Catalytic enantioselective Amination of silyl enol ethers using chiral Dirhodium(II) carboxylates: Asymmetric formal synthesis of (-)-metazocine

摘要

Dirhodium(II) tetrakis[N-tetrafluorophthaloyl-(S)-tert-leucinate], Rh-2(S-FPTTL)(4), is an exceptionally efficient catalyst for enantioselective aminations of silyl enol ethers derived from acyclic ketones or a,beta-enones with [N-(2-nitrophenyisulfonyl)imino]phenyliodinane (NsN=IPh), providing N-(2-nitrophenyisulfonyl)-alpha-amino ketones in high yields and with enantioselectivities of up to 95% ee. The effectiveness of the present catalytic protocol has been demonstrated by an asymmetric formal synthesis of (-)-metazocine.