Aspects of substituted hydrazine chemistry: The N-N bond as a chiral axis in 3-acylaminoquinazolin-4(3H)-ones.

The work contained in this thesis examines the aziridination of a number of ?-diketones via their enol forms using oxidative addition of N-aminoquinazolin-4(3H)-ones, to give N-(quinazolinone-N'-y1)-N-acyl-a-aminoketones which result from C-C cleavage of the intermediate aziridine ring. Products which have the N-N bond di-acylated are primed for reductive cleavage. One example has been studied in which reduction was successfully accomplished using aluminium amalgam to afford an N-acylated amino acid ester in good yield. The N-acetoxyaminoquinazolinone has been shown to function as an NH2+ equivalent. Aziridination of 3-methylpentan-2,4-dione using oxidation of N-aminoquinazolinone in the presence of trifluoroacetic acid (TFA) afforded the aziridine C-N cleavage product. The effects of retarded N-N bond rotation in many of the products from these aziridinations were observed in their n.m.r. spectra: the barriers involved were quantified in some cases but were too large to be measured in others. The good leaving group ability of the quinazolinone ring was revealed in attempted alkylation reactions under basic conditions a- to the exocyclic nitrogen with the N-(quinazolinone-N'-y1)-N-acyl-a-aminoketones above. Synthesis of N-(2-isopropylquinazolin-4(3H)-one-3-y1)-6-ethoxycarbony1-2-pyridone was accomplished with the expectation that elimination of the quinazolinone ring could be stereoelectronically inhibited. However, attempted methylation of this compound also resulted in elimination of the quinazolinone ring. In their reactions with stabilised anions, the N-acetoxyaminoquinazolinones function as synthetic equivalents of the NH2+ synthon. Oxidation of the N-aminoquinazolinones with lead tetra-acetate (LTA) in the presence of pyridine and its derivatives gave N-(quinazolin-4(3H)-one-3-y1)pyridinium ylides. These pyridinium ylides, on heating, functioned as aziridinating agents e.g. for styrene and diethyl fumarate. From the n.m.r. spectra of one of these pyridinium ylides at various temperatures, the barrier to rotation around both N-N bonds could be calculated. An investigation of the possible mechanisms of aziridination of alkenes using these pyridinium ylides was undertaken.