The tautomerism and bromination of some 1-hydroxyindole-2-carboxylic acid derivatives

Abstract

1-Hydroxyindole-2-carboxylic acid with diazomethane gave methyl 1-methoxyindole-2-carboxylate which was attacked by bromine at the 3,5-positions; both the 3,5- and 3,6-dibromo-derivatives were independently synthesised. The n.m.r. spectra suggest that methyl 1-hydroxyindole-2-carboxylate exists as such but 5-bromo-1-hydroxyindole-2-carboxylic acid is present as the 3H-indole 1-oxide in deuteriochloroform.