Catalytic Generation of Vinylthionium Ions. (4 + 3)-Cycloadditions and Friedel鈥揅rafts Alkylations

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• 作者：Michael Topinka ; Rama Rao Tata ; Michael Harmata
• 刊名：Organic Letters
• 出版年：2014
• 出版时间：September 5, 2014
• 年：2014
• 卷：16
• 期：17
• 页码：4476-4479
• 全文大小：272K
• ISSN：1523-7052

文摘

A 3-phenylsulfanyl-substituted allylic alcohol and an ester thereof were treated with Br酶nsted acids or a gold catalyst, respectively, to generate vinylthionium ions. These species react with dienes, primarily substituted furans, to give products of either (4 + 3)-cycloaddition or Friedel鈥揅rafts alkylation. The results are rationalized on the basis of a stepwise mechanism in which the relative rates of ring closure versus proton loss in the intermediate 蟽-complex determine the course of the reaction.