5-Aminopyrazoles from enolisable ketones and 1-cyano-1-alkylhydrazines

Article abstract of DOI:10.1016/S0040-4020(96)01074-5

The reaction of enolisable ketones with 1-alkyl-1-cyanohydrazines leads to the corresponding cyanohydrazones. These compounds cyclise under thermal or mildly basic conditions, furnishing the corresponding 5-aminopyrazoles in good yield. In some cases, the hydrazones cannot be isolated, and the pyrazole derivatives are directly obtained. Hydrazone-enehydrazine tautomerism was observed, but no subsequent [3,3] rearrangement.