A Short Review of C7 – H Bond Functionalization of Indole/Indoline

Recent progress in transition metal-catalyzed selective C–H functionalization of indoles has attracted significant interest. Indoles functionalized at the C7 position represent key structural frameworks found in numerous bioactive molecules and pharmaceutical agents. Initial advancements in C7 modifications were achieved via directed ortho metalation (DOM), followed by quenching with appropriate electrophiles or through halogenation using Cu (II) halides. Direct functionalization at the C-7 position of indoles is relatively challenging due to the intrinsic reactivity pattern of the pyrrole-type ring, which favors modifications at the C-2 and C-3 positions. Nonetheless, recent advancements in transition-metal-catalyzed, auxiliary-assisted strategies have enabled site-selective C-7 functionalization. These methods have proven to be powerful tools for forming carbon–carbon and carbon–heteroatom bonds, thereby expanding the structural diversity of indole derivatives. This review underscores the progress and applications of recent advancements in the transformation of the otherwise inert C7–H bond.