Synthesis of Diastereomeric 1,4-Diphosphine Ligands Bearing Imidazolidin-2-one Backbone and Their Application in Rh(I)-Catalyzed Asymmetric Hydrogenation of Functionalized Olefins

• Published in: Advanced synthesis & catalysis 2005-03, Vol.347 (4), p.563-570
• Main Authors: Zhang, Yong Jian, Kim, Kee Yong, Park, Jung Hwan, Song, Choong Eui, Lee, Kyungae, Lah, Myoung Soo, Lee, Sang-gi
• Format: Article
• Language: English
• Subjects: asymmetric hydrogenation; backbone chirality; diphosphine ligands; olefins; rhodium
• ISSN: 1615-4150; 1615-4169
• DOI: 10.1002/adsc.200404286

The diastereomeric 1,4‐diphosphine ligands, (S,S,S,S)‐1a, (R,S,S,R)‐1b and (R,S,S,S)‐1c, with the imidazolidin‐2‐one backbone were synthesized, and utilized for an investigation of the effects of backbone chirality on the enantioselectivity in the Rh(I)‐catalyzed hydrogenation of various functionalized olefinic substrates. It was found that the catalytic efficiencies are largely dependent on the configurations of the α‐carbons to phosphine. Thus, the Rh complex of the pseudo‐C2‐symmetrical diphosphine, (R,S,S,S)‐1c, showed excellent enantioselectivities (93.0–98.6% ees) in the hydrogenations of a broad spectrum of substrates, and especially in the hydrogenations of methyl α‐(N‐acetyamino)‐β‐arylacrylates (95.3–97.0% ees). However, the enantioselectivities obtained with the C2‐symmetrical (R,S,S,R)‐1b were largely dependent on the substrate (19.8–97.3% ees). The Rh complex of ligand 1a having the (S,S,S,S)‐configuration showed the lowest catalytic efficiency for all of the substrates examined (0–84.8% ees).