Silica supported sodium hydrogen sulfate (NaHSO4–SiO2): A novel, green catalyst for synthesis of pyrazole and pyranyl pyridine derivatives under solvent-free condition via heterocyclic β-enaminones

NaHSO4–SiO2 is used as an efficient, mild and reusable catalyst for the synthesis of novel heterocyclic pyrazole (5a–h) and pyranyl pyridine (7a–h) derivatives via heterocyclic β-enaminones (3a–d) under thermal solvent-free conditions. The remarkable features of this green, new methodology are high conversions, cleaner reaction profile, simple experimental and work-up procedures. Structures of the newly synthesized compounds have been elucidated on the basis of elemental analysis and spectral data (IR, 1H NMR, 13C NMR and mass spectrometry). The catalyst is characterized for the first time by using scanning electron microscopy–energy dispersive X-ray (SEM–EDX) and powder XRD. The catalyst can be reused several times without significant loss of its catalytic activity.

Graphical abstractNaHSO4–SiO2 is used as an efficient, recyclable heterogeneous catalyst for the synthesis of pyrazole and pyranyl pyridine derivatives via heterocyclic β-enaminones under thermal solvent-free condition in excellent yields. The catalyst has been characterized for the first time by using scanning electron microscopy–energy dispersive X-ray (SEM–EDX) and powder XRD.Figure optionsDownload full-size imageDownload high-quality image (127 K)Download as PowerPoint slideHighlights► NaHSO4–SiO2 as a non toxic, recyclable and heterogeneous catalyst. ► Catalyst has been characterized for the first time by using SEM–EDX and powder XRD. ► Synthesis of pyrazole and pyridine derivative via heterocyclic β-enaminones under solvent-free conditions. ► Excellent yields of products in shorter time period.