Graphene‐Oxide‐Catalyzed Direct CH−CH‐Type Cross‐Coupling: The Intrinsic Catalytic Activities of Zigzag Edges

• Published in: Angewandte Chemie International Edition 2018-08, Vol.57 (34), p.10848-10853
• Main Authors: Wu, Hongru, Su, Chenliang, Tandiana, Rika, Liu, Cuibo, Qiu, Chuntian, Bao, Yang, Wu, Ji'en, Xu, Yangsen, Lu, Jiong, Fan, Dianyuan, Loh, Kian Ping
• Format: Article
• Language: English
• Subjects: Aromatic compounds; Catalysis; Coupling (molecular); C−C coupling; Dehydrogenation; Functional groups; Graphene; graphene oxide; Intermediates; metal-free catalysis; Quinones; zigzag edges
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201802548

The development of graphene oxide (GO)‐based materials for C−C cross‐coupling represents a significant advance in carbocatalysis. Although GO has been used widely in various catalytic reactions, the scope of reactions reported is quite narrow, and the relationships between the type of functional groups present and the specific activity of the GO are not well understood. Herein, we explore CH−CH‐type cross‐coupling of xanthenes with arenes using GO as real carbocatalysts, and not as stoichiometric reactants. Mechanistic studies involving molecular analogues, as well as trapped intermediates, were carried out to probe the active sites, which were traced to quinone‐type functionalities as well as the zigzag edges in GO materials. GO‐catalyzed cross‐dehydrogenative coupling is operationally simple, shows reusability over multiple cycles, can be conducted in air, and exhibits good functional group tolerance. Carbocatalysis: Cross‐dehydrogenative coupling of xanthene (or thioxanthene) and arenes catalyzed by GO materials is operationally simple, recyclable, can be conducted in air, and exhibits good functional group tolerance. Mechanistic studies suggest that, compared to oxygenated groups, zigzag edge sites play a greater role in carbocatalysis than previously supposed.