An efficient method for the synthesis of enantiopure phosphine-imidazoline ligands:: application to the Ir-catalyzed hydrogenation of imines

Phosphine-imidazoline ligands 8, and the derivatives 16 and 17, which have electron-withdrawing or electron-donating groups in the aminic nitrogen, were synthesized from 2-aryl-imidazo lines, which have previously been obtained from dithioesters. The coordination of ligand 8 to Ir(I) was studied and the molecular structure of the [Ir(eta(4) -COD)8]BF4 (COD = 1,5-cyclooctadiene) determined through X-ray diffraction. The in situ prepared Ir(I)/phosphine-imidazo line catalysts were tested in the asymmetric hydrogenation of ketimines in order to evaluate the influence of the electronic parameters of the ligand on the catalytic reaction. (C) 2004 Elsevier Ltd. All rights reserved.