Reaction of 2-hydroxyethylhydrazine with a trifluoromethyl-β-diketone: Study and structural characterization of a new 5-hydroxy-5-trifluoromethyl-4,5-dihydropyrazole intermediate

The reaction of the β-diketone 4,4,4-trifluoro-1-pyridin-2-yl-butane-1,3-dione and the monosubstituted hydrazine 2-hydroxyethylhydrazine has been investigated. Two products have been identified, 2-(2-hydroxyethyl)-3-pyridin-2-yl-5-trifluoromethyl-4,5-dihydropyrazole (P) and 2-(3-pyridin-2-yl-5-trifluoromethylpyrazol-1-yl)ethanol (L) in proportion 2:8, when the reaction was done at room temperature in ethanol for 15 h. The preparation of P as a pure product was performed in ethanol at 0 °C for 7 h. P has been characterized by 1H, 13C{1H} and 19F{1H} NMR spectroscopy and by other techniques as appropriate.