Enantioselective Synthesis of Spirocyclopentane Oxindoles Bearing Five Consecutive Stereocenters through Secondary Amine‐Catalyzed [3+2] Cycloaddition

Abstract

This work delineates a Michael-initiated ring-closing [3 + 2] cycloaddition of newly designed 3-(1-benzyl-2-oxoindolin-3yl)pentane-2,4-diones with α,β-unsaturated aldehydes. During the chiral secondary amine-catalyzed cascade reaction, highly functionalized spirocyclopentane oxindole derivatives containing five consecutive stereogenic centers were formed, two of which were tetrasubstituted carbon. All the desired products are smoothly obtained in good yields (up to 90 %) with excellent enantioselectivities (up to > 99 : 1 er) and diastereoselectivities (up to > 95 : 5 dr). Meanwhile, the practicality of this strategy was highlighted by the further gram-scale experiment and a set of synthetic transformations.