Cu(II)eacetylacetone complex covalently anchored onto magnetic nanoparticles: Synthesis, characterization and catalytic evaluation in amide bond formation via oxidative coupling of carboxylic acids with N,N-dialkylformamides Dariush Saberi, Samaneh Mahdudi, Samaneh Cheraghi, Akbar Heydari * Chemistry Department, Tarbiat Modares University, P.O. Box 14155-4838, Tehran, Iran article info Article history: Received 14 August 2014 Received in revised form 15 September 2014 Accepted 21 September 2014 Available online 30 September 2014 This article is dedicated to memory of Imad Mughniyah. Keywords: Oxidative amidation Copper Acetylacetone Magnetic nanoparticles Heterogeneous catalysis abstract Magnetic nanoparticles coated with silica was modified with acetylacetone (acac) followed by copper chloride. After characterization using some different microscopic and spectroscopic techniques such as XRD, FT-IR, VSM, SEMeEDX, TEM, TGA, and ICP, its catalytic activity was investigated in the oxidative coupling of carboxylic acids with N,N-dialkylformamides for the preparation of amides. Different de- rivatives of tertiary amides were synthesized in moderate to good yields in the presence of just 0.46 mol% of this catalytic system. Magnetic properties of this nano-catalyst led to its easy separation as well as reusability. © 2014 Elsevier B.V. All rights reserved. Introduction Due to their omnipresence in the framework of natural products as well as pharmaceuticals, amides have been indispensable com- pounds in the world of chemistry [1]. This moiety is also used as a linkage to converge amino acids into proteins. Conventionally, amides are prepared through a two-step reaction including acti- vation of carboxylic acid to a more reactive form, namely acyl- chloride, and then coupling of this entity with an amine [2]. But, there are some common drawbacks associated with these methods such as production of stoichiometric amounts of wastes, use of hazardous reagents and poor atom efficiency. To address these is- sues, attempts to find some other alternative methods made which resulted in the usage of metal-free methods, such as organo- catalysts and boron reagents [3]. However, even these methods suffer from low atom efficiency and difficult isolation of product. Therefore, looking for the greener methods, metal-catalyzed amide synthesis came into play. Nowadays, direct amidation via oxidative coupling of appropriate precursors has emerged as a powerful tool for amide synthesis. The employment of simple and low cost re- agents, which render these reactions both eco-friendly and step- economical, led these methods to be developed for construction of amide bonds. Following this issue, direct amidation of aldehydes and alcohols with amines [4], methylarenes with an appropriate amine source [5], carboxylic acids, azoles, and alcohols with formamides [6], and alkynes with amines (or azides) [7] have been reported. In the most methods used for this purpose, homogeneous catalysts have been employed. Due to their improved efficacy, ho- mogeneous catalysis has received more attention and consider- ation than heterogeneous approaches [4h,8]. Given the cost and toxicity associated with metals used as catalyst in homogeneous methods, together with the loss of catalyst after one run, despite being widely used in academia, these approaches have scarcely been utilized in industry. To compensate for the deficiencies related to homogeneous catalysts, the use of either heterogeneous catalysis or heterogenized homogeneous catalysts [9] (tethering of homo- geneous catalyst on organic or inorganic supports in the liquid phase) has prevailed [10]. Although the development of new syn- thetic methods to establish important linkages in organic chemis- try, considering the principles of green chemistry, is significant and * Corresponding author. Tel.: þ98 21 82883444; fax: þ98 21 82883455. E-mail address: heydar_a@modares.ac.ir (A. Heydari). Contents lists available at ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem http://dx.doi.org/10.1016/j.jorganchem.2014.09.024 0022-328X/© 2014 Elsevier B.V. All rights reserved. Journal of Organometallic Chemistry 772-773 (2014) 222e228