A process for the preparation of 3-methyl-2-aminobenzoic acid

Abstract

The application relates to the technical field of organic chemical synthesis, and discloses a method for preparing 3-methyl-2-amino benzoic acid, which comprises the following steps: step one: sequentially adding 3-methyl-2-nitro benzoic acid, a composite catalyst, an additive and a solvent into a reaction container, stirring uniformly, and then reacting under a hydrogen atmosphere; step two: after the reaction in step one is completed, filtering the reaction liquid after adding a proper amount of solvent into the reaction liquid, so as to obtain the composite catalyst and a filtrate; distilling the filtrate, adding water into the filtrate after the amount of the solvent in the filtrate is reduced, uniformly mixing, freezing and crystallizing, pumping and filtering, and drying, so as to obtain a target product. The application solves the technical problem that toxic and harmful by-products are generated in the synthesis process of the existing 3-methyl-2-amino benzoic acid.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic chemical synthesis, in particular to a method for preparing 3-methyl-2-amino benzoic acid. BACKGROUND

[0002] Chlorantraniliprole (CAP) is a new type of pesticide with good persistence, low toxicity, no public hazard and wide insecticidal spectrum, and is a popular and widely used pesticide. In the industrial synthesis of chlorantraniliprole, 3-methyl-2-amino benzoic acid (MAA) is a very important intermediate. At present, there are two relatively mature synthesis processes for 3-methyl-2-amino benzoic acid:

[0003] 1. Using 3-methyl-2-nitrobenzoic acid as raw material and metal iron as catalyst for reduction reaction. This is the mainstream process for industrial production of 3-methyl-2-amino benzoic acid at present. However, this method produces a large amount of toxic iron sludge and wastewater containing aromatic amines during the reaction process, which causes serious environmental pollution problems. The post-treatment also needs to go through a refining process such as decolorization, and the production cost is high.

[0004] 2. Using 3-methyl-2-chlorobenzoic acid as raw material, and using ammoniating agent to ammoniate in alkaline environment. For example, the preparation method of 3-methyl-2-amino benzoic acid disclosed in Chinese patent CN111732520B. This method produces a large amount of acid byproducts such as hydrochloric acid during production, which causes serious corrosion of production equipment. In order to protect the production equipment, a large amount of alkaline substances need to be added for neutralization, which increases the production cost. SUMMARY

[0005] The present application aims to provide a method for preparing 3-methyl-2-amino benzoic acid to solve the technical problem of producing toxic and harmful byproducts in the existing synthesis process of 3-methyl-2-amino benzoic acid.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solution: a method for preparing 3-methyl-2-amino benzoic acid, comprising the following steps:

[0007] Step one: adding 3-methyl-2-nitrobenzoic acid, composite catalyst, additive and solvent into the reaction container in sequence, stirring uniformly, and then reacting under hydrogen atmosphere;

[0008] Step two: after the reaction in step one is completed, adding an appropriate amount of solvent to the reaction liquid and filtering to obtain the composite catalyst and the filtrate; distilling the filtrate, adding water of the same mass to the filtrate when the amount of solvent in the filtrate is reduced to a certain amount; uniformly mixing, freezing and crystallizing, suction filtering and drying to obtain the target product.

[0009] The principle and advantages of the present application are as follows:

[0010] 1. The composite catalyst is used in the application to replace metal iron as a reduction reaction catalyst, which can effectively avoid the generation of toxic and harmful by-products, will not affect the environment and production equipment, and reduce the cost of subsequent treatment. At the same time, compared with metal iron and ammoniation reaction catalyst, the composite catalyst can be recycled and reused, greatly reducing the production cost.

[0011] 2. The additive is directly added in the synthesis process of the application, which can effectively remove some substances in the product, improve the cleanliness and color of the product, and does not need to be subjected to subsequent decolorization and refining process, thereby improving the product quality and simplifying the production steps.

[0012] 3. In the application, hydrogen is used as a hydrogen source, which can effectively avoid the generation of inorganic salts and reduce the production and post-treatment cost.

[0013] Preferably, as an improvement, the composite catalyst includes one or more of palladium-carbon, platinum-carbon, rhodium-carbon and ruthenium-carbon, and the mass of the composite catalyst is 0.05% to 1% of the mass of 3-methyl-2-nitrobenzoic acid.

[0014] In the application, the use of transition metal composite carbon catalyst can effectively reduce the generation of toxic and harmful by-products in the reaction product, and the above-mentioned composite catalysts have the same technical effects in the technical scheme of the application. The use amount of the composite catalyst in the application will significantly affect the reaction rate of the application, and the further increase of the use amount of the composite catalyst will have little effect on the reaction, and will also cause waste of raw materials.

[0015] Preferably, as an improvement, the composite catalyst is ruthenium-carbon, and the mass of the composite catalyst is 0.1% of the mass of 3-methyl-2-nitrobenzoic acid.

[0016] In the application, compared with the other three composite catalysts or mixed catalysts, ruthenium-carbon has better catalytic hydrogenation effect, especially in the reduction of benzene nitro group, the catalytic activity of ruthenium-carbon is obviously higher than that of the other three composite catalysts of the same family.

[0017] Preferably, as an improvement, the additive includes one or more of triethylamine, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylamine and aniline.

[0018] In the application, the use of amine substances as additives can effectively remove colored impurities generated in the reaction process, and ensure the whiteness and cleanliness of the product.

[0019] Preferably, as an improvement, the additive further includes one or more of diborane, butylborane, boric acid, polyborate, borosilicate and peroxoborate.

[0020] In the present application, the use of boron-containing substances as additives can effectively remove colored impurities generated during the reaction process, ensuring the whiteness and cleanliness of the product.

[0021] Preferably, as an improvement, the mass of the additive is 1% to 3% of the mass of 3-methyl-2-nitrobenzoic acid.

[0022] In the present application, the amount of additive used is relatively small, but the actual addition effect is good. By adding a small amount of additive, the colored impurities generated during the production process can be effectively removed.

[0023] Preferably, as an improvement, the reaction pressure in step one is 0.5 to 1.5 MPa, and the temperature is 40 to 70°C.

[0024] In the present application, too low or too high reaction pressure will result in a decrease in reaction rate. The above pressure is the preferred experimental condition in the implementation process. Too low reaction temperature will significantly affect the reaction rate, but if the reaction temperature is too high, the effect on the reaction rate is small.

[0025] Preferably, as an improvement, in step two, the amount of solvent reduced in distillation is 50% to 80%, and the amount of water added is 50% to 200% of the mass of the filtrate before distillation.

[0026] In the present application, reducing the amount of solvent and then adding water to it can reduce the solubility of the target product in the solvent, which is beneficial to the precipitation of the target product. The amount of water added determines the purity and yield of the product after recrystallization. If too little water is added, the product will be dissolved in the solvent, resulting in loss during suction filtration; if too much water is added, a small amount of impurities will also be precipitated during recrystallization. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Figure is the 3-methyl-2-amino benzoic acid product prepared in Example 1 of the present application;

[0028] Figure 2 Figure is the 3-methyl-2-amino benzoic acid product prepared in Example 2 of the present application. DETAILED DESCRIPTION

[0029] The following will be further described in detail through specific embodiments:

[0030] Example 1

[0031] A method for preparing 3-methyl-2-amino benzoic acid, comprising the following steps:

[0032] Step one: sequentially add 3-methyl-2-nitrobenzoic acid, a composite catalyst, an additive, and a solvent to a reaction container, and stir uniformly before reacting in a hydrogen atmosphere;

[0033] Specifically, 150 g of 3-methyl-2-nitrobenzoic acid, 0.15 g of ruthenium-carbon and 4 g of N,N-dimethylformamide are taken into an autoclave, and 600 ml of methanol is added into the autoclave, and the above materials are mixed uniformly. Hydrogen is introduced into the autoclave for 15 min to ensure that the air in the autoclave is discharged completely and the pressure in the autoclave is kept at 0.5 MPa after the introduction of hydrogen is completed. The heating device is turned on, and the autoclave is heated to 55°C for reaction. When the pressure in the autoclave does not decrease, it is considered that the reaction is completed.

[0034] Step two: After the reaction in step one is completed, the solvent is added to the reaction solution, and then filtered to obtain a composite catalyst and a filtrate. The filtrate is distilled, and after the amount of solvent in the filtrate is reduced, water is added thereto, and then mixed uniformly, frozen, filtered and dried to obtain the target product.

[0035] Specifically, after the reaction in step one is completed, the reaction solution is transferred to a beaker, and stirred in a water bath. The temperature of the water bath is 50°C. This step is to prevent the temperature of the reaction solution from decreasing and causing the product to precipitate. The reaction solution is poured into a filtration device for filtration to obtain a filtrate and a composite catalyst, and the composite catalyst can be directly recycled. The solvent in the filtrate is removed by normal pressure distillation, and the distilled solvent can be directly recycled. When the amount of solvent in the filtrate is evaporated by about 50%-80%, the distillation is stopped, and water is added to the filtrate in an amount of 50%-200% of the amount of the filtrate before distillation, and then mixed uniformly. The mixed solution is cooled to wait for the product to crystallize and precipitate. After the crystallization is completed, the product is collected by filtration, and then the product is placed in a vacuum drying oven at 100°C to obtain the target product. The product is shown in the attached Figure 1

[0036] Example 2

[0037] The difference between this example and example 1 is that the reaction temperature in step one is 60°C.

[0038] Example 3

[0039] The difference between this example and example 1 is that the amount of ruthenium-carbon added is 0.075 g, which is equivalent to 0.5% of the amount of 3-methyl-2-nitrobenzoic acid added.

[0040] Example 4

[0041] The difference between this example and example 1 is that the amount of ruthenium-carbon added is 0.225 g, which is equivalent to 1.5% of the amount of 3-methyl-2-nitrobenzoic acid added.

[0042] Example 5

[0043] The difference between this example and example 1 is that the reaction pressure in step one is 1.2 MPa.

[0044] ​Comparative Example 1

[0045] The difference between this comparative example and Example 1 is that the reaction temperature in Step 1 is 40°C.

[0046] Comparative Example 2

[0047] The difference between this comparative example and Example 1 is that the amount of ruthenium-carbon added is 0.045 g, which is equivalent to 0.03% of the amount of 3-methyl-2-nitrobenzoic acid added.

[0048] Comparative Example 3

[0049] The difference between this comparative example and Example 1 is that the amount of ruthenium-carbon added is 0.75 g, which is equivalent to 0.5% of the amount of 3-methyl-2-nitrobenzoic acid added.

[0050] Comparative Example 4

[0051] The difference between this comparative example and Example 1 is that the reaction pressure in Step 1 is 0.2 Mpa.

[0052] Comparative Example 5

[0053] The difference between this comparative example and Example 1 is that the reaction pressure in Step 1 is 1.8 Mpa.

[0054] The reaction parameters and experimental results of the above examples and comparative examples are recorded in Table 1 below:

[0055] Table 1: Experimental conditions and results record table of examples and comparative examples

[0056]

[0057] Analysis of experimental results:

[0058] In the examples implemented according to the technical solution of the present application, the yield of the product can reach 98-99% within 7 hours of reaction time, which represents that the reaction is basically completed and the yield is relatively high.

[0059] After the reaction temperature is reduced in Comparative Example 1, the reaction rate also decreases significantly, and the yield of the product can only reach 95% after 15 hours of reaction, which is much lower than that of the examples of the present application.

[0060] After the amount of catalyst is reduced in Comparative Example 2, the reaction rate also decreases significantly. After the amount of catalyst is increased in Comparative Example 3, the reaction rate does not increase much, and there is basically no great influence.

[0061] After the reaction pressure is reduced in Comparative Example 4 and Comparative Example 5, the reaction rates of both of them decrease significantly.

[0062] Experimental Example 1: The Effect of Different Composite Catalysts on the Reaction

[0063] Experimental method: Referring to Example 1, 0.15 g of ruthenium on carbon, palladium on carbon, platinum on carbon, and rhodium on carbon were weighed out respectively, and the reactions were carried out according to the reaction conditions of Example 1. The experimental results are recorded in Table 2 below:

[0064] Table 2: Experimental Conditions and Results Record Table for Experiment Example 1

[0065]

[0066] Analysis of experimental results: The experimental results clearly show that ruthenium carbon and rhodium carbon have significantly better catalytic effects than palladium carbon and platinum carbon in this scheme, and have selective catalytic effects on the reactants and products of this invention, among which ruthenium carbon has the best catalytic effect.

[0067] Experimental Example 2: The Effect of Additives on Reaction Products

[0068] Experimental Method: Referring to Example 1, a control group was set up. The difference between the control group and Example 1 was that no additives were added. The product prepared was as shown in the attached figure. Figure 2 As shown in Table 3 below, the experimental results of Example 1 and the control group are as follows:

[0069] Table 3

[0070] Number Additive Product color Example 1 N,N-dimethylformamide White Comparative group / Reddish-brown

[0071] Experimental structure analysis:

[0072] From the appendix Figure 1 and 2 The comparison shows that the target product synthesized without additives has a reddish-brown color, while the target product with additives is white and has a higher degree of purity. This application allows for the use of additives during the preparation process to remove impurities that appear during the reaction, improving the product's purity and eliminating the need for subsequent decolorization and other purification steps, thus simplifying the production process.

[0073] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A process for the preparation of 3-methyl-2-aminobenzoic acid, characterized in that: The method comprises the following steps: Step one: adding 3-methyl-2-nitrobenzoic acid, a composite catalyst, an additive and a solvent into a reaction container in sequence, stirring uniformly and then reacting under a hydrogen atmosphere; The composite catalyst is rhodium carbon or ruthenium carbon, the mass of the composite catalyst is 0.05%-1% of the mass of 3-methyl-2-nitrobenzoic acid, the additive is N,N-dimethylformamide, and the mass of the additive is 1%-3% of the mass of 3-methyl-2-nitrobenzoic acid; Step two: after the reaction in step one is completed, adding a solvent into the reaction liquid and then filtering to obtain a composite catalyst and a filtrate, distilling the filtrate, adding water into the filtrate after the amount of the solvent in the filtrate is reduced, uniformly mixing, and then freezing crystallization, suction filtration and drying to obtain a target product.

2. A process for the preparation of 3-methyl-2-aminobenzoic acid according to claim 1, characterized in that: The composite catalyst is ruthenium carbon, and the mass of the composite catalyst is 0.1% of the mass of 3-methyl-2-nitrobenzoic acid.

3. The process for the preparation of 3-methyl-2-aminobenzoic acid as claimed in claim 1, wherein: The reaction pressure in step one is 0.5-1.5 MPa, and the temperature is 40-70℃.

4. The process of claim 1, wherein: In step two, the amount of the solvent reduced in distillation is 50%-80%, and the amount of water added is 50%-200% of the mass of the filtrate before distillation.

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