3-(4-Fluorophenyl)-1H-pyrazole-4-carbaldehyde

326-33-0

68-12-2

306936-57-2

General procedure for the synthesis of 3-(4-fluoropropyl)-1H-pyrazole-4-carbaldehyde from 2-(1-(4-fluorophenyl)ethylidene)hydrazine-1-carboxamide and N,N-dimethylformamide: Phosphorochloride (2.1 mL, 23 mmol) was slowly added dropwise to N,N-dimethylformamide (4.4 mL, 57 mmol) at 0 °C. The reaction mixture was stirred at 0 °C for 30 min, then brought to room temperature and continued stirring for 30 min. Subsequently, the reaction mixture was cooled in an ice/water bath and 2-(1-(4-fluorophenyl)ethylidene)hydrazine-1-carboxamide (1.96 g, 10 mmol) was slowly added, controlling the temperature not to exceed 50 °C. After the addition was completed, the reaction system was heated to 80 °C and stirred at this temperature for 2 hours. After completion of the reaction, the mixture was poured into ice (15 g) and the pH was adjusted to 10 with 5N NaOH solution and stirred for 2 hours. Subsequently, the reaction solution was acidified with concentrated hydrochloric acid and stirring was continued for 4 hours. The precipitated solid was collected by filtration, washed with a small amount of water and dried under high vacuum to give the target product 3-(4-fluoropropyl)-1H-pyrazole-4-carbaldehyde (1.5 g, 79% yield).