Mortar–Pestle Grinding Technique as an Efficient and Green Method Accelerates the Tandem Knoevenagel–Michael Cyclocondensation Reaction in the Presence of Ethylenediamine Immobilized on the Magnetite Nanoparticles

Abstract

In this research, we successfully designed and synthesized a new core-shell-structured inorganic-organic hybrid magnetic nanocatalyst via the ethylene diamine immobilized to the core-shell Fe₃O₄ nanomagnetic particles (Fe₃O₄@SiO₂@(CH₂)₃/EDA). A variety of analyses such as fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), elemental mapping (WDS), thermal gravimetric analysis (TGA), powder X-ray diffraction (PXRD) and Brunauer-Emmet-Teller (BET) were used to characterize the as-synthesized nanocatalysts. The activity of this as-synthesized nanocatalysts can be successfully used in the grinding synthesis of various aldehydes, malononitrile and dimedone under solvent- and metal-free conditions at room temperature to give 2-amino-4H-benzo[b]pyran derivatives within high purity and excellent yields. Easy fabrication of Fe₃O₄@SiO₂@(CH₂)₃/EDA, waste reduction, effective for large scale synthesis, simple work-up procedure, adherence to the basics of green chemistry, high catalytic efficiency in very small amounts (0.05 g), environmentally friendly and based on natural ingredients are the great advantages of the current method. In particular, due to the super magnetic behavior of the catalyst, it can be easily recovered with the use of an external magnet from the reaction mixture, and it can be reused over 7 successive times with no decrease in the yields and activity.

Keywords:

• Grinding synthesis
• Fe₃O₄@SiO₂@(CH₂)₃/EDA
• solvent- and metal-free conditions
• 2-amino-4H-benzo[b]pyran derivatives

Acknowledgments

The authors would like to appreciate the University of Zanjan for its support.

Disclosure statement

No potential conflict of interest was reported by the author(s).