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.
Highlights
Heterocyclic compounds containing nitrogen have played a major role in modern pesticide industry; it has beenHow to cite this paper: Plem, S.C., Müller, D.M. and Murguía, M.C. (2015) Key Intermediates: A Simple and Highly Selective Synthesis of 5-Amino-1-aryl-1H-pyrazole-4-carbonitriles for Applications in the Crop Protection
The additions of fluorinated and non-fluorinated aryl hydrazine (2a-f) tomalononitrile (1) in solvent at reflux resulted in the cyclized product 5-amino-1-aryl-1H-pyrazole-4-carbonitriles (3a-f) as an exclusive product
Different substituted aryl hydrazines were utilized in this work to obtain the cyclized pyrazoles in a one-step reaction with high regionselectivity
Summary
Heterocyclic compounds containing nitrogen have played a major role in modern pesticide industry; it has beenHow to cite this paper: Plem, S.C., Müller, D.M. and Murguía, M.C. (2015) Key Intermediates: A Simple and Highly Selective Synthesis of 5-Amino-1-aryl-1H-pyrazole-4-carbonitriles for Applications in the Crop Protection. Many derivatives containing pyrazole nucleus have been commercialized as herbicides, insecticides, and fungicides for plant protection [3] Several compounds of this type can be directly applied as pest-control agents, in particular as acaricides and nematicides [4]-[6], whereas others can be used for the treatment of bacterial, inflammatory diseases and some cancers [4]. As they have proven to be useful intermediates for the preparation of new biological materials, the synthesis and applications of alkyl and aryl pyrazoles have been widely studied in the past few years [7]-[9]
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