Oxidation of aromatic compounds:: XIV.: Oxidation of arylethynyl ketones in the system CF3CO2H-CH2Cl2-PbO2

Oxidation of arylethynyl ketones ArC=CCOCX3 (X = H, F) in the system CF3CO2H-CH2Cl2-PbO2 was studied on a preparative scale. The oxidation of 4-arylbut-3-yn-2-ones (X = H) involves transfer in total of four electrons, leading to (E)-3,4-bis(arylcarbonyl)hex-3-ene-2,5-diones. 4-Aryl-1,1,1-trifluorobut-3-yn-2-ones (X = F) are oxidized with transfer of only two electrons to produce 2-aryl-4-arylcarbonyl-5-trifluoromethyl-3-trifluoroacetylfurans. Possible mechanisms of radical-cation transformations of arylethynyl ketones into the final products are discussed.