Application of structurally enhanced magnetite cored polyamidoamine dendrimer for knoevenagel condensation
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ORIGINAL PAPER
Application of structurally enhanced magnetite cored polyamidoamine dendrimer for knoevenagel condensation Fatemeh Hajizadeh1 · Behrooz Maleki1 · Farrokhzad Mohammadi Zonoz1 · Amirhassan Amiri1 Received: 5 May 2020 / Accepted: 18 September 2020 © Iranian Chemical Society 2020
Abstract In this paper, the synthesis of magnetic cored amino group terminated dendrimer (Fe3O4@SiO2@PAMAM-G2) through covalent bonding was described. This catalyst was characterized by FT-IR, XRD, FE-SEM, TEM, and TGA detection methods. Next, the catalytic activity of this catalyst was investigated for the Knoevenagel condensation reaction of aldehydes with malononitrile under mild and solvent-free conditions. The Fe3O4@SiO2@PAMAM-G2 could be separated from the reaction mixture by an external magnet and reused five times. Keywords Modified polyamidoamine dendrimer · Silica-coated magnetic nanoparticles · Knoevenagel condensation · Green chemistry
Introduction Much attention has already been paid to the development of heterogenizing homogeneous catalysts to merging the benefits of homogeneous and heterogeneous catalysts [1]. Heterogenized catalysts can be readily dissociated from the solution reaction, but they have a difficulty of low reactivity and selectivity toward their homogeneous counterparts. For solving this problem, nanoparticles have been used because they possess a high specific surface area and can be easily controlled in the reaction mixture [2–4]. Recently, magnetic Fe3O4 nanoparticles have been used to make core–shell particles, and the surface of magnetic nanoparticles were protected by various organic and inorganic materials such as silica, polymers, biomolecules, and metals [5–7]. Among them, silica was considered as one of the best materials for coating Fe3O4 magnetic nanoparticles, due to its unique properties such as chemical diversity in surface modification, stability, and biocompatibility [8, 9]. The main advantages of using silica are; (i) to prevent the oxidation of Fe3O4 magnetic nanoparticles, and (ii) for linking to different functional groups and surface modification.
* Behrooz Maleki [email protected] 1
Department of Chemistry, Hakim Sabzevari University, Sabzevar 96179‑76487, Iran
Dendrimers are monodispersed macromolecules including an initial core, radial branches with end-group and interior spaces in branches [10, 11]. The core, type, the number of branches, and end-groups can be changed, so their chemical properties and structure can be controlled. The stepwise growth of the dendrimer, will provide more active sites for conjugation of many biological molecules such as enzymes, proteins, genes, and drugs because the number of surface amino groups will be doubled. In this regards, the polyamidoamine (PAMAM) dendrimer, a highly branched dendritic macromolecule, possesses a unique surface with amine chain ends, and the number of surface groups can be precisely controlled by choosing the appropriate synthetic generation. These excellent properties of the dendrimer have led to the
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