Reaktionsverhalten von β-Oxo-carbonsäurederivaten der Anthracenreihe bei der Synthese von Pyrazolen / On the Reaction Behavior of ß-Oxo Carbonic Acid Derivatives of the Anthracene Series in Pyrazole Synthesis

• Published in: Zeitschrift für Naturforschung B
• Main Authors: Knieß, Astrid, Gruner, Margit, Mayer, Roland
• Format: Article in Journal/Newspaper
• Language: English
• Published: Walter de Gruyter GmbH 1999
• Subjects: Carbonic acid
• Online Access: http://dx.doi.org/10.1515/znb-1999-0908; https://www.degruyter.com/view/journals/znb/54/9/article-p1133.xml; https://www.degruyter.com/document/doi/10.1515/znb-1999-0908/xml; https://www.degruyter.com/document/doi/10.1515/znb-1999-0908/pdf

ß-Oxo-1 and 9-anthracenepropionate (6 and 7) reacts with DMF-acetale to enaminones 10 and 11. The reaction of 2-(dimethylamino)methylen-substituted ß-oxo-1 -anthracenepropionate (10) with hydrazines yields 5-(l-anthracenyl)-pyrazol-4-carboxylates (13). In contrast, the cyclocondensation of 3-(9-anthracenyl)-2-(dimethylamino)methylen-3-oxo-propionate (11) with hydrazine hydrochlorides gives 4-(9-anthracenoyl)-5-hydroxy-pyrazoles (14). This is caused by the sterical hindrance of the carbonyl group of the anthracene derivatives in position 9; thus, the cyclocondensation proceeds via reaction of the ester group of the enaminone 11.