Synthesis of E- and Z-pyrazolylacrylonitriles and their evaluation as novel antioxidants.

A facile synthesis of (Z)- and (E)-2-(5-arylpyrazol-3-yl)-3-(pyrrol-2-yl)acrylonitriles and (Z)-2-(1,3-diarylpyrazol-5-yl)-3-pyrrol-2-yl)acrylonitriles, and isomerisation of (Z)-2-(5-arylpyrazolyl)acrylonitriles to (E)-2-(5-arylpyrazolyl)acrylonitriles under basic conditions have been reported. (Z)-2-(1,3-Diarylpyrazolyl)acrylonitriles did not undergo isomerisation under the similar conditions. New compounds were identified on the basis of their spectral data (1H-, 13C-, 1H-1H COSY, NOESY, NOE, HMQC NMR, IR, UV and EI mass). The structures of one acrylonitrile and five of their precursor 6-arylpyran-2-ones and cyanomnethylpyrazoles were confirmed by X-ray crystallographic studies. Effects of pyrazolylacrylonitriles and their precursors on rat liver-microsomal lipid peroxidation were evaluated in vitro with a view to establish structure activity relationship and to identify a lead compound.