Synthesis of new chiral aryl diphosphite ligands derived from pyranoside backbone of monosacharides and their application in copper-catalyzed asymmetric conjugate addition of diethylzinc to cyclic enones

摘要

New chiral aryl diphosphite ligands based on the pyranoside backbones of glucose and galactose were prepared. These ligands were tested in the Cu-catalyzed asymmetric conjugate addition of diethyl-zinc to cyclic enones with up to 88% ee. The stereoselectivity was found to be dependent on the ring size of the substrate as well as the ligand and copper source. The enantioselectivity depends on the absolute configuration of the C-4 stereogenic center of the ligand backbone, while the sense of enantioselectivity is mainly controlled by the configuration of the binaphthyl phosphite moieties.