Several polar molecules, such as alcohols, ketones, esters and acids, were used as co-catalysts for the cyclohexane oxidation catalyzed by manganese porphyrins, and the catalytic activity was found to be closely related to polarity of co-catalysts. The results indicated that the total selectivity of products was as high as 96.3% and glutaric acid selectivity was up to 50.9%. Thus, the proposed method provides a new approach for preparing glutaric acid. (C) 2015 Elsevier B.V. All rights reserved.