Date of Award
Doctor of Philosophy
Dr. Elke Schoffers
Dr. James Kiddle
Dr. Sherine Obare
Dr. Silvia Rossbach
Oxazoles and oxazolines are important heterocyclic scaffolds commonly used in pharmaceuticals and optoelectronic materials. Traditionally these heterocyclic compounds are prepared by condensation methodology that suffers from poor reactivity when using electron deficient or sterically crowded reaction partners. Condensation methods also exhibit low tolerance of many functional groups as the reactions typically use strong acids and high temperatures. This dissertation describes an alternate strategy for the formation of these compounds by employing an epoxide opening followed by oxidation to form these heterocyclic compounds.
Epoxide opening reactions with primary aliphatic, allylic, and benzylic amines, aminolysis reactions, often achieve high yields regardless of the sterics and electronics of the reaction partners. The aminoalcohol produced by these reactions serves as an easily diversifiable intermediate. Using mild oxidants such as manganese dioxide or N-bromosuccinimide the aminoalcohol intermediate can form a substituted oxazole or oxazoline. This method offers one of the highest atom economies of any reported syntheses.
We investigated styrene oxide in addition to 1,10-phenanthroline epoxide as substrates. The former served as an interesting substrate to explore the regioselectivity of these aminolysis reactions. Many syntheses have been developed that favor the epoxide opening on the less hindered side using aliphatic and benzylic amines, while no reaction is reported to give a high yield of the other regioisomer. Magnesium perchlorate as a Lewis acid catalyst gave unique selectivity for the regioisomer formed by the opening on the more hindered side of styrene oxide. This regioselectivity, however, is eroded by the presence of even stoichiometric amounts of water.
The reactivity of phenanthroline and phenanthrene aminoalcohols was further explored in the optical sensing of chemical warfare agents. As alcohols readily react with phosphorus halides, these aminoalcohols show potential as sensors for organophosphorus nerve agents such as Soman. This was explored for the reaction between the aminoalcohols and a nerve agents mimics by both optical spectroscopy and nuclear magnetic resonance spectroscopy.
Sellers, David L., "Preparation of Aminoalcohols and Their Application for the Synthesis of Heterocycles and as Potential Sensors for Nerve Agents" (2016). Dissertations. 2460.