The work described in this thesis is an investigation into the reactivity and possible
synthetic applications of aziridinylcarbinyl radicals. These radicals rapidly rearrange via βcleavage,
which can proceed by breakage of either the CoN or C-C bond. Cleavage of the
latter has been found when the molecule has a phenyl stabilising group attached to the
Chapter I is a review of the known radical reactions involving aziridines whilst
chapter 2 discusses the various methods of aziridine syntheses.
Chapter 3 outlines the project aims with reference to the potential of directed cleavage
of aziridinylcarbinyl radicals in synthesis.
Chapter 4, the main body of the work, describes the synthetic routes to aziridines
derived from 3-phenyl-2-cyclohexen-I-one and indenone. The radical mediated β-cleavage
reactions of these is reported and the selectivity of C-C v. CoN bond homolysis has been
Two successful approaches to the target aziridines were involved.
I) Conversion of 3-azido-3-phenylcyclohexan-I,2-diol, derived from the epoxide of 3-
phenyl-2-cyc1ohexen-I-ol, to the aziridine via reaction with triphenylphosphine. Subsequent
methylation and formation of the thiocarbonylimidazolide gave the radical precursor Nmethyl-
5-[imidazol-I-yl(thiocarbonyl)oxy]-I-phenyl-7-azabicylo[4.1.0]heptane. In the course
of this work, several unusual cyclic thiocarbonates resulting from the reaction of 3-azido-3-
phenylcyclohexan-I,2-diol and 2-azido-3-phenylcyclohexan-I,3-diol with I, I 'thiocarbonyl
diimidazole were isolated.
2) Formation of N-(2-ethylquinazolinonyl)-I-phenyl-7-azabicyclo[4.1.0]heptan-5-01 from the
reaction of 3-amino-2-ethyl-4(3H)-quinazolinone with 3-phenyl-2-cyc1ohexen-I-ol in the
presence of lead tetraacetate. These aziridines show interesting acid-catalysed rearrangements
to diazadioxabicyclo[2.2.2]octanes. Formation of the thiocarbonylimidazolide then gave the
radical precursor. A number of other aziridines have been prepared using this methodology.
It has been found that in all cases the precursors undergo CoN bond homolysis under
radical conditions. These results are discussed and conclusions are drawn. Suitable future
work is also suggested.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.