Hydrazine hydrate (1:1) → 5-ethyl-3-(trifluoromethyl)-1H-pyrazole

A solution of 1,1,1-trifluoro-2,4-hexane-dione (2.4 g, 14.3 mmol), hydrazine hydrate (1.0 g, 19.0 mmol) and acetic acid (1 drop) in water (10 mL) was heated to reflux for 1 h. The reaction mixture was then cooled in an ice bath to form a white precipitate. The precipitate was then filtered, dissolved in chloroform and dried over MgSO4. The resulting solution was concentrated under reduced pressure to provide 1.39 g of the title compound. This compound was of sufficient purity to use in subsequent reactions.