A Highly Efficient, Indirect Electrooxidation of 6β-Methyl-3β,5α-dihydroxy-16α17α-cyclohexanopregnan-20-one to the Corresponding 5α-Hydroxy-3,20-dione Using a Mediatory Couple of Sodium Bromide and Substituted 2,2,6,6-Tetramethylpiperidine-N-oxyl (TEMPO)

A cyclic voltammetry study of the η⁵-pentamethylcyclopentadi-enylrhodium (Cp&z.supast;Rh) complexes [(Cp&z.supast;Rh)₂(μ-Cl)₃]⁺ and [Cp&z.supast;Rh^III_aq]²⁺ at pH 6.05 in the absence and in the presence of nicotinamide cofactors indicates that the chloro complex is more advantageous for electrochemical reduction of NAD⁺ into NADH; the reverse oxidation of NADH by [(Cp&z.supast;Rh)₂(μ-Cl)₃]⁺ is insufficiently selective for practical applications according to the ¹H NMR data.