已开发出一种用于将多种简单和杂环芳烃与芳基碘化物、溴化物和氯化物进行分子内直接芳基化的催化剂。这些反应以极好的收率发生并且具有高度选择性。对芳基碘化物底物的研究表明,由于碘化物在反应介质中的积累,会发生催化剂中毒。这可以通过添加银盐来克服,银盐也允许这些反应在较低温度下发生。该方法的效用通过咔唑天然产物的快速合成和通过直接芳基化产物的开环反应合成空间位阻四邻位取代的联芳基来说明。机理研究提供了对催化剂的深入了解 s 作用模式并显示在钯催化的简单芳烃的直接芳基化中存在动力学上显着的 CH 键裂解。从这些研究中获得的知识导致了以前无法获得的芳烃的新分子间芳基化反应的发展,为其他新的直接芳基化过程的发展打开了大门。
Direct Arylation Reactions Catalyzed by Pd(OH)2/C: Evidence for a Soluble Palladium Catalyst
摘要:
Palladium hydroxide on carbon (Pearlman's catalyst) effectively catalyzes direct arylation reactions of aryl iodides and bromides, providing excellent arylation-to-hydrodehalogenation ratios (> 30:1) with broad scope for both intra- and intermolecular arylation processes. Studies aimed at determining the nature of the active catalyst indicate that an active homogeneous palladium species is produced under the reaction conditions.
Mild and efficient palladium-catalyzed intramolecular direct arylation reactions
作者:Marc Lafrance、David Lapointe、Keith Fagnou
DOI:10.1016/j.tet.2008.01.057
日期:2008.6
been evaluated in the context of intramoleculardirect arylation reactions. Under the optimal conditions, arylation of simple arenes can be performed under very mild conditions, with heating to 50 °C. The role of the pivalic acid additive is rationalized by invoking a concerted palladation–deprotonation pathway where the pivalate is behaving as either an intramolecular base from the palladium metal or
Adhesive Catalyst Immobilization of Palladium Nanoparticles on Cotton and Filter Paper: Applications to Reusable Catalysts for Sequential Catalytic Reactions
Palladiumnanoparticles dispersed in ammonium salts of hyperbranched polystyrenes are adhesivelyimmobilized on the surface of cotton or filter papers by simply heating with dicarboxylic acids or halide anions. The resulting Pd@cotton and Pd@filter paper behave as reusablecatalysts; in particular, Pd@filter paper is useful as catalyst for application to sequential cross‐coupling and hydrogenation