Asymmetric Catalytic Protonation of Silyl Enol Ethers with Chiral Palladium Complexes

Addition of amine is required to convert the chiral cationic palladium complex obtained from a silver salt and [PdCl 2 {(R)‐binap}] into an efficient asymmetric catalyst for the protonation of cyclic silyl enol ethers with water [Eq. (a)]. The effect of the amine is most likely based on selective deactivation of an initially formed Pd–binap comple. The “surviving” Pd species cause a reaction that is slower but proceeds with enhanced enantioselectivity.