Method for preparing high-purity white 2-hydroxy quinoxaline crystal

A technology of hydroxyquinoxaline and o-phenylenediamine, which is applied in the field of medicine and chemical industry, and achieves the effects of simple refining process, low refining temperature and high refining yield

Inactive Publication Date: 2011-04-13
TIANJIN VOCATIONAL INST
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This method also can only obtain powder product, produces a large amount of waste water containing organic matter simultaneously

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0017] Add 700mL of industrial methanol to a 1000mL four-necked reaction flask, and then add 193.3g of 40% industrial glyoxylic acid (containing 40.2% glyoxylic acid, 0.8% glyoxal, and 1.1% oxalic acid). Put it on an ice-salt bath After cooling, start the stirrer on the four-necked flask, and cool the reaction solution to -6°C. Weigh 109.1 g of o-phenylenediamine (content: 99.0%), pre-cool with dry ice, add to the reaction bottle in batches, and control the reaction temperature -6-0°C. The added o-phenylenediamine dissolved quickly, and the reaction solution became turbid after 15 minutes, and 2-hydroxyquinoxaline precipitated out continuously. The addition of o-phenylenediamine was completed in about 2 hours, and the mixture was incubated and stirred for 0.5 hours. Vacuum filter the reaction complete solution, soak the filter cake twice with 100mL methanol, and dry the filter cake at 70°C to obtain 137.1g of off-white 2-hydroxyquinoxaline crude product powder, the content det...

Embodiment 2

[0019] Add 40.0 g of the crude product obtained in Example 1 into a 500 mL four-necked reaction flask, add 100 mL of N,N-dimethylformamide and 100 mL of methanol, add 0.4 g of sodium hypophosphite, start the upper agitator on the four-necked flask, and Heating and refluxing under the protection of nitrogen for 1-4 hours, all the suspended 2-hydroxyquinoxaline powders are converted into white crystals, and the solution turns orange. Stop heating when the stirring of the suspension is stopped and the suspension becomes clear quickly. The temperature of the suspension was gradually lowered to below 10°C under stirring to precipitate the dissolved 2-hydroxyquinoxaline. Vacuum filter the refined liquid, soak the filter cake twice with 40mL methanol, add the washing liquid into the filtrate, and dry the filter cake at 70°C to obtain white 2-hydroxyquinoxaline crystals, the content of which is 99.7% as determined by liquid chromatography , melting point 271-273°C.

Embodiment 3

[0021] Add 40.0 g of the crude product obtained in Example 1 into a 500 mL four-necked reaction flask, add 200 mL of the remaining filtrate in Example 2, start the upper agitator on the four-necked flask, and heat to reflux under nitrogen protection for 1-4 hours to make the suspended 2- The hydroxyquinoxaline powder is all converted into white crystals, and the color of the solution becomes darker, and the heating is stopped when the stirring suspension is promptly clarified. The temperature of the suspension was gradually lowered to below 10°C under stirring to precipitate the dissolved 2-hydroxyquinoxaline. Vacuum filter the refined liquid, soak the filter cake twice with 40mL of methanol, add the washing liquid into the filtrate, and dry the filter cake at 70°C to obtain 38.6g of white 2-hydroxyquinoxaline crystals, and determine the content by liquid chromatography 99.5%, melting point 270-272°C, refined yield 97.5%.

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Abstract

The invention discloses a method for preparing 2-hydroxy quinoxaline by condensing glyoxylic acid and o-phenylenediamine. The method is characterized by comprising the following steps of: condensing industrial glyoxylic acid solution and dry ice-precooled o-phenylenediamine at the temperature of between -6 and 0 DEG C to obtain a crude product of the 2-hydroxy quinoxaline; heating and refluxing a colored crude product for 1 to 4 hours in a mixed solvent of N,N-dimethylformamide, diethylene glycol or N-methyl pyrrolidone and methanol in the presence of a reducing agent such as sulfur dioxide, sodium hypophosphite or potassium borohydride; dissolving impurities in the mixed solvent; converting a fine-powder crude product into white crystals; and filtering, washing and drying to obtain a refined product of the 2-hydroxy quinoxaline. Through liquid chromatography measurement, the content is 99.5 percent, the melting point is 270 to 272 DEG C and the refining yield is 97.5 percent. The 2-hydroxy quinoxaline has a simple refining process; a high-purity white crystal product can be obtained; the refining yield is high; the dosage of refining solvent is less; and the solvent can be recycled for use by heating, refluxing and discoloring by using activated carbon.

Description

technical field [0001] The invention relates to a method for preparing 2-hydroxyquinoxaline, in particular to refining the crude product in a mixed solvent of dimethylformamide, diethylene glycol or N-methylpyrrolidone and methanol to prepare high-purity white 2-hydroxyquinoxaline The invention discloses a method for morphine crystallization, which belongs to the field of medicine and chemical industry. Background technique [0002] 2-hydroxyquinoxaline (2-hydroxyquinoxaline), molecular formula C 8 h 6 ON 2 , the molecular weight is 146, the melting point of the pure product is 273-275 ° C, insoluble in water, alcohol, benzene and other solvents, soluble in N, N-dimethylformamide, diethylene glycol and N-methylpyrrolidone and other solvents, easily soluble in alkaline solution. The reaction of 2-hydroxyquinoxaline and ethyl chloride can produce the insecticide quinalphos, which is used to control pests and mites in economic crops such as grain, cotton and fruits and vege...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07D241/44
Inventor 李建生崔风歧吴静
Owner TIANJIN VOCATIONAL INST
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