A general synthesis of chiral monodentate 4,5-dihydro-3H-dinaphthophosphepines 4 and a detailed study of the catalytic performance of the resulting ligands 4a-n in benchmark hydrogenation reactions is presented. Hydrogenation of methyl alpha-acetamidocinnamate 11 and methyl alpha-acetamidoacrylate 13 proceeded with enantioselectivities up to 95% and 94%, respectively. The best enantioselectivity for the rhodium-catalyzed hydrogenation of dimethyl itaconate 15 was 88%. (C) 2004 Elsevier Ltd. All rights reserved.
Enantioselective Hydrogenation ofβ-Ketoesters with Monodentate Ligands
A general synthesis of chiral 4,5-dihydro-3H-dinaphthophosphepines 1a–g is described. The resulting ligands represent a new class of monodentate chiral phosphines. First applications of 1a–g in the rhodium-catalyzedasymmetrichydrogenation of unsaturated carboxylic acid derivatives demonstrate the usefulness of our ligands. Enantioselectivities up to 95% ee for the hydrogenation of methyl α-acetamidocinnamate