Rational Design of Chiral Tridentate Ligands: Bifunctional Cobalt(II) Complex/Hydrogen Bond for Enantioselective Michael Reactions
Xiaobing Wang, Tian Yin, Li Zhou, Ming‐Sheng Xie, Gui‐Rong Qu, Hai‐Ming Guo
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.
Topics & Concepts
ChemistryBifunctionalEnantioselective synthesisPyridineMichael reactionHydrogen bondAdductLigand (biochemistry)Medicinal chemistryRational designStereochemistryCobaltCatalysisOrganic chemistryMoleculeReceptorBiologyGeneticsBiochemistryAsymmetric Synthesis and CatalysisAsymmetric Hydrogenation and CatalysisCatalytic C–H Functionalization Methods