چكيده فارسي :
Nature has developed enzymetic catalysts for the multistep synthesis of complex chemical building blocks needed for the cells’ metabolism from nutrients in a perfect chemical factory which is called living cells [1]. The multistep synthesis of metabolites occurs via a series of sequential reactions in which the product of one reaction serves as a substrate for the subsequent reaction. The efficient catalytic ability of enzymes in these multistep reactions is due to cooperative interactions between accurately positioned functional groups such as metal centers, acids, bases, hydrogen bond donors and hydrogen bond acceptors in the active sites. These groups perform many important roles including activation and stabilization of transition states and substrate recognition through hydrogen bonding, electrostatic or covalent interactions [2]. Mimicking of the bio-system in artificial heterogeneous catalysis would be a great interest for chemists not only in industry but also in academia [3]. In this regard, most chemists have focused their attention on the development of heterogeneous multifunctional catalysts for performing multistep organic synthesis of a desired compound via one-pot tandem reactions. Using multifunctional catalysts in tandem reactions, that combine two or more catalytic transformations in the one-pot process, eliminates the time and yield losses associated with the isolation and purification of intermediates in multistep sequences [4]. These processes become green, sustainable and attractive with low-cost, step-saving, a reduced energy consumption and waste production as well as decreasing the quantities of reagents and solvents used.
To benefit the valuable applications of multifunctional catalysts in one-pot tandem reactions, and as a continuation of our recent works on the development of new heterogeneous catalysts [5], herein, we report the synthesis of immobilized palladium catalyst containing an acidic functional group on the surface of iron oxide (Scheme 1). After characterization of this newly synthesized catalyst by different methods such as ICP, CHN, SEM, TEM, XRD, TGA and FT-IR, we have successfully used it as a bifunctional heterogeneous catalyst for the synthesis of acetamides in water via reduction of nitro compounds followed by acetylation reaction. The catalyst could be easily recycled and reused repetitively. Its structure remained intact after five recoveries according to the FT-IR spectrum.
