阅读说明：本技术 2-噻吩乙醛酸的合成方法 (Synthesis method of 2-thiophene glyoxylic acid ) 是由 孙彬 王宝亮 孙秀伟 彭立增 刘晓斐 姬松涛 于 2019-10-09 设计创作，主要内容包括：本发明属于有机合成领域,具体涉及一种2-噻吩乙醛酸的合成方法。以亚硝酰硫酸为氧化剂,在硫酸溶液中与2-乙酰噻吩反应,经精制得到2-噻吩乙醛酸。精制为将反应液倒入冰水中,析晶过滤,将得到的固体加碱溶解,调pH至2～5,再加入溶剂萃取除杂,最后再继续加酸调pH至0.8～1。本发明是一种由2-乙酰噻吩制备2-噻吩乙醛酸的新方法,该方法没有盐产生,溶剂没有挥发性,减少了挥发性气体的设备腐蚀,操作条件有改善,制备得到的2-噻吩乙醛酸纯度在98.5％以上,收率在81％以上；本发明母液通过简单处理可以套用,减少了环境污染,更加环保。(The invention belongs to the field of organic synthesis, and particularly relates to a synthetic method of 2-thiophene glyoxylic acid. Nitrosyl sulfuric acid is used as an oxidant, reacts with 2-acetylthiophene in sulfuric acid solution, and is refined to obtain 2-thiophene glyoxylic acid. And refining, namely pouring the reaction liquid into ice water, crystallizing, filtering, adding alkali into the obtained solid for dissolving, adjusting the pH value to 2-5, adding a solvent for extraction and impurity removal, and finally continuously adding acid for adjusting the pH value to 0.8-1. The invention is a new method for preparing 2-thiophene glyoxylic acid from 2-acetylthiophene, the method has no salt, the solvent has no volatility, the equipment corrosion of volatile gas is reduced, the operation condition is improved, the purity of the prepared 2-thiophene glyoxylic acid is more than 98.5 percent, and the yield is more than 81 percent; the mother liquor can be recycled by simple treatment, so that the environmental pollution is reduced, and the method is more environment-friendly.)

1. A method for synthesizing 2-thiophene glyoxylic acid is characterized by comprising the following steps: nitrosyl sulfuric acid is used as an oxidant, reacts with 2-acetylthiophene in sulfuric acid solution, and is refined to obtain 2-thiophene glyoxylic acid.

2. The method for synthesizing 2-thiopheneethanoic acid according to claim 1, wherein: the concentration of the sulfuric acid solution is 20-98%.

3. The method for synthesizing 2-thiopheneethanoic acid according to claim 2, wherein: the dosage of the sulfuric acid solution is 0.5-50 times of the weight of the 2-acetylthiophene.

4. The method for synthesizing 2-thiopheneethanoic acid according to claim 1, wherein: the dosage of nitrosyl sulfuric acid is 2-10 times of the weight of 2-acetylthiophene.

5. The method for synthesizing 2-thiopheneethanoic acid according to claim 1, wherein: the reaction temperature is-10 to 40 ℃.

6. The method for synthesizing 2-thiopheneethanoic acid according to any one of claims 1 to 5, wherein: and refining, namely pouring the reaction liquid into ice water, crystallizing, filtering, adding alkali into the obtained solid for dissolving, adjusting the pH value to 2-5, adding a solvent for extraction and impurity removal, and finally continuously adding acid for adjusting the pH value to 0.8-1.

7. The method for synthesizing 2-thiopheneethanoic acid according to claim 6, wherein: mother liquor obtained after crystallization and filtration is decompressed and concentrated until the concentration of sulfuric acid is 65% -70%, and then the mother liquor is applied to the next batch.

8. The method for synthesizing 2-thiopheneethanoic acid according to claim 6, wherein: the solvent is ethyl acetate, ethyl formate, dichloromethane, dichloroethane, chloroform or toluene.

Technical Field

The invention belongs to the field of organic synthesis, and particularly relates to a synthetic method of 2-thiophene glyoxylic acid.

Background

2-Thiophenemethylenoic acid is an intermediate to 2-thiopheneacetyl chloride, and is commonly obtained by reacting 2-acetylthiophene with sodium nitrite/hydrochloric acid. The method can generate sodium chloride as solid waste in the reaction process, and meanwhile, hydrochloric acid has strong corrosion to equipment due to the volatility of the hydrochloric acid, the operation condition is severe, and the mother liquor is high-salt strong-acid waste liquor, so that the pollution is serious.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a method for synthesizing 2-thiophene glyoxylic acid, which has no salt, no volatility of solvent, reduced equipment corrosion of volatile gas and improved operating conditions; the mother liquor can be reused by simple treatment, so that the environmental pollution is reduced, and the method is more environment-friendly.

The synthesis method of 2-thiophene glyoxylic acid takes nitrosyl sulfuric acid as an oxidant, reacts with 2-acetyl thiophene in a sulfuric acid solution, and is refined to obtain the 2-thiophene glyoxylic acid.

The reaction equation is as follows:

wherein:

the nitrosyl sulfuric acid is a commercial sulfuric acid solution of nitrosyl sulfuric acid with the concentration of 40 percent, the nitrosyl sulfuric acid reacts under the condition of the sulfuric acid solution, other solvents do not need to be introduced, and meanwhile, the sulfuric acid can also be recycled.

The concentration of the sulfuric acid solution is 20-98%, preferably 50-80%.

The dosage of the sulfuric acid solution is 0.5-50 times of the weight of the 2-acetylthiophene, if the dosage of the sulfuric acid is too small, the reaction effect is poor if the system is too thick, and if the dosage of the sulfuric acid is too much, waste is caused, and the reaction effect is poor.

The dosage of nitrosyl sulfuric acid is 2-10 times of the weight of 2-acetylthiophene, and the dosage has the best reaction effect.

The reaction temperature is-10 to 40 ℃, preferably 0 to 10 ℃.

And refining, namely pouring the reaction liquid into ice water, crystallizing, filtering, adding alkali into the obtained solid for dissolving, adjusting the pH value to 2-5, adding a solvent for extraction and impurity removal, and finally continuously adding acid for adjusting the pH value to 0.8-1. The first time of adding alkali to adjust the pH value can remove 2-thiophenecarboxylic acid impurities, and the second time of adding acid to adjust the pH value back to 0.8-1 to obtain the product.

Mother liquor obtained after crystallization and filtration is decompressed and concentrated until the concentration of sulfuric acid is 65% -70%, and then the mother liquor is applied to the next batch.

The mother liquor recovery process comprises the following steps: adding 2-acetylthiophene into the recovered mother liquor, stirring and cooling, adding nitrosyl sulfuric acid into the reaction liquid, controlling the internal temperature to be-10-40 ℃, continuing to keep warm and stir for reaction after dropwise adding is finished, slowly pouring the reaction liquid into ice water, continuing to freeze and crystallize, filtering to obtain yellow solid, and refining to obtain the 2-thiophene glyoxylic acid.

The solvent is ethyl acetate, ethyl formate, dichloromethane, dichloroethane, chloroform or toluene.

Compared with the prior art, the invention has the following advantages:

(1) the invention relates to a novel method for preparing 2-thiophene glyoxylic acid from 2-acetylthiophene, which does not generate salt, has no volatility in solvent, reduces equipment corrosion of volatile gas, improves operation conditions, and ensures that the purity of the prepared 2-thiophene glyoxylic acid is more than 98.5 percent and the yield is more than 81 percent.

(2) The mother liquor can be recycled by simple treatment, so that the environmental pollution is reduced, and the method is more environment-friendly.

Detailed Description

The present invention will be further described with reference to the following examples.