Preparation, Characterization and Application of a Novel Organic-Inorganic Hybrid Magnetic Nanomaterial as a Highly Efficient Catalyst for the Synthesis of Bis-Coumarins

A novel organic-inorganic hybrid magnetic nanomaterial, namely nano-[Fe3O4@SiO2@R-NMe2][FeCl4] (nano-[FSRN][FeCl4]) was prepared, and characterized by EDX, elemental mapping, FE-SEM, FT-IR, XRD, VSM, TG and DTG analyses. Then, it was applied as a highly efficient and magnetically recyclable catalyst for the solvent-free synthesis of bis-coumarins from 4-hydroxycoumarin (2 eq.) and arylaldehydes (1 eq.). NMe2 is a basic group, and FeCl4− is a Lewis acid; thus, nano-[FSRN][FeCl4] can act as a dual-functional catalyst; based on this and the literature, a plausible mechanism was proposed for the reaction.