Cu(I)-CATALYZED SINGLE STEP ONE-POT SYNTHESIS OF 1,4-DISUBSTITUTED TRIAZOLES USING DEEP EUTECTIC SOLVENT (DES)

Abstract

The synthesis of different 1,4-disubstituted-1,2,3-triazoles were carried out in a eco-friendly, cheap and readily available deep eutectic solvent (DES) (1 : 2 molar mixture of choline chloride and glycerol) which involve reaction between alkyl halides or aryl halides, terminal alkynes and NaN3 in presence of Cu(I) catalyst at an ambient temperature giving moderate to high yield. The transformations involving alkyl halides and aryl halides as azide precursors were found to be less effective in DES (1 : 2 molar mixture of choline chloride and glycerol) because of its polar protic nature which decreases the nucleophilicity of nucleophiles via solvation. Interestingly, the use of an organic azide instead of azide precursor was found to give an excellent yield of the triazole products in DES. Aryl halide especially, bromobenzene and its derivative as aryl azide precursors are not generally effective, however this limitation can be overcome using N,N'-dimethylethylenediamine as a ligand for the transformation. High recyclability of the reaction medium was observed during the study. In addition, a drastic reduction in reaction time was observed for the reaction involving benzyl azide and phenylacetylene in the presence of excess sodium azide.