Date of Award
Doctor of Philosophy (PhD)
Marisa C. Kozlowski
Part I of this dissertation focuses on the synthetic chemistry of arylnitromethanes as both products and reactants. Use of these compounds as key building blocks in the synthesis of vicinal diamines was explored via a catalytic aza-Henry strategy. These studies resulted in the identification of simple cinchonidinium acetate as an effective catalyst for the asymmetric synthesis of syn-1,2-diarylethylenediamines with excellent diastereocontrol. Difficulties in synthesizing arylnitromethanes from existing techniques provided impetus for the development of an improved method of greater generality. Ultimately, successful conditions were identified for the palladium-catalyzed cross coupling of nitromethane with readily available aryl halide partners, providing facile access to an array of functionalized arylnitromethanes. A tandem reductive Nef process was incorporated to provide a one-pot transformation directly to aryl aldehyde or oxime, thereby exploiting the use of nitromethane as a formylation equivalent. Application of the nitromethylation conditions to vinyl halides resulted in the discovery of a unique tandem cross-coupling/π-allylation nitroethylation reaction.
Part II of this dissertation focuses on the use of colorimetric sensors for the quantitative measurement of catalyst strength via LUMO-lowering of electrophiles. Despite rampant growth in catalyst synthesis and application, understanding of controlling factors of catalyst activity, particularly for those functioning through hydrogen-bonding, remains limited. A simple pyrazinone chromophore was found to exhibit hypsochromic shifts upon binding to an array of known hydrogen-bond catalysts. These wavelength shifts showed high correlation to relative rate enhancement of the catalysts in Diels Alder and Friedel Crafts reactions. Acidity values, often used to estimate hydrogen-bond strength, were illustrated to be poor indicators of catalytic activity, in contrast to that of the wavelength shifts. The results establish the catalyst-sensor wavelength is a useful tool with which to gauge catalyst strength and also reveal catalyst structure-activity relationships. Current efforts for measuring stronger BrÃ¸nsted and Lewis Acid catalysts with an alternate colorimetric sensor are also described.
Walvoord, Ryan R., "Part I: Nitroalkane Transformations: Synthesis of Vicinal Diamines and Arylnitromethanes Part II: Quantification of Electrophile Lumo-Lowering via Colorimetric Probes" (2014). Publicly Accessible Penn Dissertations. 1490.