Efficient In-Situ Redox Catalytic NAD(P)+ Regeneration in Enzymatic Synthesis Using Transition-Metal Complexes of 1,10-Phenanthroline-5,6-dione and Its N-Monomethylated Derivative as Catalysts†

In comparative studies, we have been able to demonstrate that redox catalysts based on transition-metal complexes using 1,10-phenanthroline-5,6-dione as a ligand or based on N-methylated 1,10-phenathroline-5,6-dione acting via hydride ion abstraction are superior to alternative methods for the redox catalytic aerobic or indirect electrochemical in situ NAD(P)+ regeneration in enzymatic syntheses using alcohol dehydrogenases as production enzymes. Under preparative conditions in the gram scale we were able to obtain turnover frequencies of up to 130 turnovers per hour with respect to the redox catalyst. These are far larger than those of the presently most popular regeneration system.