The electrochemical reduction of the 6-phenyl-2,3-dihydro-1,4-diazepinium cation and its 1-methyl and 5-methyl derivatives: formation and some properties of pyrrolodiazepines

Abstract

The 6-phenyl-2,3-dihydro-1,4-diazepinium cations (VIa–c), dissolved in dimethylformamide, undergo one-electron single reduction waves at –1.2 to –1.5 V. The reductions were studied by polarography, cyclic voltammetry, and preparative electrochemistry. Rapid chemical reactions follow the initial reduction and the isolated products are pyrrolodiazepines (VIIa–c). The latter compounds are reversibly protonated to provide pyrrolodihydrodiazepinium cations (IX) and appear to form dications and stable cation radicals when they are, respectively treated with triphenylmethyl perchlorate or oxidised electrochemically.