Sulfur-Ligand/Pd-Catalyzed Cross-Coupling Reactions of Aryl Halides with Arylboronic Acids Under Aerobic Conditions
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Sulfur-Ligand/Pd-Catalyzed Cross-Coupling Reactions of Aryl Halides with Arylboronic Acids Under Aerobic Conditions Hong-ling Li • Zhi-sheng Wu • Min Yang Yan-xing Qi
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Received: 4 January 2010 / Accepted: 6 April 2010 / Published online: 20 April 2010 Ó Springer Science+Business Media, LLC 2010
Abstract An air-and moisture-stable monodentate sulfurligand was synthesized. The ligand was found to be effective in Pd-catalyzed cross-coupling reactions of various aryl halides with arylboronic acids under aerobic conditions. This catalytic system is tolerant of a wide range of functional groups. The new complex structure of the sulfur-ligand/PdII has been determined by single-crystal X-ray diffraction. Keywords Cross-coupling reaction Palladium Sulfur-ligand Catalysis
1 Introduction Suzuki cross-coupling reaction represents one of the most widely used processes for the synthesis of biaryls, important building blocks of pharmaceuticals [1], polymers [2] and ligands for catalysis [3]. As a result, considerable efforts have been directed toward the development of efficient Suzuki cross-coupling reactions [4–8]. Phosphine
Li and Wu contributed equally to this work.
Electronic supplementary material The online version of this article (doi:10.1007/s10562-010-0342-z) contains supplementary material, which is available to authorized users. H. Li Z. Wu M. Yang (&) Y. Qi (&) State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, People’s Republic of China e-mail: [email protected] Y. Qi e-mail: [email protected]
ligands are generally required to stabilize the reactive palladium intermediates, and excellent results have been reported for Pd-catalyzed Suzuki reactions [9–11]. However, many phosphines are sensitive to air and moisture resulting in limitations on their applications [12]. Therefore, the application of alternative ligands in metal-catalyzed synthetic transformations opens up new opportunities in catalysis [13–18]. Sulfur-containing compounds were traditionally categorized as catalyst poisons due to their strong coordinative and adsorptive properties, which rendered them totally ineffective as catalysts [19, 20]. Recently, efforts have been focused on the development of sulfur-ligands/metal catalyzed reactions [21–25], among which thioureas emerged as one of the most efficient ligands owing to their stability to air and moisture, desirable coordinating ability with metal, as well as their greater stability at elevated temperatures relative to phosphine ligands, which may enable their use over a broader range of reaction conditions [26–37]. However, Suzuki coupling reactions catalyzed by simple non-chiral monodentate thiourea has not been attempted so far [7, 8]. Herein we report the synthesis of bulky sulfur-ligand 4 and its application in Pd-catalyzed cross-coupling reactions of various aryl halides with arylboronic acids under aerobic conditions.
2 Experimental Chemicals and solvents were all purchased fro
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