Synthesis of pyrazole-4-carbohydrazide derivatives of pharmaceutical interest

New 1-phenylor 1-methyl-5-benzamidopyrazole-4-carbohydrazide derivatives were prepared in 70–90% yields from 1-methylor 1-phenyl-6-phenylpyrazolo[3,4-d]1,3-oxazin-4(1H)-one derivatives and hydrazine hydrate. Small quantities of the isomeric 5-aminopyrazole-4-(Nbenzoyl)hydrazides were detected in some reaction mixtures, proving that intramolecular benzoyl migration can take place in the 5-benzamidopyrazole-4-carbohydrazide molecule. The direct formation of pyrazole-4-carbohydrazides from 5-benzamidopyrazole-4-carboxylic acid ethyl esters and hydrazine hydrate was unsuccessful.