3-Hydroxy-2-naphthoic acid → 3-Hydroxynaphthalene-2-carbonyl chloride

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Reaction Steps

Also, the azo pigments of Formula I illustrated in FIG. 5 may be prepared, for example, by reacting 2-hydroxy-3-naphthoic acid with thionyl chloride to obtain 2-hydroxy-3-naphthoic acid chloride. Subsequently, the formed acid chloride is added to a solution of N,N-diethylaniline and a halo aniline to yield a halo coupler compound. A 5 millimole amount of 2,7-diaminofluoren-9-one is then tetrazotized by an excess amount of a metal nitrite such as sodium nitrite in an aqueous hydrochloric acid solution at from about 0° C. to about 30° C., and the product is reacted with HBF4. An 11 millimole amount of the halo coupler compound previously prepared is then added to the resulting tetrazonium salt in a solution of dimethylformamide at from about 0° C. to about 30° C., followed by the addition of a base, such as sodium acetate in water, to the reaction mixture. The resulting precipitated product is a disazo pigment of Formula I, the specific compound obtained depending on the dihalo aniline selected during the preparation of the coupler compound. For example, 2,3-dichlloroaniline is selected as a reactant to obtain the coupler compound 2-hydroxy-3-naphtho-2',3'-dichloroanilide, which is then used to prepare 2,7-bis(1'azo-2'-hydroxy-3'naphtho-2",3"-dichloroanilide)fluoren-9-one. The azo pigments are isolated by filtration and purified by repetitive solvent washings, and may be characterized by elemental analysis, melting point, and IR spectroscopy.

Provenance & Evidence