Click approach to the novel 1,2,3-triazolium phosphotungstate organic–inorganic hybrids for the highly promoted synthesis of spirooxindoles

Abstract

The synthesis and catalytic activity of three 1,2,3-triazole-based ionic organicinorganic 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, 1 H and 13 C 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.

Non-covalent immobilized sultone based protic ionic liquids on nano silica sulfuric acid as novel heterogeneous catalysts for the efficient synthesis of tetrazolopyrimidines

“…Ionic liquids (ILs) have attractive properties such as high thermal stability, low vapor pressure, wide liquid range, the ability to dissolve a broad series of chemical as the reaction media and ionic conductivity that make them a signi cant choice for industrial applications as solvent or catalyst [1,2]. A number of research works have been reported about the application of Brønsted acidic ILs (BAILs) as e cient acid catalysts in organic transformations [3][4][5]. However, extensive industrial application of ILs is limited by some of their problematic drawbacks, such as high viscosity leading to slow diffusion and ow of substrates, incomplete or tedious extraction of product from ionic phase, partial and time-consuming catalyst recovery and their high commercial cost [6].…”