Parthasarathy Gandeepan, Chien‐Hong Cheng

Transition-metal-catalyzed CH activation is considered to be an important tool in organic synthesis and has been accepted and widely used by chemists because it is straightforward, cost-effective, and environmentally friendly. A variety of functional groups have been used to direct metal complexes and achieve regioselective CH activation. Most directing is achieved through the σ-bond coordination of functional groups to the metal catalyst, followed by ortho-selective CH bond cleavage. However, recent work has demonstrated that π-coordinating functional groups can also assist in guiding metal complexes for site-selective CH bond activation. This emerging approach significantly expands the scope of CH activation reactions in organic synthesis. Herein, recent developments in this field are summarized.