A moderate and efficient method for oxidation of ethylbenzene with hydrogen peroxide catalyzed by 8-quinolinolato manganese(III) complexes

Abstract

The oxidation of ethylbenzene with 30% aqueous hydrogen peroxide (H 2O 2) in an acetone–water medium at 30 °C was investigated using hexadentate 8-quinolinolato manganese(III) complexes (Q 3Mn III) as catalysts. The results indicated that the Q 3Mn III complexes, with ammonium acetate and acetic acid as additives, selectively catalyzed the side chain oxidation of ethylbenzene at secondary carbon atoms, affording acetophenone as a major product. Among the Q 3Mn III complexes examined, the 5,7-dibrominated Q 3Mn III catalyst was the most active, and provided the ethylbenzene conversion of 26.1% and the oxidation yield of 65% under the optimum conditions. The influence of various parameters on the reaction was checked in detail. Based on the UV–vis spectra, a free radical mechanism for the Q 3Mn III catalytic system was also proposed.