Manganese(III)-based oxidation of 1,2-disubstituted pyrazolidine-3,5-diones in the presence of alkenes

The manganese(III)-catalyzed aerobic oxidation of 1,2-disubstituted pyrazolidine-3,5-diones in the presence of alkenes gave the corresponding pyrazolidinediones which were doubly hydroperoxyalkylated at the 4-position in high yields. On the other hand, pyrazolidinediones were oxidized with manganese(III) acetate in the presence of alkenes at elevated temperature to produce the 4,4-bis(alkenyl)pyrazolidinediones in good yields instead of the pyrazolidine-fused dihydrofuran analogue . A similar cerium(IV)-mediated oxidation of pyrazolidinedione with an alkene afforded the doubly 4-methoxyethylated derivative . The stability of the free hydroperoxyl group and the reaction pathway for the aerobic and the metal-mediated oxidation reactions were also discussed.