Synthesis of 3-Substituted Arylpyrazole-4-carboxylic Acids

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• 作者：A. V. Lebedev ; A. B. Lebedeva ; V. D. Sheludyakov ; E. A. Kovaleva ; O. L. Ustinova and I. B. Kozhevnikov
• 刊名：Russian Journal of General Chemistry
• 出版年：2005
• 出版时间：May 2005
• 年：2005
• 卷：75
• 期：5
• 页码：782-789
• 全文大小：63 KB

文摘

A method was suggested for preparing previously unknown 3-aryl-substituted pyrazole-4-carboxylic acids, involving Vilsmeier formylation of semicarbazones of 26 available mono- and disubstituted acetophenones and 2-acetylthiophene followed by oxidation of the resulting 3-aryl-substituted pyrazole-4-carboxaldehydes under the action of potassium permanganate. The mechanism of the formylation reaction is discussed. The method successfully works even with acetophenones containing alkyl substituents. In the latter case, an additional stage that involves isolation of pyrazole-4-carboxylic acids as their silyl esters is used.