Direct Asymmetric Amination of α-Branched Cyclic Ketones Catalyzed by a Chiral Phosphoric Acid

Here we report the direct asymmetric amination of alpha-substituted cyclic ketones catalyzed by a chiral phosphoric acid, yielding products with a N-containing quaternary stereocenter in high yields and excellent, enantioselectivities. Kinetic resolution of the starting ketone was also found to occur on some of the substrates under milder conditions, providing enantioenriched alpha-branched ketones, another important building block in organic synthesis. The utility of this methodology was demonstrated in the short synthesis of (S)-ketamine, the more active enantiomer of this versatile pharmaceutical.