Asymmetric Synthesis of 3-Methyleneindolines via Rhodium(I)-Catalyzed Alkynylative Cyclization of N-(o-Alkynylaryl)imines

The first asymmetric synthesis of 3-methyleneindolines from alkynyl imines has been developed via a rhodium-catalyzed tandem process: regioselective alkynylation of the internal alkynes and subsequent intramolecular addition to the imines. The reaction proceeded with unconventional chemoselectivity and provided 3-methyleneindolines with good yields (up to 82% yield) and high enantioselectivities (up to 97% ee). Moreover, this transformation also features mild reaction conditions, perfect atom economy, and a broad substrate scope.