gamma-Fe2O3@SiO2-gamma-aminobutyric acid as a novel superparamagnetic nanocatalyst promoted green synthesis of chromeno[4,3,2-de][1,6]naphthyridine derivatives

摘要

Grafting of -aminobutyric acid on the superparamagnetic -Fe2O3@SiO2 nanoparticles afforded -Fe2O3@SiO2--aminobutyric acid as a novel heterogeneous nanocatalyst, which was characterized by X-ray diffraction, Fourier transform-infrared spectroscopy, vibrating sample magnetometry, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and thermal analysis. In this research, we report a convenient and one-pot efficient direct protocol for the pseudo four-component preparation of chromeno[4,3,2-de][1,6]naphthyridine derivatives via cascade condensation reaction of malononitrile, 2,4-dihydroxyacetophenone with various aromatic aldehydes in the presence of the catalytic amount of the -Fe2O3@SiO2--aminobutyric acid under green conditions in aqueous media. This procedure offers several advantages such as: very easy reaction conditions, simple work-up, or purification, excellent yields, high purity of the desired product, atom economy, and short reaction times. The superparamagnetic nanocatalyst is magnetically separable and kept stability after recycling for at least five consecutive runs without detectable activity loss.