Ferrocene-Containing Ionic Liquid Supported on Silica Nanospheres (SiO2@Imid-Cl@Fc) as a Mild and Efficient Heterogeneous Catalyst for the Synthesis of Pyrano[3,2-b]Pyran Derivatives Under Ultrasound Irradiation

Abstract

A novel heterogeneous silica nanosphere-supported ferrocene-containing ionic liquid catalyst (SiO2@Imid-Cl@Fc) was designed and synthesised and was systematically characterised by Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analysis. The catalytic activity of the SiO2@Imid-Cl@Fc catalyst was tested in a one-pot, three-component reaction of malononitrile and kojic acid with 15 aromatic aldehydes at room temperature under ultrasound irradiation. The products were pyrano[3,2-b]pyran derivatives, four of which are new. The catalyst exhibited good catalytic performance over short reaction times (15–20 min) and could be recycled at least five times without significant loss of activity.