Highly e ffi cient synthesis and stereoselective migration reactions of chiral fi ve-membered aza-spiroindolenines: scope and mechanistic understanding †

An Ir-catalyzed asymmetric synthesis of fi ve-membered aza-spiroindolenines is achieved. Based on the detailed investigation of the reaction patterns of the aryl iminium migration, a one-pot asymmetric allylic dearomatization/migration sequence from racemic indole derivatives is realized, a ff ording enantioenriched Pictet – Spengler-type products bearing an additional allylic stereogenic center adjacent to the C3 position of the indole core.