Backside activation of σ(c-c)-bonds with Cr(VI)-reagents

Article abstract of DOI:10.1016/S0040-4039(96)02380-5

The transformations of stable propellanes 3,6-dehydrohomoadamantane (1) and 1,5-dehydrobicyclo[3.3.1]nonane (2) on treatment with chromyl oxidants in different solvents were studied. Hydrocarbon 1 with CrO₂Cl₂ in nonpolar solvents forms 3,6-dichloro- (3) and 3-chloro-6-hydroxy- (4) homoadamantanes in the course of backside oxidative addition. to the strained C-C bond and 3-oxobicyclo[3.3.1]nonane-7-spirocyclopropane (5) as a result of the oxidative cyclobutane ring contraction. CrO₂(OAc)₂/Ac₂O and CrO₂(OCOCF₃)₂/(CF₃CO)₂O result only in oxidative addition with the formation of the mixtures of the corresponding 6-hydroxy-3-acetates (7,9) and 3,6-diacetates (6,8). In the case of 2 the only oxidative addition takes place. Possible mechanisms of the backside oxidative addition to the C-C bond are discussed.