Co(II) Immobilized on Functionalized Magnetic Hydrotalcite (Fe3O4/HTNH2- CoII): A Green and Magnetically Recyclable Bifunctional Nanocatalyst for the Synthesis of Xanthenes

چکیده مقاله

Hydrotalicites (HTs) and magnetic hydrotalcites (MHTs) have been widely studied as promising supporting materials for catalysts in organic reactions. Hydrotalictes as a layer double hydroxide (LDH) with abundant surface hydroxyl groups consist of alternating cationic (Mg6Al2(OH)16+2 anionic (CO32-) interlayers and Mg–Al mixed oxides which are chemically active sites (strong basic sites) for use in catalytic reactions and also act as the anchoring sites for metal nanoparticles. By considering the fact that the separation of hydrotalcite-based catalysts from the reaction mixture is difficult to some extent, replacement of conventional separation methods with magnetic separation approaches is a fascinating technique. Thus, incorporation of magnetic nanoparticles (MNPs) into the hydrotalcite structure provides easy separation of catalysts from the reaction mixture using a simple magnetic bar along with the prevention of MNP agglomeration, as well. A variety of amines and other functional groups have been utilized in nanoparticle preparation as stabilizers on surface of MHTs, which could be useful for immobilization of metal ions [1,2]. In recent times, xanthene derivatives have greatly drawn the attention of organic chemists as they are important motifs in a variety of biologically active compounds [3]. In summary we have successfully synthesized COII immobilized on functionalized magnetic hydrotalcite (Fe3O4/HT-NH2-COII) from readily available starting materials. The applicability of nanocatalyst was explored in the synthesis of of xanthene derivatives through reaction aldehydes with 2-naphtol at 90 °C under solvent free conditions in excellent yields. H o OH O 2 Cat. Solvent-free, 90 oC R R Fig. 1 Synthesis of of xanthene derivatives in the precence of the catalyst References [1] W. Zhou, Y. Chen, J. Qian, F. Sun, M. He, Q. Chen, Catalysis Letters, 2016, 146:2157-2164. [2] C. Yuan, H. Liu, X. Gao, Catalysis Letters, 2014, 144:16-21. [3] L.A.P. Antony, T. Slanina, P. Sebej, T. Solomek, P. Klan, Organic Letters, 2013, 15:4552–4555.