Enantioselective Synthesis of Spiroindolines via Cascade Isomerization/Spirocyclization/Dearomatization Reaction

The spiroindoline skeleton featured with 2,7-diazaspiro[4.4]­nonane exists in various structurally intricate and biologically active monoterpene indole alkaloids. A catalytic asymmetric cascade enamine isomerization/spirocyclization/dearomatization succession to construct the spiroindoline was developed, which employed the indolyl dihydropyridine as a substrate under catalysis of the chiral phosphoric acid. This cascade reaction provided various spiroindolines in both diastereoselective and enantionselective fashions.