On the Reactivity of C(sp3)-H σ-Bonds: Oxygenation with Methyl(trifluoromethyl)­dioxirane

The reactivity of C–H σ‐bonds of a series of 2‐substituted adamantanes 2 towards methyl(trifluoromethyl)dioxirane (1) shows a consistent dependence on the electron‐withdrawing ability, either inductive or by resonance, of the substituent. The results are interpreted in terms of the ability of the substrate molecule to delocalize the electronic perturbation of the reacting center at the beginning of the reaction path. The model shows that the electronic demand from the reacting C–H σ‐bond is transmitted along the substrate through a chain of hyperconjugative interactions, the relative intensities of which depend on the σ‐bonds involved. The substrate molecule simultaneously provides positive and negative stabilizing hyperconjugative interactions to the reacting center, their balance defining the geometry of the system at the beginning of the reaction path. The model constitutes a new experimental approach to measurement of the perturbation induced by substituents with significant resonance contributions on an adjacent C–H σ‐bond. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)