Abstract
1,4-Disubstituted-1,2,3-triazoles, considered as an important and useful class of heterocycles with potential applications in material science and biology, have been prepared in an efficient and selective manner by copper on carbon-catalyzed [3+2] cycloaddition reactions of azides and alkynes (CuAAC) in water under strict click chemistry conditions. Copper(I) catalysts heterogenized onto commercially activated carbon materials (Cu-CC) and on another carbon material produced from vegetable biomass using Argan nut shells (Cu-CANS) were found to be versatile catalytic sources for sustainable CuAAC. These copper on carbon supports were prepared and fully characterized by using two types of activated carbons that exhibit different porosity and specific surface. The delineation of the nature of the catalytic copper species and the role of the carbon support in the CuAAC were addressed. These heterogeneous copper on carbon catalysts were recovered and reused until ten catalytic runs without any noticeable loss of activity.
Highlights
1,2,3-Triazoles are important and useful non-classical bioisostere linkage heterocycles
The Lipshutz group has described the preparation of copper-in-charcoal by impregnating of copper(II) nitrate in activated carbon (Darco-KB) using water as solvent under ultrasound radiation followed by distillation of water by azeotropic drying with toluene
The synthesis of activated carbon from the local biomass such as Argan nut shells by the chemical activation method was adopted in this study
Summary
1,2,3-Triazoles are important and useful non-classical bioisostere linkage heterocycles. Copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) (Tornøe et al, 2002; Pachón et al, 2005; Bock et al, 2006) has emerged as one of the most reliable reactions under the click chemistry regime (Kolb and Sharpless, 2003; Yadav et al, 2007) that enables the practical and efficient preparation of 1,4-disubstituted-1,2,3-triazoles, from a wide range of substrates with excellent selectivity, which cannot be achieved by traditional Huisgen non-catalyzed thermal approaches (Huisgen, 1963). The Lipshutz’s copper-in-charcoal was efficient in assisting CuAAC, the studied triazole click reactions made use of a high catalyst loading of 10 mol%, an additional base (Et3N) and were peformed at high temperature (60 ◦C) in a hazardous solvent such as dioxane. In the context of our efforts to develop green, highly eco-efficient, and practical chemical methods utilizing bio-heterogeneous catalysts in [3+2] cycloaddition reactions of azides with alkynes (Bahsis et al, 2018), we report an easy sustainable protocol for the synthesis of 1,2,3-triazoles.
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