中科院大连化物所Xingwei Li研究团队取得一项新突破。他们的最新研究揭示了以二芳基乙炔为稀有芳基试剂的基于双C-H活化的对映和非对映选择性C-H芳基化。相关论文发表在2021年6月19日出版的《德国应用化学》杂志上。
据介绍，C-H键活化是获得轴向手性双芳基的一种有效方法，其中最直接的方法是芳烃直接C-H芳基化。然而，芳基化来源仅限于几种活性和大位阻试剂。
本文报道了在铑催化下，二芳基膦酰胺与二芳基乙炔的1:2偶联，对映选择性和非对映选择性地制备具有中心手性和轴向手性的双芳基。这种双重C-H活化反应在化学选择性方面与之前研究的Miura-Satoh型芳烃和炔烃1:2偶联反应形成对比，并在温和的条件下进行，炔烃作为一种稀有的芳基化试剂。
这两个C-H活化事件是立体决定的，并在催化剂控制下，以远程的方式通过非立体决定实现第二次C-H活化。主要和副产物的立体化学分析表明初始C-H活化-脱对称过程具有适度的对映选择性。然而，次要(R)铑乙烯中间体更容易在不希望的质子分解中消耗，最终导致主要产品的高对映选择性和非对映选择性。
附：英文原文
Title: Twofold C-H Activation-Based Enantio- and Diastereoselective C-H Arylation Using Diarylacetylenes as Rare Arylating Reagents
Author: Xingwei Li, Panjie Hu, Lingheng Kong, Fen Wang, Xiaolin Zhu
Issue&Volume: 2021-06-19
Abstract: C-H bond activation has been established as an attractive strategy to access axially chiral biaryls, and the most straightforward method is direct C-H arylation of arenes. However, the arylating source has been limited to several classes of reactive and bulky reagents. Reported herein is rhodium-catalyzed 1:2 coupling of diarylphosphinic amides and diarylacetylenes for enantio- and diastereoselective construction of biaryls with both central and axial chirality. This twofold C-H activation reaction stays contrast to the previously explored Miura-Satoh type 1:2 coupling of arenes and alkynes in terms of chemoselectivity and proceeded under mild conditions with the alkyne acting as a rare arylating reagent. Both C-H activation events are stereo-determining and are under catalyst control, with the 2nd C-H activation being diastereo-determining in a remote fashion. Analysis of the stereochemistries of the major and side products suggests moderate enantioselectivity of the initial C-H activation-desymmetrization process. However, the minor (R) rhodium vinyl intermediate is consumed more readily in undesired protonolysis, eventually resulting in high enantio- and diastereoselectivity of the major product.
DOI: 10.1002/anie.202106871
Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202106871
