Remote para-C-H Functionalization of Arenes by a D-Shaped Biphenyl Template-Based Assembly
Remote para-C-H Functionalization of Arenes by a D-Shaped Biphenyl Template-Based Assembly
复制标题
DOI：
10.1021/jacs.5b06793
复制
发表时间：
2015-09-23
影响因子：
15
通讯作者：
Maiti, Debabrata
中科院分区：
文献类型：
--
作者：
Bag, Sukdev;Patra, Tuhin;Maiti, Debabrata
位点选择性C-H官能化已成为简化复杂分子合成的有效工具。大多数情况下，导向基团（DG）辅助的金属酸形成作为一种有效的策略，以确保有前途的区域选择性。在这方面，各种各样的邻位和间位C-H官能化是示例。然而，尽管取得了这一重大进展，DG辅助的芳烃中的选择性对位C-H官能化反应仍然未被探索，主要是因为它涉及几何约束的金属环过渡态的形成。在这里，我们报告了一种易于回收的新型含硅联苯基模板，通过形成D形组装体来指导甲苯远端p-C-H键的有效官能化。这种DG允许所需的灵活性，以支持形成一个超大的预过渡状态。通过克服电子和空间的偏见，对位烯烃化和乙酰氧基化成功地进行，同时破坏o和m-C-H活化。通过合成各种复杂分子证明了这种基于D形联苯模板的策略的适用性。
Site-selective C-H functionalization has emerged as an efficient tool in simplifying the synthesis of complex molecules. Most often, directing group (DG)-assisted metallacyde formation serves as an efficient strategy to ensure promising regioselectivity. A wide variety of ortho- and meta-C-H functionalizations stand as examples in this regard. Yet despite this significant progress, DG-assisted selective para-C-H functionalizalion in arenes has remained unexplored, mainly because it involves the formation of a geometrically constrained metallacyclic transition state. Here we report an easily recyclable, novel Si-containing biphenyl-based template that directs efficient functionalization of the distal p-C-H bond of toluene by forming a D-shaped assembly. This DG allows the required flexibility to support the formation of an oversized pre-transition state. By overcoming electronic and steric bias, para-olefination and acetoxylation were successfully performed while undermining oand m-C-H activation. The applicability of this D-shaped biphenyl template-based strategy is demonstrated by synthesizing various complex molecules.