Design and Synthesis of Chiral Spiro Monophosphinites with a 3-Oxo-1,1′-spirobiindane Scaffold and Their Application in Rhodium-Catalyzed Asymmetric Hydrogenation of Dehydroamino Acid Esters

A new class of chiral spiro monophosphinites, based on a unique non-C2-symmetric 3-oxo-1,1'-spirobiindane scaffold featuring a large dihedral angle, has been effectively designed and synthesized. From readily accessible resources, these chiral spiro monophosphinites were synthesized via eight steps in 16-32% yields. Their excellent performance in the rhodium-catalyzed asymmetric hydrogenation of β-dehydroamino acid esters underscores the critical impact of the large dihedral angle in enhancing the activity and enantioselectivity.