Design, synthesis and catalytic activity of novel oxazoline based ligands
Mc Cleary, Nadine
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This thesis can be viewed as two separate studies. Firstly, the design, synthesis and catalytic activity of novel 2-pyridyl mono(oxazoline). A family of mono(oxazoline) ligands were developed in which the 5-poition is substituted with various substituted esters. These ligands were then applied as organocatalysts in an asymmetric hydrosilylation reaction and an asymmetric allylation reaction. Mono(oxazoline) ligands catalysed a benchmark hydrosilylation reaction and ee's of up to 46 to 48% were obtained. The ligands in which either the adamantyl ester, p nitro phenyl ester, p-chloro phenyl ester or the p-methyl phenyl ester were present afforded these results. Use of the ligands in a benchmark allylation reaction showed low conversions. Preliminary modifications to the backbone structure were also undertaken in order to ascertain the dendicity of the ligands. It was found the ligands coordinate in a bidentate fashion. The second part of the this study involved the design and attempted synthesis of 2nd generation 4,4'-bis(oxazoline) ligands. Structural modifications were proposed in order to increase selectivity from that of the first generation of ligands within this class. Our first proposed modification was the addition of secondary binding sites on the pendant groups on the ligand. Attempted ligand formation a novel one-pot deprotection-activation-ring-closure (DARC) reaction, was not successful. The second proposed modification was the installation of a functionalised bridgehead. Racemisation issues lead to the formation of diastereomeric pairs in which separate was not possible, and the synthesis of the desired ligand proved unsuccessful. This and other synthetic results are discussed herein.