Ionic Liquid Promoted Synthesis of Aryl Ureas in Pd-catalyzed Oxidative Carbonylation Anders Riisager1; Nanette Zahrtmann1; Cyril Godard2; Carmen Claver2; Eduardo J. García Suárez1; 1DTU CHEMISTRY, Kgs. Lyngby, Denmark; 2UNIVERSITAT ROVIRA I VIRGILI, Tarragona, Spain; PAPER: 245/Molten/Regular (Oral) SCHEDULED: 12:10/Tue./Bossa (150/3rd) ABSTRACT: Ureas are important compounds found in the structures of a large number of biologically active compounds and widely used as agrochemicals, dyes, antioxidants, and HIV inhibitors, as well as key intermediates in organic synthesis [1]. Ureas can be prepared via the oxidative carbonylation of amines in the presence of a Pd-complex catalyst, usually at high pressure and temperature and under an explosive CO/O<sub>2</sub> gas mixture making the overall system unsafe [2]. Accordingly, it is desirable to develop an active catalytic system applicable for the oxidative carbonylation of amines under milder reaction conditions.<br />Ionic liquids (ILs) can have beneficial effects in many homogeneously catalyzed reactions [3]. Furthermore, the use of ILs in liquid-liquid biphasic reactions makes processes in many cases greener than when using traditional organic solvents, due to associated advantages such as low vapor pressure, as well as good thermal stability, tunable solubility, and coordination properties [4]. In addition, such systems provide good separation of reaction products and catalyst recovery.<br />In this work, we present a new efficient, robust, and versatile Pd-complex/IL catalytic biphasic system for the oxidative carbonylation of aromatic amines under mild reaction conditions [5]. Reaction parameters, including oxidant agent, pressure, temperature, catalyst and IL loading were optimized, resulting in a catalytic system which operates under mild conditions, is fully recyclable, is 100% selective and has activity two orders of magnitude higher than previously reported systems [6]. References: [1] D. J. Diaz, A. K. Darko, L. McElwee-White, Eur. J. Org. Chem., 27 (2007) 4453.<br />[2] S.-Z. Zheng, X.-G. Peng, J.-M. Liu,W. Sun, C.-G. Xia, Chin. J. Chem., 25 (2007) 1065.<br />[3] Supported Ionic Liquids: Fundamentals and Applications, R. Fehrmann, A. Riisager, M. Haumann, Wiley-VCH, 2014.<br />[4] M. Haumann, A. Riisager, Chem. Rev., 108 (2008) 1474.<br />[5] N. Zahrtmann, C. Claver, C. Godard, A. Riisager, E. J. Garcia-Suarez, ChemCatChem, DOI: 10.1002/cctc.201800004.<br />[6] B. Chen, S. S. C. Chuang, Green Chem., 5 (2003) 484. |