The Selective Reduction of Aromatic Compounds by Electrolysis. I. Reduction of Naphthalene by Electrolysis

The direct electro-reduction of naphthalene was investigated in various solvents, mainly in an acetonitrile-water solution using supporting electrolytes containing tetraethylammonium and tetra-n-butylammonium cations. The main reduction product was 1,4-dihydronaphthalene, though small amounts of 1,2-dihydronaphthalene and tetralin were also detected. Under optimum conditions, the selectivity and the current efficiency of the formation of 1,4-dihydronaphthalene were 98% and 86.4% respectively. It was found that the water concentration and the solvent had a significant influence on the reduction products and the current efficiency. 1,4-Dihydronaphthalene is mainly formed through the step-by-step addition of two electrons and protons. In addition, 1,4-dihydronaphthalene may be formed by the protonation of the dianion formed by the disproportionation of the anion radical. Further, it was proposed that the formation of the tetraethylammonium radical might partly occur by means of the electron transfer from the...