Efforts Towards C-C Bond Formations: From Ni Catalysis to Transition-Metal Free Electrolysis

Citation

Zhang, Wanji Wendy (2024) Efforts Towards C-C Bond Formations: From Ni Catalysis to Transition-Metal Free Electrolysis. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/czam-9x35. https://resolver.caltech.edu/CaltechTHESIS:08212023-202451948

Abstract

The selective construction of C-C bonds has been a critical challenge in modern synthetic organic chemistry. Among the numerous methodologies developed, cross-coupling remains an attractive strategy for direct C-C bond formation. Herein, a diverse range of cross-coupling reactions for C-C bond formations are investigated from different perspectives. First, the mechanism of a Ni/cyano-box-catalyzed asymmetric Suzuki alkynylation is studied. The existing data is consistent with a radical chain pathway that is previously proposed for other Ni-catalyzed enantioselective cross-coupling reactions. Next, moving on from the traditional electrophile-nucleophile cross-couplings, we explore Ni-catalyzed reductive coupling of alkyl halides with internal olefins in the presence of a hydrosilane. With judicious choice of the directing group, hydroalkylation of internal olefins can be achieved with high regio- and enantioselectivity. Following that, an electrochemically driven, transition-metal free cross-electrophile coupling reaction is explored as a greener alternative to constructive C(sp³)-C(sp³) bonds. Specifically, we focus on improving the Mg sacrificial anode performance in these electroreductive systems. By carefully choosing the electrolyte composition, we are able to manipulate the metal electrode interfaces for a more effective counter electrode. Finally, Al stripping in ethereal solvents is investigated for its application as a sacrificial anode in reductive electrosynthesis. Inspired by Al corrosion chemistry, we are able to achieve bulk Al stripping in THF-based electrolyte by incorporating halide co-supporting electrolytes.

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