Induline

The first reaction giving a clue to their constitution was the isolation of the intermediate azophenin by O. Witt, which was proved by Fischer and Hepp to be dianilidoquinone dianil, a similar intermediate compound being found shortly afterwards in the naphthalene series.

The indulines are prepared as mentioned above from aminoazo compounds, or by condensing oxy- and amido-quinones with phenylated ortho-diamines.

[1] The rosindulines and naphthindulines have a strongly basic character, and their salts possess a marked red color and fluorescence.

Benzinduline (aposafranine), C18H13N3, is a strong base, but cannot be diazotized, unless it be dissolved in concentrated mineral acids.

When warmed with aniline it yields anilido-aposafranine, which may also be obtained by the direct oxidation of ortho-aminodiphenylamine.