Hydrogenolysis of 1-Aminopyrazoles: Synthesis of Primary and Secondary Alkylamines

The tautomerizable N‐aminopyrazolone 9, the O‐methyl 1 and N‐methyl derivatives 4 were condensed with carbonyl compounds to give the alkenylaminopyrazoles 12, 2a‐g and 5c, which, under mild conditions, were hydrogenated to the corresponding alkylamino derivatives. The subsequent hydrogenation of the latter ones gave different results according to the structure of the starting material. The 5‐methoxy‐1‐alkylamino‐pyrazoles 3a‐g yielded the 5‐methoxypyrazole 15 and the corresponding primary amines in good yields. On the contrary, N‐methyl‐1‐alkylaminopyrazolone‐5 6c gave 1‐alkylpyrazolone‐3 8. Copyright © 1992 Journal of Heterocyclic Chemistry