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

(Chemical Equation Presented) Dirhodium(II) tetrakis[N- tetrafluorophthaloyl-(S)-tert-leucinate], Rh₂(S-TFPTTL)₄, is an exceptionally efficient catalyst for enantioselective aminations of silyl enol ethers derived from acyclic ketones or α,β-enones with [N-(2-nitrophenylsulfonyl)imino]phenyliodinane (NsN=IPh), providing N-(2-nitrophenylsulfonyl)-α-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.