**1. Introduction**

'Click chemistry' has emerged as a fast and efficient approach for synthesis of novel heterocyclic compounds [1, 2]. The Huisgen 1,3-dipolar cycloaddition of azides and alkynes resulting in 1,2,3-triazoles is one of the most powerful click reactions [3, 4]. The synthesis of 1,2,3-triazole has been intensively studied, and triazoles are widely used in pharmaceuticals, agrochemicals, dyes, photographic materials, and in corrosion inhibitory materials [5–7]. In addition, they possesses anti-HIV [8, 9] antimicrobial activities [10]. The selective β-3 adrenergic receptor agonism [11]. In the absence of a transition-metal catalyst, these reactions are not regioselective, relatively slow, and require high temperatures to reach acceptable yields. In early 2002, Meldal and co-workers reported that the use of catalytic amounts of copper(I), which can bind to terminal alkynes, leads to fast, highly efficient, and regioselective azide, alkyne cycloadditions at room temperature in organic medium [12–15]. Recently, Sharpless and co-workers have reported a high yielding synthesis of triazoles using a CuI catalyst with an excellent 1,4-regioselectivity [15–18]. The resulting 'clicked' products can even be obtained via in situ generation of the corresponding organic azides from organic halides, NaN3 in the presence of an alkyne and a copper catalyst, avoiding the need to handle organic azides [19]. Nitrogen heterocycles have received special attention in pharmaceutical chemistry due to their diverse medicinal potential [20–22]. The main aim of our research work is to replace the costly and hazardous organic solvents for the synthesis of 1,2,3-triazoles by using ecofriendly efficient unique properties such as commercial

availability, recyclable, easily degradable, having low toxicity, thermally stability and non-volatility of this PEG-400 solvent [23].
