Conversion of the quinoline ring to an indole ring

4-Nitro-3-hydroxyquinoline is readily converted to indole derivatives in aqueous alkaline and acetic acid media. The contraction of the quinoline ring to an indole ring under the conditions of mild methylation of 4-nitro-3-hydroxyquinoline in an aqueous alkaline medium proceeds through the formation of the N-methyl de rivative of 4-nitro-3-hydroxyquinoline and N-methyl-2-formyl-3-nitroindole. 3-Nitroindole is formed when 4-nitro-3-hydroxyquinoline is heated in aqueous alkali, whereas isatin is formed in acetic acid. The methylation of 4-nitro-3-hydroxyquinoline in refluxing acetic acid leads to N-methylisatin.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 513–516, April, 1979.