Synthesis of Methyl 5- and 6-Nitroindole-2-carboxylates by Nitration of Indoline-2-carboxylic Acid

Abstract

Indoline-2-carboxylic acid was transformed into 6-nitroindoline-2-carboxylic acid, the methyl ester of which was easily dehydrogenated by DDQ to methyl 6-nitroindole-2-carboxylate (total yield: 67%). Methyl 5-nitroindole-2-carboxylate was obtained by the nitration of methyl 1-acetylindoline-2-carboxylate acid followed by dehydrogenation with MnO₂ in toluene in 40% total yield.

Key words

methyl 5- and 6-nitroindole-2-carboxylate - indoline-indole method - indoles

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