Ni(II)-Catalyzed enantioselective Mukaiyama-Mannich reaction between silyl enol ethers and cyclic N-sulfonyl α-ketiminoesters

The enantioselective Mukaiyama-Mannich reaction of cyclic N-sulfonyl alpha-ketiminoesters and silyl enol ethers was realized for the first time using a Ni(II)-bis(oxazoline) complex. Both di-and tri-substituted silyl enol ethers as well as silyl dienol ethers generated from the corresponding aromatic ketones or alpha, beta-unsaturated ketones were well tolerated in this reaction. The reaction proceeded smoothly under mild conditions to provide a series of enantioenriched benzofused sultams containing an alpha-quaternary alpha-amino ester and an aromatic ketone moiety. Moreover, the products can be readily converted into potentially bioactive benzosultams including aziridine and polycyclic benzosultams.