Cobalt-Catalyzed Annulation Reactions via C−H Bond Activation

Considerable research attention has been directed towards the use of first-row transition metals in organic synthesis. The more abundant, and less expensive cobalt is considered to be an effective alternative for expensive second and third-row noble metals, especially in C-H bond functionalization reactions. In this mini-review, we will summarize the features, and recent achievements of the Co-catalyzed directing group assisted C-H activation/cyclization reactions and their mechanistic insights.