Urea immobilized silica-coated Fe3O4 MNPs as a heterogeneous magnetic nanocatalyst for the synthesis of 2-amino-4H-benzo[b]pyran derivatives

In this work, a novel urea immobilized silica-coated Fe3O4 MNP (Fe3O4@SiO2@(CH2)3-Urea) as a magnetically recoverable and metal-free nanocatalyst was designed and synthesized, and characterized using FT-IR, XRD, FE-SEM, TEM, EDX, and VSM. This system was explored in a three-component reaction to synthesize 2-amino-4H-benzo[b]pyran derivatives of dimedone, malononitrile, and aromatic aldehydes in ethanol at 80 °C. This new method has numerous merits, such as using a green and nontoxic catalyst, excellent yield, shorter reaction time, broad substrate scope, operational simplicity, and functional group compatibility. Moreover, the synthesized nanocatalyst was recovered by a magnetic field, and it was reused eight times without any appreciable change in the catalytic activity.