Process for the preparation of mesotrione intermediates

Abstract

The present application relates to the technical field of mesotrione, and particularly relates to a preparation method of mesotrione intermediate, which comprises the following steps: (1) a first reaction of a compound shown in formula (II) and sodium thiomethoxide in the presence of a first solvent to obtain a compound shown in formula (III); (2) a second reaction of the compound shown in formula (III) and hydrogen peroxide in the presence of a second solvent under the action of a catalyst to obtain a compound shown in formula (IV); (3) a third reaction of the compound shown in formula (IV) and acid liquor to obtain mesotrione intermediate shown in formula (I); wherein R1 is selected from F, Cl, Br or I; and R2 is selected from C1-C4 alkyl or aromatic group. The method can effectively improve the purity and yield of mesotrione intermediate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mesotrione, in particular to a preparation method of mesotrione intermediate (i.e. 2-nitro-4-methylsulfonylbenzoic acid). BACKGROUND

[0002] Mesotrione belongs to triketone herbicides, is a high-efficiency, low-toxicity herbicide, and has been widely used in the world. 2-nitro-4-methylsulfonylbenzoic acid is an important fine intermediate for synthesizing mesotrione, and also has great application value in dyes, medicines and other aspects. However, the synthetic process conditions of 2-nitro-4-methylsulfonylbenzoic acid are harsh, and the environmental protection pressure is huge.

[0003] CN101921215A discloses a production method of 2-nitro-4-methylsulfonylbenzoic acid. P-methylsulfonyl toluene is dissolved in concentrated sulfuric acid, and mixed acid composed of concentrated nitric acid and concentrated sulfuric acid is used for nitration at low temperature to obtain 2-nitro-4-methylsulfonyl toluene, and then potassium permanganate is used for oxidation to obtain 2-nitro-4-methylsulfonylbenzoic acid.

[0004] CN104557639A and CN105669504A use 2-nitro-4-methylsulfonyl toluene as raw material, sulfuric acid as reaction solvent, vanadium pentoxide as catalyst, nitric acid and oxygen as oxidant to prepare 2-nitro-4-methylsulfonylbenzoic acid.

[0005] CN108530326A uses 2-nitro-4-methylsulfonyl toluene as starting material, acetic acid or formic acid as solvent, one or more N-hydroxylamine compounds as catalyst, one or more of nitric acid, nitrate or nitrite as co-catalyst, and molecular oxygen as oxidant, under the conditions of 0.1-5MPa, 60-180℃, for 0.5-15h, to obtain 2-nitro-4-methylsulfonylbenzoic acid.

[0006] WO2004058698A1 and CN101921215A use hydrogen peroxide and sulfuric acid to generate peroxy sulfuric acid to oxidize 2-nitro-4-methylsulfonyl toluene to prepare 2-nitro-4-methylsulfonylbenzoic acid.

[0007] In the above methods, sulfuric acid, nitric acid, oxygen or heavy metal catalysts are used, there are flammable and explosive dangers in the reaction process, and the catalysts are difficult to handle and recycle, and the production cost is huge. SUMMARY

[0008] The purpose of the present application is to overcome the problems of harsh reaction conditions, low reaction yield and purity, and high production cost in the preparation of mesotrione intermediate (i.e. 2-nitro-4-methylsulfonylbenzoic acid), and to provide a preparation method of mesotrione intermediate.

[0009] To achieve the above objectives, the present invention provides a method for preparing a mesotrione intermediate, characterized in that the method includes the following steps:

[0010] (1) In the presence of a first solvent, the compound shown in formula (II) is reacted with sodium methanethiol to give the compound shown in formula (III).

[0011]

[0012] (2) In the presence of a second solvent, the compound shown in formula (III) and hydrogen peroxide are subjected to a second reaction in the presence of a catalyst to obtain the compound shown in formula (IV).

[0013] as well as

[0014] (3) The compound shown in formula (IV) is reacted with an acid solution in a third reaction to obtain the nicosulfuron intermediate shown in formula (I).

[0015]

[0016] R1 is selected from F, Cl, Br or I; R2 is selected from H, C1-C4 alkyl or aromatic group.

[0017] Compared with the prior art, the present invention provides a new method for preparing nicosulfuron intermediates. This method uses the compound shown in formula (II) as the starting material, which is relatively easy to obtain and reduces production costs. By cleverly designing steps (1)-(3), the target product (the compound shown in formula (I)) is finally obtained. In particular, by adjusting R1 and R2 in the compound shown in formula (II), it is more conducive to improving the purity and yield of nicosulfuron intermediates. At the same time, this method avoids the defects of safety hazards and complex process flow, and has the advantages of mild reaction conditions, high reaction yield and reaction purity, and low cost, which is convenient for industrial production. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] In the present application, unless otherwise specified, the "first", "second" and "third" do not represent the order of precedence, nor do they limit each material or step, but are used to distinguish the same material or step. For example, "first", "second" and "third" in "first reaction", "second reaction" and "third reaction" are only used to represent the same reaction.

[0020] The present application provides a preparation method of mesotrione intermediate, characterized in that the method comprises the following steps:

[0021] (1) a first reaction of a compound represented by formula (II) and sodium thiomethoxide in the presence of a first solvent to obtain a compound represented by formula (III),

[0022]

[0023] (2) a second reaction of the compound represented by formula (III) and hydrogen peroxide in the presence of a second solvent under the action of a catalyst to obtain a compound represented by formula (IV),

[0024] and

[0025] (3) a third reaction of the compound represented by formula (IV) and an acid solution to obtain a mesotrione intermediate represented by formula (I),

[0026]

[0027] wherein R1 is selected from F, Cl, Br or I; and R2 is selected from H, C1-C4 alkyl or aromatic group.

[0028] In some embodiments of the present application, when R2 in the compound represented by formula (II) is selected from H, step (3) is not required; when R2 in the compound represented by formula (II) is selected from C1-C4 alkyl or aromatic group, step (3) is required.

[0029] In some embodiments of the present application, preferably, R1 is selected from Cl; and R2 is selected from H or C1-C4 alkyl, preferably selected from C1-C4 alkyl, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and most preferably ethyl.

[0030] In some embodiments of the present application, preferably, in step (1), the amount of sodium thiomethoxide is 1.5-2.5 mol, for example, 1.5 mol, 1.8 mol, 2 mol, 2.2 mol, 2.5 mol, and any value in the range between any two of these values, preferably 1.8-2.2 mol, per 1 mol of the compound of formula (II). The use of the preferred conditions is more conducive to the conversion of -R1 in the compound of formula (II) to -SCH3 in the compound of formula (III), thereby improving the purity and yield of the compound of formula (III).

[0031] In some embodiments of the present application, preferably, in step (1), the conditions of the first reaction include a temperature of 50-180°C, preferably 100-120°C, and a time of 1-5 h, preferably 1.5-2 h.

[0032] The use of the preferred conditions is more conducive to improving the purity and yield of the compound of formula (III).

[0033] In some embodiments of the present application, preferably, in step (1), the weight ratio of the compound of formula (II) to the first solvent is 1:3-5, for example, 1:3, 1:4, 1:5, and any value in the range between any two of these values, preferably 1:4-5.

[0034] In the present application, the type of the first solvent has a wide range of choices, as long as the first reaction is carried out in the presence of the first solvent. Preferably, in step (1), the first solvent is at least one selected from 1,2-dichloroethane (DCE), toluene, methanol, ethanol, tetrahydrofuran, acetonitrile, N,N-dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide DMAC, and 1,3-dimethyl-2-imidazolidinone (DMI), preferably at least one selected from N,N-dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAC).

[0035] In some embodiments of the present application, preferably, in step (2), the amount of hydrogen peroxide is 2-3 mol, for example, 2 mol, 2.2 mol, 2.3 mol, 2.4 mol, 2.5 mol, 3 mol, and any value in the range between any two of these values, preferably 2.2-2.5 mol, per 1 mol of the compound of formula (III). The use of the preferred conditions is conducive to the conversion of -SCH3 in the compound of formula (III) to -SO2CH3 in the compound of formula (IV), thereby improving the yield and purity of the compound of formula (IV).

[0036] In some embodiments of the present application, preferably, in step (2), the catalyst is concentrated sulfuric acid and glacial acetic acid.

[0037] In some embodiments of the present application, preferably, the amount of concentrated sulfuric acid used is 0.1-0.5 mol, for example, 0.1 mol, 0.2 mol, 0.3 mol, 0.5 mol, and any value in the range between any two of the cited values, preferably 0.2-0.3 mol, per 1 mol of the compound of formula (III); and the amount of glacial acetic acid used is 0.3-1 mol, for example, 0.3 mol, 0.4 mol, 0.5 mol, 0.6 mol, 0.8 mol, 1 mol, and any value in the range between any two of the cited values, preferably 0.5-0.6 mol. The use of the preferred conditions is more conducive to improving the purity and yield of the compound of formula (IV).

[0038] In some embodiments of the present application, preferably, in step (2), the conditions of the second reaction include a temperature of 40-110°C, preferably 70-80°C, and a time of 0.1-2 h, preferably 0.3-0.7 h. The use of the preferred conditions is more conducive to improving the purity and yield of the compound of formula (IV).

[0039] In some embodiments of the present application, preferably, in step (2), the weight ratio of the compound of formula (III) to the second solvent is 1:3-5, for example, 1:3, 1:4, 1:5, and any value in the range between any two of the cited values, preferably 1:4-5.

[0040] In the present application, the type of the second solvent has a wide range of choices, as long as the second reaction is carried out in the second solvent. Preferably, in step (2), the second solvent is selected from at least one of 1,2-dichloroethane, toluene, dichloromethane, chloroform, trichloroethylene, and acetonitrile, preferably 1,2-dichloroethane.

[0041] In some embodiments of the present application, preferably, in step (3), the amount of the acid solution is 1-5 mol, for example, 1 mol, 2 mol, 3 mol, 4 mol, 5 mol, and any value in the range between any two of the cited values, preferably 2-4 mol, per 1 mol of the compound of formula (IV) in terms of H + In some embodiments of the present application, preferably, the acid solution is selected from a hydrochloric acid solution and / or a sulfuric acid solution, preferably a hydrochloric acid solution.

[0042] In some embodiments of the present application, preferably, the acid solution is selected from a hydrochloric acid solution and / or a sulfuric acid solution, preferably a hydrochloric acid solution.

[0043] In some embodiments of the present application, preferably, the acid concentration in the acid solution is 5-20wt%, for example, 5wt%, 10wt%, 12wt%, 15wt%, 20wt%, and any value in the range between any two of the values, preferably 10-15wt%.

[0044] In some embodiments of the present application, preferably, in step (3), the third reaction is carried out under the following conditions: temperature is 70-110℃, preferably 90-100℃; time is 1-5h, preferably 2-3h. With the preferred conditions, the yield and purity of the compound of formula (I) can be improved.

[0045] According to a particularly preferred embodiment of the present application, a method for preparing mesotrione intermediate comprises the following steps:

[0046] (1) a first reaction of a compound of formula (II) with sodium thiomethoxide in the presence of a first solvent to obtain a compound of formula (III),

[0047]

[0048] (2) a second reaction of the compound of formula (III) with hydrogen peroxide in the presence of a second solvent and in the presence of a catalyst to obtain a compound of formula (IV),

[0049] and

[0050] (3) a third reaction of the compound of formula (IV) with an acid solution to obtain mesotrione intermediate of formula (I),

[0051]

[0052] wherein R1 is selected from Cl; and R2 is selected from ethyl.

[0053] The present application will be described in detail below by way of examples.

[0054] In the following examples and comparative examples, the raw materials used are commercially available unless otherwise specified; and room temperature refers to 25℃.

[0055] Example 1

[0056] (1) preparation of a compound of formula (III) wherein R2 is H;

[0057] In a 1000 mL four-necked flask with thermometer and condenser, 100.78 g (0.5 mol) of the compound shown in formula II, wherein R1 is Cl and R2 is H (i.e. 4-chloro-2-nitrobenzoic acid), 403.12 g (2.0 mol) of DMSO were sequentially added, and the mixture was stirred and heated to 110-115°C. Then, 350.42 g (1.0 mol) of 20 wt% sodium methanethiolate solution was slowly added dropwise. After the addition was completed, the reaction was maintained for 1.5-2 h. After the reaction was completed, DMSO was removed by distillation under reduced pressure to obtain the compound shown in formula (III), i.e. 2-nitro-4-methylthiobenzoic acid, with a purity of 89.15 wt% and a yield of 52.64% (based on the compound shown in formula (II));

[0058] (2) Preparation of the compound shown in formula (I), wherein R2 is H;

[0059] In a 1000 mL four-necked flask with thermometer and condenser, 0.5 mol of the compound shown in formula (III) above, 15.01 g (0.15 mol) of concentrated sulfuric acid, and 18.38 g (0.3 mol) of glacial acetic acid were sequentially added, and 426.42 g of 1,2-dichloroethane was added. The mixture was slowly heated to 70-80°C, and then 141.73 g (1.25 mol) of 30 wt% hydrogen peroxide was added dropwise. After the addition was completed, the reaction was maintained for 0.5 h. After the reaction was completed, the mixture was cooled to 40-50°C, and then the organic phase was separated by standing. Then, 1,2-dichloroethane was removed by distillation under normal pressure to obtain the compound shown in formula (I), i.e. 2-nitro-4-sulfinylbenzoic acid, with a purity of 90.57 wt% and a yield of 97.59% (based on the compound shown in formula (III));

[0060] The total yield of the reactions in steps (1)-(2) above was 51.37%.

[0061] Example 2

[0062] (1) Preparation of the compound shown in formula (III), wherein R2 is CH2CH3;

[0063] In a 1000 mL four-necked flask with thermometer and condenser, 114.81 g (0.5 mol) of the compound shown in formula II, wherein R1 is Cl and R2 is CH2CH3 (i.e., 4-chloro-2-nitrobenzoic acid ethyl ester), 460 g (2.0 mol) of DMSO were sequentially added, and the mixture was stirred and heated to 110-115°C. Then, 350.42 g (1.0 mol) of 20 wt% sodium thiomethoxide solution was slowly added dropwise. After the addition was completed, the mixture was kept at the same temperature for 1.5-2 h. After the reaction was completed, the DMSO was removed by distillation under reduced pressure to obtain the compound shown in formula (III), i.e., 2-nitro-4-methylthiobenzoic acid ethyl ester, with a purity of 92.37 wt% and a yield of 93.02% (based on the compound shown in formula (II));

[0064] (2) Preparation of the compound shown in formula (IV), wherein R2 is CH2CH3;

[0065] In a 1000 mL four-necked flask with thermometer and condenser, 114.81 g (0.5 mol) of the compound shown in formula II, wherein R1 is Cl and R2 is CH2CH3 (i.e., 4-chloro-2-nitrobenzoic acid ethyl ester), 460 g (2.0 mol) of DMSO were sequentially added, and the mixture was stirred and heated to 110-115°C. Then, 350.42 g (1.0 mol) of 20 wt% sodium thiomethoxide solution was slowly added dropwise. After the addition was completed, the mixture was kept at the same temperature for 1.5-2 h. After the reaction was completed, the DMSO was removed by distillation under reduced pressure to obtain the compound shown in formula (III), i.e., 2-nitro-4-methylthiobenzoic acid ethyl ester, with a purity of 92.37 wt% and a yield of 93.02% (based on the compound shown in formula (II));

[0066] (3) Preparation of the compound shown in formula (I);

[0067] In a 1000 mL four-necked flask with thermometer and condenser, 114.81 g (0.5 mol) of the compound shown in formula II, wherein R1 is Cl and R2 is CH2CH3 (i.e., 4-chloro-2-nitrobenzoic acid ethyl ester), 460 g (2.0 mol) of DMSO were sequentially added, and the mixture was stirred and heated to 110-115°C. Then, 350.42 g (1.0 mol) of 20 wt% sodium thiomethoxide solution was slowly added dropwise. After the addition was completed, the mixture was kept at the same temperature for 1.5-2 h. After the reaction was completed, the DMSO was removed by distillation under reduced pressure to obtain the compound shown in formula (III), i.e., 2-nitro-4-methylthiobenzoic acid ethyl ester, with a purity of 92.37 wt% and a yield of 93.02% (based on the compound shown in formula (II));

[0068] The total yield of the reactions in steps (1)-(3) above was 84.12%.

[0069] Example 3

[0070] (1) Preparation of the compound shown in formula (III), wherein R2 is CH2CH3;

[0071] In a 1000 mL four-necked flask with thermometer and condenser, 114.81 g (0.5 mol) of the compound shown in formula II, wherein R1 is Cl and R2 is CH2CH3 (i.e., 4-chloro-2-nitrobenzoic acid ethyl ester), 460 g (2.0 mol) of DMSO were sequentially added, and the mixture was stirred and heated to 110-115°C. Then, 385.47 g (1.1 mol) of 20 wt% sodium methanethiolate solution was slowly added dropwise. After the addition was completed, the mixture was kept at the same temperature for 1.5-2 h. After the reaction was completed, the DMSO was removed by distillation under reduced pressure to obtain the compound shown in formula (III), i.e., 2-nitro-4-methylthiobenzoic acid ethyl ester, with a purity of 93.06 wt% and a yield of 92.18% (based on the compound shown in formula (II));

[0072] (2) Preparation of the compound shown in formula (IV), wherein R2 is CH2CH3;

[0073] In a 1000 mL four-necked flask with thermometer and condenser, 114.81 g (0.5 mol) of the compound shown in formula II, wherein R1 is Cl and R2 is CH2CH3 (i.e., 4-chloro-2-nitrobenzoic acid ethyl ester), 460 g (2.0 mol) of DMSO were sequentially added, and the mixture was stirred and heated to 110-115°C. Then, 385.47 g (1.1 mol) of 20 wt% sodium methanethiolate solution was slowly added dropwise. After the addition was completed, the mixture was kept at the same temperature for 1.5-2 h. After the reaction was completed, the DMSO was removed by distillation under reduced pressure to obtain the compound shown in formula (III), i.e., 2-nitro-4-methylthiobenzoic acid ethyl ester, with a purity of 93.06 wt% and a yield of 92.18% (based on the compound shown in formula (II));

[0074] (3) Preparation of the compound shown in formula (I);

[0075] In a 1000 mL four-necked flask with thermometer and condenser, 114.81 g (0.5 mol) of the compound shown in formula II, wherein R1 is Cl and R2 is CH2CH3 (i.e., 4-chloro-2-nitrobenzoic acid ethyl ester), 460 g (2.0 mol) of DMSO were sequentially added, and the mixture was stirred and heated to 110-115°C. Then, 385.47 g (1.1 mol) of 20 wt% sodium methanethiolate solution was slowly added dropwise. After the addition was completed, the mixture was kept at the same temperature for 1.5-2 h. After the reaction was completed, the DMSO was removed by distillation under reduced pressure to obtain the compound shown in formula (III), i.e., 2-nitro-4-methylthiobenzoic acid ethyl ester, with a purity of 93.06 wt% and a yield of 92.18% (based on the compound shown in formula (II));

[0076] The total yield of the reactions in steps (1)-(3) above was 83.34%.

[0077] Example 4

[0078] (1) Preparation of the compound shown in formula (III), wherein R2 is CH2CH3;

[0079] In a 1000 mL four-necked flask with thermometer and condenser, 114.81 g (0.5 mol) of the compound shown in formula II, wherein R1 is Cl and R2 is CH2CH3 (i.e., 4-chloro-2-nitrobenzoic acid ethyl ester), 460 g (2.0 mol) of DMSO were sequentially added, and the mixture was stirred and heated to 110-115°C. Then, 315.38 g (0.9 mol) of 20 wt% sodium methanethiolate solution was slowly added dropwise. After the addition was completed, the mixture was kept at the same temperature for 1.5-2 h. After the reaction was completed, the DMSO was removed by distillation under reduced pressure to obtain the compound shown in formula (III), i.e., 2-nitro-4-methylthiobenzoic acid ethyl ester, with a purity of 92.75 wt% and a yield of 91.65% (based on the compound shown in formula (II));

[0080] (2) Preparation of the compound shown in formula (IV), wherein R2 is CH2CH3;

[0081] In a 1000 mL four-necked flask with thermometer and condenser, 114.81 g (0.5 mol) of the compound shown in formula II, wherein R1 is Cl and R2 is CH2CH3 (i.e., 4-chloro-2-nitrobenzoic acid ethyl ester), 460 g (2.0 mol) of DMSO were sequentially added, and the mixture was stirred and heated to 110-115°C. Then, 315.38 g (0.9 mol) of 20 wt% sodium methanethiolate solution was slowly added dropwise. After the addition was completed, the mixture was kept at the same temperature for 1.5-2 h. After the reaction was completed, the DMSO was removed by distillation under reduced pressure to obtain the compound shown in formula (III), i.e., 2-nitro-4-methylthiobenzoic acid ethyl ester, with a purity of 92.75 wt% and a yield of 91.65% (based on the compound shown in formula (II));

[0082] (3) Preparation of the compound shown in formula (I);

[0083] In a 1000 mL four-necked flask with thermometer and condenser, 114.81 g (0.5 mol) of the compound shown in formula II, wherein R1 is Cl and R2 is CH2CH3 (i.e., 4-chloro-2-nitrobenzoic acid ethyl ester), 460 g (2.0 mol) of DMSO were sequentially added, and the mixture was stirred and heated to 110-115°C. Then, 315.38 g (0.9 mol) of 20 wt% sodium methanethiolate solution was slowly added dropwise. After the addition was completed, the mixture was kept at the same temperature for 1.5-2 h. After the reaction was completed, the DMSO was removed by distillation under reduced pressure to obtain the compound shown in formula (III), i.e., 2-nitro-4-methylthiobenzoic acid ethyl ester, with a purity of 92.75 wt% and a yield of 91.65% (based on the compound shown in formula (II));

[0084] The total yield of the reactions in steps (1)-(3) above was 82.42%.

[0085] Example 5

[0086] The method of Example 2 was followed, except that in step (1),

[0087] The compound shown as formula (II) is replaced by 4-chloro-2-nitrobenzoic acid isopropyl ester, wherein R1 is Cl, R2 is CHCH3CH3, and the remaining conditions are the same, to obtain a compound shown as formula (III), that is, 2-nitro-4-methylthio benzoic acid isopropyl ester, with a purity of 90.62 wt% and a yield of 91.37% (based on the compound shown as formula (II));

[0088] The total yield of the reactions of steps (1)-(3) above is 82.62% under the same remaining steps.

[0089] Comparative Example 1

[0090] 2-nitro-4-methylsulfonylbenzoic acid is prepared according to the following process route:

[0091]

[0092] In a 500 mL reaction kettle with a self-suction stirrer, 32.28 g (0.15 mol) of 2-nitro-4-methylsulfonyl toluene, 258.24 g of 80 wt% sulfuric acid, 0.65 g of V2O5 catalyst are sequentially added, stirred and dissolved, connected to an oxygen tank, the system is sealed and slowly heated to 140-145°C, the oxygen content in the reaction liquid is about 20 vol%, 161.40 g of 65 wt% nitric acid is added dropwise within 5-6 h, the reaction system pressure is maintained at 0.08-0.1 MPa, and the reaction is maintained for 4.0 h. After sampling and analysis, the reaction is completed, the temperature is lowered to room temperature, filtered, the filter cake is washed with a large amount of water, and dried to obtain 2-nitro-4-methylsulfonyl benzoic acid solid 33.83 g with a purity of 90.21 wt% and a yield of 82.97%.

[0093] The following problems exist in the comparative example 1: (1) the catalyst vanadium pentoxide is a highly toxic, carcinogenic compound, which is expensive at 140,000 yuan / ton, the catalyst obtained by suction filtration is difficult to recycle and reuse, and the post-treatment is difficult; (2) the oxidant is nitric acid and oxygen, and the oxidation is carried out at high temperature, which is a flammable and explosive operation; (3) there is a possibility of explosion during continuous oxygen supply, and it is difficult to maintain stable pressure; (4) sulfuric acid is used as the solvent, and nitric acid is used as the oxidant, which will generate a large amount of waste acid water during post-treatment, which cannot be recycled and reused, and the water treatment system is difficult to handle, which puts a huge pressure on environmental protection. Therefore, it is not suitable for industrial production.

[0094] Compared with the comparative example 1, the method provided by the present application, that is, using the compound shown as formula (II) as a starting material, through steps (1)-(3), ultimately obtaining the target product, avoids defects such as harsh reaction conditions and high cost, has the advantages of mild conditions, high reaction yield and purity, and low cost, and is more suitable for industrial production.

[0095] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A process for the preparation of a mesotrione intermediate characterized in that, The method comprises the following steps: (1) a first reaction of a compound shown in formula (II) and sodium thiomethoxide in the presence of a first solvent to obtain a compound shown in formula (III), (I), (III); (2) a second reaction of the compound shown in formula (III) and hydrogen peroxide in the presence of a second solvent and under the action of a catalyst to obtain a compound shown in formula (IV), (IV); and (3) a third reaction of the compound shown in formula (IV) and an acid solution to obtain a mesotrione intermediate shown in formula (I), （I）； wherein R1 is selected from Cl; and R2 is selected from C1-C4 alkyl; wherein the amount of sodium thiomethoxide is 1.8-2.2 mol relative to 1 mol of the compound shown in formula (II); and the first reaction is performed under the conditions including a temperature of 100-120℃ and a time of 1.5-2h. wherein the catalyst is concentrated sulfuric acid and glacial acetic acid; the amount of hydrogen peroxide is 2.2-2.5 mol, the amount of concentrated sulfuric acid is 0.1-0.5 mol, and the amount of glacial acetic acid is 0.3-1 mol relative to 1 mol of the compound shown in formula (III); and the second reaction is performed under the conditions including a temperature of 70-80℃ and a time of 0.3-0.7h. wherein the third reaction is performed under the conditions including a temperature of 90-100℃ and a time of 2-3h.

2. The method of claim 1, wherein, R2 is selected from ethyl.

3. The method of claim 1, wherein, In step (1), the weight ratio of the compound shown in formula (II) to the first solvent is 1:3-5; and / or, in step (1), the first solvent is at least one selected from 1,2-dichloroethane, toluene, methanol, ethanol, tetrahydrofuran, acetonitrile, N,N-dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and 1,3-dimethyl-2-imidazolidinone.

4. The method of claim 3, wherein, In step (1), the weight ratio of the compound shown in formula (II) to the first solvent is 1:4-5; and / or, in step (1), the first solvent is at least one selected from N,N-dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide.

5. The method of claim 1, wherein, In step (2), the amount of concentrated sulfuric acid is 0.2-0.3 mol, and the amount of glacial acetic acid is 0.5-0.6 mol relative to 1 mol of the compound shown in formula (III).

6. The method of claim 1, wherein, The weight ratio of the compound shown in formula (III) to the second solvent is 1:3-5; and / or, the second solvent is at least one selected from 1,2-dichloroethane, toluene, dichloromethane, chloroform, trichloroethylene, and acetonitrile.

7. The method of claim 6, wherein, The weight ratio of the compound shown in formula (III) to the second solvent is 1:4-5; and / or, the second solvent is 1,2-dichloroethane.

8. The method according to any one of claims 1 to 7, characterized in that, In Step (3), the amount of the acid solution is 1-5 mol per 1 mol of the compound represented by formula (IV) with respect to H + . and / or, the acid solution is selected from a hydrochloric acid solution and / or a sulfuric acid solution; and / or, the acid concentration in the acid solution is 5-20wt%.

9. The method of claim 8, wherein, In Step (3), the amount of the acid solution is 2-4 mol per 1 mol of the compound represented by formula (IV) with respect to H + . and / or, the acid solution is a hydrochloric acid solution; and / or, the acid concentration in the acid solution is 10-15wt%.

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