Beyond C2 and C3: Transition-Metal-Catalyzed C–H Functionalization of Indole

The indole scaffold will continue to play a vital part in the future of drug discovery and agrochemical development. Because of this, the necessity for elegant techniques to enable selective C–H functionalization is vast. Early developments have led to primarily C2 and C3 functionalization because of the inherent reactivity of the pyrrole ring. Despite this, elegant methods have been developed to enable selective C–H functionalization on the benzenoid moiety at C4, C5, C6, and C7. This review focuses on the contributions made in benzenoid C–H functionalization of indoles and other related heteroaromatics such as carbazoles.