Investigation of Symmetry and Electronic Effects in Asymmetric Palladium-Catalysed Allylic Substitutions

by Stranne, Robert

This thesis deals with the design of chiral ligands for asymmetric palladiumcatalysed allylic substitution reactions. The effect of the symmetry and the electronic properties of the ligands on the reactivity and selectivity of the resulting metal complexes were investigated. Preparation of ligands from the chiral pool is also described. Chiral 2-(1-hydroxyalkyl)pyridines and 2-(1-alkoxyalkyl)pyridines carrying a chiral pyrrolidine ring in the 6-position of the pyridine ring were synthesised. The effect of the conformational preferences of the ligands in the metal complexes on the reactivity and selectivity was studied. The performance of these ligands did not show a clear trend that could be rationalised by a general model. Chiral N,P-ligands with pseudo-C2 and pseudo-meso symmetry based upon pyrrolidines, pyridines, 1,1´-binaphthylazepines, phospholanes and 1,1´binaphthylphosphepines were synthesised. The performance of these ligands was compared to the performance of the corresponding C2-symmetric and meso-ligands. It was found that the steric properties, related to the symmetry of the ligands, had a major impact on the reactivity and selectivity in the catalytic reaction. It was also found that the electronic properties of the donor atoms have to be considered in detail when designing ligands with mixed donor atoms.