Please use this identifier to cite or link to this item: https://scidar.kg.ac.rs/handle/123456789/10185
Title: Theoretical study on structural and mechanistic aspects of synthesis of a 3-aminopyrazole derivative
Authors: Markovic, Svetlana
Joksović, Milan
Bombicz P.
Leovac V.
Marković, Violeta
Joksović, Ljubinka
Journal: Tetrahedron
Issue Date: 7-Aug-2010
Abstract: The structure of 5-hydroxy-3,5-dimethyl-1-S-methylisothiocarbamoyl-2- pyrazolinium iodide (HDMCPI), a cyclic intermediate for a 3-aminopyrazole derivative, was determined by means of X-ray analysis and spectroscopic techniques. In a treatment of HDMCPI in alkaline aqueous solution, 4-acetyl-3(5)-amino-5(3)-methylpyrazole (AAMP) was unexpectedly yielded. The reaction of HDMCPI was monitored by 1H and 13C NMR spectroscopy. It was shown that keto-imine tautomer appears as the only tautomeric form. Density functional theory explained the spontaneous formation of keto-imine tautomer, whose existence is the main condition for generating a carbanion in alkaline medium. The carbanion further undergoes cyclization and elimination of MeSH, thus yielding AAMP. In the reaction of acetylacetone with thiosemicarbazide instead of S-methylisothiosemicarbazide, there were no traces of AAMP. This result can be attributed to the absence of keto-imine form in the tautomeric equilibrium, which would provide the formation of a carbanion for a nucleophilic attack and further cyclization. © 2010 Elsevier Ltd. All rights reserved.
URI: https://scidar.kg.ac.rs/handle/123456789/10185
Type: journal article
DOI: 10.1016/j.tet.2010.05.093
ISSN: 00404020
SCOPUS: 77955424413
Appears in Collections:Faculty of Science, Kragujevac

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