山东大学史大永团队报道了钯催化的吲哚在C4和C6位置的远程C-H膦酰化反应的方法。相关研究成果发表在2021年4月14日出版的《德国应用化学》。

在过去的十年中，钯催化的吲哚苯类化合物直接C-H活化已经实现。然而，钯催化的吲哚的远程C-H活化非常罕见。

该文中，研究人员报道了一种具有挑战性的钯催化的吲哚远程C4-H膦酰化反应。该方法提供了一系列C4-膦酰化吲哚，包括色氨酸和含色氨酸的二肽，由于其严重依赖C3-导向基团，通常通过直接C4-H活化无法获得这些二肽。

值得注意的是，通过阻断C4位置意外获得了C6-膦酰化吲哚。初步的机理研究表明，反应可能通过C7-Palladacycle环/远程活化过程进行。基于这一策略，还介绍了BrCF  2  COOEt远程C4-H二氟甲基化的例子，表明该策略可能为其他交叉偶联提供一个总体蓝图。

附：英文原文

Title: Palladium‐Catalyzed Remote C‐H Phosphonylation of Indoles at the C4 and C6 Positions via a Radical Approach

Author: Xiaolin Shi, Zemin Wang, Yuxiu Li, Xiaowei Li, Xiangqian Li, Shi Dayong

Issue&Volume: 2021-04-14

Abstract: Palladium‐catalyzed direct C‐H activation of indole benzenoid moiety has been achieved in the past decade. However, palladium‐catalyzed remote C‐H activation of indoles is really rare. Herein, we report a challenging palladium‐catalyzed remote C4‐H phosphonylation of indoles via a radical approach. The method provides access to a series of C4‐phosphonylated indoles, including tryptophan and tryptophan‐containing dipeptides, which are typically inaccessible by direct C4‐H activation due to its heavy reliance on C3 directing groups. Notably, unexpected C6‐phosphonylated indoles were obtained through blocking of the C4 position. The preliminary mechanistic studies indicated that the reactions may proceed via a C7‐palladacycle/remote‐activation process. Based on the strategy, examples of remote C4‐H difluoromethylation with BrCF  2  COOEt are also presented, suggesting that the strategy may offer a general blueprint for other cross‐couplings.

DOI: 10.1002/anie.202103395

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202103395