A Versatile and Fast Photocatalyzed Deoxygenation of Organic N-oxides with a Rhenium Complex in the Presence of H2O

The oxidation of N-heterocycles is key to their functionalization since it enhances their reactivity in the ortho position. However, an efficient post-reduction is often required to access the targeted compound. Here, a rhenium-based photocatalyst enables the versatile and fast deoxygenation of N-heterocyclic and alkyl N-oxides, avoiding sacrificial oxophilic reagents. We demonstrate that H2O dramatically accelerates the reaction rate. The system tolerates air contamination, is scalable, and shows a high functional group tolerance towards other reducible functions (free alcohol, carboxylic acid, ester, nitrile, halogen,…) and light-sensitive N-heterocycles. Preliminary mechanistic studies demonstrate the importance of both H2O and acetonitrile as solvent, and hint at a possible coordination of the substrate to the rhenium center.