Recent Developments in Transition Metal-Catalyzed Dearomative Cyclizations of Indoles as Dipolarophiles for the Construction of Indolines

Fused polycyclic indoline skeletons are found in many natural products and bioactive molecules. Several approaches, including dearomative cyclization of functionalized indoles, have been developed for the rapid synthesis of these skeletons. As a result of extensive research over the past few decades, numerous elegant and efficient protocols for the transition metal-catalyzed dearomative cyclization of indoles to afford indolines have been reported, and recent developments in this area are discussed in detail in this review.