Catalytic Asymmetric Dearomatization of Indolyl Dihydropyridines through an Enamine Isomerization/Spirocyclization/Transfer Hydrogenation Sequence

A highly efficient synthesis of enantioenriched spiroindolines by catalytic asymmetric dearomatization of indolyl dihydropyridines through a chiral phosphoric acid catalyzed enamine isomerization/spirocyclization/transfer hydrogenation sequence has been developed. This reaction proceeds under mild reaction conditions, affording novel spiroindolines in good yields (up to 88 %) with excellent enantioselectivity (up to 97 % ee). DFT calculations provide insights into the reaction mechanism as well as the origin of stereochemistry. Born to be mild: An efficient synthesis of enantioenriched spiroindolines by catalytic asymmetric dearomatization of indolyl dihydropyridines through a chiral phosphoric acid (CPA)‐catalyzed enamine isomerization/spirocyclization/transfer hydrogenation sequence was developed (HEH=Hantzsch ester). The reaction proceeds under mild reaction conditions to afford spiroindolines in good yields (up to 88 %) with excellent enantioselectivity (up to 97 % ee).