Copper-Catalysed Asymmetric Conjugate Addition of Organometallic Reagents to Linear Enones

Methods for enantioselective 1,4-addition of main-group organometallics to linear enones are overviewed. Thiourethane and thioether 1,1′-binaphthyl-based ligands are effective for copper-catalysed 1,4-addition of ZnEt2 and AlR3 (R=Me, Et) to trans-alkyl-3-en-2-ones; enantioselectivities of up to 72% e.e. are attained. In comparison 1,4-addition of ZnEt2 to 2-cyclohexenone proceeds in up to 77% e.e. with the same ligand family.