A direct preparation of 2-aryl-4-ethoxycarbonyl-3- pyrazolin-5-ones from aryl hydrazines

Abstract Aryl hydrazines (1) possessing an electron-withdrawing substituent on the phenyl ring, on treatment with diethyl (ethoxymethylene)malonate in ethanolic sodium ethoxide solution, have directly afforded 2-aryl-4-ethoxy-carbonyl-3-pyrazolin-5-ones (4). Spectroscopic evidence is presented to differentiate these compounds (4) from their 1-aryl isomers (3).