Anthanthrone pigments

Anthanthrone is synthesized from naphthostyril (105), which is saponified to form l-aminonaphthalene-8-carboxylic acid (106). Naphthostyril itself is prepared from 1-naphthylamine with phosgene in the presence of dry aluminum chloride. 

Diazotizing 106 and boiling the solution in the presence of copper powder affords 1,1 -dinaphthyl-8,8 -dicarboxylic acid (107), which is cyclized with aluminum chloride, but preferably with concentrated sulfuric acid at 30 to 40°C to produce anthanthrone. 

The Friedel-Crafts reaction, which proceeds via electrophilic aromatic substitution, as illustrated in the following scheme, is unique to the manufacture of anthanthrone pigments. Most other polycyclic anthraquinone pigments are synthesized via nucleophilic ring closure. 

10-Dibromoanthanthrone (108) is registered as Pigment Red 168,59300. First synthesized as early as 1913 as a vat dye, this compound is the commercially most interesting halogenated anthanthrone derivative. 

Compound 108 may be prepared directly from 104 without intermediate isolation of 104 by treating the dicarboxylic acid 107 with monohydrate or with concentrated sulfuric acid at 35°C, followed by bromination in the presence of iodine as a catalyst. 

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Bromide analysis, of water, 26 41 Bromide ions, in development solution, 79 205-206 Bromides, 4 319-330 thorium, 24 763 titanium, 25 54 tungsten, 25 379 uranium, 25 439 Bromimide, 4 299, 319 Brominated additive flame retardants, 77 461-468, 471-473t Brominated Anthanthrone Orange, pigment for plastics, 7 367t Brominated aromatic compounds, 7 7 459 Brominated bisphenol A-based epoxy resins, 70 366... 

To obtain the necessary fastness properties, high-quality pigments are generally used for security printing. The range of suitable products covers disazo, disazo condensation, benzimidazolone, naphthol AS, isoindolin, perinone, anthanthrone, dioxazine and quinacridone pigments. 

This class includes polycarbocyclic compounds which are at least formally derived from the anthraquinone structure. The products are considered members of the higher condensed carbocyclic quinone series, which even in the absence of additional substituents provide yellow to red shades. Halogenation is frequently found to afford cleaner shades and improved fastness properties. Heading the list of such derivatives are pyranthrone, anthanthrone, and isoviolanthrone pigments. 

Another important qninone is anthanthrone, especially its dibromo derivative (2.73), Cl Pigment Red 168. This latter pigment is scarlet in colonr and shows excellent resistance to solvents and is one of the most light fast and weather fast pigments known. It is nsed in high-grade paints. 

The anthanthrones are classed as polycarbocychc anthraqiunone pigments. Anthanthrone itself consists of two connected... 

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