INDUSTRIAL PROCESS FOR PRODUCING 3-METHYL-PYRAZOLO-5-CARBOXYLIC ACID

摘要

3-Methylpyrazole carboxylic acid-(5) of formula (I) is prepd. by reacting acetylacetone (II) with excess trichloroacetonitrile (III) to form 1,1,1-trichloro-2-aminopenten-2-one-(4) (IV) which is reated with concn. HCl to form the 1,1,1-trichloroacetylacetone (V). This is ring closed with hydrazin hydrate to form 3-methyl-5-trichloromethylpyrazole (VI) which is hydrolysed to form (I) and opt. purified: (I) is used as inter. in the prepn. of many pharmaceutical derivs. The process is economical and can be carried out on technical scale. No isolation of individual stages is necessary.