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

A highly diastereoselective vinylogous nucleophilic 1,6-conjugate addition reaction of para-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 Z/E > 99:1).