METALLOPORPHYRIN-CATALYZED OXIDATION OF 2-METHYLNAPHTHALENE TO VITAMIN-K-3 AND 6-METHYL-1,4-NAPHTHOQUINONE BY POTASSIUM MONOPERSULFATE IN AQUEOUS-SOLUTION

The metalloporphyrin-catalyzed oxidation of 2-methynaphthalene (1) by potassium monopersulfate produced mainly two naphthoquinones: 2-methyl -1,4-naphthoquinone (2) (menadione or vitamin K-3) and 6-methyl-1,4-na phthoquinone (3). In aqueous solution and at room temperature in the p resence of 5 mol % of the water-soluble metalloporphyrins MnTPPS or Fe TMPS, 2-methylnaphthalene was quantitatively oxidized to quinones 2 an d 3. Based on experiments performed in O-18-labeled water and accordin g to the ''redox tautomerism'' mechanism previously described for such catalysts, the oxidation to quinones is proposed to be mainly due to a cytochrome P-450-type oxygenation reaction (oxygen atom transfer),ra ther than a peroxidase-type oxidation (electron transfer).