Application of Gold Catalysis in the Synthesis of Seven-Membered Ring Systems
von Kristin Sprenger
Datum der mündl. Prüfung:2023-02-16
Erschienen:2024-01-08
Betreuer:Prof. Dr. Manuel Alcarazo
Gutachter:Prof. Dr. Manuel Alcarazo
Gutachter:Prof. Dr. Dietmar Stalke
Dateien
Name:Dissertation_Kristin_Sprenger.pdf
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Zusammenfassung
Englisch
A novel synthetic strategy for the synthesis of seven-membered ring systems with and without heteroatoms applying an Au(I)-based catalyst was successfully established. The selectivity in the cyclization of the corresponding alkyne precursors was investigated through comparing BrØnsted acid and Au(I) catalysis. Au(I) catalysis generally favors the formation of the seven-membered ring via 7-endo-dig cyclization. Whereas BrØnsted acid catalysis invariably preferred the pathway in which the most stable carbocation intermediate was formed after protonation of the alkyne precursor. This facilitated 6-exo-dig cyclization and the generation of anthracene-like structures for the molecules investigated. Subsequently, the configurational stability of the embedded seven-membered ring was intensively studied. The influence of tether as well as of the substituents on the ring system was examined in detail. A combination of experimental methods, such as DHPLC and EXSY spectroscopy, and complementary DFT methods was used to evaluate the interconversion barriers of the central seven-membered ring. Fortunately, clear trends in the configurational stability could be identified. It can be determined that with increasing steric demand of the substituents and decreasing flexibility of the seven-membered ring, the barrier at interconversion also rises.
Keywords: Au(I) catalysis; α-cationic phosphines; Seven-membered rings; configurational stability; Cyloheptatrienes; Dibenzo[b,f]oxepine; Dibenzo[b,f]silepine; Dibenzo[b,f]thiepine