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Solid state photochemistry and X-ray crystallography of carbonyl-containing compounds Cheung, Eugene

Abstract

This thesis reports the role of the crystalline environment in influencing the solid state photochemistry of carbonyl-containing compounds. Two types of photochemical reactions were studied: electrocyclization and hydrogen atom abstraction. The structure-reactivity relationships in systems undergoing these reactions were revealed with the use of single crystal X-ray crystallography using the X-ray Structure-Solid State Reactivity Correlation Method. chiral conformations. The prospect of using this conformational chirality for studies of absolute asymmetric synthesis was explored. The effects of halogen substitution on the crystal packing are also discussed. A series of halo-substituted enamides (I) was synthesized and the photochemical behaviour of each enamide was studied. These substrates undergo a concerted photochemical ring closure in solution. Although formally achiral, the enamides can adopt The crystal structures of a homologous series of spirobenzoyladamantanes (III - VI) were determined. These compounds undergo photochemical y-hydrogen atom abstraction in the solid state. The fates of their 1,4- biradicals can be rationalized using biradical geometries derived from the crystal data. The crystal structures of a series of cw-9-decalyl aryl ketones (XI) were determined. These compounds undergo hydrogen atom abstraction reactions in the solid state. The role of the crystalline environment in directing the formation of regio- and diastereoselective photoproducts was determined. Asymmetric synthesis in the carboxylic acid derivatives of XI was studied using the Ionic Chiral Auxilary Concept, and the photochemical results obtained from this approach were rationalized from the crystal structures. The crystal structures of a series of a-mesitylacetophenones (XVI) were determined, and correlated with their photochemical reactivities. These compounds undergo 5- hydrogen atom abstraction in the solid state, and the photochemistry is discussed in terms of the molecular abstraction geometries derived from the crystal data. Asymmetric induction in the optically active salts of the carboxylic acid derivative of this system was also studied, and the photochemical results were rationalized from the crystal structures.

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