Synthesis of New Monodentate Spiro Phosphoramidite Ligand and Its Application in Rh-Catalyzed Asymmetric Hydrogenation Reactions

[reaction: see text] A new spirocyclic diol, 9,9'-spirobixanthene-1,1'-diol, was synthesized in two steps from readily available starting material m-phenoxyanisole. Resolution of the racemic diol was achieved by cocrystallization with N-benzylcinchonidinium chloride and N-benzylquininium chloride in acetonitrile. The corresponding spiro monodentate phosphoramidite ligand has been prepared for Rh-catalyzed asymmetric hydrogenation of alpha-dehydroamino acid derivatives and itaconic acid with excellent enantioselectivities (up to >99% ee).