Key Intermediates: A Simple and Highly Selective Synthesis of 5-Amino-1-aryl-1H-pyrazole-4-carbonitriles for Applications in the Crop Protection

Silvana C. Plem, Diana M. Müller, Marcelo C. Murguía^*

Laboratorio de Química Aplicada (LAQUIMAP), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral (UNL), Santa Fe, Argentina.

DOI: 10.4236/aces.2015.53025                

Abstract

A series of six pyrazoles was synthesized by Michael-type addition reaction. The molecules 5-amino-1-aryl-1H-pyrazole-4-carbonitrile (3a-f) were synthesized from (ethoxymethylene)malo-nonitrile (1) and fluorinated and non-fluorinated aryl hydrazines (2a-f) using ethanol and fluorinated ethanol as solvents at reflux. An excellent regio-selectivity was found when pyrazole derivatives were formed as an exclusive product. No other regioisomer or uncyclised hydrazide was observed. Their structures were confirmed by spectroscopy data (¹H, ¹³C, ¹⁹F, COSY (correlation spectroscopy), HSQC (heteronuclear single-quantum correlation spectroscopy) and HMBC (heteronuclear multiple-bond correlation spectroscopy); MS (mass-spectrometry). The yields ranged from good to excellent (47% - 93%) under mild reaction conditions. It would indicate a high selectivity in the one-step work procedure. These products (3a-f) and derivatives have a potential academic and industrial use as key intermediates, in special, for application in crop protection.

Keywords

Aryl Pyrazole, Aryl Hydrazine, Amino Pyrazole, 5-Amino-1-aryl-1H-pyrazole-4-carbonitriles

Conflicts of Interest

The authors declare no conflicts of interest.

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