title: Hydrogen-bond-directed formal [5 + 1] annulations of oxindoles with ester-linked bisenones: facile access to chiral spirooxindole δ-lactones.
abstract: 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 δ-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.
authors.affiliation: State Key Laboratory of Applied Organic Chemistry, and College of Chemistry and Chemical Engineering, Lanzhou University , Lanzhou 730000, P. R. China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Zhao
authors.forename: Jun-Bing
authors.initials: JB
authors.lastname: Lin
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Zhao
authors.forename: Yong-Min
authors.initials: YM
authors.lastname: Liang
authors.forename: Peng-Fei
authors.initials: PF
authors.lastname: Xu