One-Pot Formation of 1,3,4-Oxadiazol-2(3<i>H</i>)‑ones and Dibenzo[<i>c</i>,<i>e</i>]azepines by Concomitant Cathodic Reduction of Diazonium Salts and Phenanthrenequinones

The one-pot concomitant electrochemical reduction of phenanthrenequinones (1, 2) and arenediazonium salts (3a–f) led to the formation of 1,3,4-oxadiazol-2­(3H)-ones (4a–f, 5a) and dibenzo­[c,e]­azepines (6a–f) when N-methylformamide was used as the solvent. A new pathway, different from those previously described with other aprotic solvents, is proposed. The experimental data support a radical mechanism for the electrochemical process followed by an internal rearrangement to give the products.