Chiral Phosphoric Acid Catalyzed Enantioselective Synthesis of α-Tertiary Amino Ketones from Sulfonium Ylides.

Herein we disclose a new catalytic asymmetric approach for the synthesis of chiral α-amino ketones, which is particularly useful for the less accessible acyclic α-tertiary cases. By a protonation-amination sequence, our approach represents a rare asymmetric H-heteroatom bond insertion by α-carbonyl sulfonium ylides, an attractive surrogate of diazocarbonyls. The mild intermolecular C-N bond formation was catalyzed by chiral phosphoric acids with excellent efficiency and enantioselectivity. The products are precursors to other important chiral amine derivatives, including drug molecules and chiral ligands. The enantioselectivity was controlled by dynamic kinetic resolution in the amination step, rather than the initial protonation. This process opens up a new platform for the development of other related insertion reactions.