Kuang Cuiwen, Zhou Xin, Xie Qiqiang, Ni Chuanfa, Gu Yucheng, Hu Jinbo
Key Laboratory of Organofluorine Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Ling-Ling Road, Shanghai 200032, China.
Syngenta, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, U.K.
Org Lett. 2020 Nov 6;22(21):8670-8675. doi: 10.1021/acs.orglett.0c03258. Epub 2020 Oct 23.
A novel Friedel-Crafts-type alkylation of arenes to access valuable 1-fluoroalkyl-1,1-biaryl compounds is established under mild conditions. The key to success is the efficient generation of a destabilized benzylic carbocation intermediate via two consecutive single-electron transfer processes by virtue of visible-light photoredox catalysis. This unique activation pattern avoids using strong Lewis acids and high temperatures that are required for generation of destabilized carbocations in traditional Friedel-Crafts reactions. This protocol demonstrates the first example of photoredox-catalyzed heterolysis of electronically deactivated benzylic C-Br bonds for the formation of destabilized carbocation intermediates.
在温和条件下建立了一种新颖的芳烃傅克型烷基化反应，用于制备有价值的1-氟烷基-1,1-二芳基化合物。成功的关键在于借助可见光光氧化还原催化，通过两个连续的单电子转移过程高效生成不稳定的苄基碳正离子中间体。这种独特的活化模式避免了使用传统傅克反应中生成不稳定碳正离子所需的强路易斯酸和高温。该方法展示了光氧化还原催化电子钝化苄基C-Br键异裂以形成不稳定碳正离子中间体的首个实例。
