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)ac rylonitriles and (Z)-2-(1,3-diarylpyrazol-5-yl)-3-(pyrrol-2-yl)acrylonitril es, 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)acrylonitrile did not undergo isomerisation under t he similar conditions. New compounds were identified on the basis of their spectral data (H-1-, C-13-, H-1-H-1 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 cyanomethylpyrazoles were confirmed by X-ray crystall ographic studies. Effects of pyrazolylacrylonitriles and their precursors o n rat liver-microsomal lipid peroxidation were evaluated in vitro with a vi ew to establish structure-activity relationship and to identify a lead comp ound. (C) 1999 Elsevier Science Ltd. All rights reserved.