Abstract
The composite framework of graphitic carbon nitride (gCN) supported copper nanoparticle can act as a high-performance photoreactor for the synthesis of 1,2,3-triazole derivatives under light irradiation in the absence of alkaline condition. The photoactivity of gCN originates from an electron transition from the valence band to the conduction band, in the presence of photon energy, and the hot electron acts as a scavenger of the terminal proton of the alkyne molecule to facilitate the formation of copper acetanilide complex. In this study, we have performed the experiment under a different photonic environment, including dark condition, and in the presence and absence of base. A comparative study was also executed using Cu-TiO2 system, as a reference material, in the support of our proposed mechanism. The recycling performance and the photocorrosion effect of the catalyst have also been reported in this study.
Highlights
The copper-catalysed regioselective 1,3-dipolar cycloaddition of azide and alkyne, to produce five-membered nitrogen heterocyclic 1,2,3-triazoles compounds, is commonly known as the Click reaction [1,2], which has tremendous potential in biology and medicinal applications [3]
We have extended our experiments for glucose and galactose substituted azide molecule and we have found that the substituted azide molecule coupled with alkyne molecules to form βD- glucopyranoside and β-D-galactopyranoside substituted 1,2,3-triazole moieties, respectively, under the UV and DLB conditions in the presence of Cu-graphitic carbon nitride (gCN) catalyst
The mechanistic pathway for the copper-catalysed cycloaddition reaction for triazole synthesis is illustrated in scheme 1 (I), where a π-complex has been formed between the copper and the alkyne molecule followed by the deprotonation of the alkyne molecule, under basic condition, with the formation of copper-acetylidine complex
Summary
The copper-catalysed regioselective 1,3-dipolar cycloaddition of azide and alkyne, to produce five-membered nitrogen heterocyclic 1,2,3-triazoles compounds, is commonly known as the Click reaction [1,2], which has tremendous potential in biology and medicinal applications [3]. The Click reaction can be performed using wide varieties of copper species. Copper-based nano-catalysts have been reported in the literature for various kinds of organic transformation reactions [18,19]
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