Novel Photochemical Reactions Of Phenylethynylpyridine And Its Derivatives

Four styrylpyridine derivatives were synthesized from 4-methylpyridine and 4-R-substituted benzaldehyde,and four phenylethynylpyridines were synthesized from the corresponding styrylpyridines by the addition reaction with Br2 and the elimination reaction with alkali.In addition,fifteen 2-R-substituted phenylethynylpyridines were synthesized from phenylacetylene,4-methylphenylacetylene,4-chlorophenylacetylene and 2-methyl-4-bromopyridine,2-methoxy-4-bromopyridine,2-methoxycarbonyl-4-bromopyridine,2-cyano-4-bromopyridine and 2-chloro-4-bromopyridine by Sonogashira coupling reaction.Four 1,2,3-triarylnaphthalene derivatives were synthesized from the corresponding phenylethynylpyridine,4-methylphenylethynylpyridine,4-chlorophenylethynylpyridine and 4-bromophenylethynylpyridine by the Photo-dehydro Diels-Alder(PDDA)reaction in HCl aqueous solution.In addition,the photochemical reaction of the fifteen 2-R-substituted 4-phenylethynylpyridines were also carried out in HCl or CH3SO3H aqueous solution and 15 unreported photochemical products with 1,2,3-triarylnaphthalene structures were synthesized.Their structures were determined by 1H NMR,13 C NMR,and HRMS.These results extend the range of PDDA reaction of phenylethynylpyridines.The photoinduced valence isomerization of 1,2,3-triarylnaphthalene in ethyl acetate was also studied in this thesis.Five photochemical products of 2-phenyl-1,3-di(4-pyridyl)naphthalene,7-chloro-2-(4-chlorophenyl)-1,3-di(4-pyridyl)naphthalene,and 2-phenyl-1,3-di(2-methy l-4-pyridyl)naphthalene were isolated and characterized by 1H NMR,13C NMR,and HRMS.The single crystal structures of three products were determined.One is a benzobenzvalene derivative and the other two are 1,2,3-triarylnaphthalenes with swapped aryls substituted on 2,3-position.The introduction of substituents on the 2-position of pyridine ring of phenylethynylpyridines was achieved and the photochemical properties of these compounds were carried out,which expands the scope of PDDA reaction.Furthermore,the photoinduced valence isomerization of 1,2,3-triarylnaphthalene lead to the formation of benzobenzvalene derivative with novel structure.The isolation and characterization of benzobenzvalene supply meaningful and interesting experimental data for the study of photoinduced isomerization reaction of naphthalene.