Synthesis of Chiral β-Borylated Carboxylic Esters via Nickel-Catalyzed Asymmetric Hydrogenation.

The highly efficient Ni-catalyzed asymmetric hydrogenation of β-boronic ester substituted-α,β-unsaturated carboxylic esters was successfully developed using ( S, S)-Ph-BPE as the ligand. A series of chiral β-borylated carboxylic esters were obtained with high yields (94%-99% yields) and excellent enantioselectivities (89%-99% ee). The gram-scale asymmetric hydrogenation with a low catalyst loading (0.25 mol %) and synthetic transformation of hydrogenation product demonstrated the great synthetic utility of this methodology.