CATALYZED OXIDATION OF 2-MERCAPTOBENZOTHIAZOLE TO 2-HYDROXYBENZOTHIAZOLE

The selective oxidation of 2-mercaptobenzothiazole to 2-hydroxybenzoth iazole with molecular oxygen at temperatures of 50-150 degrees C and p ressures of 0.3-0.7 MPa has been studied in the presence of transition metal catalysts. The reaction proceeds via corresponding sulfinic and sulfonic acids which are quickly decomposed to the desired product in acetic acid as solvent at the reaction temperature. At temperatures b elow 90 degrees C, the main reaction product is 2,2'-dithiobis(benzoth iazole) which is resistant to further oxidation. The type of central a tom and ligand of the metal catalyst has a strong influence on the sel ectivity of 2-hydroxybenzothiazole formation. In the presence of FeCl2 as catalyst, 85% selectivity at 95% conversion was achieved.