The electrochem. synthesis of pyrazolidine-3,5-diones and benzoxazoles by N-N bond formation and C,O linkage, resp., represents an easy access to medicinally relevant structures. Electrochem. as a key technol. ensures a safe and sustainable approach. We gained insights in the mechanism of these reactions by combining cyclovoltammetric and synthetic studies. The electron-transfer behavior of anilides and dianilides was studied and led to the following conclusion: The N-N bond formation involves a diradical as intermediate, whereas the benzoxazole formation is based on a cationic mechanism. Besides these studies, we developed a synthetic route to mixed dianilides as starting materials for the N-N coupling. The compatibility with valuable functionalities like triflates and mesylates for follow-up reactions as well as the comparison of different electrochem. set-ups also enhanced the applicability of this method.
Gieshoff, Tile; Kehl, Anton; Schollmeyer, Dieter; Moeller, Kevin D.; Waldvogel, Siegfried R.