5-AMINO-3-ETHYL-1H-PYRAZOLE

33279-01-5

1904-24-1

GENERAL STEPS: 3-Oxopentanenitrile (XXXV; 2 g; 21 mmol) was dissolved in ethanol (60 mL) under stirring conditions, followed by the addition of hydrazine hydrate (1.3 mL; 41 mmol). The reaction mixture was heated to reflux for 12 hours. Upon completion of the reaction, the mixture was cooled to room temperature and concentrated under reduced pressure. The crude product was purified by column chromatography (eluent: 8% methanol-dichloromethane) to afford 5-ethyl-1H-pyrazol-3-amine (XXXVI; 1.8 g; 78% yield) as a brown viscous solid. The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6): δ 11.0 (broad single peak, 1H), 5.17 (single peak, 1H), 4.5 (broad single peak, 2H), 2.4 (multiple peaks, 2H), and 1.1 (triple peak, 3H). Mass spectrometry analysis showed a molecular ion peak (M+1) of 111.93.