Part~i~photoenolization Of Alpha,beta-unsaturated Ketones Part~ii~photochemical Studies Of Some N-aroyl Substituted Indoles

Part I. Ultra-violet light irradiation of {dollar}\alpha{dollar},{dollar}\beta{dollar}-unsaturated ketones possessing a {dollar}\gamma{dollar}-hydrogen as well as a {dollar}\gamma{dollar}-alkyl substituent results in isomerization to their {dollar}\beta{dollar},{dollar}\gamma{dollar}-unsaturated isomers. The process occurs by an intramolecular {dollar}\gamma{dollar}-hydrogen abstraction by the excited carbonyl to generate a dienol intermediate. The deconjugation reaction is not efficient for {dollar}\alpha{dollar},{dollar}\beta{dollar}-unsaturated ketones which do not possess a {dollar}\gamma{dollar}-alkyl substituent; this is because thermal 1,5-hydrogen transfer in the dienol intermediate gives back starting ketone efficiently. Part I of this thesis describes a procedure for trapping dienols generated photochemically from several {dollar}\gamma{dollar}-unsubstituted {dollar}\alpha{dollar},{dollar}\beta{dollar}-unsaturated ketones. The trap used is chlorotrimethylsilane in the presence of a weak organic base imidazole. This yields (Z)-2-trimethylsiloxy-2,4-dienes regioselectively and with high stereoselectivity in synthetically useful yields. Thermal procedures such as sequential treatment of the unsaturated ketone with lithium diisopropylamide and chlorotrimethylsilane, or treatment of the ketone under equilibrating conditions with triethylamine and chlorotrimethylsilane, yields predominantly the kinetic 2-trimethylsiloxy-1,3-dienes or mixtures of the kinetic and the E- and Z-siloxy-2,4-dienes.;The triplet energies of an acyclic {dollar}\alpha{dollar},{dollar}\beta{dollar}-unsaturated ketone and acyclic {dollar}\alpha{dollar},{dollar}\beta{dollar}-unsaturated ester were determined by a technique of competitive quenching of a series of triplet sensitizers of varying triplet energy. The triplet energy of the acyclic ketone and ester were both found to be 72.0 {dollar}\pm{dollar} 0.5 kcal/mol. This value is comparable to that of the cyclic analogues.;Part II. Part II of the thesis describes the fluorescence behaviour of N-benzoylcarbazole, 52, N-naphthoylindole, 89, N-mesitoylindole, 90, and Indomethacin, 91, as well as the photochemical behaviour of 89, 90, and 91 in the presence of cyclopentene. Compounds 52, 89, and 91 fluoresce weakly at anomalously long wavelength. The intensity and wavelength is dependent upon solvent polarity. The emitting state is postulated to be a charge transfer state formed from the initially formed non-emitting singlet excited state. Compound 90 photoreacts with cyclopentene to yield only the cis-anti-cis cycloadduct stereoisomer which exists as two non-interconverting conformers. Indomethacin did not give cycloaddition products but instead underwent decarboxylation to give the 2,3-dimethylindole derivative, 102, via 3-methylene intermediate, 103