Chemistry of indanthrone. Part XI. The reduction of the dihydrodinaphthophenazinediquinones

Abstract

The reduction of two of the title compounds, viz., indanthrone and its linear isomer, with various reducing agents is described. Indanthrone with warm aqueous alkaline dithionite first forms a deep blue solution (vat), for which a structure is advanced. Treatment of indanthrone with an excess of this reagent at higher temperatures, or with hydriodic acid and red phosphorus, produces a series of “over-reduction” compounds, which are formed by the progressive reduction of the two anthraquinonoid residues to anthracene residues. The structure of these “over-reduction” products are discussed, and their properties described. A mechanism for the complete reduction of indanthrone is proposed. A comparison of the behaviour on reduction of indanthrone with that of its linear isomer clearly shows the influence of the intramolecular hydorgen-bonding in the former.