Well-dispersed non-spherical PdNPs with a diameter of 39–45 nm supported on a TiO2–cellulose composite (PdNPs@TiO2–Cell) can be synthesized by a simple and clean route. The catalyst was well characterized by XRD, FE-SEM, EDS, and TEM techniques. The PdNPs have good dispersity on the TiO2–Cell support. This results in excellent catalytic activities for the synthesis of biphenyls, acrylates, acetylenes
可以通过简单干净的方法合成负载在TiO 2-纤维素复合材料(PdNPs @ TiO 2 -Cell)上的直径39-45 nm的分散良好的非球形PdNP。通过XRD,FE-SEM,EDS和TEM技术对催化剂进行了很好的表征。PdNP在TiO 2-电池载体上具有良好的分散性。这导致在较低温度下使用低Pd负载量(1 mol%)合成联苯,丙烯酸酯,乙炔和前手性酮具有出色的催化活性。碱的性质和用量,溶剂的性质,催化剂的用量和反应温度对PdNPs @ TiO 2活性的影响–对细胞进行了彻底的调查。该催化剂显示出至少四倍的可重复使用性,而没有降低催化活性。
Solvent-Controlled Switchable C–H Alkenylation of 4-Aryl-1<i>H</i>-pyrrole-3-carboxylates: Application to the Total Synthesis of (±)-Rhazinilam
作者:Youla Su、Haipin Zhou、Jiaxuan Chen、Jinyi Xu、Xiaoming Wu、Aijun Lin、Hequan Yao
DOI:10.1021/ol5023933
日期:2014.9.19
A solvent-controlled switchable C–H alkenylation of 4-aryl-1H-pyrrole-3-carboxylates via a Pd(OAc)2 catalyzed oxidative Heck reaction was first realized. The corresponding C2 and C5 alkenylation products were obtained in good yields with high regioselectivities, respectively. The selective C5-alkenylation was successfully applied to the total synthesis of (±)-rhazinilam.
Probing the Evolution of Palladium Species in Pd@MOF Catalysts during the Heck Coupling Reaction: An Operando X-ray Absorption Spectroscopy Study
作者:Ning Yuan、Vlad Pascanu、Zhehao Huang、Alejandro Valiente、Niclas Heidenreich、Sebastian Leubner、A. Ken Inge、Jakob Gaar、Norbert Stock、Ingmar Persson、Belén Martín-Matute、Xiaodong Zou
DOI:10.1021/jacs.8b03505
日期:2018.7.5
mechanism of the Heck C-C coupling reactioncatalyzed by Pd@MOFs has been investigatedusing operando X-ray absorption spectroscopy (XAS) and powder X-ray diffraction (PXRD) combined with transmission electron microscopy (TEM) analysis and nuclear magnetic resonance (1H NMR) kinetic studies. A custom-made reaction cell was used, allowing operando PXRD and XAS data collection using high-energy synchrotron
使用原位 X 射线吸收光谱 (XAS) 和粉末 X 射线衍射 (PXRD) 结合透射电子显微镜 (TEM) 分析和核磁共振 (1H) 研究了由 Pd@MOFs 催化的 Heck CC 偶联反应的机理。 NMR)动力学研究。使用定制的反应池,允许使用高能同步辐射进行操作 PXRD 和 XAS 数据收集。通过结合非原位研究分析 XAS 数据,可以跟踪钯物种从合成状态到失活形式的演变。提出了一种自适应反应机制。发现单核 Pd(II) 配合物是反应开始时的主要活性物质,然后在随后的催化转换中逐渐转变为平均具有 13-20 个 Pd 原子的 Pd 纳米团簇。可用试剂和底物的消耗导致 Cl- 离子与其表面配位,从而导致活性位点中毒。通过了解失活过程,可以调整反应条件并延长催化剂的寿命。
Triphenylphosphine oxide-catalyzed stereoselective poly- and dibromination of unsaturated compounds
作者:Tian-Yang Yu、Yao Wang、Xiu-Qin Hu、Peng-Fei Xu
DOI:10.1039/c4cc02847c
日期:——
A novel PPh3O catalyzed bromophosphonium salt-mediated dibromination of alpha,beta-unsaturated esters and beta,gamma-unsaturated alpha-ketoesters has been developed. The products were obtained with good to excellent yields and excellent diastereoselectivities. This dibromination reaction is a good complement to the field of dibromination.