Tannic Acid-Functionalized Fe3O4/SiO2 Magnetite Nanoparticles as an Efficient, Reusable and Magnetically Separable Catalyst for the Synthesis ofAcridinone Derivatives under Solvent-Free Conditions

In recent years, magnetic nanoparticles (MNPs) have emerged as attractive solid supports forthe immobilization of homogeneous catalysts [1]. This is because MNPs can be well dispersedin reaction mixtures without a magnetic field, providing a large surface that is readilyaccessible to substrate molecules. More importantly, after completing the reactions, theMNPs-supported catalysts can be isolated efficiently from the product solution through simplemagnetic separation, eliminating the need for catalyst filtration and centrifugation [2].Among various MNPs, magnetite (Fe3O4) is the material most widely used for catalyst supports[3]. Acridinones and their derivatives are well-known heterocycles in which two carbonylgroups are attached to the structure. Generally, 1,8-dioxodecahydroacridines are generallysynthesized by one-pot MCRs in the presence of various catalysts. Herein, we report thesynthesis of new silica-coated Fe3O4 nanoparticle-supported tannic acid (MNPs@TA) and itsapplication as a magnetically recoverable catalyst, for the synthesis of acridinone derivativesvia the one-pot multi-component reaction under solvent-free classical heating conditions. Thenanomagnetic catalyst could be readily separated from the solution via application of an externalmagnet, allowing straightforward recovery and reuse at least five times without noticeablyreducing catalytic activity.