key to improving catalytic activities. Amongst various catalytic reactions, supported Pd nanoparticles-catalyzed C–C cross-couplingreactions have been attracting a great deal of attention in the last decade. Although various supports have been examined, applications of hierarchically porous monolithic materials have never been reported, mainly because of difficulties in multistep synthesis of catalysts
Aerobic Oxidative Coupling of Arenes and Olefins through a Biomimetic Approach
作者:Beneesh P. Babu、Xu Meng、Jan-E. Bäckvall
DOI:10.1002/chem.201300100
日期:2013.3.25
Arenes and electron‐deficient olefins can be oxidatively coupled through a biomimetic Pd(OAc)2‐catalyzed transformation. CH activation of the arene partner is effected under reaction conditions of low catalyst loading, normal oxygen pressure, and using p‐benzoquinone and iron phthalocyanine as electron‐transfer mediators (ETMs). By controlling catalyst loading, the reaction can be made selective for
A Novel Pyridine-Bridged Bis-benzimidazolylidene Pincer Palladium Complex: Synthesis and Catalytic Properties
作者:Tao Tu、Jagadeesh Malineni、Karl Heinz Dötz
DOI:10.1002/adsc.200800244
日期:2008.8.4
A novelpyridine-bridgedbis-benzimidazolylidene CNC pincercomplex 1 was synthesized from cheap, commercially available precursors under microwave assistance in moderate yield. It catalyzes cross-coupling reactions of aryl halides with alkyl acrylates (Heck reaction) and phenylboronic acid (Suzuki reaction) under aerobic conditions with extremely high turn-over numbers (frequencies) indicating that
Synthesis and applications of polymeric N-heterocyclic carbene palladium complex-grafted silica as a novel recyclable nano-catalyst for Heck and Sonogashira coupling reactions
A new catalytic system based on palladium nanoparticles supported on polymeric N-heterocyclic carbene-grafted silica (Si–PNHC–Pd) is introduced. Aminopropylsilica was reacted with benzoylchloride to form acrylamidopropylsilica. Onto this functionalized silica, vinylimidazole monomer was copolymerized by free radical polymerization. Poly(vinylimidazole)-grafted silica was treated with methyl iodide to form a quaternary salt of poly(vinylimidazole). Si–PNHC–Pd was obtained by subsequent treatment of imidazolium salt with PdCl2. Determination of Pd content was performed using an inductively coupled plasma (ICP) analyzer and the crystalline character was determined by an XRD technique. The topography and particle size of the catalyst was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). TEM images showed that palladium was dispersed through the polymer surface in nano particle size. This catalytic system exhibited excellent activity in Heck and Sonogashira coupling reactions with various aryl halides. The catalyst was successfully re-used up to 12 runs without appreciable change in its activity. High efficiency of the catalyst along with high yields of products, easy purification, large scale synthesis and high TON and TOF are among the advantages of this heterogeneous catalyst.
density. Moreover, the immobilized catalyst also had advantages, such as readily available raw materials, chemical and thermal stability, and low synthetic cost. The Pd catalyst is an effective heterogeneous catalyst for carbon–carbon (C–C) couplingreactions, such as the Heck reaction and Suzuki–Miyaura reaction, affording good to high yields. In these reactions, the catalyst was easily recovered and reused