Rational Design of Chiral Tridentate Ligands: Bifunctional Cobalt(II) Complex/Hydrogen Bond for Enantioselective Michael Reactions

Org Lett. 2022 Jun 3;24(21):3861-3866. doi: 10.1021/acs.orglett.2c01435. Epub 2022 May 23.

Abstract

Bifunctional chiral tridentate bis(pyrroloimidazolone)pyridine (PyBPI) ligands have been designed, synthesized, and applied in an asymmetric Michael addition. With a 0.05 mol % PyBPI-Co(II) complex, β,γ-unsaturated α-keto esters reacted with 4-hydroxycoumarin to give the adducts in 93-99% yields and 90-97% ee. Experiments and DFT calculations supported the dual activation manner, in which the tridentate ligand coordinated with Co(II) to activate the keto ester, and the hydroxyl and carbonyl groups in PyBPI interacted with 4-hydroxycoumarin via two different H bonds.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4-Hydroxycoumarins*
  • Catalysis
  • Cobalt*
  • Esters
  • Hydrogen Bonding
  • Ligands
  • Stereoisomerism

Substances

  • 4-Hydroxycoumarins
  • Esters
  • Ligands
  • Cobalt