Catalytic reduction of acetophenone with transition metal systems containing chiral bis(oxazolines)

The catalytic behaviour of several Ru, Rh and It systems containing bis(oxazoline) ligands (1-6) has been tested in the asymmetric reduction of acetophenone (7) to give 1-phenylethanol (8) by hydrogenation (Ir systems), transfer hydrogenation (It and Ru systems) and hydrosilylation (Ir and Rh systems). Ligands 1 and 3 gave good activities, obtaining the best asymmetric induction with Ir-1 system in the hydrosilylation (ee up to 50% (S) of 8). In order to identify the catalytic precursors, Ru (9-11) and It (12) complexes were synthesised and characterised. NMR studies of ruthenium complexes showed the existence of two main isomers in a ca. ratio 3/1, in agreement with the PM3(tm) calculations carried out for 10. (C) 2002 Elsevier Science B.V. All rights reserved.