35277-02-2

761-88-6

35277-02-2

General procedure for the synthesis of 4-fluoro-1H-pyrazole using the compound (CAS: 761-88-6) as starting material: dihydrazine (4.48 g, 0.043 mol) was added to (Z)-3-(dimethylamino)-2-fluoroacrylaldehyde (5 g, 0.043 mol) in 100 mL of 40% (V/V) aqueous ethanol solution. Subsequently, the reaction mixture was heated at 55 °C for 30 min. After completion of the reaction, the mixture was cooled to room temperature and the pH was adjusted with saturated aqueous sodium bicarbonate to 9. The aqueous layer was extracted with ether and the organic layers were combined and dried with anhydrous sodium sulfate. Finally, the solvent was removed by distillation under reduced pressure to give 3.6 g of the title compound 28-d as a yellow oil in 77% yield.