Nitration of Dimethyl 1-Substituted Indole-2,3-dicarboxylates: Synthesis of Nitro- and Aminoindole Derivatives

Abstract

The treatment of dimethyl indole-2,3-dicarboxylate with nitronium tetrafluoroborate in the presence of tin (IV) chloride produced dimethyl 5-nitroindole-2,3-dicarboxylate as the major product. In a similar manner, the dimethyl 1-benzyl- and 1-benzenesulfonylindole-2,3-dicarboxylates provided a mixture of the corresponding 4-nitro-, 5-nitro-, 6-nitro- and 7-nitroindole derivatives. However, dimethyl 5-bromoindole-2,3- dicarboxylate gave dimethyl 5-bromo-4-nitroindole-2,3-dicarboxylate as the sole product, which was converted to dimethyl 4-aminoindole-2,3-dicarboxylate.