Green catalytic synthesis of 1,2,3-triazole derivatives from epoxide-azide-alkyne cycloaddition reaction in the presence of a new Cu(II) complex

Publish Year: 1398
نوع سند: مقاله کنفرانسی
زبان: English
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ICCO02_085

تاریخ نمایه سازی: 3 اردیبهشت 1399

Abstract:

1,2,3-Triazoles are a class of important five-membered heterocyclic compounds which have several applications in pharmaceutical sciences and medicine [1]. Due to this, the synthesis and characterization of 1,2,3-triazoles have attracted considerable attentions in synthetic organic chemistry. 1,3-Dipolar Huisgen cyclaoddition of azide-alkyne, known as click reaction , in the presence of transition metal catalysts is the most effective and popular method for production of this class of materials [2]. Various transition metal ions have been employed as catalyst for production of 1,2,3-triazoles [3-4] and the studies indicate the copper complexes show better and higher activity in this reaction. Due to this, the synthesis and employing copper complexes as catalyst for production of 1,2,3-triazoles is one of the active research field in this area. In the present paper we report the synthesis and characterization of a new Cu(II) complex, [CuCl(L)]·Cl (1). The complex is obtained by the reaction of CuCl2.H2O with tetradentate hydrazone-based Schiff base ligand (HL= bis((E)-2-(pyridin-2-ylmethylene)hydrazinyl)methaniminium chloride). The complex is characterized by spectroscopic methods, elemental analysis and single crystal X-ray studies. The obtained complex was used as catalyst in green click synthesis of β-hydroxy-1,2,3-triazoles through epoxide-azide-alkyne cycloaddition reaction (see scheme 1) which is also known as click reactions . The catalytic reactions were carried out in water as a green solvent and the effects of various effective parameters like temperature, the amount of catalyst and the substitute on the terminal-alkyne were also investigated. The catalytic studies indicated that the obtained complex is an active and selective catalyst for the green synthesis of 1,2,3-triazoles in a mild condition. The results of the catalytic studies indicated that the activity of this catalytic system is considerably depends on the temperature of the reaction since the reactions were completed in shorter time at higher temperatures. Nevertheless, two products were obtained at higher temperatures which indicate the selectivity of the reaction is low in higher temperatures. This matter can be attributed to the two kinds of epoxide ring opening reactions in higher temperatures. Using various aromatic and aliphatic alkynes indicated that the aromatic alkynes are more active than alihphatic alkynes. This matter can be attributed to the resonance effect of the aromatic ring which can increase the stability of the intermediantes while aliphatic groups can not show such effects. Scheme 1. Catalytic click synthesis of 1,2,3-triazoles by epoxide-azide-alkyne cycloaddition reaction in the presence of Cu(II) complex as a catalyst

Authors

Mehrangiz Azadehjo

Department of Chemistry, Faculty of Science, Imam Khomeini International University, Qazvin, Iran

Rahman Bikas

Department of Chemistry, Faculty of Science, Imam Khomeini International University, Qazvin, Iran