Entwicklung elektrosynthetischer Methoden zur Kohlenstoff-Heteroatom-Bindungsknüpfung und Halogen-Austausch-Reaktion
- Development of electrosynthetic methods for carbon-heteroatom bond formation and halogen exchange reaction
Jentsch, Marc; Rüping, Magnus (Thesis advisor); Niggemann, Meike (Thesis advisor)
Dissertation / PhD Thesis
Dissertation, RWTH Aachen University, 2019
In this thesis electrosynthetic methods for carbon-heteroatom-coupling and halogen-exchange-reaction were developed.1) Direct and Bromide-mediated Electrochemical Dehydrogenative C(sp3)H-Amination via Hydrogen-Atom-TransferAn electrochemical process for the synthesis of pyrrolidines was developed. Due to limitations in the scope, an indirect mediated variation was designed. Instead of predominant transition metals used for this kind of transformations bromide could be chosen as the mediator. In addition, the reaction could be scaled up to 50 g and continuous flow conditions could be successfully employed. 2) Difunctionalization of Styrene Derivatives by Electrochemical in situ Formation of Hypochlorous AcidElectrolysis of hydrochloric acid afforded hypochlorous acid by anodic oxidation. In presence of styrene derivatives, a difunctionalization was achieved, enabling the corresponding chlorohydroxylated products. The process stands out by high current efficiency for hypochlorous acid formation, low reaction times and good regioselectivity for the formation of chlorohydrines, which could be obtained in good to acceptable yields.3) Nickel-mediated Halogen Exchange of Aryl Halides via Indirect Paired ElectrolysisWith a nickel(II)-catalyst the halogen exchange of aryl bromides to afford aryl chlorides was realized in yield up to 88%. A paired electrolysis is proposed where cathodic reduction is needed for formation of the active Ni(I)-species to enable oxidative addition. Upon comproportionation a Ni(II)-species is anodically oxidized to afford a Ni(III)-species. From there the product is formed by reductive elimination.