2,4-Difluorophenylhydrazine hydrochloride → 5-(3-bromo-4-fluoro-phenyl)-1-(2,4-difluoro-phenyl)-3-pentafluoroethyl-4,5-dihydro-1H-pyrazole

Participants

Reaction Conditions

Reaction Steps

1-(3-Bromo-4-fluoro-phenyl)-4,4,5,5,5-pentafluoro-pent-1-en-3-one (2.5 g, 7.1 mmol) prepared in Step 4 and 2,4-difluorophenylhydrazine hydrochloride (1.4 g, 7.8 mmol) were added to acetic acid (35.0 mL). The reaction mixture was stirred at 125° C. for 2 hours, concentrated under reduced pressure, and then ethyl acetate was added thereto. The mixture was washed with a saturated solution of sodium hydrogen carbonate, dried on anhydrous magnesium sulfate, and then concentrated under reduced pressure to give a yellow liquid residue. The resulting residue was purified by silica gel column chromatography (eluent: ethyl acetate/n-hexane=1/30) to give 2.1 g of the titled compound as a yellow liquid.

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