Oxidation of 2-aminophenol with molecular oxygen and hydrogen peroxide catalyzed by water soluble metalloporphyrins

5,10,15,20-Tetrakis-(p-sulfonatophenyl)porphinatocobalt(II) and 5,10,15,20-tetrakis-(p-sulfonatophenyl)porphinatomanganese(III) chloride have been used as catalysts for the oxidative coupling of 2-aminophenol to 2-aminophenoxazine-3-one with molecular oxygen and hydrogen peroxide. The effects of pH and concentration of catalysts, hydrogen peroxide and oxygen on the oxidation reaction and yield of 2-aminophenoxazine-3-one have been studied. The oxidation of 2-aminophenol with molecular oxygen catalyzed by cobalt(II) tetra(4-sulfophenyl)porphyrin involves a hydrogen atom abstraction from 2-aminophenol by cobalt(II) superoxo species. UV–vis analysis indicated that oxomanganese(IV) is the active species in the oxidation of 2-aminophenol with hydrogen peroxide and manganese(III)tetra(4-sulfophenyl)porphyrin.

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► Cobalt(II) tetra(p-sulfophenyl)porphyrin is an efficient catalyst for oxidation of 2-aminophenol with molecular oxygen.
► 2-Aminophenoxazine-3-one was obtained in high yield.
► Manganese(III)tetra(p-sulfophenyl)porphyrin promoted oxidation of OAP with H2O2.
► UV–vis analysis indicated that oxomanganese(IV) is the active species in the oxidation with H2O2 and manganese(III) porphyrin.