Effects of Alkali Halide Salts on Hydrocarboxylation of Styrene Catalyzed by Water-Soluble Palladium Phosphine Complexes
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Effects of Alkali Halide Salts on Hydrocarboxylation of Styrene Catalyzed by Water-Soluble Palladium Phosphine Complexes Zhenhong He • Zhenshan Hou • Yanping Luo • Liang Zhou • Yuanfeng Liu • Wumanjiang Eli
Received: 21 November 2012 / Accepted: 11 January 2013 / Published online: 24 January 2013 Ó Springer Science+Business Media New York 2013
Abstract Hydrocarboxylation of styrene catalyzed by water-soluble Pd-TPPTS complexes was investigated. The reaction conditions, including reaction pressure, temperature, time and etc. have a significant influence on the catalytic performance. It was found that the yield of total acids and the selectivity towards 3-phenylpropionic acid were enhanced by adding a suitable amount of alkali metal halide salts. In addition, the reaction mechanism and the role of alkali metal halide salts in the reaction were discussed on the basis of the characterization of 1H NMR and 31P NMR. Keywords Aqueous two-phase system Hydrocarboxylation Palladium-phosphine complexes Alkali metal halide 1 Introduction Hydrocarboxylation of olefins as one of the important methods for the functionalization of olefinic double bond, Electronic supplementary material The online version of this article (doi:10.1007/s10562-013-0961-2) contains supplementary material, which is available to authorized users. Z. He Y. Luo L. Zhou Y. Liu W. Eli Xinjiang Technical Institute of Physics and Chemistry, The Chinese Academy of Sciences, Urumqi 830011, People’s Republic of China Z. He Y. Luo L. Zhou Y. Liu Graduate University of the Chinese Academy of Sciences, Beijing 100049, People’s Republic of China Z. Hou (&) Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, East China University of Science and Technology, Shanghai 200237, People’s Republic of China e-mail: [email protected]
is a very promising and environmentally friendly method for obtaining carboxylic acids [1]. Palladium-catalyzed hydrocarboxylation, i.e. olefins, CO and water catalyzed by palladium to produce acid has been quite extensively studied in the past several decades, especially in the synthesis of 2-phenylpropionic acids and its derivatives, which are applied as potential precursors in non-steroidal antiinflammatory drugs such as naproxen and ibuprofen [2, 3], while the linear products of hydrocarboxylation of vinyl aromatics such as 3-phenylpropionic acid, have also been found application as special chemicals [4, 5] (Scheme 1). Aqueous/organic biphasic catalysis has received widespread attention due to the advantages of environmentally benign process and the readily efficient separation of the catalyst from the products [6, 7]. Water acts not only as one of the reactant, but as the solvent in hydrocarboxylation. Water-soluble phosphine ligands are always used to coordinate with noble metal catalyst in order to separate from organic products and to recover the noble metal catalyst. In this aspect, water-soluble phosphine ligands TPPTS (trisulfonated triphenylphosphine), TPPMS (monosulfonated tri
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