Phenalenyl-Based Photocatalyst for Bioinspired Oxidative Dehydrogenation of N-Heterocycles and Benzyl Alcohols

The environmental benefits of molecular oxygen as the oxidizing agent in oxidation reactions that synthesize fine chemicals cannot be overstated. Increased interest in developing robust photocatalysts is stimulated by the fact that the current photocatalytic transformation boom has made previously inaccessible synthetic approaches possible. Motivated by enzymatic catalysis, employing a reusable phenalenyl-based photocatalyst, we have successfully developed oxidative dehydrogenation utilizing molecular oxygen as a greener oxidant. Under photoinduced oxidative dehydrogenation conditions, different types of saturated N-heterocycles and alcohols were successfully dehydrogenated. The versatility of this bioinspired protocol is demonstrated by the fact that a wide variety of N-heteroaromatics, such as quinoline, carbazole, quinoxaline, acridine, and indole derivatives, as well as aldehydes and ketones, were successfully synthesized. Detailed mechanistic studies validate the proposed mechanism. Fluorescence lifetime and CV experiments revealed the crucial role of water on the efficiency of the reaction. The present protocol also provides chemoselectivity and scalability, leading to superior results and allowing for the functionalization of bioactive molecules at a late stage in a sustainable manner.