| 摘要 |
An improved process for the manufacture of 2-isopropyl-4-methyl-6-hydroxypyrimidine, starting from 3-aminocrotonic acid amide and an acylating agent, without isolating the intermediately formed 3-isobutyrylaminocrotonic acid amide. In a first process step, the acylation is carried out with excess isobutyric acid anhydride in the presence of an alkali metal salt of isobutyric acid at temperatures of from 50 DEG to 120 DEG C. and in the absence of a solvent. In a second process step, the cyclization is carried out in the resulting reaction mixture by the addition of an aqueous alkali metal hydroxide solution at temperatures of from 80 DEG to 105 DEG C., and then the hydroxypyrimidine is isolated in known manner. The total quantities of alkali metal hydroxide added in the second process step are such that they are sufficient both for the neutralization of the isobutyric acid present in the reaction mixture and also for the cyclization. Less than 1 mole of alkali metal hydroxide per mole of the 3-aminocrotonic acid amide originally used is used for the cyclization itself.
|
