Enantioselective Synthesis of β<sup>2</sup>-Amino Acids via Rh-Catalyzed Asymmetric Hydrogenation with BoPhoz-Type Ligands: Important Influence of an N−H Proton in the Ligand on the Enantioselectivity
[GRAPHICS]A series of BoPhoz-type ligands were successfully applied in the rhodium-catalyzed asymmetric hydrogenation of a number of P-substituted or unsubstituted alpha-(phthalimidomethyl)acrylates, affording good to excellent enantioselectivities. The results suggested that the presence of an N-H proton in the BoPhoz backbone could significantly improve the enantioselectivity, and ligand (S-c,R-p)-1d, bearing two CF3-groups in the 3,5-position of the phenyl ring of aminophosphino moiety, showed the highest enantioselectivity.
Rhodium-Catalyzed Enantioselective Hydrogenation of β-Phthalimide Acrylates to Synthesis of β<sup>2</sup>-Amino Acids
[Structure: see text] The enantioselectivehydrogenation of beta-phthalimide acrylates provides the corresponding chiral beta2-amino acids in excellent enantiomeric excess catalyzed by Rh-monophosphorus.