NEW MATERIAL:Bisazo compound of formula I.
USE: Bisazo compd. which is blackish blue, has excellent fastness to solvents, light, heat, acids and alkalis and also excellent dispersibility and coloring power and is useful as an org. pigment.
PREPARATION: 3,3'-Dibromobenzidine is tetrazotized and then coupled with 2-hydroxy-N-(2-ethylphenyl)-11H-benzo[a]carbazole-3-carboxyamide in the presence of a base. Alternatively, the tetrazonium salt of 3,3'-dibromobenzidine is coupled with 2-hydroxy-N-(2-ethylphenyl)-11H-benzo[a]-carbazole-3-carboxylic acid, and two carboxyl groups in the molecule of the resulting dicarboxylic acid derivative is reacted with 2-ethylaniline to obtain the bisazo compd. of the formula.