Chemists extensively use free radical reactivity for applications in organic synthesis, materials science, and life science. Traditionally, generating radicals requires strategies that exploit the bond dissociation energy or the redox properties of the precursors. Here, we disclose a photochemical catalytic approach that harnesses different physical properties of the substrate to form carbon radicals. We use 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, which exploits a fundamental mechanistic process of ionic chemistry, grants access to open-shell intermediates from a variety of substrates that would be incompatible with or inert to classical radical-generating strategies. 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, for streamlining the preparation of a marketed drug, for the late-stage elaboration of biorelevant compounds and for enantioselective radical catalysis.
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The data supporting the findings of this study are available within the paper and its Supplementary Information. Crystallographic data for Br-11, an analogue of the major diastereoisomer of compound 11, have been deposited with the Cambridge Crystallographic Data Centre, accession number CCDC 1839232.
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We thank ICIQ and the European Research Council (ERC 681840 - CATA-LUX) for financial support. E.P.B. thanks MINECO (CTQ2016-75520-P) for a predoctoral fellowship.
The authors declare no competing interests.
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Schweitzer-Chaput, B., Horwitz, M.A., de Pedro Beato, E. et al. Photochemical generation of radicals from alkyl electrophiles using a nucleophilic organic catalyst. Nature Chem 11, 129–135 (2019). https://doi.org/10.1038/s41557-018-0173-x
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