Studies in asymmetric catalysis

Derivatives of enantiomerically pure 1,2-cyclohexanediamine and 1,2- diphenylethanediamine have been synthesised and used as organocatalysts for asymmetric reactions. The derivatives of 1,2-diphenylethanediamine have been employed for C-C, C-N bond formation reactions to determine their efficacy and selectivity. Compound 278 has shown high efficiency and selectivity for addition of aldehydes to DEAD. Novel Ru-metal complexes containing enantiomerically pure N,N-dialkylated-1,2- diamine ligands have been synthesised. Complexes 299 and 302 were used to study asymmetric transfer hydrogenation of ketones and imines. These complexes were found to be selective for the imine reduction compared to ketones reductions under the conditions used. Results obtained by these complexes also provided support for the proposal that reduction of the ketones involves a cyclic concerted mechanism for the transfer of hydrogen, while reduction of imines involves transfer of hydride from the complex through an ‘open’ transition state. Asymmetric transfer hydrogenations of α,α-disubstituted ketones were carried out using Ru-3C-tethered catalyst 181. Results obtained for asymmetric transfer hydrogenation of these compounds show that unsaturation or an aromatic group in substitution at the α-position of the ketone gave products of high enantioselectivity. This may be due to the interaction between η6-arene ring of Ru-complex and the group placed on the α-position of the ketone.EThOS - Electronic Theses Online ServiceUniversity of WarwickGBUnited Kingdo