UBC Theses and Dissertations
Development and deployment of automated monitoring methodologies mowards investigations of heterogeneous and biphasic reactions Daponte, Jordan Ashton
Mechanistic insight is fundamental to understanding a reaction and essential towards accessing desired product(s) in high yield, enantiopurity, and efficiency. Key to unlocking these investigations are developing tools that can monitor as many reactive species, intermediates, and products over the course of a reaction as possible. In the case of heterogeneous and biphasic systems, this analysis requires the development of new monitoring methodologies that can probe the complex equilibria, solubilities, mass transfer events, and catalytic cycles associated with the reaction. Herein, the development and deployment of reaction monitoring methods for the study of heterogeneous and biphasic reactions is discussed. These methodologies were deployed in two case studies, the first of which involved investigation of stereoselectivities of a proline catalyzed aldol reaction, while the second probed a biphasic reaction for an enantioselective spirocyclization catalyzed by a doubly quaternized cinchona alkaloid. The monitoring platforms allowed for the identification of water as the primary source of stereoselectivity in the proline-catalyzed aldol reaction, while also identifying the observed rate law, catalyst deactivation, and gaining insight into product behaviours. Investigations suggest that stereoselectivity likely originates from differences in transition states arising from the presence of water, rather than through kinetic phenomena. In the case of biphasic systems, a combined approach utilizing phase selective and heterogeneous sampling allowed for tracking of reaction species across both phases, allowing for insight into the reaction rate law, catalyst degradation, mass transfer behaviour, and temperature dependence studies. These results suggest that productive spirocyclization is balanced against inescapable catalyst degradation, with future optimization likely requiring new catalyst designs to counteract this relationship. The deployment of these monitoring methods provided the data necessary to carry out in-depth analysis of these two reactions which would not be accessible through end-point analysis. These methodologies promise excellent utility in the study of other heterogeneous and biphasic systems, with potential applications in mechanistic investigations and reaction optimizations.
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