Synthesis and photochromic properties of tri- and tetra-aryl-3H-naphtho[2,1-b]pyrans

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.EThOS - Electronic Theses Online ServiceGBUnited Kingdo