Abstract
The synthesis and catalytic activity of three 1,2,3-triazole-based ionic organic-inorganic hybrids as novel water-soluble catalysts for the efficient preparation of spirooxindole derivatives are described. At first, three different 1,2,3-triazoles were prepared by click reaction. Then, these synthesized compounds were reacted with 1,4-butane sultone to generate novel solid 1,2,3-triazolium-N-butyl sulfonate zwitterions. In the next step, the newly synthesized organic zwitterions were treated with an aqueous solution of phosphotungstic acid to give three novel 1,2,3-triazolium-N-butyl sulfonic acid phosphotungstates as targeted organic-inorganic hybrid catalysts. The prepared catalysts were fully characterized using FTIR, H-1 and C-13 NMR, XRD, elemental analysis (CHNS), ESI-MS, DSC, and TG techniques. The introduced novel SO 3 H-functionalized ionic hybrid catalysts have a cationic organic triazolium with phosphotungstate anion and are water-soluble with appropriate thermal stability. Their catalytic activity was explored for the synthesis of spirooxindoles via the three-component reaction of 1,3-dicarbonyl compounds, barbituric acid, and isatin derivatives. The synthesis of desired spirooxindole products was performed in acceptable times with excellent yields in the presence of low loading amount of the prepared 1,2,3-triazolium-N-butyl sulfonic acid phosphotungstate catalysts (10 mmol%) in water. Some highlighted superiorities of the introduced organic-inorganic hybrids in comparison with most of the previously reported catalysts are as follows: clean and straightforward preparation, novelty of the catalysts, green conditions, ease of recovery, and reusability up to three repeated runs with no significant decrease in the catalytic stability.
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