ISSN print edition: 0366-6352
ISSN electronic edition: 1336-9075
Registr. No.: MK SR 9/7
Regioselective synthesis of 5-aminopyrazoles from reactions of amidrazones with activated nitriles: NMR investigation and X-ray structural analysis
Ashraf A. Aly, Mohamed Ramadan, Mohamed Abd El-Aziz, Stefan Bräse, Alan B. Brown, Hazem M. Fathy, and Martin Nieger
Chemistry Department, Faculty of Science, Minia University, El-Minia, Egypt
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.
Keywords: Amidrazones; Activated nitriles; E-Aminopyrazoles; Conjugate addition; NMR; X-ray structure analyses
Full paper is available at www.springerlink.com.
Chemical Papers 71 (8) 1409–1417 (2017)