The effects of solvent on switchable stereoselectivity: copper-catalyzed asymmetric conjugate additions using D2-symmetric biphenyl phosphoramidite ligands

Abstract

A highly enantioselective copper-catalyzed conjugate addition of diethylzinc to acyclic aromatic enones was developed with phosphoramidite ligands bearing a D₂-symmetric biphenyl backbone. This type of reaction demonstrated that toluene and THF solvents can completely reverse the absolute configuration of the products, thus simplifying the process of accessing either enantiomer (S: 92% ee, 94% yield; R: 99% ee, 96% yield).