Cu-Catalyzed Asymmetric Conjugate Addition of Dialkylzincs to Enones Using a (±)-trans-1,2-Cyclohexanediamine-Based Bis(NHC) Derived from l-Leucinol

Abstract

A hydroxyamide-functionalized azolium salt as the precursor of a (±)-trans-1,2-cyclohexanediamine-based bis(NHC) ­ligand was designed and synthesized from readily accessible l -leucinol. The combination of a Cu salt with this chiral ligand precursor promoted the asymmetric conjugate addition of Et2Zn to 2-cyclohexen-1-one at room temperature without the need for temperature control to afford the corresponding 1,4-adduct with up to 95% ee.