Sugar–phosphite–oxazoline and phosphite–phosphoroamidite ligand libraries for Cu-catalyzed asymmetric 1,4-addition reactions

Sugar–phosphite–oxazoline L1–L5a–g and phosphite–phosphoroamidite L6a–c ligand libraries were tested in the asymmetric Cu-catalyzed 1,4-conjugate addition reactions of cyclic and acyclic enones. Systematically varying the electronic and steric properties of the oxazoline and biaryl phosphite substituents and the functional groups attached to the basic sugar-backbone had a strong effect on the catalytic performance. In general, good activities and enantioselectivities were obtained. The enantioselectivity (up to 80%) was optimized with catalyst precursors containing the phosphite–oxazoline ligands L1c and L1f that contain encumbered biaryl phosphite moieties and a phenyl oxazoline group.