Studies on synthetic methods for 5-amino-4(3H)-pyrimidones. I. A novel ring expansion reaction of 4-aminoantipyrines to 5-amino-4(3H)-pyrimidones.

Abstract

4-Anilino (or amino) antipyrines (Ia, b) were transformed into 5-anilino (or amino)-4 (3H)-pyrimidones (IIa, b) in the presence of bases such as sodium hydride, sodium amide, sodium hydroxide, or sodium ethoxide in refluxing xylene. Treatment of IIa with hydrazine hydrate gave 4-anilino-5-hydroxy-3-methyl pyrazole (V). However, the reaction of IIb with hydrazine hydrate gave 3, 5-diamino-6-methyl-4 (3H)-pyrimidone (VI) and 4-(5-oxo-3-methyl-pyrazolinyliden) amino-5-hydroxy-3-methyl pyrazole (VII).