Chloroaluminate ionic liquid-modified silica-coated magnetic nanoparticles: Efficient and reusable catalyst for selective synthesis of mono- and bis-dihydropyrano[3,2-b]chromenediones

The synthesis, characterization and catalytic activity of chloroaluminate ionic liquid-modified silica-coated magnetic nanoparticles ([SiPrPy]AlCl4@MNPs) are described. The prepared magnetic nanocatalyst was characterized using Fourier transform infrared spectroscopy, elemental analysis, vibrating sample magnetometry, scanning and transmission electron microscopies, X-ray diffraction and inductively coupled plasma analysis. The results showed that the ionic liquid had been successfully immobilized onto the magnetic support, and the resulting nanoparticles exhibited high catalytic activity for the synthesis of a diverse range of dihydropyrano[3,2-b]chromenediones via a one-pot, three-component and solvent-free reaction of aromatic aldehydes, 1,3-diones and kojic acid. This catalytic system also showed excellent activity in the selective synthesis of mono- and bis-dihydropyrano[3,2-b]chromenediones from dialdehydes. The procedure gave the products in excellent yields and in very short reaction times. Moreover, the catalyst could be reused eight times without loss of its catalytic activity.