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Preparation method of 3,5-dichloro-4-methylbenzoic acid

A technology of toluic acid and p-toluic acid, applied in 3 fields, can solve the problems of not being able to be used in large-scale production, high raw material prices, high operation requirements, etc., to reduce the difficulty of separation and purification, easy to obtain raw materials, and simple production process Effect

Active Publication Date: 2015-01-07
新岸诺亚(北京)催化科技有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, this method uses benzonitriles as raw materials, which is highly toxic, requires relatively high operating requirements, and has relatively high raw material prices. Although the reaction yield is slightly higher, it cannot be used as a route for large-scale production.

Method used

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  • Preparation method of 3,5-dichloro-4-methylbenzoic acid

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] Embodiment 1: 3, the preparation method of 5-dichloro-4-methylbenzoic acid

[0028] The invention uses p-toluic acid as a raw material, undergoes esterification, chlorination and hydrolysis in sequence to obtain 3,5-dichloro-4-methylbenzoic acid product. The reaction equation is:

[0029]

[0030] The preparation method of 3,5-dichloro-4-methylbenzoic acid disclosed by the present invention comprises the following steps (the volume or volume involved in it all adopts mL as the unit; the mass or weight involved in it all adopts g as unit):

[0031] A. Install a mechanical stirrer on a three-necked flask with 1000 parts by volume, add 700 parts by weight of thionyl chloride and 200 parts by weight of p-toluic acid, add 3 drops of DMF dropwise, heat up and reflux for 5 hours, and there will be no more bubbles. stop, 68 degrees of reflux temperature; steam excess thionyl chloride under normal pressure, steam to 100 degrees of liquid temperature and stop, cool to 30 deg...

Embodiment 2

[0034] Embodiment 2: The ratio selection research of p-toluic acid (A) and thionyl chloride (B), relevant data results are summarized in the following table:

[0035] A / B (molar ratio)

[0036] It can be seen from the above table that if too little thionyl chloride is used, a large amount of raw material p-toluic acid will remain, and in the next esterification process, the raw material will still remain in it, and the purity of the final product will be greatly reduced. After purification If the loss is too much, the usage of thionyl chloride should not be too much, too much will cause waste. Therefore, the molar ratio of p-toluic acid (A) to thionyl chloride (B) was selected as 1:4, which was used as the optimal condition.

Embodiment 3

[0037] Embodiment 3: The ratio selection research of p-toluic acid (A) and tert-butanol (C), the relevant data are summarized in the following table:

[0038] A / C (molar ratio)

[0039] Since the reaction speed of acid chloride itself and alcohols is relatively fast, a large excess of tert-butanol is not required to increase the reaction speed. It can be seen from the above table that in order to ensure the complete esterification of the acid chloride, the optimal molar ratio of p-toluic acid (A) to tert-butanol (C) is selected as 1:1.1, and the reaction results also prove that this ratio is sufficient to completely esterify the acid chloride. transform.

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Abstract

The invention discloses a preparation method of 3,5-dichloro-4-methylbenzoic acid, which comprises the following steps: A. in a reaction kettle containing thionyl chloride, adding p-methylbenzoic acid, dropwisely adding DMF (N,N-dimethylformamide), carrying out reflux reaction, distilling off the thionyl chloride under atmospheric pressure, dropwisely adding tert-butyl alcohol into the distilled substrate, keeping the temperature at 50 DEG C, and stirring for 0.5 hour to obtain the tert-butyl alcohol p-methylbenzoate; B. dissolving the tert-butyl alcohol p-methylbenzoate with dichloromethane, adding anhydrous aluminum trichloride and hydroquinone, reacting in a dark place, and introducing a nitrogen-chlorine gas mixture to obtain tert-butyl 3,5-dichloro-4-methylbenzoate; and C. distilling off the dichloromethane solvent, dropwisely adding ice water to quench the aluminum trichloride, dropwisely adding a 10% sodium hydroxide solution to carry out alkaline hydrolysis on the tert-butyl 3,5-dichloro-4-methylbenzoate until the pH value is 14, filtering, acidifying the filtrate with hydrochloric acid, filtering, and recrystallizing the filter cake with methanol to obtain the 3,5-dichloro-4-methylbenzoic acid product. By using the simple and accessible p-methylbenzoic acid as the raw material and using relatively milder conditions, the esterification, chlorination, hydrolysis and other steps are performed to finally obtain the 3,5-dichloro-4-methylbenzoic acid, thereby greatly enhancing the safety of the production process.

Description

technical field [0001] The invention relates to a preparation method of 3,5-dichloro-4-methylbenzoic acid, belonging to the technical field of organic synthesis. Background technique [0002] 3,5-dichloro-4-methylbenzoic acid is an important chemical and pharmaceutical intermediate, widely used in fungicides, insecticides, pharmaceutical intermediates and other fields. In recent years, with the arrival of the patent renewal cycle of major chemical companies, the research on halogenated chemistry has entered a new stage. 3,5-dichloro-4-methylbenzoic acid, as an intermediate with multiple connection sites, is widely used in the development of pesticides and drugs, and has huge market potential. Currently reported 3, the preparation methods of 5-dichloro-4-methylbenzoic acid have the following three categories. [0003] The first type: use 2-amino-4-methylbenzoic acid as raw material, dichloromethane, DMF as solvent, chlorination with sulfuryl chloride to obtain 2-amino-4-met...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C27/02C07C63/70
CPCC07C51/09C07C51/60C07C67/14C07C67/307C07C63/70C07C69/76C07C63/04
Inventor 王总超高于刘琳苗慧时金彪李红艳约翰尼斯·海克曼
Owner 新岸诺亚(北京)催化科技有限公司
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