The Reaction of Phenylhydrazine with Sterically Congested Stabilized Phosphorus Ylides in the Presence of Silica Gel Powder in Solvent-Free Conditions: A Novel Synthesis of Fully Substituted Pyrazole Derivatives

Author: Noshiranzadeh Nader   Ramazani Ali  

Publisher: Taylor & Francis Ltd

ISSN: 1042-6507

Source: Phosphorus, Sulfur, and Silicon and the Related Elements, Vol.183, Iss.5, 2008-05, pp. : 1109-1115

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Abstract

Reactions of sterically congested stabilized phosphorus ylides with phenylhydrazine in the presence of silica gel powder in solvent-free conditions proceed smoothly at 100°C to afford dialkyl 2-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)-2-butenedioates in good yields. The structures of the products were deduced from their IR, 1H NMR, and 13C NMR spectra. The mass spectra of these compounds displayed molecular ion peaks at the appropriate z values. The 1H NMR (CDCl3) spectra of the compounds show the presence of two estereoisomers (E and Z) for each pyrazoles. The relative population of E and Z isomers were determined via their 1H NMR spectra The reaction is fairly stereoselective.

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