Radical-stimulated nucleophile release
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Experimental and computational results have shown that deprotonation was enhanced for precursors containing radical centers (RED-shift). An examination of whether the inverse heterolytic dissociations that release nucleophiles instead of electrophiles could also be stimulated by suitably sited radicals is reported in this paper. A DFT method was employed to assess the free energies of heterolytic dissociations releasing C-centered and O-centered nucleophiles. In most instances a radical adjacent to the incipient positive charge in the precursors led to significant enhancement of heterolytic dissociation, but inhibition was found in some cases. Greater enhancements were obtained with C-centered rather than O-centered radicals. Exergonic dissociations for both O- and C-centered nucleophiles could be achieved with fluorenylmethyl- and cyclohepta-2,4,6-trienylmethyl-containing precursors. Heterolytic phosphate release from ribose and deoxyribose nucleotide C4' radicals was also found to be enhanced. This provided supporting evidence of the importance of these radicals in DNA and RNA strand breaking. The effect of ethyne, ethene, and phenyl spacer units between the radical center and the incipient positive charge was examined. Evidence was obtained that the key factor promoting heterolytic dissociation was the resonance stabilization of the coreleased radical-cations.
Walton , J C 2019 , ' Radical-stimulated nucleophile release ' , Journal of Organic Chemistry , vol. 84 , no. 19 , pp. 12606-12616 . https://doi.org/10.1021/acs.joc.9b02159
Journal of Organic Chemistry
Copyright © 2019 American Chemical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1021/acs.joc.9b02159
DescriptionJ.C.W. thanks EaStCHEM for financial support.
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