A reverse (water in oil) microemulsion has been designed to oxidize hydrophobic organic substrates with singlet oxygen ( 1 O 2 , 1 ∆ g ) generated from the disproportionation of hydrogen peroxide catalyzed by molybdate ions. The microemulsion was prepared by mixing methylene chloride, sodium dodecylsulfate, n-butanol, and aqueous molybdate. Flash photolysis studies have shown that in such media singlet oxygen exhibits a similar kinetic behavior that under homogeneous conditions (τ ∆ ≈ 42 µs). Various typical organic substrates have been oxidized on the preparative scale with this chemically generated singlet oxygen, and the expected oxidation products have been isolated in high yields.

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A new liquid-phase catalytic oxidation system for the low temperature, high conversion benzylic mono-oxyfunctionalization of 10,11-dihydrocarbamazepine (1) into oxcarbazepine (4) with dioxygen has been developed. The method is based on a co-oxidation of 1 with benzaldehyde in the presence of a four-component catalyst system consisting of Co(-OAc) 2 , Ni(OAc) 2 , Cr(NO 3 ) 3 , and N-hydroxyphthalimide (NHPI). The influence of the catalyst system on the formation and decomposition of the crucial hydroperoxide intermediate

The chiral allylic alcohols 1a-d and their acetate (1e) and silyl ether (1f) derivatives have been oxidized by the H2O2/MoO4(2)- system, a convenient and efficient chemical source of singlet oxygen. This chemical peroxidation (formation of the allylic hydroperoxides 2) has been conducted in various media, which include aqueous solutions, organic solvents, and microemulsions. The reactivity, chemoselectivity, and diastereoselectivity of this chemical oxidation are compared to those of the sensitized photooxygenation, with the emphasis on preparative applications in microemulsion media. While a similar threo diastereoselectivity is observed for both modes of peroxidation, the chemoselectivity differs significantly, since in the chemical oxidation with the H2O2/MoO4(2)- system the undesirable epoxidation by the intermediary peroxomolybdate competes efficiently with the desirable peroxidation by the in situ generated singlet oxygen. A proper choice of the type of microemulsion and the reaction conditions furnishes a high chemoselectivity (up to 97%) in favor of threo-diastereoselective (up to 92%) peroxidation.