Cobalt‐Catalyzed C(sp²)−O Bond Formation by Directing Group Assisted C−H Activation

Abstract

Metal-catalyzed C sp2 À H oxygenation is a synthetically invaluable transformation that enables the incorporation of synthetically useful functional groups, such as ethers and acetates, using a simple protocol. Compared to the well-developed palladium catalysis, the catalysis of cobalt, a 3d-transition metal, is recognized as a sustainable alternative for C sp2 À H oxygenation because of the natural abundance of cobalt and cost-effectiveness of the catalyst. In this Review, recent advances in cobaltcatalyzed C sp2 À H alkoxylation and acetoxylation are highlighted and several types of directing groups are discussed.

Ni‐Catalyzed/mediated C−X (X=N, O, S) Bond Formation Chelation‐Assisted by Bidentate Directing Groups

“…With the rapid development of methodology, how to rapidly construct the CÀ O bond was attracted more and more attention. In the past, the method of CÀ H functionalization reaction is largely limited to palladium, [84][85][86][87] copper, [88,89] cobalt [90][91][92] to construct CÀ O bond. Recently, lowpriced metal catalyzed CÀ H Acyloxylation [83] reactions have been attracted more attention, especially nickel salts as promising promoter during CÀ O bond forming process.…”