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Umpolung Kharasch-type haloalkylation of activated alkenes via photo-induced copper catalysis

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Dawor,  Mahiob Ihab
Research Department Ritter, Max-Planck-Institut für Kohlenforschung, Max Planck Society;

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Citation

Dawor, M. I. (2024). Umpolung Kharasch-type haloalkylation of activated alkenes via photo-induced copper catalysis. Master Thesis, Philipps-Universität, Marburg.


Cite as: https://hdl.handle.net/21.11116/0000-0010-796D-D
Abstract
In this master's thesis, the aim was to address the limitations of the Kharasch radical addition, a challenge that has remained largely unexplored for the past 80 years since its initial report. The objective was to conduct reactions involving a redox-active ester 58, an alkene 9, and a halide source, catalyzed by a copper complex and irradiated with a 456 nm wavelength lamp (light-mediated radical decarboxylative processes). The expected products are activated halides 59, which, theoretically, can undergo elimination, replacement, and substitution reactions (scheme 12).
The synthesis of the redox-active ester 58 was planned as an in-situ step, simplifying the reaction process in terms of purification. This approach also addresses the limitations associated with the polyhalogenated compounds used in the Kharasch addition, as the starting materials (carboxylic acids 57) are inexpensive, widely available, non-toxic, and stable. So the first plan is divided into two parts. The first part aims to demonstrate the diversity of the reaction through a substrate scope, focusing on the screening of various carboxylic acids 57. The second part involves screening different alkenes 9 to further illustrate the reaction's versatility in that component.
The second objective of this work was to synthesize a tetrapeptide 70 from a dipeptide 62 using the Kharasch radical addition approach (Scheme 13).
The third goal of this project was to test the reactivity of one of the synthesized activated halides compounds 64 through substitution processes to generate an asymmetric compound, which has potential applications in the pharmaceutical industry (Scheme 14).
The fourth goal of this project was to conduct a thorough mechanistic study of the photocatalyzed reaction using UV-Vis spectroscopy, cyclic voltammetry (CV), and Stern-Volmer experiments.