| abstract |
A method of preparing indole carboxylic acid derivatives from aniline derivatives is described which can be carried out in a single reaction vessel without any isolation of intermediate products. The method involes reacting an aniline derivative with a soluble nitrite in an acid medium, reducing the resulting nitrosamine by treating the acidic nitrosamine containing reaction solution with zinc in the presence of sufficient acid, optionally with addition of additional acid and/or a solvent such as a lower alcohol, reacting the resulting hydrazine derivative containing solution with a lower alkyl ester of pyruvic acid to obtain a corresponding hydrazone which cyclizes to yield an indole carboxylic acid ester, and if desired, hydrolyzing the ester to obtain the corresponding carboxylic acid. |