Privilege-Structure-Oriented Three-Component Asymmetric Aminomethylation: Assembly of Chiral 3-Aminomethyl Indolones.

The asymmetric aminomethylation reaction of 3-diazooxindoles with electronic-rich arenes and N,O-acetals cooperatively catalyzed by achiral dirhodium complex and chiral phosphoric acid is reported. The reaction provides a novel method for the facile synthesis of chiral 3-aminomethyl oxindoles with an all-carbon quaternary center in good yields (82-98%) with high to excellent enantioselectivities (up to 97% ee). The transformation proceeds through a convergent addition of a reactive zwitterionic intermediate with a chiral methylene iminium generated in situ via asymmetric counteranion-directed catalysis (ACDC). This work represents the first asymmetric aminomethylation method of mixed 3,3'-bisindoles with structural diversity.