First synthesis of 3-aryl-5-dichloromethyl-2-pyrazolines. The electrochemical generation of 2,2-dichlorovinylacetophenones as a key step

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• 作者：Guirado ; Antonio ; Martiz ; Bruno ; Andreu ; Raquel
• 关键词：Pyrazolines ; Chloral ; Acetophenones ; Electrosynthesis ; Reduction ; Dechlorination
• 刊名：Tetrahedron Letters
• 出版年：2004
• 期刊代码：109_00404039
• 类别：ch
• 出版时间：November 8, 2004
• 卷：45
• 期：46
• 页码：8523-8526
• 文件大小：254 K

摘要

An efficient synthetic route to the title compounds has been established. Chloralacetophenones 2 were prepared by treatment of acetophenones 1 with anhydrous chloral. Dehydration of intermediates 2 under acidic conditions yielded 2,2,2-trichloroethylideneacetophenones 3, which were transformed to 2,2-dichlorovinylacetophenones 5 in nearly quantitative yields by selective electrochemical monodechlorination at either mercury or graphite electrodes. Finally, 3-aryl-5-dichloromethyl-2-pyrazolines 7 were efficiently obtained on treatment of compounds 5 with either hydrazine or methylhydrazine.