Enantioselective Synthesis of α-Hydroxy and α-Amino Phosphonates via Catalytic Asymmetric Hydrogenation
作者:Mark J. Burk、Timothy A. Stammers、Judith A. Straub
DOI:10.1021/ol9906099
日期:1999.8.1
[GRAPHICS]Cationic rhodium catalysts of the C-2 symmetric DuPHOS (1) and BPE (2) ligands have demonstrated the ability to asymmetrically hydrogenate a novel series of enol phosphonates (3) in good to excellent enantiomeric excess under mild conditions. Initial studies toward the catalytic asymmetric hydrogenation of enamido phosphonates (6 and 7) using the DuPHOS-Rh+ catalysts are also reported.
Readily Available Chiral Phosphine−Aminophosphine Ligands for Highly Efficient Rh-Catalyzed Asymmetric Hydrogenation of α-Enol Ester Phosphonates and α-Enamido Phosphonates
[GRAPHICS]A new class of unsymmetrical hybrid phosphine-aminophosphine ligands has been prepared from commercially available, inexpensive (S)-1-phenylethylamine through a concise synthetic procedure. These ligands are not very sensitive to air and moisture, and displayed good enantioselectivities in the Rh-catalyzed asymmetric hydrogenation of various dimethyl alpha-benzoyloxyethenephosphonates bearing beta-aryl, beta-alkyl, and beta-alkoxy substituents and N-benzyloxycarbonyl alpha-enamido phosphonates, in which up to 97% ee was obtained. A side-by-side comparison study disclosed that these new phosphine-aminophosphine ligands showed better enantioselectivity than BoPhoz ligands.