One-Pot Magnetic Iron Oxide–Carbon NanodotComposite-Catalyzed Cyclooxidative Aqueous Tandem Synthesis of Quinazolinonesin the Presence of tert-Butyl Hydroperoxide

摘要

The development of synthetic protocols for biologically important molecules using biocompatible catalysts in aqueous medium holds the key in green and sustainable chemistry. Herein, a magnetically recoverable iron oxide–carbon dot nanocomposite has been demonstrated as an effective catalyst for cyclooxidative tandem synthesis of quinazolinones in aqueous medium using alcohols as starting materials. Fluorescent carbon dots, the newest entrant in the nanocarbon family, were used as the stabilizing agent for the iron oxide nanoparticles, and a continuous layer of carbon dots decorates the iron oxide nanoparticle surface as observed by transmission electron microscopy. The fluorescence studies demonstrated the effective electron transfer from carbon dots to the iron oxide nanoparticles resulting in complete quenching of emission owing to carbon dots, once it binds with iron oxide nanoparticles. The nanocatalyst showed high activity with significant reusability for the syntheses of quinazolinones in the presence of tert-butyl hydroperoxide (TBHP) in an aqueous medium. Controlled experiments revealed the synergistic effect of carbon dots in enhancing the catalyticactivity of iron oxide, as they might influence the decompositionof TBHP into radicals owing to their peroxidase activity. These radicalsstabilized over the nanoparticle surface are known to have increasedlifetime compared to solution-based radicals. These surface-stabilizedradicals then could catalyze the tandem reaction resulting in theformation of the quinazolinone derivatives in high yields.