Synthesis of 2,2,2-trifluoroethyl 1H-pyrazole carboxylates: Insight into the mechanism of trichloromethyl group hydrolysis

•Use of green trifluoroethanol;.•Easy diversification of products from trichloromethyl-substituted precursors;.•The route proposed allows to obtain novel products with trifluoroethyl chain;.•The products obtained are all unpublished and with high potential biological activity.

This paper reports one-pot synthesis of 2,2,2-trifluoroethyl 1H-pyrazole-5(3)-carboxylates via cyclocondensation of 1,1,1-trichloro-4-alkoxy-3-alken-2-ones [Cl3CC(O)C(R2) = C(R1)OMe, where R1 = H, CH3, n-octyl, n-nonyl, n-decyl, n-undecyl, n-tridecyl, −(CH2)2Ph, 4-ClC6H4, 4-BrC6H4 and R2 = H] and 1,1,1-trichloro-2,4-alkanediones, 1-aryl-4,4,4-trichloro-1,3-butanediones [Cl3CC(O)CHR2C(O)R1, where R1 = H, CH3, −(CH2)2Ph, Ph, 4-FC6H4, 4-BrC6H4, R2 = H, R1 = Ph and R2 = CH3 and R1, R2 = cyclo-(CH2)5-] with hydrazine hydrochloride in 2,2,2-trifluoroethanol (TFE). Considering the low nucleophilicity of TFE in relation to methanol or ethanol, the results provide evidence for the mechanism of hydrolysis of the trichloromethyl group attached to the 1H-pyrazol ring.

Graphical abstractSynthesis of novel 2,2,2-trifluoroethyl 1H-pyrazol-5(3)-carboxylates from cyclocondensation between hydrazine hydrochloride and 1,1,1-trichloro-4-alkoxy-3-alken-2-ones and trichloromethyl-1,3-diketones in TFE.Figure optionsDownload full-size imageDownload as PowerPoint slide