Calcium-Catalyzed Asymmetric Synthesis of 3-Tetrasubstituted Oxindoles: Efficient Construction of Adjacent Quaternary and Tertiary Chiral Centers.

The asymmetric addition of N-Boc-imines (II) to 3-substituted oxindoles (I) leads to chiral 3,3-disubstituted oxindoles with 86-96% diastereoselectivity (the main diastereomer is readily isolated by a column chromatography).