Co/Alumina as an effective heterogeneous catalyst for selective oxidation of benzyl alcohols to carboxylic acids

The oxidation of primary alcohols to carboxylic acids is an important reaction in both organic chemistry and industry.1Traditionally, this oxidation involves a two-step process involving oxidation of the alcohol to an aldehyde followed by further oxidation to the carboxylic acid. Given that the use of catalytic reactants with higher selectivity is one of the 12 principles of green chemistry, selective oxidation of alcohols to carboxylic acids can be important. Owing to improved efficacy, homogeneous catalysis has grabbed more attention and interest than heterogeneous approaches.2 Given the cost and sometimes toxicity associated with homogeneous methods, together with the loss of catalyst after one run, despite being widely used in academia, these approaches have scarcely been utilized in industry. To compensate for the deficiencies related to homogeneous catalysts, the use of either heterogeneous catalysis or heterogenized homogeneous catalystshas prevailed.3Today, heterogeneous catalysis has opened up a new avenue to chemists as a fundamental procedure from the standpoint of recovery and product purification, especially in the production of fine chemicals. It is also worth mentioning that the use of catalyst in more than one run is environmentally and economically advantageous. Here, we are going to report the Co/Alumina as a heterogeneous and reusable catalyst for selective oxidation of alcohols to carboxylic acids. In this transformation, tert-butyl hydroperoxide (TBHP, 70 wt% in water) was employed as an external oxidant (Fig. 1).