ZnS nanoparticles as an efficient and reusable catalyst for synthesis of 4H-pyrano[2,3-c]pyrazoles

Abstract

An efficient procedure has been reported for the synthesis of 4H-pyrano[2,3-c]pyrazoles in the presence of ZnS nanoparticles as a heterogeneous catalyst at the room temperature by grinding method. The ZnS nanoparticles were synthesized by hydrothermal method and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N₂ adsorption–desorption isotherm analysis. The 4H-pyrano[2,3-c]pyrazoles were obtained with high yields (87–97 %) in a short reaction time (5–21 min) under solvent-free condition. This method has advantages such as it is solvent free, uses simple grinding method that can be carried out at room temperature, requires short reaction times and production of pure products without any by product. The nanocatalyst can be easily recovered and reused for five runs without appreciable loss of its catalytic activity.