Rapid Four-component Synthesis of Dihydropyrano[2,3-c]pyrazoles using Nano-egg Shell/Ti(IV) as a Highly Compatible Natural Based Catalyst

Nano-egg shell/Ti(IV) (NEST) as a novel naturally based catalyst was prepared, characterized and applied for the synthesis of dihydropyrano[2,3- c ]pyrazole [DHPP] derivatives. The characterization of NEST was performed using Fourier Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray Spectroscopy (EDX), and Thermo Gravimetric Analysis (TGA). DHPPs were synthesized in the presence of NEST via a four component reaction of aldehydes, ethyl acetoacetate, malononitrile and hydrazine hydrate at room temperature under solvent free conditions. The principal affairs of this procedure are easy work-up, high yields of pure products without the use of any toxic organic solvents, mild condition and short reaction times.