Electrochemical reduction of the 5,7-diphenyl-2,3-dihydro-1,4-diazepinium cation

Abstract

The 5,7-diphenyl-2,3-dihydro-1,4-diazepinium cation (II), dissolved in dimethylformamide, is reduced in two steps. The first wave, at –1.23 V with respect to an aqueous Ag–AgCl–KCl (saturated) reference, provides a radical which disproportionates to give the corresponding dihydrodiazepine base (I) and a tetrahydrodiazepine (IV). The second wave is at –2.00 V and produces the anion (IV). The reduction was studied by polarography, cyclic voltammetry, and preparative electrochemistry. The dihydrodiazepine base is electroinactive to –2.1 V, whereat it displays an apparently two-electron reduction wave.