DD265894A1 - PROCESS FOR PREPARING 5- (3'-HYDROXYNAPHTHOYL-2'-AMINO) -BENZIMIDAZOLONE - Google Patents

Abstract

The invention relates to a process for the preparation of 5- (3-hydroxynaphthoyl-2-amino) -benzimidazolone in high yield. The 5- (3-hydroxynaphthoyl-2-amino) benzimidazolone is used as an intermediate for the preparation of pigmentary dyes. The starting material used is 5-aminobenzimidazolone, which is reacted in excess of xylene in the presence of phosphorus trichloride with excess 3-hydroxy-2-naphthoic acid.

Description

Characteristic of the known state of the art

The preparation of 3-hydroxy-2-Naphthoesäurearyliden is described several times in the literature. They are generally prepared by condensation of 3-hydroxynaphthoic acid-2 with the corresponding aromatic amine in an inert solvent, for example toluene. The condensing agent is generally phosphorus trichloride used. Thionyl chloride and phosphorus oxychloride are also mentioned in the literature as condensing agents (DRP 264527). In the AT-PS 193399 a method is given, in which the condensation with thionyl chloride in chlorobenzene with the addition of dimethylformamide takes place as a catalyst. The reaction can also be carried out in other inert solvents such as xylene, mono- or dichlorobenzene (DRP 264527, DE-PS 2405986, DRP 293897).

DE-PS 2405986 describes a procedure for the preparation of 3-hydroxy-2-Naphthoesäurearylamiden in a required for the azo pigment production, particularly pure form. This purity is said to be achieved by treating the reaction mixture or reaction product with a chelating agent.

In DE-PS 869638 it is proposed to carry out the condensation with an excess of amine, whereby 0.22 moles of 3-hydroxy-2-naphthoic acid should be more converted to the aryl amide than in the usual procedure in an acidic medium.

The preparation of 5- {3'-hydroxynaphthoyl-2-amino) benzimidazoles should be possible according to the knowledge known in the literature in the following manner:

Condensation of 3-hydroxynaphthoic acid with 5-aminobenzimidazolone in toluene in the presence of phosphorus trichloride in molar ratios.

However, the practical implementation of the above general synthetic concepts did not give satisfactory results in the preparation of 5- (3'-hydroxynaphthoyl-2'-amino) benzimidazolone. The yield was a maximum of 67% despite 15 to 18 hours reaction time, and the final product almost always contained starting materials.

The use of higher-boiling solvents, such as chlorobenzene or xylene, did not produce any better results. When reworking the specified in AT-PS 193399 procedure, he came to only low implementation. Also, the proposed in DE-PS 869638 condensation with an excess of amine did not lead to the result found in the patent.

The yield was only an average of 60%, and the final product in each case still contained 3-hydroxy-2-naphthoic acid and 5-aminobenzimidazolone.

Object of the invention

The aim of the invention is the discovery of a synthesis process for 5- (3'-hydroxynaphthoyl-2'-amino) benzimidazolone, which avoids the disadvantages mentioned.

Explanation of the essence of the invention

The object of the invention was to produce 5- (3'-hydroxynaphthoyl-2'-amino) -benzimidazoles in the highest possible yield and to isolate the end product in a quality required for the preparation of the azo pigment.

According to the invention, a pure end product is obtained in high yield if the condensation is carried out with an excess of 3-hydroxy-2-naphthoic acid. Under these conditions, the 5- (3'-hydroxynaphthoyl-2'-amino) benzimidazolone is produced in a yield of 84% of theory.

In the process according to the invention, 1.5 to 2.5 mol (preferably 2 mol) of 3-hydroxy-2-naphthoic acid are heated to boiling with 1 mol of 5-aminobenzimidazolone in xylene. 1 mol of phosphorus trichloride dissolved in xylene is added dropwise at boiling temperature. It is stirred, made alkaline with soda and then subjected to the mixture of a steam distillation. The 5- (3'-hydroxynaphthoyl-2'-amino) benzimidazolone is isolated by suction of the distillation residue.

After washing with hot water, the excess 3-hydroxy-2-naphthoic acid is precipitated by addition of hydrochloric acid from the filtrate combined with the washing water and recovered by suction. It can be used again after drying for the next batch.

embodiments example 1

In 1000 ml of xylene with stirring 282g (1.5 mol) of З-НусІгоху-2-naphthoic acid and 166g (1 mol) of 5-aminobenzimidazolone (90%) are added. The mixture is heated to boiling and boiled until the adhering water from the starting materials and the xylene is azeotropically removed from the reaction mixture by means of a water separator and the temperature is constantly the boiling point of the xylene.

At boiling temperature, the solution of 137 ml (1 mol) of phosphorus trichloride and 400 ml of dry xylene is added dropwise within 1 to 2 hours.

The result is a thick, but easy to stir mixture. After the addition is stirred for 4 hours under reflux.

The reaction mixture is cooled to 80 ° C. with stirring. At this temperature, 4 liters of water are added. Then it is made alkaline with about 160g soda (pH9-10).

After completion of the addition for 0.5 hours at 8O ⁰ C is then stirred and then the mixture is subjected to a steam distillation. The distillation residue is filtered off with suction and washed neutral with hot water.

This gives 5- (3'-hydroxynaphthoyl-2'-amino) benzimidazolone in a yield of 84% of theory. Filtrate and washings are combined and adjusted with stirring to pH 1.5 to 2 with concentrated hydrochloric acid. The excess 3-hydroxy-2-naphthoic acid is recovered by suction. It can be used after drying at 100 ⁰ C in the oven for the next batch.

Example 2

The procedure is analogous to Example 1, but 470 g (2.5 mol) of 3-hydroxy-2-naphthoic acid are used. This gives 5- (3'-hydroxynaphthoyl-2'-amino) -benzimidazo) on m a yield of 84% of theory.

Claims (1)

A process for the preparation of 543'-hydroxynaphthoyl-2'-amino) -benzimidazolone by condensation of α-hydroxy-naphthoic acid with 5-aminobenzimidazolone in xylene and in the presence of phosphorus trichloride, characterized in that the condensation with an excess of 3-hydroxy -2-naphthoic acid in the ratio of 1.5 mol: 1 mol to 2.5 mol: 1 mol. Field of application of the invention The invention relates to a process for the preparation of 5- (3'-hydroxynaphthoyl-2'-amino) benzimidazolone, which is used primarily as an intermediate for the preparation of pigment dyes.