Chiral Squaramide-Catalyzed Asymmetric Mannich Reactions for Synthesis of Fluorinated 3,3-Bisoxindoles

A squaramide-catalyzed asymmetric Mannich reaction of 3-fluorooxindoles to isatin-derived imines for synthesis of fluorinated 3,3-bisoxindoles with two contiguous stereocenters under mild conditions was developed. The corresponding 3,3-bisoxindoles were obtained in excellent yields with excellent diastereo- and enantioselectivities (up to 99% yield, >99:1dr and >99% ee). What's more, this reaction can be gram-scaled without compromising yield and stereoselectivity.