Me2AlCl-mediated carboxylation, ethoxycarbonylation, and carbamoylation of indoles
作者:Koji Nemoto、Shinya Tanaka、Megumi Konno、Satoru Onozawa、Masafumi Chiba、Yuuki Tanaka、Yosuke Sasaki、Ryo Okubo、Tetsutaro Hattori
DOI:10.1016/j.tet.2015.12.028
日期:2016.2
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 Me2AlCl 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 Me2AlCl to the substrate followed by de-protonation 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. (C) 2015 Elsevier Ltd. All rights reserved.