AZO PIGMENTS AND THEIR INTERMEDIATES - A FACILE SYNTHESIS OF PHOTORECEPTOR GRADE ANILIDE COUPLERS FROM 2-HYDROXY-11H-BENZO(A)CARBAZOLE-3-CARBOXYLIC ACID

A facile, two-step synthesis for anilide couplers of 2-hydroxy-11H-ben zo (a) carbazole-3-carboxylic acid, by first converting the acid to it s phenyl ester and then condensing the phenyl ester with an aniline de rivative to form an anilide, is reported. The synthesis is very genera l and a variety of anilides have been synthesized in an overall yield of greater-than-or-equal-to 60%. The synthesized anilides are of high purity and can be used to synthesize photoreceptor-grade (IR-sensitive ) azo pigments without further purification. The procedure described i n this work is shown to be more efficient than other processes reporte d in the literature, such as direct condensation of the acid with an a niline or indirect condensation of the acid with an aniline through an acid chloride or methyl ester intermediate. More importantly, we have demonstrated that neither yield-loss nor deterioration in product pur ity is observed as the scale of the synthesis increases.