PdII-Catalysed C-H Functionalisation of Indoles and Pyrroles Assisted by the Removable N-(2-Pyridyl)sulfonyl Group: C2-Alkenylation and Dehydrogenative Homocoupling
PdII-Catalysed C-H Functionalisation of Indoles and Pyrroles Assisted by the Removable N-(2-Pyridyl)sulfonyl Group: C2-Alkenylation and Dehydrogenative Homocoupling
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DOI：
10.1002/chem.201001126
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发表时间：
2010-01-01
影响因子：
4.3
通讯作者：
Carlos Carretero, Juan
中科院分区：
文献类型：
--
作者：
Garcia-Rubia, Alfonso;Urones, Beatriz;Carlos Carretero, Juan
易于安装和去除的 N-(2-吡啶基)磺酰基对 Pd-II 催化的吲哚和吡咯的 C-H 烯基化发挥完全的 C2 区域控制，以良好的分离收率（通常 >= 70%）提供相应的产物。该催化剂体系的一个显着特点是它能耐受多种取代烯烃，包括共轭缺电子烯烃、苯乙烯和1,3-二烯，以及共轭1,1-和1,2-二取代烯烃。最终的还原脱磺酰化以良好的收率提供了 C2 取代的游离 NH 吲哚和吡咯。这种 N-(2-吡啶基)-磺酰基导向策略也已扩展到吲哚分子间脱氢自偶联方案的开发，提供 2,2'-双吲哚。基于与同位素标记起始材料的反应和电子变化底物的竞争动力学研究的机理研究表明，螯合辅助的亲电芳香取代钯化机制。
The easily installed and removed N-(2-pyridyl)sulfonyl group exerts complete C2 regiocontrol over the Pd-II-catalysed C-H alkenylation of indoles and pyrroles, affording the corresponding products in good isolated yields (typically >= 70%). A remarkable feature of this catalyst system is that it tolerates a wide variety of substituted alkenes, including conjugated electron-deficient alkenes, styrenes and 1,3-dienes, as well as conjugated 1,1- and 1,2-disubstituted olefins. The final reductive desulfonylation affords the C2-substituted, free-NH indoles and pyrroles in good yield. This N-(2-pyridyl)-sulfonyl-directing strategy has also been extended to the development of a protocol for the intermolecular, dehydrogenative homocoupling of indoles, providing 2,2'-biindoles. Mechanistic work based upon reactions with isotopically labelled starting materials and competitive kinetic studies of electronically varied substrates suggests a chelation-assisted electrophilic aromatic substitution palladation mechanism.