title: Organocatalytic Friedel-Crafts Alkylation/Lactonization Reaction of Naphthols with 3-Trifluoroethylidene Oxindoles: The Asymmetric Synthesis of Dihydrocoumarins.
abstract: 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.
authors.affiliation: State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, Guangdong, 510530, China.
authors.forename: Yun-Long
authors.initials: YL
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, Guangdong, 510530, China.
authors.forename: Qin-Xin
authors.initials: QX
authors.lastname: Lou
authors.affiliation: Institute of POM-based Materials, School of Material and Chemical Engineering, Hubei University of Technology, Wuhan, 430068, China.
authors.forename: Long-Sheng
authors.initials: LS
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, Guangdong, 510530, China.
authors.forename: Wen-Hui
authors.initials: WH
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, Guangdong, 510530, China.
authors.forename: Jun-Ling
authors.initials: JL
authors.lastname: Zhao
keywords: amides; arenes; heterocycles; organocatalysis; synthetic methods