Organocatalytic Asymmetric Tandem Reaction of Indene-Based Dienes for the Synthesis of Enantioenriched Spirodihydrofluorenes and Fluorenylamine-ketoximes Containing Axial Elements

An efficient asymmetric tandem reaction of indene-based dienes with isoxazole-5-ones catalyzed by chiral cinchona alkaloid-derived thioureas has been established, constructing a diverse array of novel enantioenriched spirodihydrofluorene compounds bearing isoxazolone moieties. More importantly, the spirodihydrofluorene frameworks can be effortlessly transformed into an atropisomeric fluorene skeleton bearing oxime groups. This work not only addresses the challenges in the construction of enantioenriched spirodihydrofluorene frameworks but also provides a powerful strategy for structurally novel fluorenylamine-ketoximes containing axial elements.