Asymmetric organocatalytic synthesis of chiral 3,3-disubstituted oxindoles via a 1,6-conjugate addition reaction.

A highly efficient synthesis of chiral 3,3-disubstituted oxindoles was developed using a chiral spirocyclic phosphoric acid catalyzed 1,6-conjugate addition reaction of para-quinone methides derived from N-unprotected isatins with indoles. The reaction proceeds under mild reaction conditions to provide indole-containing N-unprotected oxindoles bearing quaternary stereocenters in good yields and with moderate to excellent enantioselectivities (up to 97% ee).