Chlorosulfonation of 2-acylthiophenes: an examination on the reaction regiochemistry

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• 作者：Arduini ; Arturo ; Pochini ; Andrea ; Secchi ; Andrea ; Ugozzoli ; Franco
• 关键词：thiophenes ; chlorosulfonation ; heterocyclic compounds
• 刊名：Tetrahedron Letters
• 出版年：2003
• 出版时间：July 21, 2003
• 年：2003
• 卷：44
• 期：30
• 页码：5755-5757
• 全文大小：135 K

文摘

Chlorosulfonation of thenoyltrifluoroacetone with neat chlorosulfuric acid was found to give a 25:75 mixture of 3- and 2-chlorosulfonated thenoyltrifluoroacetone isomers in 33 % overall yield. The use of dichloromethane as solvent for the chlorosulfonation reaction gave only the 2-chlorosulfonated isomer in 45 % yield. On the contrary, the reaction of 2-acetylthiophene with neat chlorosulfuric acid gave only the 3-chlorosulfonated-5-acetylthiophene in 35 % yield. The identity of these chlorosulfonated compounds was unambiguously established by NMR techniques and confirmed by the crystal structure determination of the 2-chlorosulfonated isomer.