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**//B3LYP/6-31G* density functional theory level for the propellanes 3,6-dehydrohomoadamantane (2) and 1,3-dehydroadamantane (3). The sigma(C-C) activation of 3 with DMD (Delta G(*) = 23.9 kcal mol(-1) and Delta G(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 exergonic (Delta G(r) = -74.4 kcal mol(-1)) and follows a concerted pathway (Delta G(*) = 34.8 kcal mol(-1)), in contrast to its endergonic molecule-induced homolysis (Delta G(*) = 28.8 kcal mol(-1) and Delta G(r) = +9.2 kcal mol(-1)). The reactivities of 2 and 3 with CrO(2)Cl(2), which follow a molecule-induced homolytic activation mechanism, parallel the DMD results only for highly reactive 3, but differ considerably for more stable propellanes such as 4-phenyl-3,6-dehydrohomoadamantane (1) and 2.
Fokin
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AA
Department of Organic Chemistry, Kiev Polytechnic Institute, 37 Pobeda Avenue, 03056 Kiev, Ukraine.
Tkachenko
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BA
Korshunov
O I
OI
Gunchenko
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PA
Schreiner
P R
PR