Me2AlCl-mediated carboxylation, ethoxycarbonylation, and carbamoylation of indoles. Issue 5 (4th February 2016)

• Record Type: Journal Article
• Authors: Nemoto, Koji; Tanaka, Shinya; Konno, Megumi; Onozawa, Satoru; Chiba, Masafumi; Tanaka, Yuuki; Sasaki, Yosuke; Okubo, Ryo; Hattori, Tetsutaro
• Is Part Of: Tetrahedron. Volume 72:Issue 5(2016)
• Page Start: 734
• Page End: 745
• Publication Date: 2016-02-04
• Subjects: Indole -- Alumination -- Carboxylation -- Alkoxycarbonylation -- Carbamoylation; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2015.12.028
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: Various 1-methyl-, 1-triisopropylsilyl-, and 1-benzylindoles are carboxylated under CO2 pressure (3.0 MPa) with the aid of 1.0 molar equiv of Me2 AlCl to give 1-substituted indole-3-carboxylic acids in good to excellent yields. Mechanistic studies suggest that the intermediate, an indol-3-ylaluminum ate complex, was reversibly formed by electrophilic addition of Me2 AlCl to the substrate followed by deprotonation of the resulting adduct. This method is successfully extended to alkoxycarbonylation with ethyl chloroformate and carbamoylation with naphthalen-1-yl isocyanate, which afford ethyl indole-3-carboxylates and N -naphthalen-1-ylindole-3-carboxamides, respectively. Graphical abstract: