Molecule-induced alkane homolysis with dioxiranes

The mechanisms of C-H and C-C bond activations with dimethyldioxirane (DMD) were studied experimentally and computationally at the B3LYP/6-311+G**//B3 LYP/6-31G* density functional theory level for the propellanes 3,6-dehydroh omoadamantane (2) and 1,3-dehydroadamantane (3). The sigma (C-C) activation of 3 with DMD (DeltaG(double dagger) = 23.9 kcal mol(-1) and DeltaG(r) = - 5.4 kcal mol(-1)) is the first example of a molecule-induced homolytic C-C bond cleavage. The C-H bond hydroxylation observed for 2 is highly exergoni c (AG, = -74.4 kcal mol(-1)) and follows a concerted pathway (DeltaG(double dagger) = 34.8 kcal mol(-1)), in contrast to its endergonic molecule-induc ed homolysis (DeltaG(double dagger) = 28.8 kcal mol(-1) and DeltaG(r) = +9. 2 kcal mol(-1)). The reactivities of 2 and 3 with CrO2Cl2, which follow a m olecule-induced homolytic activation mechanism, parallel the DMD results on ly for highly reactive 3, but differ considerably for more stable propellan es such as 4-phenyl-3,6-dehydrohomoadamantane (1) and 2.