1152785-29-9Relevant academic research and scientific papers
Impact of incorporating substituents onto the P-o-anisyl groups of DiPAMP ligand on the rhodium(I)-catalyzed asymmetric hydrogenation of olefins
Zupancic, Borut,Mohar, Barbara,Stephan, Michel
supporting information; experimental part, p. 2024 - 2032 (2009/09/07)
The introduction of 1,2-bis[(o-anisyl)-(phenyl)phosphino]ethane (DiPAMP) as a P-stereogenic ligand for rhodium(I)-catalyzed hydrogenation by Knowles et al. came after their evaluation of several diphosphines. However, no in-depth study was carried out on incorporating various substituents on its P-o-anisyl groups. In this work, we have prepared a large series of enantiopure and closely related DiPAMP analogues possessing various substituents (MeO, TMS, t-Bu, Ph, fused benzene ring) on the o-anisyl rings. The new ligands were evaluated in rhodium-catalyzed hydrogenation of several model substrates: methyl α-acetamidoacrylate, methyl (Z)-α-acetamidocinnamate, methyl (Z)-β-acetamidocrotonate, dimethyl itaconate, and atropic acid. They displayed enhanced activities and increased enantioselectivities, particularly the P-(2,3,4,5-tetra-MeO-C6H)-substituted ligand (4MeBigFUS). Interestingly enough, 88% ee was obtained in the hydrogenation of atropic acid using the Rh-(4MeBigFUS) catalyst under mild conditions (10 bar H2, room temperature) versus 7% ee using Rh-DiPAMP. Conversely, the ligand possessing P-(2,6-di-MeO-C6H3) groups proved to slow down considerably the hydrogenation. X-Ray structures of their corresponding Rh complexes are presented and discussed.
