Aerobic Oxidation with Singlet Oxygen

Liquid Phase Aerobic Oxidation Catalysis Industrial Applications and Academic Perspectives, 

First Edition. Edited by Shannon S. Stahl and Paul L. Alsters. 

Industrial Prospects for the Chemical and Photochemical Singlet Oxygenation of Organic Compounds 

Veronique Nardello-Rataj, Paul L Alsters, and Jean-Marie Aubry 

Oxygen in the singlet excited state Ag, subsequently noted 02, was detected for the first time in the upper atmosphere. However, it has been regarded as an important reactive oxygen species (ROS) by chemists only after its fortuitous detection in 1963 by Kasha and Khan [1] of its formation through the oxidation of hydrogen peroxide by sodium hypochlorite (Eq. (22.1))  

---

The reaction mechanism for the aerobic oxidation of the pz to seco-pz can be attributed to a formal 2 + 2 cycloaddition of singlet oxygen to one of the pyrrole rings, followed by cleavage (retro 2 + 2) of the dioxetane intermediate to produce the corresponding seco-pz (160). This mechanism is shown in Scheme 29 for an unsymmetrical bis(dimethylamino)pz. Further photophysical studies show that the full reaction mechanism of the photoperoxidation involves attack on the reactant by singlet oxygen that has been sensitized by the triplet state of the product, 159. As a consequence, the kinetics of the process is shown to be autocatalytic where the reactant is removed at a rate that increases with the amount of product formed. 

---