This thesis describes the use of both, a carbanion Payne-type rearrangement and η4-dienyl and η5-pentadienyl iron tricarbonyl complexes in organic chemistry. A carbanion Payne-type rearrangement has been developed and its reactivity investigated, with the subsequent trapping of a series of aldehydes or imines. The results are disappointing with no desired tetrahydrofuran-, tetrahydropyran- or pyrrolidine-containing molecules synthesised, although reasons for this are discussed. A novel 1,3-dipole containing a η5-iron tricarbonyl pentadienyl complex was synthesised on opening of a cyclopropane, subsequently trapping with a series of aldehyde and imines to efficiently form tetrahydrofuran and pyrrolidine ring structures, respectively.

The advantage of solid phase synthesis is that the products can be isolated and purified simply by filtration. However, the reaction conditions required often lead to different kinetic behaviour, differences in reactivity and solvation and other problems, not encountered in solution phase reactions. This thesis describes an approach at utilising the ease of purification associated with solid-phase synthesis without encountering the problems associated with two-phase reaction systems. It was achieved by selectively immobilising a bipyridyl-tagged chiral auxiliary and a bipyridyl-tagged oxazaborolidine catalyst by interaction by with a resin-bound transition metal upon completion of the solution-phase reaction. Chapter one is a literature review detailing some of the different approaches that have been reported in exploiting the benefits of solid-phase purifications whilst avoiding the associated problems. Soluble polymeric supports, fluorous labelling and some more unusual methods are investigated. Chapter two is a general introduction to how chiral auxiliaries can stereochemically influence reactions. Chiral auxiliary mediated alkylations, aldol reactions, conjugate additions and Diels-Alder reactions are focussed on. Chapter three details the complete synthesis of (R,R)-4,4'-bis-[1-(4,5-diphenyl-3-propionyl-imidazolidinonyl)-N-methyl]-2,2'-bipyridine, a bipyridyl-tagged chiral auxiliary. An investigation into its ability to reversibly bind to a resin-bound transition metal is then reported. Chapter four describes the extensive study on the reactivity of the tagged chiral auxiliary, concentrating on chiral alkylations, halogenations and aldol reactions. Chapter five is an account of how the selective immobilisation approach was extended to include chiral oxazaborolidine catalysts. A general introduction to oxazaborolidine catalysts is provided. The total synthesis of the bipyridyl-tagged oxazaborolidine, (S,S)-4,4'-bis-[4-(2-amino-3-hydroxy-3,3-diphenyl-propyl)phenoxymethyl]-2,2'-bipyridine is reported and the investigation into its ability to reversibly bind to a resin- bound transition metal is described. The chiral reduction of acetophenone using the tagged catalyst and the subsequent recovery of the catalyst is then explored.

Because the measured thermodynamic properties of ethane did not agree with those calculated from statistical mechanics, Pitzer proposed the existence of energy barriers hindering internal rotation about single bonds. A consequence of hindered rotation is that molecules may exist in more than one stable conformation: these conformations are referred to as "rotational isomers". Depending on the magnitude of the energy barrier relative to thermal energy, the conformers (or rotamers) may be individually isolable (as in <u>ortho</u>-substituted biphenyls) or in dynamic equilibrium (as in halogeno-ethanes). There is no simple explanation for the magnitudes of energy barriers: the various theories which have been proposed are reviewed by Dale and Lowe. Irrespective of the barrier height, the infra red spectrum of a mixture of two rotamers often shows doubling of characteristic group bands. Thus chloroacetone (I), in carbon tetrachloride solution, has two carbonyl bands which may be assigned to rotamers (la) and (Ib).

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Soai’s discovery of chiral amplification in the autocatalytic alkylation of pyrimidine-5-carbaldehyde with diisopropylzinc is one of the most noteworthy findings of the last decade of the 20th century. This is the first experimental confirmation of an early theoretical rationalisation of autocatalysis as a mechanism for the evolution of biological homochirality from a racemic environment (Frank, 1953). This thesis describes kinetic and spectroscopic investigations that were conducted with the aim of better understanding the mechanism under which chiral amplification is achieved in the Soai system. The methodology used to perform the kinetic studies that are presented in this thesis focuses on the use of reaction calorimetry as in-situ tool coupled with the appropriate analytical technique for enantiomeric excess measurements. Observations of an unusual temperature effect on the reaction rate and a profound induction period are reported together with extensive kinetic investigations. Kinetic experiments were designed and carried out following Reaction Progress Kinetic Analysis methodology, which is described in detail. These experiments were carried out in order to ascertain the concentration dependence of the substrates and the reaction product, and revealed a 1.6 order in pyrimidyl aldehyde, a zero order in diisopropylzinc and a first order in the reaction product. Meticulous NMR studies of the alkoxide product at low temperature demonstrated its tendency to form tetrameric complexes, which could be either directly involved in the autocatalysis or be the precursors of the active catalytic species. Possible mechanisms that involve tetramers formation are proposed and supported by simulations carried out using COPASI simulation software. This thesis also includes a separate Chapter on the MIB mediated alkylation of benzaldehyde with diethylzinc, a system characterised by a marked nonlinear effect. Kinetic studies demonstrate how the high degree of chiral amplification comes at the expense of the reaction rate.

This thesis examines the issues of acyclic stereocontrol in the Claisen rearrangement, with particular emphasis on the effects of exopericyclic stereocentres – i.e. those adjacent to the array of atoms directly involved in the sigmatropic process. It is divided into three main parts: The first section provides a review of the field of acyclic stereocontrol. The models used to explain the development of relationships between stereocenters in systems lacking well-defined conformational constraints are discussed. This is an established field and particular emphasis is given to recent developments in the modelling of such systems. The second section discusses the results of our studies. Previous examples of exopericyclic stereocontrol in sigmatropic rearrangements are shown. Studies are presented that explore the importance of heteroatom-bearing stereocenters and effects of olefin substitution pattern on the manner and extent of stereoselectivity. Our efforts to exploit these stereochemical effects in the synthesis of small molecules are then presented. A novel reaction sequence is presented in which equilibrating mixtures of allylic azides undergo stereoselective Claisen rearrangements and further chemistry of the products of this transformation is then explored. These studies, and attempts to deploy them in synthesis allow us to draw conclusions on the nature of acyclic stereocontrol in the Claisen rearrangement. The third section contains experimental procedures and characterisation data for all compounds prepared.

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