Partial electrooxidation of nitrogenated heterocycles: novel synthesis of 1,10-phenanthroline-5,6-quinone by electrooxidation of 1,10-phenanthroline

An electrosynthetic route to 1,10-phenanthroline-5,6-quinone is described. The oxidation of 1,10-phenanthroline to its 5,6-quinone over a platinum anode was studied by cyclic voltammetry and by controlled potential electrolysis in acetonitrile (MeCN) containing varied proportions of water. Tetrabutylammonium hexafluorophosphate and sodium perchlorate were used as supporting electrolytes. The best preparative electrolysis experimental conditions were found at 2.4 V (vs. SCE) applied potential, using a MeCN + 0.8 vol.% water solvent, with 0.1 M NaClO4 as supporting electrolyte. Under these conditions, ca. 60% of the initial 1,10-phenanthroline was electrooxidized to its 5,6-quinone, with the consumption of ca. 9 mol electrons mol−1.