Thermal and photochemical regeneration of nicotinamide cofactors and a nicotinamide model compound using a water-soluble rhodium phosphine catalyst

Chlorotris[diphenyl(m-sulphonatophenyl)phosphine]rhodium(I) acts as a homogeneous catalyst in the thermal and photoinduced regeneration of natural nicotinamide adenine dinucleotide cofactors, NAD(P)⁺, and of a model compound 1-benzylnicotinamide. The thermal regeneration system uses formate as the hydride donor. The kinetics of the system has been studied and shows enzyme-like characteristics. The photoinduced regeneration system with Ru(bpy)₃²⁺ as the photosensitizer and ascorbate as the electron donor proceeds through formation of a rhodium-hydrido active species. The photoregenerated cofactors are subsequently coupled to the enzymatic reduction of acetaldehyde to ethanol, or to the model enzymatic reduction of benzil to benzoin.