Oxidation of styrene by various oxidants with different kinds of metalloporphyrins

Abstract In CH 3 CN:H 2 O=1:1 (v/v) medium, the oxidation of styrene by water-soluble oxidants (KHSO 5 , NaClO, NaIO 4 or H 2 O 2 ) catalyzed by metalloporphyrins (MPs) with various structures and central ions was investigated. The effect of imidazole and pyridine was also studied. The results indicated that the oxidation of styrene catalyzed by MPs is related to the pH of reaction medium, structure and central ions of MPs, oxidants and axial ligands. In neutral medium, MPs showed higher activity and yield of epoxide compared with that in acidic medium. For different MPs, phenyl-substituted manganese porphyrins can effectively catalyze KHSO 5 and NaClO to oxidize styrene and pyridine-substituted manganese porphyrin can effectively catalyze KHSO 5 and NaIO 4 to oxidize styrene. But all MPs studied cannot effectively catalyze H 2 O 2 to oxidize styrene. For different central metal ions, KHSO 5 is effective for manganese and cobalt porphyrins, NaClO is effective for manganese porphyrins and NaIO 4 is effective for iron porphyrins. Imidazole can markedly enhance the activity of MPs when KHSO 5 , NaIO 4 and H 2 O 2 were used as oxidants and inhibit the activity of MPs when NaClO was used as oxidant. Pyridine can markedly enhance the activity of MPs when KHSO 5 and NaClO were used as oxidants, but no effect was found when NaIO 4 and H 2 O 2 were used as oxidants.