Reaction of 1,2-diarylhydrazines with acetic anhydride catalyzed by 4-(dimethylamino)pyridine

Research paper by Gertraud Chiste, Helmut Egg, Klemens Kraus, Elisabeth Pipitz, Elisabeth Spanyar

Indexed on: 01 Jun '91Published on: 01 Jun '91Published in: Monatshefte für Chemie - Chemical Monthly


A new method for the synthesis of 1,2-diaryl-1,2-dihydro-5-methyl-3H-pyrazol-3-ones3 and 4-acetyl-1,2-diaryl-1,2-dihydro-5-methyl-3H-pyrazol-3-ones5 is presented. The reaction of 4,4′-disubstituted 1,2-diarylhydrazines1 with acetic anhydride in the presence of an equimolar amount of 4-(dimethylamino)pyridine leads to mixtures of the corresponding acetyl derivatives2 and3. Under the same conditions, 2,2′-disubstituted 1,2-diarylhydrazines yield mixtures of3 and5.