Highly enantioselective copper-catalyzed conjugate addition of diethylzinc to cyclic enones with spirocyclic phosphoramidite ligands

Abstract

A series of spirocyclic phosphoramidite ligands 6– 9 with different substituents on the amine moiety were synthesized from the chiral spirocyclic diol ( R)- 5 . These monodentate ligands have been applied in copper-catalyzed conjugate addition of diethylzinc to cyclic enones. Excellent enantioselectivities (up to 99% ee) can be achieved by the use of ligand ( R, S, S)- 9 bearing stereochemically matched structure derived from the C 2-symmetric ( S, S)-bis(α-methylbenzyl)amine.