Hydrogen-Bonding-Promoted Oxidative Addition and Regioselective Arylation of Olefins with Aryl Chlorides
作者:Jiwu Ruan、Jonathan A. Iggo、Neil G. Berry、Jianliang Xiao
DOI:10.1021/ja1081926
日期:2010.11.24
supports that the arylation is turnover-limited by the oxidative addition step and, most importantly, that the oxidative addition is accelerated by ethylene glycol, most likely via hydrogen bonding to the chloride at the transition state as shown by DFT calculations. Ethylene glycol thus plays a double role in the arylation, facilitating oxidative addition and promoting the subsequent dissociation of chloride
已经开发出第一个通用且高效的催化系统,该系统允许各种活化和未活化的芳基氯化物区域选择性地与烯烃偶联。Heck 芳基化反应很可能通过将 ArCl 氧化加成到 Pd(0) 来控制。因此,引入了富电子二膦 4-MeO-dppp 以促进催化。然而,溶剂的选择很关键。在 DMF 或 DMSO 中仅观察到缓慢的芳基化反应,而在 0.1-1 mol% 催化剂负载量的乙二醇中反应进行得很好,显示出优异的区域选择性。机理证据支持芳基化受氧化加成步骤限制,最重要的是,氧化加成被乙二醇加速,最有可能通过氢键与过渡态的氯化物结合,如 DFT 计算所示。因此,乙二醇在芳基化中起着双重作用,促进氧化加成并促进氯化物随后从 Pd(II) 解离以得到阳离子 Pd(II)-烯烃物质,这是观察到的区域选择性的关键。