Magnetic Catalysts Palladium Immobilized onto Functionalized Magnetic Nanoparticles as Robust Catalysts for Amination and Room-Temperature Ullmann Homocoupling of Aryl Halides: A Walk Around the CÀ F Bond Activation Firouz Matloubi Moghaddam,* Raheleh Pourkaveh, Ashkan Karimi, and Seyed Ebrahim Ayati [a] Abstract: The first example of a heterogeneous catalytically active system for Buchwald–Hartwig and Ullmann homocou- pling of unactivated aryl halides (fluorobenzene) is present- ed. The novel magnetic heterogeneous palladium catalyst was synthesized by immobilization of palladium ions onto an aminopyridine-functionalized Fe 3 O 4 . The catalyst was fully characterized by FTIR spectroscopy, temperature-pro- grammed reduction, thermogravimetric analysis, CHN ele- mental analysis, transmission electron microscopy, field-emis- sion scanning electron microscopy, X-ray diffraction, energy- dispersive X-ray spectroscopy, and atomic absorption spec- troscopy. By using this catalyst system, various types of pri- mary and secondary amines reacted with different types of aryl halides, even fluorobenzene. This catalyst can also effi- ciently transform all types of haloarenes into biaryl deriva- tives by Ullmann reaction at room temperature. Therefore, it is a promising catalyst in the area of C ÀF bond activation. The catalyst was reused several times and no significant loss of activity was observed. Introduction Aromatic amines and biphenyl derivatives are important subu- nits in a broad range of pharmaceutical and biologically active compounds. [1, 2] Among the arsenal of synthetic methods used for the formation of such motifs, coupling reactions play an important role. [3–5] Until now, different metal catalysts such as palladium, [6] copper, [7] nickel, [8] silver, [9] platinum, [10] and more recently, iron [11] have been used for organic transformations. Palladium competes strongly with the aforementioned metals because it possesses a higher activity than its metal alterna- tives, enabling the conversion of less-reactive substrates, [12] and because of its performance at relatively low tempera- tures [13] and high catalyst turnover numbers. In addition, other metals have shown limitations in practical applications due to the requirement for stoichiometric amounts of metal reagents and harsh reaction conditions. The development of novel li- gands for palladium and optimization of catalytic conditions are important aspects of Pd-catalyzed reactions. To date, sever- al efficient Pd–ligand systems have been developed to pro- mote C ÀC and C ÀN bond formation in Ullmann and Buch- wald–Hartwig reactions, respectively. [14, 15] Direct homocoupling of aryl halides (Ullmann reaction) is the best method for the construction of aryl–aryl bonds. Traditionally, this reaction has been carried out in harsh reaction conditions including high temperatures, extended reaction times, and the use of toxic solvents and strong bases. [16] However, up to now, a substantial number of recent investigations have been directed towards these coupling reactions to improve conditions. [17] As an example, Hajipour et al. introduced a homogeneous palladium-based catalytic system for homocoupling reactions of aryl halides at 120 8C that suffers from difficult separation from the reaction mixture and non-recyclability. [18] Then, Karimi et al. reported a heterogeneous palladium-based catalyst for formation of symmetrical biaryls at 75 8C for 12 h. [19] Also, fur- ther improvement in Buchwald–Hartwig reaction conditions was achieved previously in our laboratory by using nickel fer- rite nanoparticles. [20] Despite these advances, some limitations remain to be solved. These challenging issues are: 1) in order to meet functional group tolerance and high chemoselectivity, room-temperature Pd-catalyzed reactions are especially attrac- tive due to their mild conditions; 2) in this context, C ÀF bond activation remains a challenge owing to the strength of the C À F bond compared with C ÀCl and C ÀBr bonds. So, owing to the remarkable thermal and chemical stability of organofluorine compounds, transition-metal-catalyzed C ÀF bond transforma- [a] F. M. Moghaddam, R. Pourkaveh, A. Karimi, S. E. Ayati Laboratory of Organic Synthesis and Natural Products Department of Chemistry Sharif University of Technology Azadi Street, PO Box 111559516 Tehran (Iran) E-mail : matloubi@sharif.edu Supporting information and the ORCID identification number(s) for the au- thor(s) of this article can be found under https://doi.org/10.1002/ ajoc.201800041. Asian J. Org. Chem. 2018, 00,0–0  2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1 && These are not the final page numbers! ÞÞ Full Paper DOI: 10.1002/ajoc.201800041