Synthesis of Triazoles by Electro-Assisted Click Reaction Using a Copper Foil Electrode

Abstract

This paper presents an innovative pathway for the synthesis of triazoles using the well-known “click chemistry” assisted by the electrochemical oxidation of metallic Cu0. The click reaction is used to couple a wide range of biological interest compounds. In this case, faster and less polluting methods for a biological environment was achived by in situ Cu0 electrooxidation, providing the suitable quantity of catalyst required by click reaction. The electrochemical cell was composed of a copper foil as the working electrode, a platinum wire serving as a counter electrode, and an Ag/AgCl wire as the reference electrode. Linear anodic sweep voltammetry in a tert-butanol-water medium (1:1), an electrolyte of tetrabutylammonium tetrafluoroborate (TBATFB), showed the onset potential of Cu0 electrooxidation. Using the same electrode configuration three different triazoles were prepared under constant electrode potential, in a short time (60 min), and splendid yields (78-90%). These results indicate that the in situ CuI formation occurs on the surface of the copper foil. A pulse potential program has also been implemented in which a yield of 92% was achieved, reducing electrode passivation and consequently increasing the process efficiency. The electroassisted click reactions are highly efficient to produce triazoles by an innovative electrochemical reaction. The products were characterized by infrared (IR), nuclear magnetic resonance (1H and 13C NMR), and mass spectrometry (MS).