Precise Synthesis of ChiralZ‐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.

Expedient and divergent synthesis of unnatural peptides through cobalt-catalyzed diastereoselective umpolung hydrogenation

“…On the basis of the above observations and literature studies (82,83,85,89), a plausible Co I /Co III redox mechanism has been proposed (Fig. 9D).…”

“…According to literature precedents, both Co I and Co 0 active species could be obtained by single-electron reduction of Co II complexes using the Zn protocol (82)(83)(84)(85). To identify the active species involved in this catalytic cycle, several experiments were conducted.…”