Catalytic Asymmetric Synthesis of (-)-Ritodrine Hydrochloride via Silyl Enol Ether Amination Using Dirhodium(II) Tetrakis[tetrafluorophthaloyl-(S)-tert-leucinate

Abstract

- A catalytic asymmetric synthesis of (-)-ritodrine hydrochloride was achieved, incorporating an enantioselective amination of (Z)-silyl enol ether derived from 4-benzyloxypropiophenone with [(2-nitrophenylsulfonyl)imino]-phenyliodinane (NsN=IPh) and a chelation-controlled reduction of the ketone carbonyl group with Zn(BH 4 ) 2 as the key steps. The use of dirhodium(II) tetrakis[tetrafluorophthaloyl-(S)-tert-leucinate] as a catalyst produced the targeted α-amino ketone in 94% yield with 91% ee.