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

Luceldi Carre-Rangel,Mercedes Oropeza-Guzmán,Ignacio Rivero,Karla Espinoza

doi:10.21577/0103-5053.20210035

Luceldi Carre-Rangel, Mercedes Oropeza-Guzmán + Show 2 more

Open Access

https://doi.org/10.21577/0103-5053.20210035

Copy DOI

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).

Highlights

The click chemistry is a green, selective, qualitative, pH-sensitive, and economical affordable,[1] suitable for the synthesis of a variety of bioconjugates including peptides,[2] proteins,[3] and polysaccharides,[4] among others.The purpose of the click chemistry is to selectively bind two molecular building blocks, under mild reaction conditions, obtaining high yields and harmless byproducts
The click chemistry reaction was carried out with benzyl bromide, sodium azide, and phenylacetylene as a starting material, using the base reaction shown in Scheme 1a, consisting of the addition of benzyl bromide and sodium azide to produce benzyl azide
This fact was demonstrated by the formation of triazoles using Cu0 electrooxidation as the source of catalyst used in click reaction.[10]

Summary

Introduction

The click chemistry is a green, selective, qualitative, pH-sensitive, and economical affordable,[1] suitable for the synthesis of a variety of bioconjugates including peptides,[2] proteins,[3] and polysaccharides,[4] among others.The purpose of the click chemistry is to selectively bind two molecular building blocks, under mild reaction conditions, obtaining high yields and harmless byproducts. In the electrochemical cell of 20.0 mL the supporting electrolyte was placed (4.0 mL) as well as electrodes (Cu0 (working electrode), Ag/AgCl/Cl−sat KCl (tert-butyl alcohol/water) (reference electrode) and Pt (counter electrode)), the reaction reagents were added; benzyl bromide (144 mg, 0.84 mmol), sodium azide (60 mg, 0.92 mmol) and phenylacetylene (86 mg, 0.84 mmol).

Results

Conclusion