Nanomagnetic organic-inorganic hybrid (Fe@Si-Gu-Prs): a novel magnetically green catalyst for the synthesis of tetrahydropyridine derivatives at room temperature under solvent-free conditions

A novel nanomagnetic organic-inorganic hybrid catalyst (Fe@Si-Gu-Prs) was prepared by the chemical anchoring of Preyssler heteropolyacid (H-14[NaP5W30O110]) onto the surface of modified Fe3O4 magnetic nanoparticles with guanidine-propyl-trimethoxysilane linker. The synthesized magnetically green catalyst has been characterized with several methods (FTIR, SEM, TEM, EDS, VSM, TGA-DTG, XRD, BET, and ICP) and these techniques confirmed that the Preyssler heteropolyacid is well dispersed on the surface of the solid support and its structure is retained after immobilization on the modified silica-coated Fe3O4 nanoparticles, also the content of W in catalyst was measured by inductively coupled plasma optical emission spectroscopy (ICP-OES). After full characterization, its catalytic activity investigated in the synthesis of tetrahydropyridine derivatives at room temperature under solvent-free conditions. This nano hybrid catalyst can carry out the reactions in lower than 45 min with excellent yields, and the catalyst is easily isolated from the reaction mixture by an external magnet and reused at least five times without significant loss of activity. (C) 2014 Elsevier Ltd. All rights reserved.