1242024-31-2Relevant academic research and scientific papers
Ureaphosphanes as hybrid, anionic or supramolecular bidentate ligands for asymmetric hydrogenation reactions
Meeuwissen, Jurjen,Detz, Remko,Sandee, Albertus J.,De Bruin, Bas,Siegler, Maxime A.,Spek, Anthony L.,Reek, Joost N. H.
, p. 2992 - 2997 (2010)
We report the coordination behavior of ureaphosphane ligand 1-[2-(diphenylphosphanyl)ethyl]-3-phenylurea (L1) towards different rhodium precursor complexes. Depending on the nature of the anion and the ligand/metal ratio, L1 acts either as a hybrid P,O-coordinating chelate, as an anionic P,N-coordinating chelate or as a supramolecular (hydrogenbonded) bidentate ligand. The different types of complexes were investigated in the asymmetric hydrogenation of three olefinic substrates using ureaphosphanes L2 and L3, which are chiral analogues of L1. For methyl 2-acetamidoacrylate (S1) and dimethyl itaconate (S2) the neutral complex [Rh(L2-κ2P,N)(cod)], containing an anionic P,N-coordmatmg ureaphosphane ligand, provided the best enantioselectivity (69.2 and 24.3%, respectively). For N-(3,4-dihydro-2- naphthalenyl)acetamide (S3) the best enantioselectivity was obtained with the cationic complex [R.h(L3-κ2P,O)(nbd)]BF4, containing a hybrid P,O-coordinating ureaphosphane ligand (86.1%).
