Hydrogen-Bond-Directed Formal [5+1] Annulations of Oxindoles with Ester-Linked Bisenones: Facile Access to Chiral Spirooxindole δ-Lactones

A novel bifunctional thiourea catalyzed formal [5 + 1] cycloaddition of oxindoles and ester-linked bisenones was successfully developed. This strategy involves two sequential Michael additions, leading to spirooxindole lactones with three contiguous stereocenters including an all-carbon quaternary center with high diastereo- and enantioselectivites. In addition, a remarkable N-substituent effect was observed on the reactivity and selectivity.