Preparation method of 2-amino-5-chloro-N, 3-dimethyl benzamide

Abstract

The invention relates to the technical field of materials, in particular to a preparation method of 2-amino-5-chloro-N, 3-dimethyl benzamide, which comprises the following steps: adding raw materials and a catalyst into a solvent, stirring, heating, introducing chlorine, reacting, cooling, filtering and extracting to obtain the 2-amino-5-chloro-N, 3-dimethyl benzamide. The problems of more side reactions, low reaction rate, harsh reaction conditions and high production cost in the chlorination reaction process can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of materials, and in particular to a method for preparing 2-amino-5-chloro-N,3-dimethylbenzamide. Background Art

[0002] Chlorantraniliprole is a new type of insecticide that is slightly toxic. It is very safe for people who apply the pesticide, beneficial to rice fields, and very safe for fish and shrimp. It has an effective period of more than 15 days, has no residual effect on agricultural products, and mixes well with other pesticides.

[0003] 2-Amino-5-chloro-N,3-dimethylbenzamide is an important intermediate of chlorantraniliprole, with wide applications and high demand, and plays an important role in the pesticide industry. At present, the manufacturing process of the chemical raw material 2-amino-5-chloro-N,3-dimethylbenzamide mainly includes: hydrogenation, cyclization, methyl amination and chlorination reaction steps; among them, chlorination is an important link in the synthesis of 2-amino-5-chloro-N,3-dimethylbenzamide. Commonly used processes for chlorination reactions include hydrogen peroxide method, sulfonyl chloride method and liquid chlorine method. However, the existing technology has the following obvious problems:

[0004] The hydrogen peroxide method, patent application publication number CN110845341A, discloses a method for preparing 2-amino-5-chloro-N,3-dimethylbenzamide, using hydrochloric acid as a chlorine source. This protonic acid easily reacts with amino groups, making the subsequent process more complicated, and a large amount of hydrochloric acid is in excess, resulting in low atomic utilization and high post-processing costs.

[0005] Sulfonyl chloride method, patent application publication number CN101492387B, discloses the preparation method of 2-amino-5-chloro-N,3-dimethylbenzamide, using sulfonyl chloride as the chlorine source, but the substance is very easy to hydrolyze to generate hydrochloric acid and sulfuric acid during the reaction process, not only too many side reactions reduce the reaction rate, but also the waste salt produced in the post-treatment is a mixed salt, which increases the difficulty of the subsequent treatment process and also causes additional costs in terms of equipment corrosion protection. It can be seen that it is extremely important to develop and promote new green processes.

[0006] The liquid chlorine method, patent application publication number CN118439967A, discloses a new method for preparing 2-amino-5-chloro-N,3-dimethylbenzamide compound, using liquid chlorine as the chlorine source. The raw material needs to be stored at low temperature, which is inconvenient to transport and store. In addition, low-temperature feeding is required during use, which has high energy consumption, harsh conditions, and complex equipment, and is not conducive to industrial production. Summary of the invention

[0007] The invention provides a preparation method of 2-amino-5-chloro-N,3-dimethylbenzamide, which can solve the problems of many side reactions, low reaction rate, harsh reaction conditions and high production cost in the chlorination reaction process.

[0008] This application provides the following technical solutions:

[0009] A method for preparing 2-amino-5-chloro-N,3-dimethylbenzamide, characterized in that the compound represented by chemical formula (I) is used as a raw material, the raw material and a catalyst are added to a solvent, stirred and heated, chlorine gas is introduced to react, cooled, filtered, and extracted to obtain 2-amino-5-chloro-N,3-dimethylbenzamide;

[0010]

[0011] In the chemical formula (I), R 1 is halogen or alkyl, R 2 It is an alkyl group.

[0012] Beneficial effects:

[0013] 1) Compared with the prior art, the technical solution uses chlorine as a chlorination agent to carry out chlorination reaction, which has good stability and controllability, reduces the danger in the reaction process, and is highly safe. Chlorine has high reactivity, effectively improves the atomic utilization rate of the chlorination reaction step, and no additional impurities or by-products are introduced during the reaction process. The by-product produced by the tail gas absorption of the chlorination reaction of chlorine is sodium hypochlorite, which is the main component of the most common chlorine bleach in household washing, is more environmentally friendly, and can also produce good economic benefits. Chlorine, as a common industrial chemical, is easy to obtain and has low cost. Moreover, using chlorine as a chlorine source is convenient for transportation and storage, and the equipment is simple, which saves equipment cost. Feeding at room temperature or supplementing the feed during the reaction can save energy consumption.

[0014] 2) Using a catalyst and adjusting the reaction conditions, chlorine gas is used as a chlorination reagent to prepare 2-amino-5-chloro-N,3-dimethylbenzamide, thereby shortening the reaction time and improving the product yield and purity. The catalyst can be recycled, effectively reducing the production cost.

[0015] Preferably, the solvent is one or a combination of N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, acetone, dimethyl carbonate, and ethyl acetate.

[0016] Beneficial effects: The above solvent or solvent combination can significantly improve the selectivity, yield and catalyst activity of the reaction, and simplify the subsequent separation and purification steps.

[0017] Preferably, the catalyst is AlCl 3 , FeCl 3One or a combination of .

[0018] Beneficial effect: Taking AlCl 3 , FeCl 3 As a catalyst, it can effectively shorten the reaction time and increase the product yield. The catalyst can be reused to reduce production costs.

[0019] Preferably, the weight ratio of the raw material, the catalyst and the solvent is 10:1.25:50.

[0020] Beneficial effects: When the weight ratio of raw materials, catalysts and solvents is 10:1.25:50, the conversion rate of the reactants is high, and the yield and purity of the final product can be guaranteed. When the weight ratio of raw materials, catalysts and solvents is less than this range, the reaction rate will slow down; when it is greater than this range, the product yield will decrease.

[0021] Preferably, the flow rate of the chlorine gas is 5 to 10 cm 3 / min, and the reaction time of introducing chlorine gas for reaction is 10 to 15 hours.

[0022] Beneficial effect: The amount of chlorine used is determined by the flow rate of chlorine and the reaction time. The flow rate of chlorine is 5-10cm 3 / min, if it is lower than this flow rate range, the reaction is incomplete; if it is higher than this flow rate range, it will cause chlorine waste and increase production costs. The reaction time of the chlorination reaction is controlled at 10 to 15 hours, which can ensure that the raw materials and chlorine react fully, ensure the conversion rate of the reactants, and improve the product yield. If the reaction time is less than 10 hours, the reaction is incomplete, resulting in a lower yield; if the reaction time is higher than 15 hours, the reaction is prone to produce impurities, resulting in a lower yield.

[0023] Preferably, the heating temperature is 35-90°C.

[0024] Beneficial effects: The reaction temperature of the chlorination reaction is controlled at 35-90°C, which can ensure that the chlorine atoms enter a specific position and improve the product yield. If the reaction temperature is lower than 30°C, the reaction rate will slow down or even be incomplete; if the reaction temperature is higher than 90°C, the reaction will produce impurities, resulting in a lower product yield.

[0025] Preferably, in the extraction, an extractant is added for extraction, and an organic phase is formed after extraction. The extractant is separated to obtain a crude product of 2-amino-5-chloro-N,3-dimethylbenzamide, which is recrystallized with an ethanol solution to obtain the product 2-amino-5-chloro-N,3-dimethylbenzamide.

[0026] Beneficial effects: The purity of the crude product obtained by extraction is 95% to 97%. After recrystallization, the purity of the final product can be effectively improved. The purity of the final product can reach more than 99%, which can meet the production and use requirements. 10% ethanol aqueous solution is the best solvent system. The product after treatment has high purity and little loss. If other solvents are replaced, the product purity will decrease or the product loss will be large.

[0027] Preferably, in the extraction, the extractant is one or a combination of chloroform, dichloromethane and ethyl acetate.

[0028] Beneficial effects: The above extractants or extractant combinations have good solubility, low boiling point and are easy to recover. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a method for preparing 2-amino-5-chloro-N,3-dimethylbenzamide. 2-amino-N,3-dimethylbenzamide in Example 1 reacts with chlorine to generate a liquid chromatography detection result of a chlorinated product 2-amino-5-chloro-N,3-dimethylbenzamide; the peak at 3.0 min is the raw material 2-amino-N,3-dimethylbenzamide, and the peak at 7.7 min is the product 2-amino-5-chloro-N,3-dimethylbenzamide; wherein, Figure (a) is a liquid chromatography detection result at the beginning of the reaction; Figure (b) is a liquid chromatography detection result during the reaction; and Figure (c) is a liquid chromatography detection result after the reaction is completed. DETAILED DESCRIPTION

[0030] The following is further described in detail through specific implementation methods:

[0031] A method for preparing 2-amino-5-chloro-N,3-dimethylbenzamide comprises the following steps:

[0032] S1. The compound represented by chemical formula (I) is used as a raw material. The raw material and the catalyst are added to a solvent, stirred rapidly and heated to 35-90°C until the raw material is completely dissolved. Chlorine gas is introduced to react for 10-15 hours; after the reaction is completed, the reaction is cooled to room temperature to obtain a reaction solution.

[0033] S2. Filter the reaction solution obtained in step S1, recover the catalyst, and obtain a filtrate.

[0034] S3, adding water and an extractant to the filtrate obtained in step S2, extracting, forming an organic phase after extraction, and separating the extractant by evaporation under reduced pressure to obtain a crude product of 2-amino-5-chloro-N,3-dimethylbenzamide, and recrystallizing with a 10% ethanol solution to obtain the product 2-amino-5-chloro-N,3-dimethylbenzamide. The obtained 2-amino-5-chloro-N,3-dimethylbenzamide is a compound having a chemical formula (II).

[0035]

[0036] In the chemical formula (I) and the chemical formula (II), R 1 are halogen or alkyl, R 2 All are alkyl groups.

[0037] The solvent is one or a combination of N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, acetone, dimethyl carbonate and ethyl acetate.

[0038] The catalyst is AlCl 3 , FeCl 3 One or a combination of .

[0039] The extractant is one or a combination of chloroform, dichloromethane and ethyl acetate.

[0040] The reagents used are all commercially available.

[0041] Example 1

[0042] In a stirred flask, add 50g of solvent acetonitrile, 1.25g of catalyst AlCl 3 and 10g of raw material 2-amino-N,3-dimethylbenzamide. Then stir rapidly in an oil bath and heat to 35°C until the raw material is completely dissolved. Pass chlorine gas at a flow rate of 5-10cm 3 / min, react for 15 hours, and detect the reaction by liquid chromatography. The conversion rate is 98%. After the reaction is completed, cool it to room temperature to obtain a reaction solution. Filter the reaction solution and recover the catalyst AlCl 3 , and obtain a filtrate. Add 200g of water to the filtrate, add ethyl acetate as an extractant for extraction, extract 3 times, each time adding 300g of ethyl acetate, combine the extracted organic phases, evaporate under reduced pressure to separate the extractant, and obtain a crude product of 2-amino-5-chloro-N,3-dimethylbenzamide, and then use 10% ethanol solution for recrystallization to obtain the product 2-amino-5-chloro-N,3-dimethylbenzamide. The relevant reaction formula is as follows:

[0043]

[0044] Examples 2-8 and Comparative Examples 1-2 were prepared using the same method as Example 1, with the following differences from Example 1 as shown in Table 1. The conversion rate of the raw materials, the yield and purity of the final product were detected by liquid chromatography.

[0045] Table 1

[0046]

[0047] As shown in Table 1, the catalyst can significantly reduce the chlorination reaction time and increase the yield of the final product (2-amino-5-chloro-N,3-dimethylbenzamide); when other reaction conditions are the same, the use of AlCl 3 As a catalyst, it can achieve a higher raw material conversion rate in a shorter chlorination reaction time. When the catalyst and other reaction conditions are the same, choosing different solvents will have obvious differences in the chlorination reaction time, raw material conversion rate and final product yield. The catalyst is AlCl 3 , when the solvent is dimethyl carbonate, the chlorination reaction time is 10 to 12 hours, the raw material conversion rate is above 99%, and the final product yield is above 87%. Among them, when the reaction temperature is 75°C, the chlorination reaction time is the shortest, which is 10 hours, that is, the amount of chlorine used is the least, the raw material conversion rate can reach 99%, but the final product yield is 87%; when the reaction temperature is 35°C, the chlorination reaction time is 12 hours, and the amount of chlorine used is slightly more than when the reaction temperature is 75°C, but the final product yield is significantly improved to 91%.

[0048] This technical solution uses 2-amino-N,3-dimethylbenzamide as raw material, dimethyl carbonate as solvent, and AlCl 3 The catalyst is used to control the reaction temperature, and chlorine is introduced to react. The raw material conversion rate is 98% to 99%, the yield of the final product can reach 91%, and the purity of the final product can reach more than 99.5%. The technical solution has high raw material utilization rate, simple production equipment, low energy consumption, low post-processing cost, high economic benefit, and is easy to use in industrialization.

[0049] The above are only embodiments of the present invention. The invention is not limited to the field involved in this implementation case. The common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing 2-amino-5-chloro-N,3-dimethylbenzamide, characterized in that: The compound represented by chemical formula (I) is used as a raw material, the raw material and a catalyst are added to a solvent, stirred and heated, chlorine gas is introduced to react, cooled, filtered, and extracted to obtain 2-amino-5-chloro-N,3-dimethylbenzamide; In the chemical formula (I), R1 is a halogen or an alkyl group, and R2 is an alkyl group.

2. The preparation method according to claim 1, characterized in that: The solvent is one or a combination of N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, acetone, dimethyl carbonate, and ethyl acetate.

3. The preparation method according to claim 1, characterized in that: The catalyst is one or a combination of AlCl3 and FeCl3.

4. The preparation method according to claim 1, characterized in that: The weight ratio of the raw material, the catalyst and the solvent is 10:1.25-2.5:50-80.

5. The preparation method according to claim 1, characterized in that: The flow rate of the chlorine gas is 5-10 cm 3 / min, and the reaction time of introducing chlorine gas for reaction is 10 to 15 hours.

6. The preparation method according to claim 1, characterized in that: The heating temperature is 35-90°C.

7. The preparation method according to claim 1, characterized in that: In the extraction, an extractant is added for extraction, and an organic phase is formed after the extraction. The extractant is separated to obtain a crude product of 2-amino-5-chloro-N, 3-dimethylbenzamide, which is recrystallized with an ethanol solution to obtain the product 2-amino-5-chloro-N, 3-dimethylbenzamide.

8. The preparation method according to claim 1, characterized in that: In the extraction, the extractant is one or a combination of chloroform, dichloromethane and ethyl acetate.

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