Copper(II)–diaminosarcophagine- functionalized SBA-15: a heterogeneous nanocatalyst for the synthesis of benzimidazole, benzoxazole and benzothiazole derivatives under solvent-free conditions Ghasem Rezanejade Bardajee a *, Marzieh Mohammadi b and Nahale Kakavand a Solvent-free organic reactions were studied over periodic mesoporous silica (SBA-15) containing a Cu(II) organometallic complex. This heterogeneous catalyst was achieved by coordination of Cu(II) ions with the diaminosarcophagine ligand and then its grafting onto the surface of SBA-15. This catalyst displayed ordered mesoporous channels, which implies an extremely high dis- persion of the Cu(II) complex and the convenient diffusion of reactant molecules into the pore channels. Therefore, this catalyst can offer high activity and also facile separation or recycling when compared with its homogeneous counterparts. Copyright © 2015 John Wiley & Sons, Ltd. Keywords: heterogeneous catalysis; Cu(II)–DiAmSar complex; benzimidazole; benzoxazole; benzothiazole Introduction Mesoporous materials, such as M41s and SBA families, were ini- tially studied at the beginning of the 1990s. They have received considerable attention in catalysis due to their large pore sizes (2.0–50.0 nm), high surface areas (up to 1200 m 2 g À1 ) and organic solvent tolerance. Furthermore, pore sizes and surface areas facil- itate the covalent anchoring of bulky organic species to their walls, and these surface-functionalized mesoporous materials have been applied as heterogeneous catalysts in organocatalysis, metallic catalysis and organometallic catalysis. [1–6] Heterogeneous catalysts are rather effective from environmental and economic viewpoints, [7] since they have the benefits of easy recovery and re- use after the completion of the reactions. Recently, we have reported the synthesis of metal complexes of Schiff-base supported SBA-15 as organometallic catalysts and used them for the synthesis of quinoxaline heterocycles; attachment of catalytic centers to SBA-15 by covalent linkages is a practical way to produce heterogeneous catalysts and avoids leaching of catalyst centers to the reaction mixture. [8–10] Diaminosarcophagine (DiAmSar) as a new class of chelator based on sarcophagine has good properties for encapsulation of a variety of metal ions, the resulting complex cations being extraordinarily stable and kinetically inert against leaching of metal ions. [11–15] This multifunctional chelator also has diverse kinds of biological sites. DiAmSar can conjugate to peptides, sugars, antibodies and biolog- ically compatible polymers via its end group, and the products can be radiolabeled with radioisotopes such as 64 Cu. [16–23] These prop- erties lead to some important usages, especially in diagnostic positron emission tomography imaging. [24–29] Molecular imaging is a developing technology that helps visualize interactions among molecular excavators and biological targets. [30–35] Leaching of the metal ions from metal ion-based catalysts into the reaction solution is, however, a central problem in heteroge- neous catalysis. Metal leaching to the supernatant reduces the per- formance of a catalyst, in terms of either catalyst replacement or additional purification and recovery processes. In drug synthesis, there are strict limits on residual metals in active pharmaceutical in- gredients. DiAmSar is useful in this regard because the six nitrogen donor atoms of the macrobicyclic cages bind very strongly to many metal ions; for example, this ligand coordinates the metal ion Cu 2+ within the multiple macrocyclic rings comprising the sarcophagine cage structure, yielding extraordinarily stable complexes that are in- ert to dissociation of the metal ion (<6% in 18 h at ca 25 °C). [36–39] In this paper, in continuation of our earlier work, [40,41] we report the application of Cu(II)–DiAmSar (as an organometallic complex) covalently bonded to SBA-15 (Cu(II)-DiAmSar/SBA-15), as a non- leaching and heterogeneous organometallic catalyst for the * Correspondence to: Ghasem Rezanejade Bardajee, Department of Chemistry, Payame Noor University (PNU), PO Box 19395-3697, Tehran, Iran. E-mail: rezanejad@pnu.ac.ir a Department of Chemistry, Payame Noor University (PNU), PO Box 19395-3697, Tehran, Iran b Department of Chemistry, Faculty of Science, Urmia University, 57159, Urmia, Iran Appl. Organometal. Chem. 2016, 30, 51–58 Copyright © 2015 John Wiley & Sons, Ltd. Full paper Received: 21 September 2015 Revised: 3 October 2015 Accepted: 6 October 2015 Published online in Wiley Online Library: 6 November 2015 (wileyonlinelibrary.com) DOI 10.1002/aoc.3400 51