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-Co^I 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 Co^I /Co^III 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.

Keywords: Asymmetric Catalysis; Cobalt; Enynes; Sequential Hydrogenations; Z-Allylamides.