Fe₃O₄@SiO₂@Taurine: A Magnetically Recoverable Green Nanocatalyst for Efficient Synthesis of Pyrano[2,3-d]pyrimidine derivatives

Abstract

The development of recyclable and eco-friendly catalysts for heterocyclic synthesis remains a central theme in sustainable chemistry. Here, we present a magnetically recoverable Fe 3 O 4 @SiO 2 @taurine catalyst, prepared by sequential silica coating and taurine functionalization of Fe 3 O 4 nanoparticles. Structural, morphological, and magnetic characteristics were established through FT-IR, XRD, TEM, SEM-EDS, VSM, and TGA analyses. This catalytic system promotes a one-pot, three-component reaction of aromatic aldehydes, malononitrile, and barbituric or thiobarbituric acid in aqueous ethanol under reflux, affording pyrano[2,3-d]pyrimidine derivatives in high yields and short reaction times. Ease of magnetic recovery, operational simplicity, and stable activity over multiple cycles highlight its practical applicability. Collectively, these findings demonstrate Fe 3 O 4 @SiO 2 @taurine as a green, efficient, and recyclable platform for sustainable organic transformations. bioseparation, enzyme immobilization, and catalysis. [16][17][18] Chemical co-precipitation offers a lowtemperature, cost-effective route to prepare well-dispersed Fe 3 O 4 nanoparticles with controlled size. 19 Their performance can be further improved by surface coating techniques. 20 Recently, coreshell nanocomposites that integrate inorganic nanoparticles with metal-organic frameworks (MOFs) have emerged as multifunctional materials. NP@MOF hybrids show wide applications across medicine, environment, and energy. 21,22 Among various MOFs, Fe-based systems stand out as heterogeneous catalysts due to their high dispersibility, abundance of active sites, and structural stability arising from strong Fe³⁺-carboxylate interactions, combined with their low toxicity, redox activity, and cost-effectiveness.