Remote lone pairs in radical reactions fragmentations

6 Remote lone pairs in radical reactions fragmentations 

In the final example, we will switch to bond cleavage reactions (fragmentations). We can apply the same stereoelectronic concepts because, according to the principle of macroscopic reversibility, bond formation and scission proceed through the same transition state. 

The above paradox can only be resolved if the presence of oxygen leads to selective TS stabilization that exceeds such stabilization of the reactant. Indeed, the odd-electron TB communication between the radical and the lone pair through the o-bridge is increased at the transition state. 

Transition state stabilization via strengthened interactions with weakened bonds 

(a) Winstein, S., Holness, N. J. (1955). Neighboring Carbon and Hydrogen. XIX. t-Butylcyclohexyl Derivatives. Quantitative Conformational Analysis. J. Am. Chem. See.. 77(21), 5562-5578. (b) The conformational equilibrium values are corrected by using the newer A-value for OTs Schneider, H. J., Hoppen, V. (1978). Carbon-13 nuclear magnetic resonance substituent-induced shieldings and conformational equilibriums in cyclohexanes. The Journal of Organic Chemistry, 43(20), 3866-3873. 

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