Complementary Strategies for Directed C(sp3)−H Functionalization: A Comparison of Transition‐Metal‐Catalyzed Activation, Hydrogen Atom Transfer, and Carbene/Nitrene Transfer

Abstract The functionalization of C(sp 3 )−H bonds streamlines chemical synthesis by allowing the use of simple molecules and providing novel synthetic disconnections. Intensive recent efforts in the development of new reactions based on C−H functionalization have led to its wider adoption across a range of research areas. This Review discusses the strengths and weaknesses of three main approaches: transition‐metal‐catalyzed C−H activation, 1, n ‐hydrogen atom transfer, and transition‐metal‐catalyzed carbene/nitrene transfer, for the directed functionalization of unactivated C(sp 3 )−H bonds. For each strategy, the scope, the reactivity of different C−H bonds, the position of the reacting C−H bonds relative to the directing group, and stereochemical outcomes are illustrated with examples in the literature. The aim of this Review is to provide guidance for the use of C−H functionalization reactions and inspire future research in this area.