Disperse Dyes Derived from 4-Phenylazo-1-naphthylamine and 4-Phenylazo-5-hydroxy-1-naphthylamine

Application of the Bucherer reaction between 1-naphthol and alky lamines gave a satisfactory synthesis of N-substituted 1-naphthylamines. A method avoiding the use of pressurised reaction vessels, i.e. reaction of 1-naphthol with alkylamines in the presence of zinc chloride and hydrochloric acid, is reported. Coupling of diazotised 6-chloro-2,4-dinitroaniline to the above intermediates affords blue dyes which colour synthetic-polymer fibres in deep shades of generally good fastness to light and sublimation. Similar use as coupling components of 5-hydroxy-1-naphthylamines enables blue dyes to be obtained without the use of trisubstituted anilines as diazo component. Dyes thus derived from 2-chloro-2-nitroaniline absorb at longer wavelength than those from 6-chloro-2,4-dinitroaniline with analogous 1-naphthyl-amine-based couplers. Similar bathochromic shifts are observed in dyes derived from 2-methoxy-1-naphthylamines as coupling components, but these dyes have poor stability. Relationships between colour and dye structure are reported, and the use of 4-amino-1,8-naphthalimides as diazo components was additionally investigated. These give, with N-substituted 1-naphthylamines as coupling components, deep bluish-violet dyes of good fastness properties.