A mild and highly effective H2O2 oxidation of tertiary amines has been developed by the use of flavin catalysis. Eight aliphatic amines were oxidized to their corresponding N-oxides in fast and selective reactions. For all substrates a considerable rate enhancement was observed compared to the noncatalyzed reactions. The product N-oxides were isolated in good yields using this mild oxidation system based on the environmentally attractive oxidant H2O2. As the catalyst, an N1,N5-dialkylated flavin was used as an analogue of the biologically important flavin redox cofactor. The catalytic cycle proposed for the flavin catalysis accounts for the observation that, in addition to the hydrogen peroxide oxidant, molecular oxygen is required for the initiation of the process.

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The heteropolyacid H5PMo10V2O40·34H2O was found to be an efficient oxygen activating agent in palladium-catalyzed reactions. Aerobic 1,4-oxidations of conjugated dienes were carried out by employing a triple catalytic system consisting of palladium−quinone−heteropolyacid. With this system a mild electron transfer from the organic substrate to molecular oxygen occurs. 1,4-Diacyloxylations and 1,4-dialkoxylations were studied using this mild reoxidation system. 1,4-Diacetoxylation of 1,3-cyclohexadiene was studied in some detail. Some advantages of the heteropolyacid over previously employed metal macrocycles are high stability, easy access to an active catalyst, and simpler workup procedures.

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