None-catalyst and clean synthesis of symmetric and asymmetric indoles from electrochemical oxidation of 4-aminophenol and p-phenylenediamine in the presence of malononitrile in green media

•Progress in green media.•Electro-synthesis of new indoles.•Synthesis of indoles without any catalyst and hard condition.•Use of potential instead chemical reagents.

The mechanism of electrochemical oxidation of p-phenylenediamine and 4-aminophenol in the presence of malononitrile, as a nucleophile is studied in a phosphate buffer solution (0.15 M) mixed with ethanol (v:v) using the cyclic voltammetry, controlled-potential coulometry and UV-spectroscopy methods. The results obtained indicate that the oxidation form of p-phenylenediamine and 4-aminophenol participate in the 1,4-michael addition reactions with malononitrile via the ECECCC mechanism (E: electrochemical and C: chemical) for the electrochemical synthesis of new indole derivatives with good yield under controlled potential conditions. The products obtained were characterized after purification by the FT-IR, 1H NMR, 13C NMR, mass spectroscopy and elemental analysis.

Graphical abstractThe electro-oxidation of 4-aminophenol and p-phenylenediamine has been studied in the presence of malononitrile as a nucleophile. The results obtained confirm the synthesis of new indoles via the electro-organic synthesis.Figure optionsDownload full-size imageDownload as PowerPoint slide