The protoadamantane radical cation

Abstract

DFT (B3LYP) and MP2 computations with a 6-31G* basis set show that a unique protoadamantane radical cation (1·+) structure with an elongated, half-broken C6-H bond prevails both in the gas phase and in solution. This is in agreement with the observed regioselectivity of the single electron-transfer oxidation of protoadamantane (1) with photoexcited 1,2,4,5-tetracyanobenzene, which only gives 5-(6-protoadamantyl)-1,2,4-tricyanobenzene (5), for which the X-ray crystal structure is reported. The regioselectivities for the functionalizations of 1 with electrophiles support this oxidation pathway. The H-coupled electron-transfer mechanism recently proposed for the C-H activation of alkanes with electrophilic oxidizers explains the high C6 positional selectivities in the functionalization of 1 in electrophilic media