Selective aerobic allylic oxidation of α-pinene catalyzed by metalloporphyrins in the absence of solvents and additives

Abstract

Selective aerobic oxidation of α-pinene to high-value products is a major challenge in chemistry. Metalloporphyrins are proved to be selective catalysts for aerobic oxidation of simple hydrocarbons. Herein, we extend this method to more complex substrates using metallodeuteroporphyrins as model catalysts. It was found that the oxidation occurs mainly on the C=C and allylic C–H bonds of α-pinene influenced by the reaction temperature, reaction time, catalyst concentration, and oxygen flow rate. Allylic C–H oxidation products are obtained with a maximum selectivity value of 78.4% using the following reaction conditions: 105°C, 7 h, 5 ppm, and 60 mL/min. The influence of the metal nuclei of the metallodeuteroporphyrins on this reaction is also investigated. It was found that metallodeuteroporphyrins with Fe3+ as the metal nucleus exhibit the highest catalytic activity.