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Abstract
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Application of palladacycles in coupling reactions such as Heck cross coupling reactions have become an extremely useful method for the formation of C–C building blocks in organic synthesis [1]. Phosphorus ylides, due to their ready preparation and modification, high activity and relative stability are very interesting ligands in organometallic chemistry [2] and Pd(II) complexes of these compounds are also can catalyze some important organic reactions [3]. Sabounchei et al. reported the use of these complexes in the some cross-coupling reactions [3]. In this work, we report the synthesis, characterization and application of new Pd(II) complex [PdCl2(Ph2PCH2PPh2C(H)C(O)Ph-m-Br)] toward the Heck-Mizoroki cross-coupling reaction. Reaction of α-keto stabilized phosphorous ylides [Ph2PCH2PPh2C(H)C(O)Ph-m-Br] with PdCl2(COD) in 1:1 ratios leads to mononuclear products of the palladacycle. Characterization of the complex by IR, 1H, 31P and 13C NMR spectroscopy confirmed coordination of the ylide to the metal through the carbon atom (Fig. 1). Moisture and air-stable, robust palladacycle phosphine–ylide complex was found to exhibit excellent catalytic activity in the Pd-catalyzed Heck-Mizoroki cross-coupling reactions. The ease of preparation of the catalyst precursors, its high solubility in organic solvents, low catalyst loading, and stability toward air make these complex ideal starting materials for the above transformations.
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