Triptycenyl Sulfide: A Practical and Active Catalyst for Electrophilic Aromatic Halogenation Using N-Halosuccinimides
Triptycenyl Sulfide: A Practical and Active Catalyst for Electrophilic Aromatic Halogenation Using N-Halosuccinimides
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DOI：
10.1021/jacs.9b12672
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发表时间：
2020-01-22
影响因子：
15
通讯作者：
Miura, Masahiro
中科院分区：
文献类型：
--
作者：
Nishii, Yuji;Ikeda, Mitsuhiro;Miura, Masahiro
介绍了一种刘易斯碱催化剂Trip-SMe（Trip =三蝶烯基）用于N-卤代琥珀酰亚胺（NXS）的芳族亲电卤代反应。在适当的活化剂（作为非配位阴离子源）存在下，一系列未活化的芳香族化合物在室温下使用NXS卤化。该催化体系适用于目前除了使用Br-2或Cl-2之外无法实现的转化：例如，萘的多卤代反应，BINOL的区域选择性溴化反应等。对照实验表明，三蝶烯基取代基发挥了至关重要的作用，催化活性，和动力学实验表明，发生的锍盐[Trip-S（Me）Br][SbF 6]作为一个活性物种。与简单的二烷基硫醚相比，Trip-SMe在卤配合物中表现出明显的电荷分离离子对特征，其结构信息通过单晶X射线分析获得。初步的计算研究揭示了三蝶烯基官能团的π系统是巩固亲电性增强的关键基序。
A Lewis base catalyst Trip-SMe (Trip = triptycenyl) for electrophilic aromatic halogenation using N-halosuccinimides (NXS) is introduced. In the presence of an appropriate activator (as a noncoordinating-anion source), a series of unactivated aromatic compounds were halogenated at ambient temperature using NXS. This catalytic system was applicable to transformations that are currently unachievable except for the use of Br-2 or Cl-2: e.g., multihalogenation of naphthalene, regioselective bromination of BINOL, etc. Controlled experiments revealed that the triptycenyl substituent exerts a crucial role for the catalytic activity, and kinetic experiments implied the occurrence of a sulfonium salt [Trip-S(Me)Br][SbF6] as an active species. Compared to simple dialkyl sulfides, Trip-SMe exhibited a significant charge-separated ion pair character within the halonium complex whose structural information was obtained by the single-crystal X-ray analysis. A preliminary computational study disclosed that the pi system of the triptycenyl functionality is a key motif to consolidate the enhancement of electrophilicity.