- Reagent-dictated site selectivity in intermolecular aliphatic C-H functionalizations using nitrogen-centered radicals
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The site selectivities of intermolecular, aliphatic C-H bond functionalizations are central to the value of these transformations. While the scope of these reactions continues to expand, the site selectivities remain largely dictated by the inherent reactivity of the substrate C-H bonds. Herein, we introduce reagent-dictated site selectivity to intermolecular aliphatic C-H functionalizations using nitrogen-centered amidyl radicals. Simple modifications of the amide lead to high levels of site selectivity in intermolecular C-H functionalizations across a range of simple and complex substrates. DFT calculations demonstrate that the steric demand of the reacting nitrogen-centered radical is heavily affected by the substitution pattern of the starting amide. Optimization of transition state structures consistently indicated higher reagent-dictated steric selectivities using more hindered amides, consistent with experimental results.
- Carestia, Anthony M.,Ravelli, Davide,Alexanian, Erik J.
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p. 5360 - 5365
(2018/06/27)
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- γ-Silyl-stabilized tertiary ions? Solvolysis of 4-(trimethylsilyl)-2-chloro-2-methylbutane
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Rate constant, isotope-effect, and product studies of the solvolysis of 4-(trimethylsilyl)-2-chloro-2-methylbutane, 11, and its carbon analog, 2-chloro-2,5,5-trimethylhexane, 10, in aqueous ethanol and aqueous 2,2,2-trifluoroethanol (TFE) indicate very little participation of the γ-silyl substituent. These results are in sharp contrast to earlier reports on secondary γ-silyl substituted systems, in which the back lobe of the silicon-carbon bond has been shown to overlap with the carbocation p-orbital to form a so-called 'percaudally' stabilized intermediate. While the solvolytic behaviors of 11 and 10 are nearly identical in ethanol, differences in the TFE lead to the conclusion that there is a minor amount of participation by the silyl substituent in that solvent. Interestingly, this observation lends credence to an earlier suggestion that TFE is better than ethanol at stabilizing more highly delocalized ions. Copyright
- Tilley, Leon J.,Shiner Jr.
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p. 564 - 576
(2007/10/03)
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- Synthesis and purification of 3,3-dimethylbutyraldehyde via oxidation of 1-chloro-3,3-dimethylbutane with dimethyl sulfoxide
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1-chloro-3,3-dimethylbutane is oxidized by dimethyl sulfoxide, in the presence of an effective amount of inorganic bromide or iodide, and in the present of an effective amount of base, to produce 3,3-dimethylbutyraldehyde.
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- Evidence for Electron Transfer, Radical and Ionic Pathways in the Decomposition of Diacyl Peroxide
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The thermal decomposition mechanism of 4,4-dimethylpentanoyl m-chlorobenzoyl peroxide and its α- and β-dideuteriated analogues is described.Product analyses and CIDNP studies suggest that all three pathways, electron transfer, radical and ionic, are operative in decomposition of these peroxides.Two pulsed-NMR techniques have been employed to eliminate distortions of CIDNP intensities arising from spin-lattice relaxation.These quantitative CIDNP studies have revealed an additional pure ionic pathway which competes with the radical pair electron transfer pathway to form rearranged reaction products.
- Lee, Sueg-Geun
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p. 1361 - 1372
(2007/10/02)
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