New Strategies for Enantioselective Catalysis of Photochemical Reactions

Identifier:  TDX:2673

Handle: https://hdl.handle.net/20.500.11797/TDX2673

Authors:  Wozniak, Lukasz

Abstract:
The thesis describes novel strategies to implement enantioselective photochemical reactions promoted by visible light. The first part focuses on the development of chemical transformations that rely on the formation of electron-donor acceptor (EDA) complexes. Specifically, the enantioselective photochemical perfluoroalkylation of β-ketoesters mediated by a chiral enolate was developed. This study established the ability of chiral enolates, generated under phase transfer (PTC) conditions, to act as suitable donors in the formation of photoactive EDA complexes with perfluoroalkyl iodides, while providing effective asymmetric induction in the generation of quaternary perfluoroalkyl stereogenic centers. The second part of the thesis details a new strategy to design organocatalytic asymmetric cascade processes. The new approach combines the distinct reactivity of two chiral organocatalytic intermediates, namely the excited-state reactivity of chiral iminium ions with the ground-state reactivity of enamines. The photochemical organo-cascade reaction leads to stereochemically dense cyclopentanols with high yields and excellent selectivity, compounds that cannot be accessed by other methods. The observed excellent selectivity originated by an asymmetric amplification mechanism, which is due to a kinetic resolution process operative in the second step of the cascade process.