The Role of Oxygen in the Electrochemical Reduction of Ethyl 2-(2-(Bromomethyl)phenoxy)acetate at Carbon Cathodes in Dimethylformamide

Abstract

Cyclic voltammetry (CV) and controlled-potential electrolysis (CPE) were employed to examine the direct reduction of ethyl 2-(2-(bromomethyl)phenoxy)acetate at carbon cathodes in dimethylformamide (DMF) containing tetramethylammonium tetrafluoroborate (TMABF4) as the electrolyte. Cyclic voltammogram of the substrate exhibits a single irreversible cathodic wave with a peak potential of –1.75 V vs SCE, which is characteristic for the reduction of organic halides in aprotic solvents. Bulk electrolyses of ethyl 2-(2-(bromomethyl)phenoxy)acetate were carried out in the absence and presence of oxygen. The product distributions were obtained by gas chromatograph (GC) as well as gas chromatograph coupled to a mass spectrometer (GC−MS). Two bicyclic compounds, ethyl 2,3-dihydro-1-benzofuran-2-carboxylate and ethyl benzofuran-2-carboxylate, were found to be formed in a total yield of more than 40% in the presence of oxygen. The reaction mechanism, in which the oxygen plays a significant role, was proposed and discussed on the basis of this study.