Organocatalytic Enantioselective Michael–Michael–Michael–Aldol Condensation Reactions: Control of Six Stereocenters in a Quadruple-Cascade Asymmetric Synthesis of Polysubstituted Spirocyclic Oxindoles

An
organocatalyzed enantioselective Michael–Michael–Michael–aldol
cascade reaction for the construction of cyclopentane fused spirooxindoles
was achieved. The domino reaction provided the spirooxindoles with
six contiguous stereocenters including a quaternary center in good
yields (55–64%) with excellent enantioselectivities (up to
>99% ee). Enantioselective Michael–Michael–Michael–aldol
condensation–aromatization reactions of an isomeric product
were observed.