Dual Transition Metal/Photoredox Catalysis for the Synthesis of Quaternary Carbon Stereocenters

Identifier:  TDX:3557

Handle: https://hdl.handle.net/20.500.11797/TDX3557

Authors:  Xue, Sijing

Abstract:
Quaternary carbon stereocenters are ubiquitous in bioactive and pharmaceutically relevant molecules. However, the construction of C-C bonds leading to chiral quaternary carbons still remains underdeveloped. Our group has explored allylic substitution reactions by employing vinyl cyclic carbonates (VCCs) as privileged substrate motifs, thereby enabling the versatile formation of stereo-defined building blocks. However, at the time of the start of this thesis work, the focus had been merely on preparative methods giving rise to tetrasubstituted C-X (X = N, B, S and O) bonds. Therefore, in order to expand the repertoire of methodologies that lead to sterically demanding carbon centers, the main objective of this doctoral dissertation was the development of novel enantioselective and/or diastereoselective synthetic protocols that involve C-C bond formations while leading to quaternary carbon stereocenters via dual TM catalyzed or dual photoredox/TM catalyzed allylic alkylation reactions. It was hypothesized that dual catalytic methods could help to bridge the known reactivity of electrophilic allylic-Pd species with their nucleophilic congeners, whereas the merger of photoredox and TM catalysis should allow for direct cross-coupling of VCCs and otherwise inaccessible reactive radical species. These alternative reactivity paradigms should create new impetus for the conception of elusive quaternary carbon stereocenters in the area of allylic substitution that go beyond the current limitations.