Manganese(III)-catalyzed facile direct hydroperoxidation of some heterocyclic 1,3-dicarbonyl compounds

[reaction: see text] The aerobic oxidation of 4-monosubstituted 1,2-diphenylpyrazolidine-3,5-diones 1 was carried out in the presence of a catalytic amount of manganese(III) acetate to quantitatively give the corresponding 4-hydroperoxypyrazolidinediones 2. A similar autoxidation of the 5-monosubstituted barbituric acids 5 and 3-butyl-4-hydroxy-2-quinolinone 7 also gave the corresponding hydroperoxides 5 and 8, respectively, in moderate to excellent yields.