惰性C-H键的选择性活化是避免传统偶联反应浪费的一种有效手段。简单芳香族化合物的氧化偶联使双芳基的合成具有成本效益。然而，该技术的应用受到区域选择性差和先进的均相钯催化剂稳定性的限制。
亮点
● 本文展示了阳离子钯限制在分子筛的孔隙中，在没有功能手柄或电子偏压的情况下，对简单芳烃进行择形C-H
活化。例如，在六种可能的异构体中，4,4-二甲苯在钯-β上的氧化偶联反应中具有较高的形状选择性（80%）。
● 不仅得到了一个强大的多相催化体系，而且将此概念应用于过渡金属催化芳烃C-H活化反应中，通过空间限制来控制选择性。
图文解析
钯催化剂在沸石宿主中的作用。芳烃氧化偶联反应活跃的均相催化剂通常包括钯盐、强酸性添加剂，例如对甲苯磺酸(TsOH)或三氟乙酸(TFAH)和乙酸(AcOH)。当将这种均相催化剂应用于甲苯时(图1)，可以得到一个无偏压的区域异构体分布，所有的碳氢键都被Pd活化到相似的程度。
The selectve activation of inert C-H bond is an effective means to avoid the waste of traditional coupling reaction. The oxidative coupling of simple aromatic compounds makes the synthesis of diaryl groups cost-effective. However, the application of this technology is limited by the poor regional selectivity and the stability of the most advanced homogeneous palladium catalyst.
Highlights of this article
● This paper shows that cationic palladium is confined in the pores of molecular sieves, and performs shape-selective C-H activation on simple aromatics without functional handles or electronic bias. For example, among the six possible isomers, 4,4-xylene in palladium- β It has high shape selectivity (80%) in oxidative coupling reaction.
● Not only has a powerful heterogeneous catalytic system been obtained, but also this concept has been applied to the transition metal-catalyzed aromatics C-H activation reaction, and the selectivity is controlled by space limitation.