DERIVATIZATION OF SATURATED-HYDROCARBONS - THE MECHANISM OF RUO4 OXIDATIONS

The reaction mechanism of RuO4 oxidations of saturated hydrocarbons has been investigated by several methods. (1) By oxidation of endo-tetrahydrodicyclopentadiene (1H) and 2,6-dideuterio-endo-tetrahydrodicyclopentadiene (1D) a kinetic deuterium isotope effect of 5.3 was observed, indicating transfer of a hydrogen species and not a single electron in the rate-determining step. (2) No chlorinated products were formed from the reaction in CCl4. Radical intermediates are therefore not likely. (3) In the presence of chloride ion, 2-chloro-endo-tetrahydrodicyclopentadiene (2-Cl) was formed in addition to endo-tetrahydrodicyclopentadien-2-ol (2-OH), indicating a carbocation intermediate. (4) Further oxidation of 2-OH to bicyclo[5.2.1]decane-2,6-dione (8) proceeds via a ruthenium complex with the hydroxy group as the corresponding acetate 2-OAc was not oxidised. These points indicate that the reaction proceeds by hydride abstraction and carbocation formation and not by a cyclic one-step formation of the ruthenium ester from the saturated hydrocarbon.