Lewis Acidic Ionic Liquid Immobilized on Graphene Oxide: Synthesis, Characterization, and Application in the Ultrasound-Assisted Condensation Reactions

The catalytic activity of a novel Lewis acidic Fe(III)/caffeine-based ionic liquid immobilized on graphene oxide (Caff-IL-GO/Fe) was studied in three condensation reactions in water under sonication. This catalyst was characterized by Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance, thermal gravimetric analysis, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, powder X-ray diffraction, and atomic force microscopy. The performance of the synthesized Caff-IL-GO nanocatalyst was investigated in the one-pot ultrasound-assisted synthesis of substituted 4H-pyrans, dihydropyrimidinones and benzimidazoles. The Caff-IL-GO/Fe nanocatalyst exhibited excellent activity and delivered corresponding products in high to excellent yields. Additionally, the reusability and stability of the Caff-IL-GO was also investigated. Our study indicated that the nanocatalyst could be reused up to 10 times without any significant loss of activity.