Cesium-saponites as excellent environmental-friendly catalysts for the synthesis of N-alkyl pyrazoles

An easy and efficient procedure for the synthesis of N-alkyl pyrazoles is reported. The reaction is carried out by alkylation of pyrazole with three different alkyl bromides using acetonitrile or dimethylformamide as solvents and different pillared saponites impregnated with cesium as catalysts. The best experimental condition was the use of DMF at 80 °C, the pillared saponite impregnated with cesium carbonate being the most active catalyst. N-Alkyl pyrazoles, which are key intermediates in the synthesis of pharmacologically active compounds, are obtained in almost quantitative yield at very short reaction times. The loading of cesium slightly affected the conversion values.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Cs+-saponites as efficient catalysts for the N-alkylation of pyrazole. ► N-Alkyl pyrazoles as key intermediates in the synthesis of pharmaceuticals. ► 100% Selectivity and almost quantitative yields to N-alkyl pyrazoles.