The asymmetric counteranion-directed catalysis (ACDC) concept has been extended and exploited by Benjamin List and co-workers, Max Planck Institute for Coal Research, Mülheim an der Ruhr, Germany. A simple combination of commercially available reagents was used to design a catalyst capable of delivering good ee values with high yields in the Overman rearrangement of allylic imidates. The chiral TRIP counteranion combined with a simple commercially available palladacycle gave the palladium complex shown in the scheme below.
The observed enantioselectivity — and reaction mechanism — is explained in a qualitative manner based on the X-ray structure of the proposed ion-pair catalyst.
- A Highly Enantioselective Overman Rearrangement through Asymmetric Counteranion-Directed Palladium Catalysis
G. Jiang, R. Halder, Y. Fang, B. List,
Angew. Chem. Int. Ed. 2011.
- Angew. Chem. 2011.