Preparation method of mesotrione compounds

Abstract

The present invention relates to the field of herbicides, and discloses a method for preparing mesotrione compounds. The method comprises: 1) subjecting a compound having the structure shown in formula (1) to an acylation reaction with a chlorinating agent to obtain an acylation reaction product; 2) subjecting the acylation reaction product obtained in step 1) to an esterification reaction with a compound having the structure shown in formula (2) to obtain an esterification reaction product; 3) contacting the esterification reaction product obtained in step 2) with a rearrangement reagent having the structure shown in formula (4) to obtain a compound having the structure shown in formula (3). This method does not use cyanide-based rearrangement reagents, and has simple operation and low cost, and is very suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the field of herbicides, and particularly to a preparation method of mesotrione compounds. Background Art

[0002] Mesotrione is a broad-spectrum selective pre-emergence and post-emergence herbicide that can inhibit hydroxyphenylpyruvate dioxygenase (HPPD), and can effectively control major broad-leaved weeds and some gramineous weeds.

[0003] Currently, it is mainly prepared by the following synthetic route. This route uses 2-nitro-4-methylsulfonylbenzoic acid as the starting material, which is subjected to acyl chlorination, esterification, rearrangement, and then post-treatment to obtain mesotrione. During the rearrangement reaction process, a cyanide catalyst is used, which poses safety hazards during production and there are problems such as difficult treatment of the generated wastewater.

[0004]

[0005] In addition, CN108440352A uses an inorganic base + a tertiary amine organic base as a rearrangement agent, and CN113233998A uses a compound containing an unsaturated double bond to carry out a rearrangement reaction under the synergistic action of the double bonds. Although these methods avoid the use of highly toxic rearrangement catalysts, they increase the difficulty of post-treatment and purification of the reaction products, not only increasing the raw material cost but also causing difficulties in subsequent treatment. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above problems existing in the prior art, and provide a preparation method of mesotrione compounds. This method does not use cyanide rearrangement reagents, is simple in operation, low in cost, and is very suitable for industrial production.

[0007] To achieve the above purpose, the present invention provides a preparation method of mesotrione compounds, wherein the method includes the following steps.

[0008] 1) React a compound having the structure shown in formula (1) with a chlorinating agent to carry out an acyl chlorination reaction to obtain an acyl chlorination reaction product;

[0009] 2) React the acyl chlorination reaction product obtained in step 1) with a compound having the structure shown in formula (2) to carry out an esterification reaction to obtain an esterification reaction product;

[0010] 3) Contact the esterification reaction product obtained in step 2) with a rearrangement reagent having the structure shown in formula (4) to obtain a compound having the structure shown in formula (3).

[0011]

[0012] In the formula, R1 - R6 each independently represent hydrogen or an alkyl group having 1 - 3 carbon atoms;

[0013] A represents an alkylene group having 1 to 3 carbon atoms;

[0014] R7 is an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms;

[0015] R8 is hydrogen, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms;

[0016] R9 is hydrogen, an alkyl group having 1 to 6 carbon atoms, an aryl group having 1 to 6 carbon atoms or a hydroxyalkyl group having 1 to 6 carbon atoms;

[0017] X is a chloride ion or a bromide ion.

[0018] Preferably, the rearrangement reagent is one or more of 3-benzyl-5-(2-hydroxyethyl)-4-methylthiazolium chloride, 3-ethyl-5-(2-hydroxyethyl)-4-methylthiazolium bromide, 3-ethylthiazolium bromide, 3,5-diethyl-4-methylthiazolium bromide, and 4,5-dimethyl-3-(2-oxo-2-phenylethyl)thiazolium chloride.

[0019] Preferably, in step 1), the acyl chlorination reaction is carried out in the presence of an aprotic solvent and a catalyst.

[0020] Preferably, the aprotic solvent is one or more of 1,2-dichloroethane, toluene, ethyl acetate, dichloromethane, n-hexane, chloroform, and acetonitrile.

[0021] Preferably, relative to 1 mole of the compound having the structure shown in formula (1), the amount of the aprotic solvent used is 50 - 500 mL.

[0022] Preferably, the catalyst is one or more of triethylamine, N,N-dimethylformamide, pyridine, 3-aminopyridine, potassium carbonate, sodium carbonate, sodium acetate, sodium hydroxide, and potassium hydroxide.

[0023] Preferably, relative to 1 mole of the compound having the structure shown in formula (1), the amount of the catalyst used is 0.01 - 0.5 mol.

[0024] Preferably, the chlorinating agent is one or more of solid phosgene, thionyl chloride, phosphorus pentachloride, phosphorus trichloride, and diphosgene.

[0025] Preferably, relative to 1 mole of the compound having the structure shown in formula (1), the amount of the chlorinating agent used is 1 - 5 mol.

[0026] Preferably, in step 1), the conditions of the acyl chlorination reaction include: the reaction temperature is 60 - 90 °C, and the reaction time is 60 - 240 minutes.

[0027] Preferably, in step 2), the compound having the structure shown in formula (2) is added to the acyl chloride reaction product obtained in step 1) to carry out the esterification reaction.

[0028] Preferably, relative to 1 mole of the compound having the structure shown in formula (1), the amount of the compound having the structure shown in formula (2) used is 1 - 3 mol.

[0029] Preferably, in step 2), the esterification reaction is carried out in the presence of an acid-binding agent.

[0030] Preferably, the acid-binding agent is one or more of triethylamine, N,N-dimethylformamide, pyridine, 3-aminopyridine, potassium carbonate, sodium carbonate, sodium acetate, sodium hydroxide, and potassium hydroxide.

[0031] Preferably, relative to 1 mole of the compound having the structure shown in formula (1), the amount of the acid-binding agent used is 1 - 5 mol.

[0032] Preferably, in step 2), the conditions of the esterification reaction include: the reaction temperature is 10 - 45 °C, and the reaction time is 0.5 - 5 hours.

[0033] Preferably, in step 3), the rearrangement reagent having the structure shown in formula (4) is added to the esterification reaction product obtained in step 2) to carry out the rearrangement reaction.

[0034] Preferably, the amount of the rearrangement reagent used is 0.1 - 10% by weight of the compound having the structure shown in formula (1).

[0035] Preferably, in step 3), the conditions of the contact include: the contact temperature is 10 - 45 °C, and the contact time is 1 - 10 hours.

[0036] Preferably, the method further includes a step of acidifying the reaction product obtained in step 3) with an acidic aqueous solution.

[0037] According to the method of the present invention, it does not use a cyanide-based rearrangement reagent, and has simple operation and low cost, and is very suitable for industrial production. Detailed embodiments

[0038] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0039] The present invention provides a method for preparing a mesotrione compound, wherein the method includes the following steps,

[0040] 1) React the compound of the structure shown in formula (1) with a chlorinating agent to obtain an acylation reaction product;

[0041] 2) React the acylation reaction product obtained in step 1) with the compound of the structure shown in formula (2) to obtain an esterification reaction product;

[0042] 3) Contact the esterification reaction product obtained in step 2) with a rearrangement reagent of the structure shown in formula (4) to obtain a compound of the structure shown in formula (3),

[0043]

[0044] In the formula, R1-R6 each independently represent hydrogen or an alkyl group having 1-3 carbon atoms;

[0045] A represents an alkylene group having 1-3 carbon atoms;

[0046] R7 is an alkyl group having 1-6 carbon atoms or an aryl group having 6-10 carbon atoms;

[0047] R8 is hydrogen, an alkyl group having 1-6 carbon atoms or an aryl group having 6-10 carbon atoms;

[0048] R9 is hydrogen, an alkyl group having 1-6 carbon atoms, an aryl group having 1-6 carbon atoms or a hydroxyalkyl group having 1-6 carbon atoms;

[0049] X is a chloride ion or a bromide ion.

[0050] In the present invention, examples of the alkyl group having 1-3 carbon atoms include: methyl, ethyl, propyl, etc.

[0051] In the present invention, examples of the alkylene group having 1-3 carbon atoms include: methylene, ethylene, propylene, etc.

[0052] In the present invention, examples of the alkyl group having 1-6 carbon atoms include: methyl, ethyl, propyl, butyl, pentyl, hexyl, etc.

[0053] In the present invention, examples of the aryl group having 6-10 carbon atoms include: phenyl, benzyl, phenethyl, o-tolyl, 1-naphthyl (or α-naphthyl), 2-naphthyl, etc.

[0054] In the present invention, examples of the hydroxyalkyl group having 1-6 carbon atoms include: hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl, hydroxyhexyl, etc.

[0055] According to the present invention, preferably, R1-R6 represent hydrogen.

[0056] According to the present invention, preferably, A represents methylene.

[0057] In a preferred embodiment of the present invention, the compound of the structure shown in formula (1) is

[0058] In a preferred embodiment of the present invention, the compound of the structure shown in formula (2) is

[0059] In a preferred embodiment of the present invention, the compound of the structure shown in formula (3) is

[0060] In a preferred embodiment of the present invention, the rearrangement reagent of the structure shown in formula (4) is one or more of 3-benzyl-5-(2-hydroxyethyl)-4-methyl thiazolium chloride, 3-ethyl-5-(2-hydroxyethyl)-4-methyl thiazolium bromide, 3-ethyl thiazolium bromide, 3,5-diethyl-4-methyl thiazolium bromide, and 4,5-dimethyl-3-(2-oxo-2-phenylethyl) thiazolium chloride; preferably, the rearrangement reagent of the structure shown in formula (4) is one or more of 3-benzyl-5-(2-hydroxyethyl)-4-methyl thiazolium chloride, 3-ethyl thiazolium bromide, and 3,5-diethyl-4-methyl thiazolium bromide.

[0061] According to the present invention, preferably, in step 1), the acyl chlorination reaction is carried out in the presence of an aprotic solvent and a catalyst. The aprotic solvent is preferably one or more of 1,2-dichloroethane, toluene, ethyl acetate, dichloromethane, n-hexane, chloroform, and acetonitrile; more preferably, the aprotic solvent is 1,2-dichloroethane.

[0062] According to the present invention, the amount of the aprotic solvent can be selected according to the amount of the compound of the structure shown in formula (1). Preferably, relative to 1 mole of the compound of the structure shown in formula (1), the amount of the aprotic solvent is 50-500 mL; more preferably, relative to 1 mole of the compound of the structure shown in formula (1), the amount of the aprotic solvent is 100-200 mL.

[0063] According to the present invention, preferably, the catalyst is one or more of triethylamine, N,N-dimethylformamide, pyridine, 3-aminopyridine, potassium carbonate, sodium carbonate, sodium acetate, sodium hydroxide, and potassium hydroxide; more preferably, the catalyst is one or more of triethylamine, N,N-dimethylformamide, and pyridine.

[0064] According to the present invention, the dosage of the catalyst can be selected according to the dosage of the compound having the structure shown in formula (1). Preferably, relative to 1 mole of the compound having the structure shown in formula (1), the dosage of the catalyst is 0.01 - 0.5 mol; more preferably, relative to 1 mole of the compound having the structure shown in formula (1), the dosage of the catalyst is 0.01 - 0.1 mol.

[0065] According to the present invention, the chlorinating agent is various reagents commonly used for acyl chlorination in the art. Preferably, the chlorinating agent is one or more of triphosgene, thionyl chloride, phosphorus pentachloride, phosphorus trichloride, and diphosgene; more preferably, the chlorinating agent is thionyl chloride.

[0066] According to the present invention, the dosage of the chlorinating agent can be selected according to the dosage of the compound having the structure shown in formula (1). Preferably, relative to 1 mole of the compound having the structure shown in formula (1), the dosage of the chlorinating agent is 1 - 5 mol; more preferably, relative to 1 mole of the compound having the structure shown in formula (1), the dosage of the chlorinating agent is 1.05 - 2 mol.

[0067] According to the present invention, in step 1), the conditions for the acyl chlorination reaction may include: the reaction temperature is 60 - 90 °C, and the reaction time is 60 - 240 minutes. Preferably, the acyl chlorination reaction is carried out under reflux conditions.

[0068] According to the present invention, after the acyl chlorination reaction is completed, preferably, the compound having the structure shown in formula (2) is added to the acyl chlorination reaction product obtained in step 1) to carry out the esterification reaction.

[0069] According to the present invention, since the acyl chlorination reaction proceeds almost completely, therefore, the dosage of the compound having the structure shown in formula (2) can be selected according to the dosage of the compound having the structure shown in formula (1). Preferably, relative to 1 mole of the compound having the structure shown in formula (1), the dosage of the compound having the structure shown in formula (2) is 1 - 3 mol; more preferably, relative to 1 mole of the compound having the structure shown in formula (1), the dosage of the compound having the structure shown in formula (2) is 1 - 2 mol; further preferably, relative to 1 mole of the compound having the structure shown in formula (1), the dosage of the compound having the structure shown in formula (3) is 1 - 1.5 mol; further preferably, relative to 1 mole of the compound having the structure shown in formula (1), the dosage of the compound having the structure shown in formula (3) is 1 - 1.2 mol.

[0070] According to the present invention, in order to enable the esterification reaction to proceed sufficiently, preferably, in step 2), the esterification reaction is carried out in the presence of an acid-binding agent. As the acid-binding agent, various basic reagents commonly used for acid-binding in the art can be used, for example, it can be one or more of triethylamine, N,N-dimethylformamide, pyridine, 3-aminopyridine, potassium carbonate, sodium carbonate, sodium acetate, sodium hydroxide, and potassium hydroxide, and preferably triethylamine.

[0071] According to the present invention, preferably, relative to 1 mole of the compound having the structure shown in formula (1), the amount of the acid-binding agent used is 1 - 5 mol; more preferably, relative to 1 mole of the compound having the structure shown in formula (1), the amount of the acid-binding agent used is 1.5 - 3 mol.

[0072] According to the present invention, in step 2), the conditions of the esterification reaction include: the reaction temperature is 10 - 45 °C, and the reaction time is 1 - 10 hours, preferably 1 - 6 hours.

[0073] According to the present invention, preferably, in step 3), the rearrangement reagent having the structure shown in formula (4) is added to the esterification reaction product obtained in step 2) for a rearrangement reaction.

[0074] In the present invention, the amount of the rearrangement reagent used can be selected according to the amount of the compound having the structure shown in formula (1). Preferably, the amount of the rearrangement reagent used is 0.1 - 10% by weight of the compound having the structure shown in formula (1); more preferably, the amount of the rearrangement reagent used is 0.2 - 8% by weight of the compound having the structure shown in formula (1); more preferably, the amount of the rearrangement reagent used is 0.5 - 5% by weight of the compound having the structure shown in formula (1); more preferably, the amount of the rearrangement reagent used is 0.5 - 2% by weight of the compound having the structure shown in formula (1); more preferably, the amount of the rearrangement reagent used is 0.5 - 1.5% by weight of the compound having the structure shown in formula (1); more preferably, the amount of the rearrangement reagent used is 0.8 - 1.2% by weight of the compound having the structure shown in formula (1).

[0075] According to the present invention, in step 3), the conditions of the contact include: the contact temperature is 10 - 45 °C, and the contact time is 1 - 10 hours, preferably 1 - 6 hours.

[0076] According to the present invention, after the rearrangement reaction is completed, the post-treatment is extremely simple. Only after acidifying the reaction product obtained in step 3) with an acidic aqueous solution, separating the organic phase, and removing the solvent, the target product can be obtained with high purity and high yield.

[0077] The present invention will be described in detail below by way of examples, but the present invention is not limited to the following examples.

[0078] Example 1

[0079] Into a four-necked reaction flask, add 25 g of 2-nitro-4-methylsulfonylbenzoic acid, 125 ml of 1,2-dichloroethane, and 0.05 g of N,N-dimethylformamide. Heat to reflux, and dropwise add 13.35 g of thionyl chloride. After the addition is complete, reflux and react for 2 hours to obtain 2-nitro-4-methylsulfonylbenzoyl chloride. Cool to 10 °C, add 12 g of 1,3-cyclohexanedione, and dropwise add 22.4 g of triethylamine. After the addition is complete, keep the temperature at 10 - 20 °C and react for 1 hour. Then add 0.3 g of 3-benzyl-5-(2-hydroxyethyl)-4-methylthiazolium chloride, and keep the temperature at 20 - 25 °C and react for 4 hours. Add water, acidify with hydrochloric acid, separate the layers, and remove the solvent to obtain mesotrione (the structure is confirmed as mesotrione by NMR and mass spectrometry), with a content of 98.5% and a yield of 91.38%.

[0080] Example 2

[0081] Into a four-necked reaction flask, add 25 g of 2-nitro-4-methylsulfonylbenzoic acid, 125 ml of 1,2-dichloroethane, and 0.05 g of N,N-dimethylformamide. Heat to reflux, and dropwise add 13.35 g of thionyl chloride. After the addition is complete, reflux and react for 2 hours to obtain 2-nitro-4-methylsulfonylbenzoyl chloride. Cool to 10 °C, add 12 g of 1,3-cyclohexanedione, and dropwise add 22.4 g of triethylamine. After the addition is complete, keep the temperature at 10 - 20 °C and react for 1 hour. Then add 0.2 g of 3-ethylthiazolium bromide, and keep the temperature at 25 - 30 °C and react for 6 hours. Add water, acidify with hydrochloric acid, separate the layers, and remove the solvent to obtain mesotrione, with a content of 98.25% and a yield of 90.12%.

[0082] Example 3

[0083] Into a four-necked reaction flask, add 25 g of 2-nitro-4-methylsulfonylbenzoic acid, 125 ml of 1,2-dichloroethane, and 0.05 g of N,N-dimethylformamide. Heat to reflux, and dropwise add 13.35 g of thionyl chloride. After the addition is complete, reflux and react for 2 hours to obtain 2-nitro-4-methylsulfonylbenzoyl chloride. Cool to 10 °C, add 12 g of 1,3-cyclohexanedione, and dropwise add 22.4 g of triethylamine. After the addition is complete, keep the temperature at 10 - 20 °C and react for 1 hour. Then add 0.24 g of 3,5-diethyl-4-methylthiazolium bromide, and keep the temperature at 25 - 30 °C and react for 6 hours. Add water, acidify with hydrochloric acid, separate the layers, and remove the solvent to obtain mesotrione, with a content of 98.13% and a yield of 90.31%.

[0084] Example 4

[0085] Into a four-necked reaction flask, add 25 g of 2-nitro-4-methylsulfonylbenzoic acid, 125 ml of 1,2-dichloroethane, and 0.05 g of N,N-dimethylformamide. Heat to reflux, and dropwise add 13.35 g of thionyl chloride. After the addition is complete, reflux and react for 2 hours to obtain 2-nitro-4-methylsulfonylbenzoyl chloride. Cool to 10 °C, add 12 g of 1,3-cyclohexanedione, and dropwise add 22.4 g of triethylamine. After the addition is complete, keep the temperature and react for 1 hour, then add 0.25 g of 3-ethyl-5-(2-hydroxyethyl)-4-methylthiazolium bromide. Keep the temperature at 25 - 30 °C and react for 6 hours. Add water, acidify with hydrochloric acid, separate the layers, and remove the solvent to obtain mesotrione with a content of 98.03% and a yield of 90.11%.

[0086] Example 5

[0087] Into a four-necked reaction flask, add 25 g of 2-nitro-4-methylsulfonylbenzoic acid, 125 ml of 1,2-dichloroethane, and 0.05 g of N,N-dimethylformamide. Heat to reflux, and dropwise add 13.35 g of thionyl chloride. After the addition is complete, reflux and react for 2 hours to obtain 2-nitro-4-methylsulfonylbenzoyl chloride. Cool to 10 °C, add 12 g of 1,3-cyclohexanedione, and dropwise add 22.4 g of triethylamine. After the addition is complete, keep the temperature and react for 1 hour, then add 0.2 g of 4,5-dimethyl-3-(2-oxo-2-phenylethyl)thiazolium chloride. Keep the temperature at 25 - 30 °C and react for 6 hours. Add water, acidify with hydrochloric acid, separate the layers, and remove the solvent to obtain mesotrione with a content of 98.08% and a yield of 90.07%.

[0088] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A preparation method of mesotrione compounds, characterized in that, The method comprises the following steps: 1) Subjecting the compound of the structure shown in formula (1) to an acyl chlorination reaction with a chlorinating agent to obtain an acyl chlorination reaction product; 2) Subjecting the acyl chlorination reaction product obtained in step 1) to an esterification reaction with the compound of the structure shown in formula (2) to obtain an esterification reaction product; 3) Contacting the esterification reaction product obtained in step 2) with a rearrangement reagent of the structure shown in formula (4) to obtain a compound of the structure shown in formula (3), wherein R1-R6 each independently represent hydrogen or an alkyl group having 1-3 carbon atoms; A represents an alkylene group having 1-3 carbon atoms; R7 is an alkyl group having 1-6 carbon atoms or an aryl group having 6-10 carbon atoms; R8 is hydrogen, an alkyl group having 1-6 carbon atoms or an aryl group having 6-10 carbon atoms; R9 is hydrogen, an alkyl group having 1-6 carbon atoms, an aryl group having 1-6 carbon atoms or a hydroxyalkyl group having 1-6 carbon atoms; X is a chloride ion or a bromide ion.

2. The method according to claim 1, wherein The rearrangement reagent is one or more of 3-benzyl-5-(2-hydroxyethyl)-4-methyl thiazolium chloride, 3-ethyl-5-(2-hydroxyethyl)-4-methyl thiazolium bromide, 3-ethyl thiazolium bromide, 3,5-diethyl-4-methyl thiazolium bromide, and 4,5-dimethyl-3-(2-oxo-2-phenylethyl) thiazolium chloride.

3. The method according to claim 1, wherein, In step 1), the acyl chlorination reaction is carried out in the presence of an aprotic solvent and a catalyst.

4. The method according to claim 3, wherein, The aprotic solvent is one or more of 1,2-dichloroethane, toluene, ethyl acetate, dichloromethane, n-hexane, chloroform, and acetonitrile.

5. The method according to claim 3, wherein Relative to 1 mole of the compound of the structure shown in formula (1), the amount of the aprotic solvent used is 50-500 mL.

6. The method according to claim 3, wherein, The catalyst is one or more of triethylamine, N,N-dimethylformamide, pyridine, 3-aminopyridine, potassium carbonate, sodium carbonate, sodium acetate, sodium hydroxide, and potassium hydroxide.

7. The method according to claim 3, wherein Relative to 1 mole of the compound of the structure shown in formula (1), the amount of the catalyst used is 0.01-0.5 mol.

8. The method according to claim 3, wherein, The chlorinating agent is one or more of solid phosgene, thionyl chloride, phosphorus pentachloride, phosphorus trichloride, and diphosgene.

9. The method according to claim 3, wherein Relative to 1 mole of the compound of the structure shown in formula (1), the amount of the chlorinating agent used is 1-5 mol.

10. The method according to any one of claims 1-9, wherein In step 1), the conditions of the acyl chlorination reaction include: the reaction temperature is 60-90 °C, and the reaction time is 60-240 minutes.

11. The method according to any one of claims 1-9, wherein, In step 2), the compound of the structure shown in formula (2) is added to the acyl chlorination reaction product obtained in step 1) to carry out the esterification reaction.

12. The method according to claim 11, wherein, Relative to 1 mole of the compound of the structure shown in formula (1), the amount of the compound of the structure shown in formula (2) used is 1-3 mol.

13. The method according to any one of claims 1-9, wherein, In step 2), the esterification reaction is carried out in the presence of an acid-binding agent.

14. The method according to claim 13, wherein, The acid-binding agent is one or more of triethylamine, N,N-dimethylformamide, pyridine, 3-aminopyridine, potassium carbonate, sodium carbonate, sodium acetate, sodium hydroxide, and potassium hydroxide.

15. The method according to claim 13, wherein, Relative to 1 mole of the compound of the structure shown in formula (1), the amount of the acid-binding agent used is 1-5 mol.

16. The method according to any one of claims 1-9, wherein, In step 2), the conditions of the esterification reaction include: the reaction temperature is 10-45 °C, and the reaction time is 0.5-5 hours.

17. The method according to any one of claims 1-9, wherein, In step 3), a rearrangement reagent having the structure shown in formula (4) is added to the esterification reaction product obtained in step 2) to carry out a rearrangement reaction.

18. The method according to claim 17, wherein, The dosage of the rearrangement reagent is 0.1-10% by weight of the compound having the structure shown in formula (1).

19. The method according to any one of claims 1-9, wherein In step 3), the conditions for the contact include: the temperature of the contact is 10-45 °C, and the contact time is 1-10 hours.

20. The method according to any one of claims 1-9, wherein, This method further includes a step of acidifying the reaction product obtained in step 3) with an acidic aqueous solution.

Images