Synthesis and application of ligands for the asymmetric addition of organolithium reagents to imines
作者:Catrin A. Jones、Iwan G. Jones、Mushtaq Mulla、Michael North、Lucia Sartori
DOI:10.1039/a702028g
日期:——
Amino acid derived ligands 4d,e are prepared from (S)-valine and (S)-proline respectively, and can be used as chiral ligands during the asymmetricaddition of organolithium reagents to N-arylimines. Ligand 4e, which is prepared by two independent routes, is found to induce addition of organolithium reagents to the si-face of the imines, whilst ligand 4d in common with the previously reported catalysts
Unsymmetrical terdentate phosphorus-nitrogen-nitrogen (PNN) ligands: effect of the M/L ratio and the pendant group on stereoselectivity
作者:Xiaohui Cheng、King Kuok (Mimi) Hii
DOI:10.1016/s0957-4166(03)00361-6
日期:2003.7
Twelve novel, unsymmetrical terdentate pyrrolidine-based phosphorus-nitrogen ligands were prepared. These ligands promoted very high catalytic activity in the palladium-catalysed allylic substitution reactions of 1,3-diphenylpropenyl acetate with malonate esters (100% conversion at 0degreesC in <2 h). Enantioselectivities up to 94% were attained. An unusual effect of metal-to-ligand ratio was observed. Various structural features affecting the enantioselectivity and stereoinduction were examined and discussed. (C) 2003 Elsevier Ltd. All rights reserved.