Thermally Initiated SRN1 Reactions of Ketone Enolates with Iodobenzene in Dimethyl Sulfoxide. Relative Reactivities of Enolate Ions with Phenyl Radical

Article abstract of DOI:10.1021/jo00199a027

The enolate ions of acetone, pinacolone, cyclohexanone, 2-butanone, and 3-pentanone react smoothly in the dark with iodobenzene in Me2SO to give high yields of substitution product.Phenylacetone enolate reacts very slowly, and 2-acetylcyclohexanone enolate fails to react.The relative reactivities of these enolate ions as determined from competition experiments in which pairs of enolates are allowed to react with PhI in Me2SO are pinacolone 1.00, acetone 1.09, cyclohexanone 0.67, 2-butanone 1.10 (total reactivity), 3-pentanone 1.40, and phenylacetone 0.39.The data show that there is less than a 4-fold difference in reactivity among the enolate nucleophiles despite a basicity difference of nearly 10⁸.These reactivities are interpreted as measurements of the relative rates of reaction of the enolates with phenyl radical.The results are consistent with the notation that the reaction of enolate ions (and other nucleophiles) with phenyl radical occurs at or near the encounter controlled limit.