Development of catalysts for asymmetric hydrogenation

The application of tetradentate aminoalcohol ligands to the KOtBu-catalysed \nhydrogenation of benzophenone has been studied. Hydrogenation was found to \nproceed via a transfer hydrogenation process with the ligands acting as hydrogen \ndonors. \nA series of bidentate and tetradentate ligands containing a variety of coordinating \ngroups including amino, hydroxy, silyl, phosphine and amido functionalities have \nbeen prepared and applied to the transition metal-catalysed asymmetric transfer \nhydrogenation of ketones using iron, ruthenium and rhodium metals although none \nwere found to be enantioselective for the hydrogenation of acetophenone. \nA series of asymmetric tethered ruthenium half sandwich complexes have been \napplied to the asymmetric pressure hydrogenation of ketones. Studies have \ninvestigated the effect of changing the sulfonamide group, halide and tether length \non the activity of the catalysts. The application of an achiral tethered ruthenium half \nsandwich complex as a catalyst for the pressure hydrogenation of aldehydes is also \nreported. \nA novel synthesis of tethered ruthenium complexes using aryl substitution \nmethodology has been developed and applied to the preparation of a series of novel \ncomplexes which were found to be highly active for asymmetric pressure \nhydrogenation of ketones. The application of the synthesis to the preparation of \npoly(methyl methacrylate) supported complexes is also discussed. Application of the \nsupported catalysts to asymmetric pressure and transfer hydrogenation of \nacetophenone has shown potential for the development of an active heterogeneous \ncatalyst for transfer hydrogenation of ketones in aqueous media.