Redox catalysis versus heterogeneous one-electron catalysis. Mixed reduction of arenes and alkyl halides at specific palladized electrodes

Reduction of aromatic compounds (A) is achieved in the presence of alkyl halides RX (X = I or Br) at Ag–Pd electrodes in organic solvents. Those electrodes allow the one-electron reduction of RX with the selective formation of free radicals R. This new process (heterogeneous one-electron catalysis, H1EC) was used to alkylate in situ arenes. This mode of alkylation leads to re-visit previous results concerning redox catalysis published by Henning Lund when more conventional electrodes (like glassy carbon or mercury) were used and afforded similar results within a totally different potential scale. These preliminary results underline the reactivity differences between the molecular electrode (A−) and the almost ideal catalysis process (facile and specific liberation of free alkyl radicals).