The generation and functionalization of carbon- or nitrogen-centered
radicals are of great interest for their potential synthetic utility.
Here, we report the anaerobic electrocatalytic oxidation of two primary
benzylic amines, benzylamine and 2-picolylamine, in the presence of
a catalytic quantity of an electron deficient ferrocene derivative
as a single-electron redox mediator. The use of the appropriate redox
mediator prevented fouling of the electrode surface and significantly
decreased the potential at which the catalytic oxidation reaction
occurred. Simulation of the electrochemical results revealed an ErCi′ catalytic process between the redox
mediator and both substrates and significant difference in the electron
transfer rate between the two substrates and electrochemically oxidized
mediator. Through anaerobic controlled-potential electrolysis, we
demonstrated a method with a Faradaic efficiency of 90% forming the
desired coupled imine product of benzylamine oxidation while avoiding
an excess of problematic overoxidation, hydrolysis, and other side
reactions. Based on the electrochemical data along with the product
analyses using IR and 1H and 13C NMR spectroscopies,
the proposed mechanistic steps for the redox mediated electrocatalytic
process were laid out.