Facile synthesis of chiral indolines through asymmetric hydrogenation of in situ generated indoles

A concise and enantioselective procedure for the synthesis of optically active indolines has been developed through intramolecular condensation, deprotection and palladium-catalyzed asymmetric hydrogenation in a one-pot process with up to 96% ee. A strong Bronsted acid played an important role in both the formation of indoles and asymmetric hydrogenation process. This strategy could be scaled-up with excellent reactivity and enantioselectivity.