Development of novel catalytic methods for reductive transformations utilizing visible light irradiation
- Entwicklung neuartiger katalytischer Methoden für reduktive Stoffumwandlungen unter Nutzung sichtbaren Lichts
Bülow, Raoul Frederic; Rüping, Magnus (Thesis advisor); Niggemann, Meike (Thesis advisor)
Dissertation / PhD Thesis
Dissertation, RWTH Aachen University, 2020
The presented thesis focuses on net reductive transformations utilizing visible light-photocatalysis in different roles and combinations. In the first part of this work, through a dual strategy combining nickel and photoredox catalysis, a highly selective reductive cross-coupling-reaction of aryl halides with polyfluoro arenes to access highly fluorinated bi- and triaryls was developed. Furthermore, palladium (II) complexes formed from aryl triflates could be successfully intercepted by a photoredox cycle, leading to selective hydrodetriflation without formation of alcohols as side product. In the second part of this thesis, a highly selective photocatalytic reductive defluorination strategy was presented, yielding a novel and unique structural motif with potential synthetic value. Mechanistic investigation hints, that perfluoroalkyl chains are activatable by forming an EDA complex with amines which undergoes triplet-triplet energy transfer. With acridine orange as organic photocatalyst, in the third part of this thesis a direct reduction of both, electron deficient and electron rich olefins resulting in hydrodimerization of them was made possible. Changing the reaction conditions slightly facilitated Birch-type reduction of polycyclic hydrocarbons (PCA), even in gram scale. Through comprehensive mechanistic studies, a two-photon process was revealed.