Ionic liquid as catalyst in the synthesis of N-alkyl trifluoromethyl pyrazoles

The efficacy of ionic liquids was evaluated in the N-alkylation reaction of 3,5-dimethyl- and 5-trifluoromethyl-3-methyl-1H-pyrazoles, from the reaction of N–H pyrazoles with alkyl halides (R1–X, where R1 = Bu, octyl, allyl, benzyl, –CH2CH2CONEt2, –CH2C(O)Ph, CH2CH2C(O)Ph and X = Cl, Br, I). Novel trifluoromethylated pyrazoles are among the compounds obtained. The reaction was chemoselective for trifluoromethylpyrazoles and 1-alkyl-3-trifluoromethyl-5-methyl-1H-pyrazoles were preferentially formed. The reaction time and yields were investigated and this method showed shorter reaction times and better yields in comparison with the reaction performed in molecular solvents.