Novel dyes and intermediates for synthetic‐polymer fibres: Synthesis and dyeing performance of 1‐aryl‐5‐hetarylphenylazo‐4‐hydroxypyrazole derivatives and their isomeric 1‐hetarylphenyl‐5‐arylazo analogues as disperse dyes for polyester fibre

Abstract

AbstractIn a multi‐step synthesis, a series of 5‐arylazo‐4‐hydroxy‐1‐(substituted imidazol‐5‐on‐2‐ylphenyl)pyrazole‐3‐carboxanilide dyes (VIIIa—i), their isomeric 4‐hydroxy‐1‐phenyl‐5‐(substituted imidazol‐5‐on‐2‐ylphenylazo)pyrazole‐3‐carboxanilide analogues (XIIa—i) and a related series of 4‐hydroxy‐1‐phenyl‐5‐(substituted oxazol‐5‐on‐2‐ylphenylazo)pyrazole‐3‐carboxanilide derivatives (XIa—h) were prepared with a view to evaluating and comparing the assessment of their dyeing performance on synthetic polymer fibres. Fastness ratings were generally good, particularly for the imidazolonylphenylazo series (XIIa—i). Substituents of the latter type are of greater value in attaining optimum light fastness in these dyestuffs. The structures of the synthesized dyes were inferred from elemental and spectral data and, whenever possible, by alternative synthetic routes.