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Title: | Synthesis of di(Imdazolium) and di(Pyrazolium) Salts as Precursors for N-heterocyclic Dicarbene Complexes |
Authors: | Goncharova, T. V. Zatonskaya, L. V. Potapov, Andrey Sergeevich |
Keywords: | пиразолы; имидазолы; соли; синтезы; прекурсоры; комплексы; pyrazole; imidazole; N-heterocyclic carbenes; imidazolium salts; pyrazolium salts |
Issue Date: | 2014 |
Publisher: | Elsevier |
Citation: | Goncharova, T. V. Synthesis of di(Imdazolium) and di(Pyrazolium) Salts as Precursors for N-heterocyclic Dicarbene Complexes [Electronic resource] / T. V. Goncharova, L. V. Zatonskaya, A. S. Potapov // Procedia Chemistry . — 2014 . — Vol. 10 : Chemistry and Chemical Engineering in XXI century . — [P. 485-489] . |
Abstract: | Alpha,omega-bis(pyrazol-1-yl)alkanes and alpha,omega-bis(imidazol-1-yl)alkanes with spacers consisting of four to ten methylene groups have been prepared from pyrazole, 3,5-dimethylpyrazole or imidazole and corresponding dibromoalkanes in a superbasic medium KOH-DMSO. The proposed method of synthesis allowed the preparation of new flexible bidentate ligands without the need to use toxic solvents and tedious workup procedures. Bis(pyrazol-1-yl)alkanes were further functionalized for their use as precursors for “non-classical” mesoionic N-heterocyclic carbene ligands. One the first step, iodine atoms were introduced to positions 4 of pyrazole rings by oxidative iodination using I[2]-HIO[3] system. On the next step, nitrogen atoms in positions 2 of pyrazole rings were alkylated using several agents. Reaction with methyliodide unexpectedly led to the formation of only mono-alkylated products even after 7 days of refluxing in a neat alkyliodide. Methylation by trimethyloxonium tetrafluoroborate or methyltriflate led to dimethylated products in high yields. Bis(imidazol-1-yl)alkanes were easily alkylated by methyliodide to give di(imidazolium) salts – precursors to “classic” N-heterocyclic dicarbenes. |
URI: | http://earchive.tpu.ru/handle/11683/35535 |
Appears in Collections: | Материалы конференций |
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dx.doi.org-10.1016-j.proche.2014.10.081.pdf | 322,51 kB | Adobe PDF | View/Open |
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