Highly Efficient and Green Synthesis of Indole and Benzofuran Derivatives via Electrochemical Methods under ECECCC Mechanism

Abstract

Electrochemical synthesis of novel benzofuran and indole derivatives (8a–8f) has been carried out by the electrochemical oxidation of hydroquinone, 4-aminophenol and p-phenylenediamine in the presence of cyanoacetamide and 2-cyano-n-ethylacetamide as nucleophiles in a phosphate buffer solution (PBS) mixed with ethanol as a green solvent using cyclic voltammetry, controlled-potential coulometry, and UV-spectroscopy methods. The results revealed that the oxidized form of hydroquinone, 4-aminophenol, and p-phenylenediamine participate in the 1,4-Michael addition reactions with cyanoacetamides via the ECECCC mechanism for the electrochemical synthesis of new benzofuran and indole derivatives with good yield and high purity under controlled potential conditions. In this method, a carbon rod was used as the anode and the use of toxic and/or hazardous reagents was avoided. The obtained products were characterized after purification by the FT-IR, 1HNMR, 13C NMR and elemental analysis. The present work has led to the development of a facile and environmentally friendly reagent-less electrochemical method with high atom economy and safer waste under green conditions.