Campeau Louis-Charles, Parisien Mathieu, Jean Annie, Fagnou Keith
Center for Catalysis Research and Innovation, Department of Chemistry, University of Ottawa, Canada.
J Am Chem Soc. 2006 Jan 18;128(2):581-90. doi: 10.1021/ja055819x.
A catalyst for the intramolecular direct arylation of a broad range of simple and heterocyclic arenes with aryl iodides, bromides, and chlorides has been developed. These reactions occur in excellent yield and are highly selective. Studies with aryl iodides substrates revealed that catalyst poisoning occurs due to the accumulation of iodide in the reaction media. This can be overcome by the addition of silver salts which also permits these reactions to occur at lower temperature. The utility of the methodology is illustrated by a rapid synthesis of a carbazole natural product and by the synthesis of sterically encumbered tetra-ortho-substituted biaryls via ring-opening reactions of the direct arylation products. Mechanistic investigations have provided insight into the catalyst's mode of action and show the presence of a kinetically significant C-H bond cleavage in palladium-catalyzed direct arylation of simple arenes. Knowledge garnered from these studies has led to the development of new intermolecular arylation reactions with previously inaccessible arenes, opening the door for the development of other new direct arylation processes.
已开发出一种催化剂,可用于多种简单芳烃和杂环芳烃与芳基碘化物、溴化物和氯化物的分子内直接芳基化反应。这些反应产率优异且具有高度选择性。对芳基碘化物底物的研究表明,由于反应介质中碘化物的积累会发生催化剂中毒现象。这可通过添加银盐来克服,银盐还能使这些反应在较低温度下进行。该方法的实用性通过咔唑天然产物的快速合成以及通过直接芳基化产物的开环反应合成空间位阻较大的四邻位取代联芳基得以体现。机理研究深入了解了催化剂的作用模式,并表明在钯催化的简单芳烃直接芳基化反应中存在动力学上重要的C-H键裂解。从这些研究中获得的知识促使开发出与以前难以实现的芳烃的新型分子间芳基化反应,为其他新的直接芳基化过程的开发打开了大门。