Controlling site selectivity in palladium-catalyzed C-H bond functionalization.
Controlling site selectivity in palladium-catalyzed C-H bond functionalization.
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DOI：
10.1021/ar300014f
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发表时间：
2012-06-19
影响因子：
18.3
通讯作者：
Sanford, Melanie S.
中科院分区：
文献类型：
--
作者：
Neufeldt, Sharon R.;Sanford, Melanie S.
有效的C-H键功能化方法需要克服在复杂有机分子中存在的大量C-H键之间进行区分的关键挑战。本文重点介绍了我们在过去十年中使用以下方法开发位置选择性Pd催化的C-H功能化反应的工作：通过使用定向基团基于底物控制选择性(方法1)，通过使用电子激活底物控制底物(方法2)，或基于催化剂控制(方法3)。在我们对第一种方法的广泛探索中，对sp2和sp3的C-H官能化反应都出现了一些选择性趋势，这些趋势适用于涉及不同导向基团的各种转化。官能化倾向于发生在受阻较小的SP2C-H键邻位到定向基团，发生在β到定向基团的初级SP3C-H键上，并且当存在多个定向基团时，发生在最基本定向基团附近的C-H位。使用方法2，它利用底物中的电子偏置，我们的小组已经实现了吲哚和吡咯的C-2选择性芳基化反应，使用的是二芳基碘的氧化剂。当杂环的C-2位被封闭时，这些转化的选择性被改变，导致在C-3位形成C-C键。虽然方法3(基于催化剂的控制)仍处于探索的早期阶段，但我们已经取得了令人振奋的结果，表明可以通过改变Pd催化剂上支撑配体的结构来调节中心选择性。例如，通过调节N~N双齿配体的结构，我们已经在萘的α位实现了精致的芳基化选择性。类似地，我们证明了芳烃乙酰氧基化的速率和位置的选择性都取决于吡啶(配体)与钯的比例。最后，通过将Pd上的配体从醋酸酯切换到碳酸酯，我们逆转了1，3-二甲氧基苯/苯并[h]喹啉偶联的中心选择性。结合文献中越来越多的报道，这些研究突出了基于催化剂的位置选择性控制在新的C-H键功能化方法开发中的前沿。
Effective methodology to functionalize C–H bonds requires overcoming the key challenge of differentiating among the multitude of C–H bonds that are present in complex organic molecules. This Account focuses on our work over the past decade toward the development of site-selective Pd-catalyzed C–H functionalization reactions using the following approaches: substrate-based control over selectivity through the use of directing groups (approach 1), substrate control through the use of electronically activated substrates (approach 2), or catalyst-based control (approach 3). In our extensive exploration of the first approach, a number of selectivity trends have emerged for both sp2 and sp3 C–H functionalization reactions that hold true for a variety of transformations involving diverse directing groups. Functionalizations tend to occur at the less-hindered sp2 C–H bond ortho to a directing group, at primary sp3 C–H bonds that are β to a directing group, and, when multiple directing groups are present, at C–H sites proximal to the most basic directing group. Using approach 2, which exploits electronic biases within a substrate, our group has achieved C-2-selective arylation of indoles and pyrroles using diaryliodonium oxidants. The selectivity of these transformations is altered when the C-2 site of the heterocycle is blocked, leading to C–C bond formation at the C-3 position. While approach 3 (catalyst-based control) is still in its early stages of exploration, we have obtained exciting results demonstrating that site selectivity can be tuned by modifying the structure of the supporting ligands on the Pd catalyst. For example, by modulating the structure of N~N bidentate ligands, we have achieved exquisite levels of selectivity for arylation at the α site of naphthalene. Similarly, we have demonstrated that both the rate and site selectivity of arene acetoxylation depend on the ratio of pyridine (ligand) to Pd. Lastly, by switching the ligand on Pd from an acetate to a carbonate, we have reversed the site selectivity of a 1,3-dimethoxybenzene/benzo[h]quinoline coupling. In combination with a growing number of reports in the literature, these studies highlight a frontier of catalyst-based control of site-selectivity in the development of new C–H bond functionalization methodology.
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影响因子：
15
作者：
Desai, Lopa V.;Stowers, Kara J.;Sanford, Melanie S.
通讯作者：
Sanford, Melanie S.
影响因子：
16.6
作者：
Chen, Xiao;Engle, Keary M.;Wang, Dong-Hui;Yu, Jin-Quan
通讯作者：
Yu, Jin-Quan
影响因子：
15
作者：
Hull, Kami L.;Anani, Waseem Q.;Sanford, Melanie S.
通讯作者：
Sanford, Melanie S.
DOI：
10.3891/acta.chem.scand.27-1249
发表时间：
1973-01-01
期刊：
ACTA CHEMICA SCANDINAVICA
影响因子：
--
作者：
EBERSON, L;GOMEZGON.L
通讯作者：
GOMEZGON.L
影响因子：
18.3
作者：
Daugulis O;Do HQ;Shabashov D
通讯作者：
Shabashov D