Chemistry of allene oxides

Chapter One reviews aspects of the chemistry of allene oxides reported in the chemical literature. The review is organised into three sections describing the available methods for the preparation of allene oxides, the reactions of allene oxides and allene oxides in biological systems. Chapter Two discusses attempts to develop new methods for the generation and trapping of allene oxides. Firstly, an unsuccessful attempt to employ a selenoxide elimination to generate an allene oxide is described. This is followed by a section detailing an improved method for the generation and in situ capmre of allene oxides with alcohols. Sodium alkoxides were found to trigger elimination in β,y-epoxy-β-trimethylsilyl mesylates to afford allene oxides and also act as the nucleophilic trapping component. This methodology was used to synthesise a range of α alkoxyketones. Attempts to employ other nucleophiles in this process are also discussed. Chapter Three describes how the successful chemistry described in Chapter Two was modified in order to generate and trap chiral, non-racemic allene oxides. The preparation of homochiral β,y-epoxy-β-trimethylsilyl mesylates and their subsequent reaction with potassium alkoxides at low temperature under aprotic conditions is described. The α;alkoxyketone products were found to be of high enantiomeric excess and the absolute configuration of the product was determined in one case. Finally, attempts to effect a threecomponent coupling of an aIlene oxide, by reaction of an allene oxide with a nucleophile and subsequently an electrophile, are discussed. Chapter Four describes pioneering work towards a general method for the preparation of methylene cyclic sulfites as potential allene oxide equivalents is presented. A series of such compounds were prepared by reaction of α;-hydroxyketones with thionyl chloride and via selenoxide elimination chemistry. Chapter Five describes the detailed experimental work undertaken in this thesis.