Zirconium Schiff-Base Complex Modified Mesoporous Silica as an Efficient Catalyst for the Synthesis of Nitrogen Containi
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Zirconium Schiff-Base Complex Modified Mesoporous Silica as an Efficient Catalyst for the Synthesis of Nitrogen Containing Pyrazine Based Heterocycles Reihaneh Malakooti • Ghasem Rezanejade Bardajee Hesamaldin Mahmoudi • Nahale Kakavand
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Received: 3 February 2013 / Accepted: 17 March 2013 / Published online: 2 April 2013 Ó Springer Science+Business Media New York 2013
Abstract Zirconium Schiff-base complex modified SBA15 was synthesized and characterized by powder X-ray diffraction (XRD), BET nitrogen adsorption–desorption methods, IR spectroscopy and thermogravimetric analysis. The XRD and BET analyses show that textural properties of SBA-15 were retained during the grafting procedure. The modified SBA was successfully applied as a heterogeneous catalyst for the synthesis of a library of nitrogen containing pyrazine based heterocycles in good to excellent yields in water media. Keywords Zr(IV)-Schiff-base SBA-15 Heterogeneous catalyst Pyrazine
1 Introduction In recent years, transition metal complexes have gained a considerable attention as catalyst in organic reactions. In spite of high selectivity and activity of homogeneous catalysts, however, they suffer from limitations in separation,
Electronic supplementary material The online version of this article (doi:10.1007/s10562-013-0999-1) contains supplementary material, which is available to authorized users. R. Malakooti (&) H. Mahmoudi Nanochemistry Research Laboratory, Department of Chemistry, University of Birjand, PO Box 97175-615, Birjand, Iran e-mail: [email protected]; [email protected] G. R. Bardajee N. Kakavand Department of Chemistry, Payame Noor University, PO Box 19395-3697, Tehran, Iran
reusability and stability. One promising solution to overcome these problems could be the covalent grafting of metal complexes on mesoporous materials. SBA-15, the most well-known member of this family, with a large pore size, thick pore walls, considerable hydrothermal stability, and its easy synthesis has become a potential and promising candidate for this purpose. Despite the fact that zirconium complexes exhibited attractive catalytic activity in organic chemistry as a homogeneous [1–6] or heterogeneous catalyst [7–9] until now, there are limited reports on the anchoring of zirconium Schiff base complex on mesoporous silica materials. Quinoxalines and their derivatives are well-known for their pharmacological activities [10]. The most common method for the synthesis of quinoxaline based scaffold is the double condensation of an aromatic 1,2-diamine with a 1,2-dicarbonyl compound refluxing by ethanol or acetic acid for 2–12 h to give 34–85 % yield of the product [10]. Other catalysts including Lewis acids [gallium(III) triflate, montmorillonite K10, sulfamic acid, cupric sulfate pentahydrate, Zn (L-proline), I2, Ni nanoparticles, cellulose sulfuric acid (CSA), silica sulfuric acid (SSA), sulfated titania, Zn2?-montmorillonite K10 clay, methanol/acetic acid [10] and zirconium tetrakis(dodecyl sulfate)] [11] were applied for the synt
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