New Organic Catalysts for the Photochemical Generation of Radicals

Identifier:  TDX:3810

Handle: https://hdl.handle.net/20.500.11797/TDX3810

Authors:  de Pedro Beato, Eduardo

Abstract:
Chemists extensively use free radical reactivity for applications in organic synthesis, materials science, and life science. Traditionally, the generation of radicals requires strategies that exploit either bond dissociation energy or the redox properties of the precursors. The main objective of this doctoral thesis was to study and develop new strategies for the photochemical generation of radicals that exploit the electrophilicity of the substrates rather than their redox properties. We used a nucleophilic dithiocarbamate anion catalyst, adorned with a well-tailored chromophoric unit, to activate alkyl electrophiles via an SN2 pathway. The resulting photon-absorbing intermediate affords radicals upon homolytic cleavage induced by visible light. This catalytic SN2-based strategy was further expanded for the generation of acyl and carbamoyl radicals from the corresponding chlorides. We also describe how the method’s mild reaction conditions and high functional group tolerance could be advantageous for developing C–C bond-forming reactions. In the second part of the thesis, we implemented the use of dithiocarbamate as a catalytic donor for the formation of photoactive electron donor-acceptor (EDA) complexes with a variety of radical precursors. Excitation with visible light granted access to open-shell intermediates under mild conditions, including non-stabilized carbon radicals and nitrogen-centered radicals. The modular nature of the organocatalyst offered a versatile EDA complex catalytic platform for developing mechanistically distinct radical reactions