J. N. Freskos, G. W. Morrow, and G. S. Swenton, “Synthesis of functionalized hydroxyphthalides and their conversion to 3-cyano-1(3M-isobenzofuranones. The Diels-Alder reaction of methyl 4, 4-diethoxybutynoate and cyclohexadienes,” J. Org. Chem. Vol. 50, No. 6, 1985, pp. 805-810.

has been cited by the following article:

• TITLE: TsOH·H2O-Catalyzed Friedel-Crafts of Indoles of 3-Hydroxyisobenzofuran-1(3H)-One with Indoles: Highly Synthesis of 3-Indolyl-Substituted Phthalides

  AUTHORS: Hongying Tang, Xinyu Zhang, Airu Song, Zhongbiao Zhang

  KEYWORDS: Synthesis; 3-Indolyl-Substituted Phthalides; Friedel-Crafts Alkylation; 3-Hydroxyisobenzofuran-1(3H)-One; Indole

  JOURNAL NAME: Modern Research in Catalysis, Vol.1 No.2, July 24, 2012

  ABSTRACT: An efficient and facile method for the synthesis of 3-indolyl-substituted phthalides by Friedel-Crafts alkylation of indoles with 3-hydroxyisobenzofuran-1(3H)-one has been developed. Using only 2 mol-% TsOH·H2O as the catalyst, various substituted indoles can react smoothly at room temperature to give the corresponding phthalides products in good to excellent yields (up to 96%).