This thesis investigates the use of arene chromium complexes as phenyl cation synthons in the synthesis of homochiral N-phenylamino esters, and the dianion formation of a series of complexed aryl ethers. Chapter 1 reviews the properties of arene chromium tricarbonyl complexes and discusses in detail the ability of some of these complexes to undergo nucleophilic aromatic substitution. Chapter 2 outlines the biological importance of homochiral N-phenylamino esters. The N-phenylation of a series of amino alcohols are first investigated both by direct reaction of haloarene complexes with amino alcohols and also via a Smiles rearrangement of an aryl ether derivative. In addition, methodology is developed for the synthesis of a series of homochiral N-phenyl-α-amino esters and N-phenyl-β-amino esters. The synthetic strategy is then applied to the synthesis of some N-phenyl-β-lactams, in particular (+)SCH 48461. Chapter 3 reviews the directed metallation of complexed and uncomplexed arene compounds and discusses the mechanism involved. The generation of dianions in a series of complexed aryl ethers is investigated. Regioselective deprotonation is observed using different alkyllithium bases and the degree of dianion formation is confirmed by electrophilic quench of the dianionic intermediates with CD₃OD and TMSC1.

M.Sc. / Please refer to full text to view abstract.

The purpose of this thesis was to determine the kinetics and stoichiometry for the aquation of the pentaaquomonobromonmethylchromium(III) complex. The complex was prepared by the reduction of dibromomethane by chromium(II). The products of aquation, in the absence of oxygen, were found to be hexaaquachromium(III), methanol, and bromide. The balanced net ionic reaction can be written: 2H2O + (H2O)5CrCH2Br2+ → (H2O)6Cr3+ + CH3OH + Br-

This organometallic study involves the use organostannanes and organolithiums as precursors to chromium Fischer carbene complexes. Fischer carbenes are typically electrophilic and are stabilized by a single π-donor substituent, and contain low oxidation state metals (often but not always from Group 6). They are highly reactive and can give access to a range of biologically active compounds through cyclopropanations, insertions, coupling and photochemical reactions. Synthesis and characterization of three MOM-protected α-alkoxy organostannanes was successfully carried out via a nucleophilic addition of tributylstannyllithium to suitable aldehydes, and immediate protection of the alcohol with MOM. Two N-BOC protected α-amino organostannanes were successfully synthesized and characterized via α-lithiation and tin-lithium exchange in the presence of TMEDA. Tin-lithium transmetallation of the organostannanes allowed access to the organolithiums required for the synthesis of novel Fischer carbenes. Addition of chromium hexacarbonyl to the organolithiums formed the acylpentacarbonyl chromate salt which was alkylated with Meerwein salt, resulting in the Fischer carbene and a by-product, tetrabutyltin, which proved difficult to remove. Several Fischer carbenes were synthesized and characterized, some simple and known and some novel. In silico work explored the reaction coordinate of the [2+2] cycloaddition towards the formation of β-lactams, and the photoactivation cycle that precedes this process. Computational work also showed the effect of the ligand on the stability and reactivity of the carbene. It was found that in some cases the oxygen on the ligand could negatively influence the stability of the carbene (when compared to a simple methyl carbene). A link between bond orders and back donation in Fischer carbenes was explored in an attempt to theoretically predict the stability of a range of carbenes. / Microsoft� Office Word 2007