Precise Synthesis of Chiral Z-Allylamides by Cobalt-Catalyzed Asymmetric Sequential Hydrogenations.

ABSTRACT

Asymmetric sequential hydrogenations of conjugated enynes have been developed using a Ph-BPE-CoI catalyst for the precise synthesis of chiral Z-allylamides in high activity (up to 1000 substrate/catalyst (S/C)) and with excellent enantioselectivity (up to >99 % enantiomeric excess (ee)). Mechanism experiments and theoretical calculations support a cationic CoI /CoIII redox catalytic cycle. The catalytic activity difference between cobalt complexes of Ph-BPE and QuinoxP* was explained by the process decomposition of rate-determining step in the second hydrogenation.