A kind of preparation method of 4-methyl-5-ethoxy oxazole

Abstract

The invention relates to a preparation method of 4-methyl-5-ethoxyxazole, a key intermediate of vitamin B6, and belongs to the technical field of preparation of raw materials. The preparation method of 4-methyl-5-ethoxyxazole described in the present invention, first in the hydrolysis reaction kettle, drop into 4-methyl-5-ethoxyl-1,3-oxazole-2 sequentially in a certain proportion ‑Ethyl carboxylate, toluene, drinking water and sodium hydroxide, stir and keep warm for reaction; separate liquid, use hydrochloric acid to adjust the pH value of the aqueous phase in the range of 1.0‑2.5; add organic solvent to the system obtained in the second step, 30‑50 °C Control the temperature and react until no carbon dioxide is released; after decarboxylation, adjust the pH value to ≥9.0, separate the liquids, and distill the organic phase under reduced pressure to obtain the intermediate 4-methyl-5-ethoxyoxazole. The technological operation is simple and safe, and the industrial production is easy.

Description

A kind of preparation method of 4-methyl-5-ethoxyoxazole technical field The present invention relates to a kind of preparation method of the key intermediate 4-methyl-5-ethoxyoxazole of vitamin B6, belong to The technical field of raw medicine preparation. Background technique 4-methyl-5-ethoxyoxazole is one of the main intermediates of synthesizing vitamin B6. Its production process mainly adopts What is: 4-methyl-5-ethoxy-1,3-oxazole-2-ethyl carboxylate carries out alkali hydrolysis-acid precipitation-decarboxylation-neutralization-distillation. existing technology During the operation, after the alkali hydrolysis of ethyl 4-methyl-5-ethoxy-1,3-oxazole-2-carboxylate, the liquid is separated and the water layer is retained. The water layer was evaporated under reduced pressure Ethanol was removed by distillation, then acid precipitation and heating decarboxylation. Chinese patent CN102321043A, discloses 5-ethoxy-4-methyl-1,3-oxazole-2-carboxylic acid ethyl est...

AI Technical Summary

Problems solved by technology

[0006] After alkaline hydrolysis of ethyl 4-methyl-5-ethoxy-1,3-oxazole-2-carboxylate, distill off ethanol, the product solution obtained at this time basically does not contain organic solvent; then add acid to it to precipitate 5-ethoxy-4-methyl-oxazole-2-carboxylic acid, 5-ethoxy-4-methyl-oxazole-2-carboxylic acid has very low solubility in water, and the reaction proceeds in two phases, The reaction temperature is high (60°C). Once triggered, a large amount of gas will be generated instantly, which will easily cause material flushing and cause danger.

[0007] The 4-methyl-5-ethoxy oxazole generated by the decarboxylation reaction is directly in contact with a strong acidic aqueous solution, and is easily decomposed at 60°C, resulting in low product yield and purity; and the post-treatment requires steam distillation to remove the product from the system After the distillation is completed, the crude product is separated, and then the crude product is extracted with a solvent, dried, and distilled to obtain the product, which consumes a lot of energy and takes a long time