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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