Development and Mechanistic Understanding of Photochemical Reactions

Identifier:  TDX:2564

Handle: https://hdl.handle.net/20.500.11797/TDX2564

Authors:  Bahamonde Jiménez, Ana

Abstract:
This doctoral thesis describes the development and mechanistic understanding of photochemical organocatalytic reactions. Initially, I focused on designing new chemical transformations that relied on the formation of electron-donor acceptor (EDA) complexes. Specifically, we developed an enamine-mediated enantioselective photochemical α-alkylation of ketones with electron-poor alkyl bromides. Subsequently, we expanded this EDA complex-mediated strategy to the photochemical alkylation of indoles with electron-poor alkyl bromides. The second part of my PhD work was characterized by a progressive transition from reaction development towards a mechanistically-oriented approach. In particular, I focused on detailed mechanistic studies of some photochemical enantioselective transformations previously developed in the group. We studied the mechanism of the enamine-mediated photochemical α-alkylation of aldehydes. Quantum yield measurements revealed that a radical chain mechanism was operative. Moreover, kinetic studies established the trapping of the carbon-centered radical by the enamine, to form the carbon-carbon bond, as the turnover-limiting step. Additionally, we uncovered the turnover-limiting step of the iminium ion-mediated radical conjugate addition to β,β-disubstituted cyclic enones which had been previously developed by the group.