Benzimidazolone coupling components

The most important coupling component for pigments in the yellow range is 5-acetoacetylamino-benzimidazolone (25), while red pigments are derived primarily from 5-(2 -hydroxy-3 -naphthoyl)-aminobenzimidazolone (26). 

The chemistry and manufacture of the coupling components for yellow/orange and red benzimidazolone pigments are treated separately. 

Yellow and Orange Benzimidazolone Pigments -Coupling Component... 

Benzimidazolone pigments are azo colorants that derive their name from the benzimidazolone group which is introduced as part of the coupling component. Apart from one exception ) there are two coupling components of commercial importance 5-acetoacetylaminobenzimidazolone (1) and 5-(2 -hydroxy-3 -naphthoylamino)-benz-imidazolone [Naphtolon ] (2) (see Figure 10-1). 

Figure 10-1 The two commercially relevant coupling components for benzimidazolone pigments.

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