ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

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

E-mail: ashrafaly63@yahoo.com

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.

DOI: s11696-017-0131-x

Chemical Papers 71 (8) 1409–1417 (2017)