Organocatalytic Friedel-Crafts Alkylation/Lactonization Reaction of Naphthols with 3-Trifluoroethylidene Oxindoles: The Asymmetric Synthesis of Dihydrocoumarins

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• 作者：Yun-Long Zhao ; Qin-Xin Lou ; Long-Sheng Wang ; Dr. Wen-Hui Hu and Jun-Ling Zhao
• 刊名：Angewandte Chemie International Edition
• 出版年：2017
• 出版时间：January 2, 2017
• 年：2017
• 卷：56
• 期：1
• 页码：338-342
• 全文大小：744K
• ISSN：1521-3773

文摘

Naphthols and 3-trifluoroethylidene oxindoles were found to undergo an asymmetric Friedel–Crafts alkylation/lactonization reaction, catalyzed by only 2.5 mol % of a quinine-derived squaramide catalyst, to afford the corresponding α-aryl-β-trifluoromethyl dihydrocoumarin derivatives in high yields (up to 99 %) with excellent enantio- and diastereoselectivities (up to 98 % ee, >20:1 d.r.). Importantly, the lactonization proceeded by nucleophilic attack of the naphthol hydroxy group at the amide motif of the oxindoles under mild reaction conditions. This protocol represents a new strategy for the formation of dihydrocoumarins by an efficient intramolecular amide C−N bond-cleavage and esterification process.