content was 87.70%.

[0085] Comparative Example 5

[0086] This comparative example provides a production process of a tembotrione intermediate, and the specific steps are as follows:

[0087] Step a, add 214.72g (1.00mol) of 3-chloro-2-methyl-4-methylthioacetophenone into the reactor, then add 1720g of pure methanol and 2.15g of vanadium pentoxide, mix well, heat to 60°C, start to introduce air at a ventilation rate of 100mL / min, for about 5h, take a sample and control the raw material content to 74.07%, after the control is qualified, cool to 0°C, filter, and obtain a crude product of 3-chloro-2-methyl-4-methylsulfonylacetophenone;

[0088] Step b, according to the mass ratio of 1:2, the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone was added into pure methanol, the temperature was raised to 60°C, the temperature was kept for 1 hour, the temperature was lowered to -10°C and the crystallization was kept for 0.5 hour, the crystallization was filtered and dried to obtain 60.44 g of 3-chloro-2-methyl-4-methylsulfonylacetophenone product, the weight yield was 24.57%, and the total area content was 91.51%.

[0089] Comparative Example 6

[0090] This comparative example provides a production process of a tembotrione intermediate, and the specific steps are as follows:

[0091] Step a, add 214.72g (1.00mol) of 3-chloro-2-methyl-4-methylthioacetophenone into the reactor, then add 1720g of pure methanol, 10.75g of concentrated sulfuric acid, and 2.15g of sodium tungstate, mix well, heat to 60°C, start to introduce air, the ventilation rate is 100mL / min, about 5h, sample the raw material content of 72.62%, after the control is qualified, cool to 0°C, filter, and obtain crude 3-chloro-2-methyl-4-methylsulfonylacetophenone;

[0092] Step b, according to the mass ratio of 1:2, the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone was added into pure methanol, the temperature was raised to 60°C, the temperature was kept for 1 hour, the temperature was lowered to -10°C and the crystallization was kept for 0.5 hour, the crystallization was filtered and dried to obtain 35.92g of 3-chloro-2-methyl-4-methylsulfonylacetophenone product, the weight yield was 14.60%, and the total area content was 88.25%.

[0093] Comparative Example 7

[0094] This comparative example provides a production process of a tembotrione intermediate, and the specific steps are as follows:

[0095] Step a, add 214.72g (1.00mol) of 3-chloro-2-methyl-4-methylthioacetophenone into the reactor, then add 1720g of pure methanol, 10.75g of sodium tungstate, and 2.15g of vanadium pentoxide, mix well, heat to 60°C, start to introduce air, the ventilation rate is 100mL / min, about 5h, sample the raw material content of 73.69%, after the control is qualified, cool to 0°C, filter, and obtain crude 3-chloro-2-methyl-4-methylsulfonylacetophenone;

[0096] Step b, according to the mass ratio of 1:2, the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone was added into pure methanol, the temperature was raised to 60°C, the temperature was kept for 1 hour, the temperature was lowered to -10°C and the crystallization was kept for 0.5 hour, the crystallization was filtered and dried to obtain 62.31 g of 3-chloro-2-methyl-4-methylsulfonylacetophenone product, the weight yield was 25.33%, and the total area content was 91.70%.

[0097] In summary, the embodiment of the present invention uses vanadium-containing compounds and acid substances as catalysts and air as an oxidant to prepare a 3-chloro-2-methyl-4-methylsulfonylacetophenone product with a yield of more than 95% and a purity of more than 97%. The yield and purity are higher than those of the sodium tungstate-hydrogen peroxide process, and the reaction solvent and the catalyst can be recycled, the amount of three wastes generated is small, and the process safety, economy and environmental protection are significantly improved, which has a high practical value.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synthesizing a tembotrione intermediate, characterized in that: The steps include: Under alcohol solvent conditions, 3-chloro-2-methyl-4-methylthioacetophenone is used as a raw material, a vanadium-containing compound and an acid substance are used as a catalyst, and air is used as an oxidant. Through an oxidation reaction, 3-chloro-2-methyl-4-methylsulfonylacetophenone is obtained; wherein the acid substance is a strong acid or a medium-strong acid.

2. The method for synthesizing a tembotrione intermediate according to claim 1, wherein: The vanadium-containing compound is one or more of vanadium pentoxide, ammonium metavanadate, sodium metavanadate, sodium orthovanadate or ammonium orthovanadate; and / or The acid substance is one or more of concentrated sulfuric acid, concentrated phosphoric acid, concentrated nitric acid or hydrogen chloride gas.

3. The method for synthesizing a tembotrione intermediate according to claim 1, wherein: The added amount of the vanadium-containing compound is 0.1% to 1% of the mass of 3-chloro-2-methyl-4-methylthioacetophenone.

4. The method for synthesizing a tembotrione intermediate according to claim 1, wherein: The amount of the acid substance added is 0.1% to 5% of the mass of 3-chloro-2-methyl-4-methylthioacetophenone.

5. The method for synthesizing a tembotrione intermediate according to claim 1, wherein: The alcohol solvent is methanol.

6. The method for synthesizing the tembotrione intermediate according to claim 5, characterized in that: The added amount of the alcohol solvent is 1 to 8 times the mass of 3-chloro-2-methyl-4-methylthioacetophenone.

7. The method for synthesizing a tembotrione intermediate according to any one of claims 1 to 6, characterized in that: The specific steps include: Step a, adding 3-chloro-2-methyl-4-methylthioacetophenone, a vanadium-containing compound and an acid substance to an alcohol solvent and mixing them evenly, heating the temperature to 60° C. to 70° C., introducing air, sampling and monitoring until the content of 3-chloro-2-methyl-4-methylthioacetophenone in the system is less than 1%, cooling the temperature to -10° C. to 10° C., and performing solid-liquid separation to obtain a crude product of 3-chloro-2-methyl-4-methylsulfonylacetophenone; Step b, adding the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone into an alcohol solvent, heating the solvent to 60°C to 70°C, then cooling the solvent to -10°C to 10°C, separating the solid from the liquid, and drying the solvent to obtain the 3-chloro-2-methyl-4-methylsulfonylacetophenone product.

8. The method for synthesizing a tembotrione intermediate according to claim 7, wherein: In step b, the alcohol solvent is methanol, and the amount of methanol added is 1 to 3 times the quality of the crude 3-chloro-2-methyl-4-methylsulfonylacetophenone; and / or In step b, the insulation time is 0.5h to 1h.

9. The method for synthesizing a tembotrione intermediate according to claim 7, wherein: In step b, activated carbon is added to the mother liquor obtained by solid-liquid separation for decolorization, and the solid-liquid separation is performed. The obtained filtrate is returned to step a and reused as a reaction solvent.

10. The method for synthesizing a tembotrione intermediate according to claim 9, characterized in that: In step b, the amount of activated carbon added is 1‰ to 5‰ of the mother liquor mass; and / or In step b, the decolorization temperature is 40° C. to 60° C., and the decolorization time is 0.5 h to 1 h.

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