Dearomative cycloaddition: current trends in polycyclic indoline synthesis

Dearomative cycloaddition of indoles has become a key strategy in synthetic organic chemistry. It allows the transformation of flat aromatic molecules into complex, three-dimensional structures with high stereochemical control. This review discusses the recent advancements in dearomative cycloadditions of indoles from 2019 to 2025, focusing on their strategic application in constructing polycyclic indoline frameworks with high regio- and stereoselectivity. The review categorizes the dearomative cycloadditions of indoles by the type of cycloaddition employed-namely [2 + 2], [3 + 2], [4 + 2], and miscellaneous transformations-each offering distinct mechanistic pathways and structural outcomes. By integrating synthetic applications, mechanistic insights, and future directions, this review underscores the expanding role of dearomative cycloaddition in modern heterocyclic chemistry and its growing impact on complex molecule synthesis.