Hydrogen-bonding-promoted oxidative addition and regioselective arylation of olefins with aryl chlorides.
Hydrogen-bonding-promoted oxidative addition and regioselective arylation of olefins with aryl chlorides.
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DOI：
10.1021/ja1081926
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发表时间：
2010-10
影响因子：
15
通讯作者：
J. Ruan;J. Iggo;N. Berry;Jianliang Xiao
中科院分区：
文献类型：
--
作者：
J. Ruan;J. Iggo;N. Berry;Jianliang Xiao
第一，通用的，高效的催化体系，允许广泛的活化和未活化的芳基氯与烯烃的区域选择性偶联已经开发。Heck芳基化反应很可能是由ArCl与Pd（0）的氧化加成反应控制的。因此，富电子双膦，4-MeO-dppp，被引入以促进催化。溶剂的选择是至关重要的，然而，只有缓慢的芳基化反应中观察到的DMF或DMSO，而反应进行良好的乙二醇在0.1-1摩尔%的催化剂负载，显示出优异的区域选择性。机理证据支持，芳基化是周转限制的氧化加成步骤，最重要的是，氧化加成是加速乙二醇，最有可能通过氢键在过渡态的氯化物，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随后的氯化物从Pd（II）中解离，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。
The first, general, and highly efficient catalytic system that allows a wide range of activated and unactivated aryl chlorides to couple regioselectively with olefins has been developed. The Heck arylation reaction is likely to be controlled by the oxidative addition of ArCl to Pd(0). Hence, an electron-rich diphosphine, 4-MeO-dppp, was introduced to facilitate the catalysis. Solvent choice is critical, however; only sluggish arylation is observed in DMF or DMSO, whereas the reaction proceeds well in ethylene glycol at 0.1-1 mol % catalyst loadings, displaying excellent regioselectivity. Mechanistic evidence 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 from Pd(II) to give a cationic Pd(II)-olefin species, which is key to the regioselectivity observed.