Iodine-catalyzed synthesis of indole derivatives: a review

The indole scaffold is an important and versatile heterocyclic class that supports important developments in the fields of material and pharmaceutical science. Because of iodine’s special redox flexibility, gentle reaction conditions, and environmental compatibility, the usage of iodine reagents in the synthesis of indole scaffold has recently attracted a lot of attention. The iodine chemistry generally enables electrophilic iodination, oxidative coupling, and C–H functionalization. The mechanistic insights show that the iodine activates the indole nuclei toward nucleophilic or radical pathways. Thus, this review focuses on significant advancements in molecular iodine-catalyzed or promoted carbon-carbon bond formation at the C-2 and C-3 positions of indole citing the examples of the synthesis of bis/tris indoles, indole fused skeletons, and benzylation/alkylation/alkenylation/formylation covering the advancements from 2013 to 2026. This review highlights about iodine-based, sustainable procedures enable the effective creation of different scaffolds and structurally varied libraries, offering implications for organic synthesis and medicinal chemistry.