This thesis describes an investigation into the asymmetric induction found in the electrocyclisation of diazo-componds having α, β, γ, δ-unsaturation. It is thought that the reaction involves two steps, first, an 8 π electron 1,7-electrocyclisation in which orbital overlap at the termini of the π system is achieved <i>via</i> a helical transition state; and second, an intramolecular suprafacial sigmatropic [1,5] hydrogen shift. The results reported here are concerned with the effect of the presence of a chiral substituent at the terminal <i>trans</i> position of the conjugated system in the first step. The second step transfers the chirality stereospecifically, creating a new chiral centre. By measurement of the diastereomeric ratio and a determination of the relative configuration of the two chiral centres, the face selectivity of the chosen chiral groups were assessed. When the medium sized group in the chiral substituent was an alkoxy or hydroxy group, cyclisation at the <i>more</i> hindered face of the alkene in its lowest energy conformation predominated. Polar repulsion effects are thought to be the factors controlling the conformation of the chiral group. When the medium sized group was an alkyl group or an alkoxide ion, the <i>less</i> hindered face was preferred. In the former, steric repulsion effects are believed to dominate the conformation. While, in the latter, polar attraction between the cation and the nitrogen of the diazo-group may stabilize the preferred conformation.

The study of ligands of the general formula [E(L₂D)₃] (E = bridgehead atom, L = linking atom, D = donor atom) was undertaken. Complexation of such ligands is of interest as it provides intrinsically chiral <i>C</i>₃-symmetric complexes with both octahedral and tetrahedral metal centers. The possible exploitation of the chirality of <i>C</i>₃-symmetric complexes of such ligands would be crucially dependant upon the energy barriers to their racemisation. To this end, complexes of the novel ligand hydrotris(2-mercapto-1-ethylimidazolyl)borate (NaTm^Et) and the previously synthesised hydrotris(2-mercapto-1-benzylimidazolyl)borate (NaTm^Bn) were synthesised and Variable Temperature NMR was employed to investigate the energy barrier to racemisation in a range of tetrahedral and octahedral complexes. The results from <i>ab initio</i> calculations on a number of structures were compared to the findings of the VT NMR calculations. The novel complexes [MnTm(CO)₃], [RuTm(<i>p</i>-cym)]Cl, [RuTm{C₆H₅(CO)OEt}]Cl and [SnTmCl₃] (Tm = hydrotris(methimazolyl)borate) were synthesised. [MnTm(CO)₃] is the first example of a manganese complex of the Tm ligand. The isoelectronic but structurally different complexes [Ru{κ³-HB(mt)₃}Cp] and [Ru{κ²-(μ-H)B(mt)₃}Cp] (mt = methimazole) were also synthesised. Although a crystal structure of [Ru{κ²-(μ-H)B(mt)₃}Cp] has not been obtained we suggest that the complex is coordinated in a <i>bis</i>-chelate fashion by two thione sulphur atoms of the tripodal Tm ligand, and the coordination sphere is completed by a Cp ring and one hydrogen atom which is involved in an agnostic B-H^…Ru interaction.

The work described in this thesis is primarily concerned with a series of asymmetric transformation reactions employing a newly developed (-)-D-fructose derived 1,3-oxazin-2-one (77) as a chiral derivatising agent. The synthetic route utilised the well-known but little used stereospecific nitrene insertion process. The ability of the auxiliary to successfully participate in these reactions ranged from excellent, as was the case in aldol reactions, to disappointingly poor when failing to react at all, as was the case in alkylation reactions. The auxiliary was also utilised in Lewis-acid catalysed Diels-Alder cycloaddition reactions in which contrasting results were achieved. For α-bromination of the N-propionyl derivative, almost total asymmetric stereocontrol was obtained, whereas the performance of the auxiliary in asymmetric conjugate addition reactions of the corresponding N-acrylate compounds, once again produced mixed results. When employed in acylation reactions, Manders reagent (methylcyanoformate) was required to promote the return of the desired product. The competence of 77 as a resolving agent was highly favourable in the resolution of a racemic primary amine as well as a racemic acid halide. In summation, the overall performance of this auxiliary was very promising. Although the reactions conducted have on occasion exposed ambiguous reactivity, any weaknesses present are now well-defined and most can be avoided or overcome. Adequate diastereofacial differentiation is usually achieved and product separation is effected routinely and non-destructively by mild hydrolysis. Furthermore, a high incidence of crystallinity is found in products and intermediates which greatly facilitates product separation and identification. Towards the end of the thesis a further auxiliary (147) derived from isosorbide is described. The synthesis of this 1,3-oxazolidin-2-one based auxiliary required selective protection procedures which resulted in an overall workable yield.

An efficient route for the synthesis of a new highly selective and easily displaced chiral auxiliary I for the asymmetric boron-mediated aldol reaction has been developed in 5 steps from norephedrine. The novel chiral auxiliary has been shown to mediate <i>anti </i>and <i>syn</i> propionate and glycolate aldol reactions with a range of aldehydes in excellent yield (60-98%) and with good to excellent diastereoselectivity. Details of the methods which have been used to assign the absolute and relative stereochemistry of the aldol adducts are also summarised. The facile displacement of auxiliary I with a range of nucleophiles under very mild conditions to give the corresponding phosphonate esters, alcohols, acids, SNAc thiolesters and methyl esters has been demonstrated.

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