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Regioselective synthesis of 5-aminopyrazoles from reactions of amidrazones with activated nitriles: NMR investigation and X-ray structural analysis |
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| Authors: | Ashraf A. Aly Mohamed Ramadan Mohamed Abd El-Aziz Stefan Bräse Alan B. Brown Hazem M. Fathy Martin Nieger |
| Affiliation: | 1.Chemistry Department, Faculty of Science,Minia University,El-Minia,Egypt;2.Department of Organic Chemistry, Faculty of Pharmacy,Al-Azhar University, Assiut Branch,Assiut,Egypt;3.Medicinal Department, Faculty of Pharmacy,Minia University,El Minia,Egypt;4.Institute of Organic Chemistry,Karlsruhe Institute of Technology,Karlsruhe,Germany;5.Chemistry Department,Florida Institute of Technology,Melbourne,USA;6.Chemistry Department,University of Helsinki,Helsinki,Finland |
| Abstract: | N-Arylbenzamidrazones and ethyl 2-cyano-3-ethoxybut-2-enoate reacted together in ethanol and catalyzed by triethylamine (Et3N) to give 5-amino-3-methyl-1-(aryl(phenylimino)methyl)-1H-pyrazole derivatives. Reaction of the target amidrazones with bis-(methylthio)methylidene)malononitrile in EtOH/Et3N/DMF mixture proceeded to give the corresponding 5-aminopyrazoles. The structure of the obtained products was proved by IR, mass, and NMR spectra and elemental analyses. Two-dimensional NMR spectroscopy and X-ray structural analyses were used to differentiate the assigned structures from other possible ring systems and regioisomers. The reaction mechanism is discussed. |
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