Bismuth Triflate-Catalyzed Vinylogous Nucleophilic 1,6-Conjugate Addition of <i>para</i>-Quinone Methides with 3‑Propenyl-2-silyloxyindoles

A highly diastereoselective vinylogous nucleophilic 1,6-conjugate addition reaction of <i>para</i>-quinone methides with 3-propenyl-2-silyloxyindoles by a bismuth triflate catalyst has been developed. A number of diphenylmethane type compounds functionalized with oxindole motifs was obtained with excellent yields (up to 99%) and very good diastereoselectivities (up to <i>Z</i>/<i>E</i> > 99:1)