The use of dimethyldioxirane as the epoxidizing agent for polyunsaturated fatty acids has been investigated. With fatty acid methyl esters this is a convenient method for avoiding acidic conditions, using different solvents, and simplifying the isolation procedures, with less contamination due to by-products. The reagent was also tested with free fatty acids in water. In this case, the supramolecular organization of fatty acids influenced the reaction outcome and the epoxidation showed interesting regioselective features. The double bonds closest to the aqueous-micelle interface is the most favored in the interaction with dimethyldioxirane. The preferential epoxidation of linoleic acid to the 9,10-monoepoxide was achieved, with a high yield and 65% regioselectivity. In case of arachidonic acid micelles, the regioselective outcome with formation of the four possible monoepoxide isomers was studied under different conditions. It resulted to be a convenient synthesis of cis-5,6-eicosatrienoic acid, whereas in reverse micelles epoxidation mostly gave cis-14,15-eicosatrienoic acid.
2006, Volume 89, Issue 10, 2243–2253

Dimethyl- (DMD) and methyl(trifluoromethyl)-dioxiranes were used for oxyfunctionalization of spiro{1',7-cyclopropan-2-(E)-methyl-bicyclo[2.2.1]heptane} (1), tricyclo[3.2.2.0(2,4)]nonane (2), exo-endo-endo- (3) and exo-exo-exo-heptacyclo¬[9.3.1.0(2,10).0(3,8).0(4,6).0(5,9).0(12,14)]pentadecane (4), yielding tertiary alcohols as the main products. The rate constants for oxidation of 1-4 by DMD were measured and the Arrhenius parameters determined. The DFT theory (B3LYP and B3PW91) using restricted and unrestricted methods was employed to study the oxidation reaction of the C–H bond of cage hydrocarbons 1-4, adamantane, and acetone with DMD. The kinetic isotopic effect calculated using unrestricted methods agree with experiment. The reaction mechanism in terms of the concerted oxygen insertion vs the radical part is discussed.
2007, V.5, No.14, 2302 – 2310