Nonenzymatic and Metal-Free Organocatalysis for in Situ Regeneration of Oxidized Cofactors by Activation and Reduction of Molecular Oxygen

The application of synthetic flavinium organocatalysts for the in situ regeneration of oxidized cofactors NAD­(P)+ using O2 as the terminal oxidant without any special illumination or equipment is reported. With the aid of the highly active bridged flavinium catalyst, the rate of NAD­(P)H oxidation is accelerated by 3 orders of magnitude. The results show that the catalytic activity of the bridged flavinium catalyst is not dependent on light but on only oxygen. Furthermore, this catalyst is compatible with various preparative enzymatic oxidation reactions. A hydride transfer mechanism is proposed for the presented system.