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A kind of preparation method of benzothiazole-2-carboxylic acid

A technology of benzothiazole and methylbenzothiazole, which is applied in the field of benzothiazole-2-carboxylic acid, can solve the problems of high environmental hazards, increased operational risk, and increased difficulty in separation and purification of target products, achieving Operational Security Effects

Inactive Publication Date: 2017-04-19
BEIJING UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] (1) Sulfuric acid reaction system has strong corrosiveness to reaction equipment;
[0006] (2) Sodium metabisulfite processes the sulfuric acid reaction liquid, emits sulfur dioxide gas and generates corresponding salt, which is harmful to the environment and increases the difficulty of separation and purification of the target product;
[0007] (3) The whole reaction process is carried out under the concentrated sulfuric acid system, which increases the danger of operation
[0008] At present, the method of synthesizing benzothiazole-2-carboxylic acid by catalyzing oxygen or 30% hydrogen peroxide oxidation of 2-methylbenzothiazole with metalloporphyrin as a catalyst has not been reported in the literature

Method used

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  • A kind of preparation method of benzothiazole-2-carboxylic acid
  • A kind of preparation method of benzothiazole-2-carboxylic acid
  • A kind of preparation method of benzothiazole-2-carboxylic acid

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0034] Take 2g sodium hydroxide, 0.57g 2-methylbenzothiazole, 1.0×10 -3 g four-(p-methoxyphenyl) manganese porphyrin (i.e. R in formula (I) 11 = H, R 12 =OCH 3 ,M 1 =Mn), put into a 200mL autoclave, add 30mL ethanol, feed in oxygen with a pressure of 1.42MPa, react in an oil bath at a temperature of 120°C for 4h, add 80mL ultrapure water to dilute the reaction solution after the reaction, and take out 0.185 mL, acidify with hydrochloric acid, and filter to obtain benzothiazole-2-carboxylic acid. Detected by high performance liquid chromatography, the conversion rate of 2-methylbenzothiazole is 30.13%, the selectivity of benzothiazole-2-carboxylic acid is 30.12%, and the yield of benzothiazole-2-carboxylic acid is 9.08%. .

Embodiment 2

[0036] Take 2.2g sodium hydroxide, 0.57g 2-methylbenzothiazole, 1.1×10 -3 g four-(p-methoxyphenyl) manganese porphyrin (i.e. R in formula (I) 11 = H, R 12 =OCH 3 ,M 1 =Mn), add in 200mL autoclave, add 29.6mL ethanol, add 0.4mL30% hydrogen peroxide, react 8h under temperature control 100 ℃ in oil bath, add 80mL ultrapure water to dilute reaction solution after reaction, and take out 0.185 mL, acidify with hydrochloric acid, and filter to obtain benzothiazole-2-carboxylic acid. Detected by high performance liquid chromatography, the conversion rate of 2-methylbenzothiazole is 32.27%, the selectivity of benzothiazole-2-carboxylic acid is 41.26%, and the yield of benzothiazole-2-carboxylic acid is 13.31%. .

Embodiment 3

[0038] Take 1.8g sodium hydroxide, 0.57g 2-methylbenzothiazole, 1.1×10 -3 g tetrakis chloride - (p-chlorophenyl) manganese porphyrin (that is, R in formula (II) 21 = H, R 22 = Cl, X = Cl, M 2 =Mn), put into a 200mL autoclave, add 30mL ethanol, feed oxygen with a pressure of 1.0MPa, react in an oil bath at a temperature of 140°C for 6h, add 80mL ultrapure water to dilute the reaction solution after the reaction, and take out 0.185 mL, acidify with hydrochloric acid, and filter to obtain benzothiazole-2-carboxylic acid. Detected by high performance liquid chromatography, the conversion rate of 2-methylbenzothiazole is 16.64%, the selectivity of benzothiazole-2-carboxylic acid is 93.17%, and the yield of benzothiazole-2-carboxylic acid is 15.5%. .

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Abstract

The invention relates to a preparation method of benzothiazole-2-carboxylic acid, and relates to the technical field of benzothiazole-2-carboxylic acid. According to the method, 2-methylbenzothiazole is adopted as a raw material; water and ethanol are adopted as a solvent, wherein the contents of water and ethanol are respectively 0-80% and 20-100%; 10-200ppm of mononuclear metalloporphyrin with a structure represented by the formula (I) or (II) is adopted as a catalyst; sodium hydroxide with a concentration of 0.5-2mol / L is adopted as an auxiliary agent; 0.5-2.0MPa oxygen and 30% hydrogen peroxide are adopted as oxidants; and a reaction is carried out for 2-12h under a temperature of 40-140 DEG C, such that benzothiazole-2-carboxylic acid is obtained. According to the invention, metalloporphyrin is adopted as the catalyst, such that dose is low, and pollution is prevented. Ethanol or an alkali solution of an ethanol and water mixed system is adopted as the solvent, such that the solvent is green, nontoxic and environment-friendly. Oxygen and hydrogen peroxide are adopted as oxidants, such that equipment corrosion caused by potassium permanganate and concentrated sulfuric acid is greatly reduced, and experimental operation safety and environment-friendliness are greatly improved.

Description

technical field [0001] The present invention relates to a kind of method for preparing benzothiazole-2-carboxylic acid, specifically, relate to a kind of metalloporphyrin green catalytic oxygen or 30% hydrogen peroxide oxidation 2-methylbenzothiazole to prepare benzothiazole-2- The method for 2-carboxylic acid belongs to the technical field of benzothiazole-2-carboxylic acid. Background technique [0002] Benzothiazole-2-carboxylic acid is a nitrogen-containing heterocyclic compound with good biological and pharmacological activities. It is an important organic pharmaceutical intermediate and is widely used in the fields of medicine and pesticides; at the same time, it has a rigid planar structure And it has a delocalized large π bond, so it can be used as an optical material and a fluorescent material. Currently, there are three main methods for synthesizing benzothiazole-2-carboxylic acid: carbon dioxide carboxylation, ester hydrolysis, and potassium permanganate oxidatio...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07D277/68
CPCC07D277/68
Inventor 白金泉侯巍巍李建荣谢亚波吴翠敏郭瑞梅
Owner BEIJING UNIV OF TECH