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■ A Novel Ring Expansion Reaction of 4-Aminoantipyrines to 5-Amino-4(3H)-pyrimidinones

Taisei Ueda,* Noriichi Oda, and Isoo Ito

*Faculty of Pharmaceutical Sciences, Nagoya City University, Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan

Abstract

4-Amino(or anilino)antipyrines (I, II) were transformed into 5-amino(or anilino)-4(3H)-pyrimidinones (III, IV) in the presence of bases such as sodium hydride, sodium amide, sodium hydroxide, or sodium ethoxide in refluxing xylene. Treatment of III with hydrazine hydrate gave 4-anilino-5-hydroxy-3-methylpyrazole (V). However, the reaction of IV with hydrazine hydrate gave 3,5-diamino-6-methyl-4(3H)-pyrimidinone (VII) and 4-(5-oxo-3-methyl-pyrazolinyliden-4-amino)-5-hydroxy-3-methyl-pyrazole (VIII).