阅读说明：本技术 一种2-氨基-3-甲基-5-氯苯甲酸的制备方法 (Preparation method of 2-amino-3-methyl-5-chlorobenzoic acid ) 是由 王栋伟 赵宏洋 王诚 刘涛 于 2020-12-30 设计创作，主要内容包括：本发明属于有机合成技术领域,具体涉及一种2-氨基-3-甲基-5-氯苯甲酸的制备方法。本发明提供的制备方法将间甲基苯甲酸和硝酸混合,进行硝化反应,得到2-硝基-3-甲基苯甲酸；所述硝酸的质量浓度为60～75％,将所述2-硝基-3-甲基苯甲酸、加氢还原反应溶剂和加氢催化剂混合,在氢气气氛中进行加氢还原反应,得到2-氨基-3-甲基苯甲酸；将所述2-氨基-3-甲基苯甲酸、氯代试剂、过氧化苯甲酰和氯化反应溶剂混合,进行氯化反应,得到2-氨基-3-甲基-5-氯苯甲酸。本发明提供的制备方法反应原料廉价易得,产品的收率高且纯度高,易于工业化生产。(The invention belongs to the technical field of organic synthesis, and particularly relates to a preparation method of 2-amino-3-methyl-5-chlorobenzoic acid. The preparation method provided by the invention mixes m-toluic acid and nitric acid to carry out nitration reaction to obtain 2-nitro-3-toluic acid; the mass concentration of the nitric acid is 60-75%, the 2-nitro-3-methylbenzoic acid, a hydrogenation reduction reaction solvent and a hydrogenation catalyst are mixed, and a hydrogenation reduction reaction is carried out in a hydrogen atmosphere to obtain 2-amino-3-methylbenzoic acid; mixing the 2-amino-3-methylbenzoic acid, a chlorination reagent, benzoyl peroxide and a chlorination reaction solvent, and carrying out chlorination reaction to obtain the 2-amino-3-methyl-5-chlorobenzoic acid. The preparation method provided by the invention has the advantages of cheap and easily available reaction raw materials, high product yield and high product purity, and is easy for industrial production.)

1. A preparation method of 2-amino-3-methyl-5-chlorobenzoic acid is characterized by comprising the following steps:

mixing m-toluic acid and nitric acid, and carrying out nitration reaction to obtain 2-nitro-3-toluic acid, wherein the mass concentration of the nitric acid is 60-75%;

mixing the 2-nitro-3-methylbenzoic acid, a hydrogenation reduction reaction solvent and a hydrogenation catalyst, and carrying out hydrogenation reduction reaction in a hydrogen atmosphere to obtain 2-amino-3-methylbenzoic acid;

mixing the 2-amino-3-methylbenzoic acid, a chlorination reagent, benzoyl peroxide and a chlorination reaction solvent, and carrying out chlorination reaction to obtain the 2-amino-3-methyl-5-chlorobenzoic acid.

2. The method according to claim 1, wherein the volume ratio of the m-toluic acid to the nitric acid is 1g: (3-5) mL.

3. The preparation method according to claim 1 or 2, wherein the temperature of the nitration reaction is 0 to-20 ℃ and the time is 1 to 2 hours.

4. The method of claim 1, wherein the hydrogenation catalyst comprises one or more of Pd/C, Pt/C and Raney nickel;

the mass of the hydrogenation catalyst is 3-7% of that of the 2-nitro-3-methylbenzoic acid.

5. The production method according to claim 1, wherein the hydrogenation-reduction reaction solvent is one or more of ethanol, methanol, and tetrahydrofuran;

the volume ratio of the mass of the 2-nitro-3-methylbenzoic acid to the volume of the hydrogenation reduction reaction solvent is 1g (2-4) mL.

6. The preparation method according to claim 1, 4 or 5, wherein the temperature of the hydrogenation reduction reaction is 40-60 ℃ and the time is 2-3 h.

7. The process according to claim 1, wherein the chlorinating reagent is N-chlorosuccinimide or dichlorohydantoin.

8. The production method according to claim 1 or 7, characterized in that the amounts of the substances of 2-amino-3-methylbenzoic acid and chlorinating agent are in a ratio of 1: (0.5 to 1.2);

the mass of the benzoyl peroxide is 1-2% of the mass of the 2-amino-3-methylbenzoic acid.

9. The production method according to claim 1, wherein the chlorination reaction solvent is one or more of N, N-dimethylformamide, N-dimethylacetamide, sulfolane, and DMSO;

the volume ratio of the mass of the 2-amino-3-methylbenzoic acid to the volume of the chlorination reaction solvent is 1g: 3-5 mL.

10. The preparation method according to claim 1 or 9, wherein the chlorination reaction is carried out at a temperature of 90-110 ℃ for 1-2 hours.

Technical Field

The invention belongs to the technical field of organic synthesis, and particularly relates to a preparation method of 2-amino-3-methyl-5-chlorobenzoic acid.

Background

The chlorantraniliprole pesticide is a broad-spectrum pesticide, is mainly used for preventing and controlling lepidoptera pests of various crops, has a good prevention effect on other pests, and has the action mechanism of activating ryanodine receptors, releasing calcium stored in smooth muscle cells and striated muscle cells, causing muscle conditioning weakness and paralysis until the pests die, and the action mode is stomach toxicity and contact toxicity. The chlorantraniliprole is named as 3-bromo-N- [ 4-chloro-2-methyl-6- [ (methylcarbamoyl) benzene]-1- (3-chloropyridin-2-yl) -1H-pyrazole-5-carboxamide, common name in english: chloratraniniprole, CAS registry number: 500008-45-7, molecular formula: c₁₈H₁₄BrCl₂N₅O₂Relative molecular mass: 483.1, having the following chemical formula:

the preparation of 2-amino-3-methyl-5-chlorobenzoic acid, a key intermediate of chlorantraniliprole, has the following preparation methods reported at present:

the first method comprises the following steps: taking 7-methylindole-2, 3-diketone as a raw material, dropwise adding hydrogen peroxide into a sodium hydroxide aqueous solution to obtain 2-amino-3-methylbenzoic acid, adding NCS into a DMF solution dissolved with the 2-amino-3-methylbenzoic acid, heating a reaction solution to 100 ℃, and reacting for 40 minutes to obtain the 2-amino-3-methyl-5-chlorobenzoic acid. The method has the advantages that the price of the raw material 7-methylindole-2, 3-diketone is high, the chlorination reaction has large demand on hydrogen peroxide, the temperature is required to be 0 ℃ when the hydrogen peroxide is dripped, the reaction liquid is heated to 50 ℃ after the dripping is finished, the energy consumption is high, and the yield is low. The reaction equation is as follows:

and the second method comprises the following steps: the preparation method comprises the steps of introducing chlorine into a mixed solution of 7-methylindole-2, 3-diketone and chloroform to react for 24 hours by taking the 7-methylindole-2, 3-diketone as a raw material, carrying out ice bath to obtain 5-chloro-7-methylindole-2, 3-diketone, adding the 5-chloro-7-methylindole-2, 3-diketone into a sodium hydroxide solution, stirring for half an hour, dropwise adding a mixed solution of hydrogen peroxide and a sodium hydroxide aqueous solution, and reacting for 1.5 hours to obtain the 2-amino-3-methyl-5-chlorobenzoic acid. The raw material 7-methylindole-2, 3-diketone used in the method has high price, and chlorine gas is introduced to cause great pollution to the environment, the reaction time is too long, and the yield is low. The reaction equation is as follows:

disclosure of Invention

In view of the above, the invention provides a preparation method of 2-amino-3-methyl-5-chlorobenzoic acid, and the preparation method provided by the invention has the advantages of high yield of 2-amino-3-methyl-5-chlorobenzoic acid, easily available and low-priced reaction raw materials, short reaction time and environmental protection.

The invention provides a preparation method of 2-amino-3-methyl-5-chlorobenzoic acid, which comprises the following steps:

mixing m-toluic acid and nitric acid, and carrying out nitration reaction to obtain 2-nitro-3-toluic acid, wherein the mass concentration of the nitric acid is 60-75%;

mixing the 2-nitro-3-methylbenzoic acid, a hydrogenation reduction reaction solvent and a hydrogenation catalyst, and carrying out hydrogenation reduction reaction in a hydrogen atmosphere to obtain 2-amino-3-methylbenzoic acid;

mixing the 2-amino-3-methylbenzoic acid, a chlorination reagent, benzoyl peroxide and a chlorination reaction solvent, and carrying out chlorination reaction to obtain the 2-amino-3-methyl-5-chlorobenzoic acid.

Preferably, the volume ratio of the mass of the m-toluic acid to the nitric acid is 1g: (3-5) mL.

Preferably, the temperature of the nitration reaction is 0-20 ℃ below zero, and the time is 1-2 h.

Preferably, the hydrogenation catalyst comprises one or more of Pd/C, Pt/C and Raney nickel;

the mass of the hydrogenation catalyst is 3-7% of that of the 2-nitro-3-methylbenzoic acid.

Preferably, the hydrogenation reduction reaction solvent is one or more of ethanol, methanol and tetrahydrofuran;

the volume ratio of the mass of the 2-nitro-3-methylbenzoic acid to the volume of the hydrogenation reduction reaction solvent is 1g (2-4) mL.

Preferably, the temperature of the hydrogenation reduction reaction is 40-60 ℃, and the time is 2-3 h.

Preferably, the chlorinating reagent is N-chlorosuccinimide or dichlorohydantoin.

Preferably, the mass ratio of the 2-amino-3-methylbenzoic acid to the chlorinating agent is 1: (0.5 to 1.2);

the mass of the benzoyl peroxide is 1-2% of the mass of the 2-amino-3-methylbenzoic acid.

Preferably, the chlorination reaction solvent is one or more of N, N-dimethylformamide, N-dimethylacetamide, sulfolane and DMSO;

the volume ratio of the mass of the 2-amino-3-methylbenzoic acid to the volume of the chlorination reaction solvent is 1g: 3-5 mL.

Preferably, the temperature of the chlorination reaction is 90-110 ℃, and the time is 1-2 h.

The invention provides a preparation method of 2-amino-3-methyl-5-chlorobenzoic acid, which comprises the following steps: mixing m-toluic acid and nitric acid, and carrying out nitration reaction to obtain 2-nitro-3-toluic acid, wherein the mass concentration of the nitric acid is 60-75%; mixing the 2-nitro-3-methylbenzoic acid, a hydrogenation reduction reaction solvent and a hydrogenation catalyst, and carrying out hydrogenation reduction reaction in a hydrogen atmosphere to obtain 2-amino-3-methylbenzoic acid; mixing the 2-amino-3-methylbenzoic acid, a chlorination reagent, benzoyl peroxide and a chlorination reaction solvent, and carrying out chlorination reaction to obtain the 2-amino-3-methyl-5-chlorobenzoic acid. The preparation method provided by the invention uses m-methylbenzoic acid as a raw material, and obtains the 2-amino-3-methyl-5-chlorobenzoic acid only through a nitration reaction, a hydrogenation reduction reaction and a chlorination reaction in sequence, the reaction raw materials of the preparation method provided by the invention are cheap and easy to obtain, the product is high in yield and good in quality, and industrial production is easy to realize, and the results of the embodiment show that the total yield of the 2-amino-3-methyl-5-chlorobenzoic acid obtained by the preparation method provided by the invention is 63.0-68.4%, the melting point is 238-243 ℃, and the purity is 99.0-99.5%.

Drawings

FIG. 1 is a schematic diagram of the process for preparing 2-amino-3-methyl-5-chlorobenzoic acid according to the present invention.

Detailed Description

The invention provides a preparation method of 2-amino-3-methyl-5-chlorobenzoic acid, which comprises the following steps:

mixing m-toluic acid and nitric acid, and carrying out nitration reaction to obtain 2-nitro-3-toluic acid, wherein the mass concentration of the nitric acid is 60-75%;

mixing the 2-nitro-3-methylbenzoic acid, a hydrogenation reduction reaction solvent and a hydrogenation catalyst, and carrying out hydrogenation reduction reaction in a hydrogen atmosphere to obtain 2-amino-3-methylbenzoic acid;

mixing the 2-amino-3-methylbenzoic acid, a chlorination reagent, benzoyl peroxide and a chlorination reaction solvent, and carrying out chlorination reaction to obtain the 2-amino-3-methyl-5-chlorobenzoic acid.

In the present invention, the starting materials are all commercially available products well known to those skilled in the art, unless otherwise specified.

The method takes m-methylbenzoic acid as a raw material, and sequentially carries out nitration reaction, hydrogenation reduction reaction and chlorination reaction to obtain the 2-amino-3-methyl-5-chlorobenzoic acid, wherein the reaction flow chart is shown in figure 1.

M-toluic acid and nitric acid are mixed and subjected to nitration reaction to obtain 2-nitro-3-toluic acid; in the invention, the mass concentration of the nitric acid is 60-75%, preferably 63.5-70%; the volume ratio of the mass of the m-toluic acid to the nitric acid is preferably 1g: (3-5) mL, more preferably 1g:4 mL. In the present invention, the mixing is preferably performed by adding the m-toluic acid to nitric acid, more preferably by adding the m-toluic acid to nitric acid in portions, and the present invention does not require any particular batch for the portion.

In the present invention, the temperature of the mixing is preferably 0 to-20 ℃, more preferably 0 to-10 ℃; in the present invention, the mixing is preferably carried out under stirring, and there is no particular requirement for the specific embodiment of the stirring.

In the present invention, the temperature of the nitration reaction is preferably 0 to-20 ℃, more preferably-2 to-15 ℃, and most preferably-5 to-10 ℃; the time of the nitration reaction is preferably 1-2 h, and more preferably 1 h. In the present invention, the nitration reaction is preferably carried out under stirring, and the present invention does not particularly require the specific embodiment of the stirring. In the examples of the present invention, when the laboratory protocol is used, the nitration reaction is preferably carried out in a four-neck flask, preferably a four-neck glass flask.

The end point of the nitration reaction is preferably judged by liquid chromatography, more preferably, the end point of the nitration reaction is judged by measuring the content of the m-toluic acid by liquid chromatography, and in the invention, when the area normalized content of the m-toluic acid is less than 0.3%, the invention judges that the nitration reaction is finished. In a specific embodiment of the invention, the chromatographic column of the liquid chromatography is a big-concierge 250 x 4.6 (mum) C18(ODS) reversed-phase chromatographic column, an Shimadzu liquid chromatograph LC-20AT is adopted, the mobile phase is methanol and water, the volume ratio is 50:50, the flow rate is 1ml/min, the column temperature is 30 ℃, and the wavelength is 265 nm.

In the present invention, after the completion of the nitration reaction, the nitration reaction liquid is preferably subjected to a post-treatment to obtain 2-nitro-3-methylbenzoic acid. In the invention, the post-treatment preferably comprises solid-liquid separation, washing and drying, in the invention, the solid-liquid separation is preferably filtration, the specific implementation process of the filtration is not particularly required, in the invention, the solid product after the solid-liquid separation is preferably washed, in the invention, the washing is preferably water washing, the washing temperature is preferably 0 ℃, in the invention, the washing is preferably rinsing, the volume of the washing water and the mass ratio of the m-toluic acid is preferably 1-2 mL: 1g of a compound; the washed solid product is preferably dried, the drying mode is preferably drying, the drying temperature is preferably 60-80 ℃, and the drying time is preferably 70 ℃.

The present invention preferably determines the purity of the product 2-nitro-3-methylbenzoic acid of the nitration reaction by liquid chromatography.

After the 2-nitro-3-methylbenzoic acid is obtained, the 2-nitro-3-methylbenzoic acid, a hydrogenation reduction reaction solvent and a hydrogenation catalyst are mixed, and a hydrogenation reduction reaction is carried out in a hydrogen atmosphere to obtain the 2-amino-3-methylbenzoic acid.

In the invention, the hydrogenation catalyst is preferably one or more of Pd/C, Pt/C and Raney nickel, more preferably Pd/C, in the invention, the Pd/C is metal Pd supported on C, the C is preferably carbon nano tube or activated carbon, and the Pd/C is preferably Pd/C with Pd mass content of 10%.

In the present invention, the mass of the hydrogenation catalyst is preferably 3 to 7%, more preferably 5% of the mass of 2-nitro-3-methylbenzoic acid. In the invention, the hydrogenation reduction reaction solvent is preferably one or more of ethanol, methanol and tetrahydrofuran, more preferably ethanol, methanol or tetrahydrofuran, and in the invention, the mass ratio of the 2-nitro-3-methyl benzoic acid to the volume ratio of the hydrogenation reduction reaction solvent is preferably 1g (2-4) mL, more preferably 1g:3 mL.

In the invention, the temperature of the hydrogenation reduction reaction is preferably 40-60 ℃, more preferably 45-55 ℃, more preferably 48-50 ℃, the time of the hydrogenation reduction reaction is preferably 2 hours, and the pressure of the hydrogenation reduction reaction is preferably normal pressure. In the embodiment of the present invention, the hydrogenation reduction reaction is preferably performed in a four-neck flask, and before the hydrogenation reduction reaction, the reactor of the hydrogenation reduction reaction is preferably evacuated, after air in the reactor is removed, H is introduced into the reactor₂And (3) performing gas replacement, wherein the frequency of the gas replacement is preferably 3 times, and the invention exhausts the air in the reactor through the gas replacement.

The end point of the hydrogenation reduction reaction is preferably judged by liquid chromatography, more preferably the end point of the nitration reaction is judged by measuring the content of the 2-nitro-3-methylbenzoic acid by liquid chromatography, and in the invention, when the area normalized content of the 2-nitro-3-methylbenzoic acid is less than 0.3%, the invention judges that the hydrogenation reduction reaction is finished. In a specific embodiment of the invention, the chromatographic column of the liquid chromatography is a big-concierge 250 x 4.6 (mum) C18(ODS) reversed-phase chromatographic column, an Shimadzu liquid chromatograph LC-20AT is adopted, the mobile phase is methanol and water, the volume ratio is 50:50, the flow rate is 1ml/min, the column temperature is 30 ℃, and the wavelength is 265 nm.

In the present invention, after the completion of the hydrogenation reduction reaction, the hydrogenation reduction reaction liquid is preferably subjected to a post-treatment to obtain 2-amino-3-methylbenzoic acid. In the present invention, the post-treatment preferably includes cooling, solid-liquid separation, washing and distillation, and in the present invention, the cooling temperature is preferably room temperature, and the cooling mode is preferably natural cooling; in the present invention, the solid-liquid separation is preferably filtration, the present invention has no special requirement on the specific implementation process of the filtration, the present invention preferably washes the solid product after the solid-liquid separation, in the present invention, the washing solvent is preferably ethanol, the washing manner is preferably rinsing, and the volume of the washing solvent and the mass ratio of the m-toluic acid is preferably 1 to 2 mL: 1g of a compound; in the invention, the distillation is preferably carried out after the liquid product after solid-liquid separation and the washing liquid are mixed, in the invention, the distillation is preferably reduced pressure distillation, and the invention has no special requirement on the specific implementation process of the reduced pressure distillation so as to remove the hydrogenation reduction reaction solvent and the washing solvent and obtain the solid 2-amino-3-methylbenzoic acid.

The purity of the product 2-amino-3-methylbenzoic acid of the hydrogenation reduction reaction is preferably determined by liquid chromatography. In a specific embodiment of the invention, the chromatographic column of the liquid chromatography is a big-concierge 250 x 4.6 (mum) C18(ODS) reversed-phase chromatographic column, an Shimadzu liquid chromatograph LC-20AT is adopted, the mobile phase is methanol and water, the volume ratio is 50:50, the flow rate is 1ml/min, the column temperature is 30 ℃, and the wavelength is 265 nm.

After the 2-amino-3-methylbenzoic acid is obtained, the 2-amino-3-methylbenzoic acid, a chlorination reagent, benzoyl peroxide and a chlorination reaction solvent are mixed for chlorination reaction to obtain the 2-amino-3-methyl-5-chlorobenzoic acid. In the present invention, the mass of the benzoyl peroxide is preferably 1% of the mass of 2-amino-3-methylbenzoic acid; the chlorinating agent is preferably N-chlorosuccinimide or dichlorohydantoin, more preferably dichlorohydantoin, and in the present invention, the ratio of the amounts of the substances of 2-amino-3-methylbenzoic acid and chlorinating agent is preferably 1: (0.5 to 1.2), in a specific embodiment of the present invention, when the chlorinating agent is N-chlorosuccinimide, the mass ratio of the 2-amino-3-methylbenzoic acid to the N-chlorosuccinimide is 1 (0.5 to 0.6), and when the chlorinating agent is dichlorohydantoin, the mass ratio of the 2-amino-3-methylbenzoic acid to the dichlorohydantoin is 1: (1-1.2).

In the invention, the chlorination reaction solvent is preferably one or more of N, N-dimethylformamide, N-dimethylacetamide, sulfolane and DMSO, more preferably N, N-dimethylformamide, N-dimethylacetamide, sulfolane or DMSO, and most preferably N, N-dimethylacetamide or sulfolane, and in the invention, the volume ratio of the mass of the 2-amino-3-methylbenzoic acid to the chlorination reaction solvent is preferably 1g: 3-5 mL, more preferably 1g:4 mL.

In the invention, the temperature of the chlorination reaction is preferably 90-110 ℃, more preferably 100 ℃, and the time of the chlorination reaction is preferably 1-2 h. In the embodiment of the present invention, the chlorination reaction is preferably performed in a four-necked flask, and the four-necked flask is preferably a four-necked glass flask.

The present invention preferably judges the end point of the chlorination reaction by liquid chromatography, more preferably judges the end point of the chlorination reaction by measuring the content of the 2-amino-3-methylbenzoic acid by liquid chromatography, and in the present invention, the present invention judges that the chlorination reaction is ended when the normalized content of the area of the 2-amino-3-methylbenzoic acid is less than 0.3%. In a specific embodiment of the invention, the liquid chromatography column is a big-Cascade 250 x 4.6 (mum) C18(ODS) reversed phase chromatography column, Shimadzu liquid chromatograph LC-20AT is adopted, the mobile phase is methanol and water, the volume ratio is 50:50, the flow rate is 1ml/min, the column temperature is 30 ℃, and the wavelength is 265nm

In the present invention, after the completion of the chlorination reaction, the obtained chlorination reaction solution is preferably subjected to a post-treatment to obtain 2-amino-3-methyl-5-chlorobenzoic acid. In the present invention, the post-treatment preferably includes cooling, precipitation, solid-liquid separation, washing, and drying, in the present invention, the cooling temperature is preferably room temperature, the cooling mode is preferably natural cooling, in the present invention, the solvent for precipitation is preferably water, the temperature of the water is preferably 0 to 5 ℃, in the present invention, the volume of the solvent for precipitation and the mass ratio of the m-toluic acid is preferably 4 mL: 1g of a compound; in the present invention, the solid-liquid separation is preferably filtration, the present invention has no special requirement on the specific implementation process of the filtration, the present invention preferably washes the solid product after the solid-liquid separation, in the present invention, the washing is preferably water washing, the washing temperature is preferably 0 ℃, in the present invention, the washing is preferably rinsing, the volume of the washing water and the mass ratio of the m-toluic acid is preferably 1 mL: 1g of a compound; the washed solid product is preferably dried in the invention, the drying mode is preferably drying, the drying temperature is preferably 70 ℃, and the drying time is preferably 4 h.

The present invention preferably determines the purity of the product 2-amino-3-methyl-5-chlorobenzoic acid of the chlorination reaction by liquid chromatography. In a specific embodiment of the invention, the liquid chromatography column is a big-Cascade 250 x 4.6 (mum) C18(ODS) reversed phase chromatography column, Shimadzu liquid chromatograph LC-20AT is adopted, the mobile phase is methanol and water, the volume ratio is 50:50, the flow rate is 1ml/min, the column temperature is 30 ℃, and the wavelength is 265nm

The preparation method provided by the invention uses m-methylbenzoic acid as a raw material, and sequentially carries out nitration reaction, hydrogenation reduction reaction and chlorination reaction to obtain the 2-amino-3-methyl-5-chlorobenzoic acid, the reaction raw materials of the preparation method provided by the invention are cheap and easy to obtain, the product yield is high, the purity is high, the industrial production is easy to realize, and the results of the embodiment show that the three-stage total yield of the 2-amino-3-methyl-5-chlorobenzoic acid obtained by the preparation method provided by the invention is 63.0-68.4%, the melting point is 238-243 ℃, and the purity is 99.0-99.5%.

In order to further illustrate the present invention, the following embodiments are described in detail, but they should not be construed as limiting the scope of the present invention.

Example 1

Adding 400ml of 65% nitric acid into a 1L four-neck glass flask, cooling to-10 ℃, adding 100g (0.734mol) of m-toluic acid in batches, stirring at 0 ℃ for 1 hour under heat preservation, detecting the area normalization content of the m-toluic acid to be less than 0.3% by liquid chromatography, ending the reaction, filtering the obtained nitration reaction system, leaching the solid with 100ml of cold water, drying to obtain 106.2g of 2-nitro-3-toluic acid, determining the purity of the 2-nitro-3-toluic acid to be 98.7%, the yield to be 79.8% and the melting point to be 217-219 ℃ by liquid phase measurement.

Adding 106.2g (0.586mol) of 2-nitro-3-methylbenzoic acid into a 1L four-neck flask, adding 318.6ml of ethanol, stirring for dissolving, adding 5.3g of 10% Pd/C, connecting the four-neck flask with a hydrogen bag, vacuumizing, introducing hydrogen, circulating for 3 times, ensuring that air is completely removed, introducing hydrogen, heating to 40 ℃ under normal pressure, reacting for 2 hours, detecting the area normalization content of the 2-nitro-3-methylbenzoic acid by a liquid phase, ending the reaction when the area normalization content of the 2-nitro-3-methylbenzoic acid is less than 0.3%, cooling the obtained hydrogenation reaction system to room temperature, filtering, leaching the solid by 100ml of ethanol, combining the filtrates, distilling under reduced pressure to remove the ethanol to obtain 87.3g of the product 2-amino-3-methylbenzoic acid, detecting the purity of the 2-amino-3-methylbenzoic acid by the liquid phase to be 99.1%, the yield thereof was found to be 98.5%.

87.3g (0.577mol) of 2-amino-3-methylbenzoic acid, 350ml of N, N-dimethylformamide, 56.8g (0.288mol) of dichlorohydantoin and 0.87g of benzoyl peroxide as a catalyst are added into a 1L four-neck flask, the temperature is raised to 100 ℃ for chlorination reaction for 1 hour, liquid phase detection shows that the area of the 2-amino-3-methylbenzoic acid is normalized to be less than 0.3 percent, the reaction is finished, the obtained chlorination reaction system is cooled to room temperature, the system is poured into 400ml of ice water, white solid is separated out, the white solid is filtered, the solid is leached and dried by 100ml of water to obtain 93.2g of the product 2-amino-3-methyl-5-chlorobenzoic acid, the melting point is 240-243 ℃, the purity of the product 2-amino-3-methyl-5-chlorobenzoic acid was 99.3% and the yield was 87.0% by liquid phase assay.

The total yield of the product 2-amino-3-methyl-5-chlorobenzoic acid calculated as m-methylbenzoic acid was 68.4%.

The nuclear magnetic spectrum of the product 2-amino-3-methyl-5-chlorobenzoic acid can show that the product has characteristic peaks at chemical shifts of 2.10ppm, 5.87ppm, 7.21ppm, 7.78ppm and 11.51ppm respectively, wherein the chemical shift at 2.10ppm is 3H, CH₃Characteristic peak of (2H, NH) at 5.87₂The characteristic peak of (1), 7.21 is a characteristic peak of 1H, ArH, 7.78 is a characteristic peak of 1H, ArH, and 11.51ppm is a characteristic peak of 1H, OH.

Example 2

Adding 800ml of 65% nitric acid into a 2L four-mouth glass flask, cooling to-10 ℃, adding 200g (1.469mol) of m-toluic acid in batches, stirring at-10 ℃ for 1 hour after the addition is finished, detecting that the area normalization content of the m-toluic acid is less than 0.3% by liquid chromatography, finishing the reaction, filtering the obtained nitration reaction system, leaching the solid with 200ml cold water, drying to obtain 210.4g of 2-nitro-3-toluic acid, and determining that the purity of the 2-nitro-3-toluic acid is 98.8%, the yield is 79.0% and the melting point is 217-219 ℃ by liquid phase.

Adding 210.4g (1.161mol) of 2-nitro-3-methylbenzoic acid into a 2L four-neck flask, adding 631ml of ethanol, stirring for dissolving, adding 10.5g of 10% Pd/C, connecting the four-neck flask with a hydrogen bag, vacuumizing, introducing hydrogen, circulating for 3 times, ensuring that air is completely removed, introducing hydrogen, heating to 50 ℃ under normal pressure, reacting for 2 hours, detecting the content of the 2-nitro-3-methylbenzoic acid in an area of less than 0.3% by a liquid phase, cooling the obtained hydrogenation reaction system to room temperature, filtering, leaching the solid with 200ml of ethanol, combining filtrates, distilling under reduced pressure to remove the ethanol to obtain 173.1g of the product 2-amino-3-methylbenzoic acid, detecting the purity of the 2-amino-3-methylbenzoic acid by the liquid phase to be 99.2%, the yield thereof was found to be 98.6%.

A2L four-necked flask was charged with 173.1g (1.145mol) of 2-amino-3-methylbenzoic acid, 692ml of N, N-dimethylformamide, 112.9g (0.573mol) of dichlorohydantoin and 1.73g of benzoyl peroxide as a catalyst, heated to 100 ℃ for chlorination reaction for 1 hour, detecting the area normalization content of the 2-amino-3-methylbenzoic acid to be less than 0.3 percent by liquid phase detection, finishing the reaction, cooling the obtained chlorination reaction system to room temperature, pouring the system into 800ml of ice water, white solid is separated out, the white solid is filtered, the solid is leached and dried by 200ml of water to obtain 186.4g of the product 2-amino-3-methyl-5-chlorobenzoic acid, the melting point is 241-243 ℃, the purity of the product 2-amino-3-methyl-5-chlorobenzoic acid was determined by liquid phase to be 99.5% with a yield of 87.7%.

The total yield of the product 2-amino-3-methyl-5-chlorobenzoic acid calculated as m-methylbenzoic acid was 68.3%.

Example 3

Adding 800ml of 65% concentration nitric acid into a 2L four-mouth glass flask, cooling to-10 ℃, adding 200g (1.469mol) of m-toluic acid in batches, stirring at-10 ℃ for 1 hour under heat preservation, detecting the area normalization content of the m-toluic acid by liquid chromatography to be less than 0.3%, ending the reaction, filtering the obtained nitration reaction system, leaching and drying the solid by 200ml of cold water to obtain 210.4g of 2-nitro-3-toluic acid, determining the purity of the 2-nitro-3-toluic acid by liquid phase to be 98.8%, the yield to be 79.0% and the melting point to be 217-219 ℃.

Adding 210.4g (1.161mol) of 2-nitro-3-methylbenzoic acid into a 2L four-neck flask, adding 631ml of ethanol, stirring for dissolving, adding 10.5g of 10% Pd/C, connecting the four-neck flask with a hydrogen bag, vacuumizing, introducing hydrogen, circulating for 3 times, ensuring that air is completely removed, introducing hydrogen, heating to 50 ℃ under normal pressure, reacting for 2 hours, detecting the area normalization content of the 2-nitro-3-methylbenzoic acid to be less than 0.3% by a liquid phase, cooling the obtained hydrogenation reaction system to room temperature, filtering, leaching the solid with 200ml of ethanol, combining filtrates, distilling under reduced pressure to remove the ethanol to obtain 173.1g of the product 2-amino-3-methylbenzoic acid, detecting the purity of the 2-amino-3-methylbenzoic acid to be 99.2% by the liquid phase, the yield thereof was found to be 98.6%.

Adding 173.1g (1.145mol) of 2-amino-3-methylbenzoic acid, 692ml of N, N-dimethylformamide, 153.5g (1.15mol) of N-chlorosuccinimide and 1.73g of benzoyl peroxide serving as a catalyst into a 2L four-neck flask, heating to 100 ℃, carrying out chlorination reaction for 1 hour, detecting the area normalization content of the 2-amino-3-methylbenzoic acid to be less than 0.3% by using a liquid phase, ending the reaction, heating the obtained chlorination reaction system to room temperature, pouring the system into 800ml of ice water, precipitating a white solid, filtering, drying the solid by using 200ml of water to obtain 186.4g of 2-amino-3-methyl-5-chlorobenzoic acid serving as a product, carrying out leaching at a melting point of 238-243 ℃, detecting the purity of the 2-amino-3-methyl-5-chlorobenzoic acid serving as a product by using the liquid phase to be 99.3%, the yield thereof was found to be 87.7%.

The total yield of the product 2-amino-3-methyl-5-chlorobenzoic acid calculated as m-methylbenzoic acid was 68.3%.

Example 4

Adding 400ml of 65% concentration nitric acid into a 1L four-mouth glass flask, cooling to 0 ℃, adding 100g (0.734mol) of m-toluic acid in batches, keeping the temperature at 10 ℃ after the addition is finished, stirring for 1 hour, detecting the area normalization content of the m-toluic acid to be less than 0.3% through liquid chromatography, finishing the reaction, filtering the obtained nitration reaction system, leaching the solid with 100ml of cold water, drying to obtain 100.2g of 2-nitro-3-toluic acid, determining the purity of the 2-nitro-3-toluic acid to be 98.5% through liquid phase measurement, the yield to be 75.3%, and the melting point to be 217-219 ℃.

Adding 100.2g (0.553mol) of 2-nitro-3-methylbenzoic acid into a 1L four-neck flask, adding 318.6ml of ethanol, stirring for dissolving, adding 5.3g of 10% Pd/C, connecting the four-neck flask with a hydrogen bag, vacuumizing, introducing hydrogen, circulating for 3 times, ensuring that air is completely removed, introducing hydrogen, heating to 40 ℃ under normal pressure, reacting for 3 hours, detecting the area normalization content of the 2-nitro-3-methylbenzoic acid to be less than 0.3% by a liquid phase, cooling the obtained hydrogenation reaction system to room temperature, filtering, leaching the solid by 100ml of ethanol, combining filtrates, distilling under reduced pressure to remove the ethanol to obtain 82.3g of the product 2-amino-3-methylbenzoic acid, detecting the purity of the 2-amino-3-methylbenzoic acid to be 99.0% by the liquid phase, the yield thereof was found to be 98.5%.

Adding 82.3g (0.544mol) of 2-amino-3-methylbenzoic acid, 329ml of N, N-dimethylformamide, 53.6g (0.272mol) of dichlorohydantoin and 0.82g of benzoyl peroxide serving as a catalyst into a 1L four-neck flask, heating to 90 ℃ for chlorination reaction for 1 hour, detecting the area normalization content of the 2-amino-3-methylbenzoic acid to be less than 0.3% by liquid phase detection, cooling the obtained chlorination reaction system to room temperature, pouring the system into 400ml of ice water to precipitate white solid, filtering, leaching and drying the solid by 100ml of water to obtain 86.7g of 2-amino-3-methyl-5-chlorobenzoic acid, determining the melting point to be 238-243 ℃, and determining the purity of the product 2-amino-3-methyl-5-chlorobenzoic acid to be 99.0% by liquid phase detection, wherein the yield is 85.9%.

The total yield of the product 2-amino-3-methyl-5-chlorobenzoic acid calculated as m-methylbenzoic acid was 63.0%.

Example 5

Adding 400ml of 65% nitric acid into a 1L four-neck glass flask, cooling to-20 ℃, adding 100g (0.734mol) of m-toluic acid in batches, stirring at-20 ℃ for 1 hour under heat preservation, detecting the area normalization content of the m-toluic acid to be less than 0.3% by liquid chromatography, finishing the reaction, filtering the obtained nitration reaction system, leaching and drying the solid by 100ml of cold water to obtain 102.5g of 2-nitro-3-toluic acid, determining the purity of the 2-nitro-3-toluic acid by liquid phase, wherein the yield is 77.0%, and the melting point is 217-219 ℃.

Adding 102.5g (0.566mol) of 2-nitro-3-methylbenzoic acid into a 1L four-neck flask, adding 318.6ml of ethanol, stirring for dissolving, adding 5.3g of 10% Pd/C, connecting the four-neck flask with a hydrogen bag, vacuumizing, introducing hydrogen, circulating for 3 times, introducing hydrogen after air is completely removed, heating to 60 ℃ under normal pressure, reacting for 2 hours, detecting the area normalization content of the 2-nitro-3-methylbenzoic acid by a liquid phase to be less than 0.3%, cooling the obtained hydrogenation reaction system to room temperature, filtering, leaching the solid by 100ml of ethanol, combining the filtrates, distilling under reduced pressure to remove the ethanol to obtain 84.2g of the product 2-amino-3-methylbenzoic acid, detecting the purity of the 2-amino-3-methylbenzoic acid by the liquid phase to be 99.1%, the yield thereof was found to be 98.5%.

Adding 84.2g (0.557mol) of 2-amino-3-methylbenzoic acid, 337ml of N, N-dimethylformamide, 54.89g (0.279mol) of dichlorohydantoin and 0.84g of benzoyl peroxide as a catalyst into a 1L four-neck flask, heating to 110 ℃, carrying out chlorination reaction for 1 hour, detecting the content of 2-amino-3-methylbenzoic acid by a liquid phase, finishing the reaction, heating the obtained chlorination reaction system to room temperature, pouring the system into 400ml of ice water, precipitating white solid, filtering, leaching and drying the solid by 100ml of water to obtain 89.9g of 2-amino-3-methyl-5-chlorobenzoic acid as a product, wherein the melting point is 239-243 ℃, and the purity of the 2-amino-3-methyl-5-chlorobenzoic acid is 99.1% and the yield is 87.0% by liquid phase detection.

The total yield of the product 2-amino-3-methyl-5-chlorobenzoic acid calculated as m-methylbenzoic acid was 66.0%.

Comparative example 1

Adding 161.2g of 7-methylindole-2, 3-diketone and 500ml of chloroform into a 1L four-mouth bottle, introducing chlorine gas at 25 ℃ for reaction for 24 hours, pouring the system into 1000ml of ice water, separating, concentrating an organic layer to obtain 143.2g of 5-chloro-7-methylindole-2, 3-diketone, adding 300ml of 30% sodium hydroxide aqueous solution, dropwise adding 30% of hydrogen peroxide, reacting at 70 ℃ for 2 hours, extracting the system with 300ml of chloroform for 2, concentrating an organic phase to obtain 90.3g of a product, namely 2-amino-3-methyl-5-chlorobenzoic acid, the yield is 48.6 percent, and the purity is 98.6 percent as determined by liquid chromatography

Although the present invention has been described in detail with reference to the above embodiments, it is only a part of the embodiments of the present invention, not all of the embodiments, and other embodiments can be obtained without inventive step according to the embodiments, and the embodiments are within the scope of the present invention.