Five-membered ring systems: pyrroles and benzo analogues

The reactions and synthesis of pyrroles, indoles, isatins, carbazoles and related fused heterocyclic ring systems from the year 2020 are reviewed. Pyrroles and indoles are treated in separate sections with the ring-forming reactions discussed by intramolecular or intermolecular bond disconnection. Other sections include nucleophilic, electrophilic or radical reactivity of the parent rings, C–H functionalization/organometallic reactions, reactions of side chains and examples in total synthesis.