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The objective of this study was to investigate the influence of 6-aryl-, 5-aryl- and 5,6-diaryl- substituents upon the photochromic properties [A-max and fading kinetics (tv,)] of 3,3-diaryl-3H- naphtho[2,1-b]pyrans. 1-Aryl-3-methoxynaphthalenes, prepared by cross-coupling of arylboronic acids or esters with 3-methoxy-1-(trifluoromethanesulfonyloxy)naphthalene, were demethylated to provide a series of 4-aryl-2-naphthols. The latter were subjected to acid-catalysed condensation with 1, l-diarylprop-z-yn-l-ols providing a novel series of 3,3,6-triaryl-3H-naphtho[2, 1-b ]pyrans. Electron rich 6-aryl substituents provided hypsochromicaIly shifted absorption maxima and slower fading kinetics whereas, electron deficient 6-aryl substituents induced bathochromicaIly shifted absorptions and fast fading kinetics compared to-the unsubstituted naphthopyran derivative. A series of 2-aryl-3- methoxynaphthalenes, prepared by cross-coupling of aryl halides with 3-methoxynaphthalene-2- boronic acid or, by complementary cross-coupling of arylboronic acids with 2-bromo-3- methoxynaphthalene, were demethylated to afford the corresponding 3-aryl-2-naphthols from which a novel range of 3,3,5-triaryl-3H-naphtho[2, 1-b ]pyrans were prepared. Similar trends were observed for the changes in Amax as noted for the 3,3,6-triaryl series. However, whilst Amax did not change significantly, the fading kinetics (tv,) showed dramatic differences. The 5-aryl series exhibited much larger ty, values, generally by a factor of two, than those of the 6-aryl series. A range of3,4-diaryl-2- naphthols was prepared by two routes that involved: (i) palladium-catalysed cycloaddition of diarylacetylenes to (o-boronatophenyl)acetic esters or, (ii) functionalisation of 2-methoxynaphthalene or 2,3-dihydroxynaphthalene to provide a new and versatile entry to unsymmetrically substituted 3,4- diaryl-2-naphthols. A series of novel 3,3,5,6-tetraaryl-3H-naphtho[2,1-b]pyrans has been prepared. Symmetrical 5,6-diarylnaphthopyrans containing either electron rich or electron deficient aryl groups exhibited similar spectrokinetic trends to the 3,3,5- and 3,3,6-triarylnaphthopyrans. Unsymmetrical 5,6-diarylnaphthopyrans also exhibited similar trends in ~nax but had larger tv, valuescompared to that of their 'monoaryl' counterparts. Two examples of 5,6-bis(2,5-dimethyl-3-thienyl)-3,3-diaryl-3H- naphtho[2, 1-b ]pyrans which represent a novel type of multi-addressable T - and P-type photochromic system have been prepared. These systems contain a dithienylethene motif embedded within the naphthopyran nucleus.

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This thesis describes the catalytic asymmetric epoxidation of olefins mediated by chiral iminum salts. The first chapter introduces some of the most novel and effective catalytic asymmetric methods for preparing chiral oxiranes. The second chapter is divided into three sections. The first section of chapter two is dedicated to our efforts to develop new aqueous oxidative conditions using both hydrogen peroxide and sodium hypochlorite as efficient, green oxidants that remove the temperature boundaries observed with the use of Oxone® as the stoichiometric oxidant. A wider range of available temperatures was examined allowing optimization of both oxidative systems. Ethereal hydrogen peroxide was observed to mediate asymmetric epoxidation within an acetonitrile monophasic co-solvent system giving enantioselectivities of up to 56%. When sodium hypochlorite was used in a biphasic solvent system in conjunction with dichloromethane; it was observed to mediate oxidation of the substrate alkenes in up to 71% ee. The second and third sections of chapter two are dedicated to our efforts to synthesize chiral iminium salts as catalysts for asymmetric epoxidation based on a biphenyl azepinium salt catalyst structure. From previous work within the Page group, the asymmetric synthesis and subsequent defined stereochemistry of a chiral carbon atom α to the iminium nitrogen atom was shown to have significant effect on the enantiocontrol of epoxidation using the iminium salt catalyst. Work was completed on biphenyl azepinium salt catalysts, inserting an alkyl or aryl Grignard reagent into the iminium bond using a pre-defined dioxane unit as a chiral auxiliary. Oxidation of the subsequent azepine gave a single diastereoisomerically pure azepinium salt. The methyl analogue of this sub-family of azepinium catalysts has been shown to give up to 81% ee for epoxidation of 1-phenylcyclohexene, furthermore, the binaphthalene azepinium salt with an additional methyl group was also synthesized and was shown to give up to 93% for epoxidation of 1-phenylcyclohexene. Continuation of the substitution α to the nitrogen atom gave rise to an interesting tetracyclic (biphenyl) azepinum salt catalyst. Construction of an asymmetric oxazolidine ring unit encapsulating the azepinium nitrogen and one of the methylene carbon atoms was achieved. In doing so two chiral centres α to the nitrogen atom were generated. The azepinium chiral carbon atom was populated by an addition methyl group with variation in the substitution on the oxazolidine chiral carbon atom. The benzyl analogue of this sub-family of tetracyclic azepinium catalysts has shown to give up to 79% ee for epoxidation 1-phenylcyclohexene. The third chapter is the experimental section and is dedicated to the methods of synthesis and characterization of the compounds mentioned in the previous chapter. X-ray reports regarding the crystallographic analysis of the structures presented in chapter two are provided in appendix A. Appendix B contains the analytical spectra for the determination of enantiomeric excess of the epoxides.