Tertiary Amine-Catalyzed Chemoselective and Asymmetric [3 + 2] Annulation of Morita–Baylis–Hillman Carbonates of Isatins with Propargyl Sulfones

A chemo- and enantioselective [3 + 2] annulation of Morita-Baylis-Hillman carbonates of isatins with propargyl sulfones was catalyzed by a β-ICD O-MOM ether 1c, affording spirocyclic 2-oxindoles bearing an unusual cyclopentadiene motif in outstanding ee values (up to >99%). More electrophiles, such as N-phenylmaleimide, have been also utilized to deliver complex spirocyclic 2-oxindoles with good results.