Ultrasonic-assisted preparation of nano eggshell powder: A novel catalyst in green and high efficient synthesis of 2-aminochromenes

• Ultrasonic-assisted preparation of nano eggshell powder (NESP) has been developed.
• Eggshell Characterization with XRD, XRF, IR spectra, BET, TGA, TEM and FESEM.
• Green and rapid synthesis of 2-aminochromenes in the presence of nanosized eggshell.
• High catalytic activity and reusability of nano catalyst even after five cycles.
• Catalytic activity comparison of pure CaCO3 and NESP as heterogeneous catalyst..

The nano eggshell powder (NESP) has been prepared by ultrasound irradiation and used as a novel and biodegradable catalyst with high catalytic activity and reusability in green synthesis of 2-aminochromenes via condensation of α- or β-phathol, malononitrile and aromatic aldehydes at 120 °C under solvent-free conditions. The reaction proceeds to completion within 10–35 min in 91–98% yield. Nano eggshell catalyst was characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and X-ray fluorescence, thermal gravimetric, surface area and elemental analyses. In addition, the catalytic activity and chemical structure of nano-sized eggshell were compared with pure CaCO3.

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