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.