Highly enantio- and diastereoselective generation of two quaternary centers in spirocyclopropanation of oxindole derivatives

Spirocyclopropanes: only one out of eight possible stereoisomers was obtained in the asymmetric cascade cyclopropanation of alkylidene oxindoles with ethyl 2-chloroacetoacetate. Improved catalyst design ensured that spirocyclopropyl oxindoles featuring two quaternary centers were synthesized in high yield and high enantio-and diastereoselectivity.