Asymmetric Organocatalytic Synthesis of 3-Diarylmethine-Substituted Oxindoles Bearing a Quaternary Stereocenter via 1,6-Conjugate Addition to para-Quinone Methides

A highly stereoselective organocatalytic 1,6-conjugate addition of 3-substituted oxindoles to para -quinone methides to construct all-carbon quaternary stereocenters is described. In the presence of 10 mol % of a bifunctional squaramide organocatalyst, this 1,6-addition reaction occurs with excellent yields, diastereoselectivities and very good enantioselectivities, providing an efficient approach to a series of oxindole derivatives containing the diarylmethine motif attached to an all-carbon quaternary stereogenic center.