Me2AlCl-mediated carboxylation, ethoxycarbonylation, and carbamoylation of indoles

作者：Nemoto Koji; Tanaka Shinya^*; Konno Megumi; Onozawa Satoru; Chiba Masafumi; Tanaka Yuuki; Sasaki Yosuke; Okubo Ryo; Hattori Tetsutaro^*

来源：Tetrahedron, 2016, 72(5): 734-745.

DOI：10.1016/j.tet.2015.12.028

• Indole
• Alumination
• Carboxylation
• Alkoxycarbonylation
• Carbamoylation

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.

• 出版日期2016-2-4