DE1113938B - Process for the preparation of 4,4-bis- [benzimidazolyl- (2)] - stilbene - Google Patents

Description

Process for the preparation of 4,4'-bis- [benzimidazolyl- (2)] - stilbene The invention relates to a new and advantageous method for the production of 4,4'-bis- [benzimidazolyl- (2)] stilbene, a compound with valuable properties as a bluing and lightening agent and as an intermediate product for manufacture other bluing and lightening agents.

4,4'-Bis- [benzimidazolyl- (2)] - was carried out according to the previously known method by converting a reactive, functional derivative of 4,4'-stilbenedicarboxylic acid, for example of the diacid chloride, with o-nitroaniline or o-phenylenediamine for corresponding dianilide implemented, which then - in the case of nitroanilide under reducing Conditions - cyclized to the desired product. Object of the present invention is a new process in which 4,4'-bis- [benznmidazolyl- (2)] - stilbene by direct Action of o-phenylenediamine on 4,4'-stilbene dicarboxylic acid or on a simple one Ester or a salt of this compound can be prepared.

According to the invention, o-phenylenediamine and 4,4'-stilbene dicarboxylic acid or a low molecular weight alkyl ester, an alkali or ammonium salt of this compound are heated together in a reaction medium of polyphosphoric acid, the desired 4,4'-bis- [benzimidazolyl- (2) ] -stilbene directly and conveniently in a single reaction according to the equation: receives. In this formula, the radicals R and R ', 1, which can be identical or different, denote hydrogen, a low molecular weight alkyl radical, an alkali metal or an ammonium radical. The expression “low molecular weight alkyl radical” is to be understood as meaning a low molecular weight alkyl radical with 1 to 4 carbon atoms, such as a methyl, ethyl, isopropyl or n-butyl radical.

From the equation it can be seen that 2 molecules o-Phenylenediamine react with 1 molecule of the stilbene dicarboxylic acid compound. To the For best results it was found to be desirable for feasibility of the procedure, however, found these two reactants not strictly necessary to use in a molar ratio of approximately 2: 1 to match the desired End product to reduce the mixed amount of unreacted substances. The good water-soluble polyphosphoric acid can easily be derived from the water-insoluble end product 4,4'-bis- [benzimidazolyl- (2)] - stilbene are removed and therefore does not pose any problems in terms of cleaning.

The 4,4'-bis- [benzimidazolyl- (2)] - produced according to the invention can be easily isolated from the reaction mixture by mixing with a large amount of water and filtering the solid precipitate obtained. Because of the simple manufacturing process is the process product of less undesirable By-products accompanied as the product of the previously known process, starting from the diacid chloride.

All starting products of the process according to the invention are light accessible: the mono- and diesters and the salts of 4,4'-stilbene dicarboxylic acid are, if they are needed, easily accessible from the acid by conventional esterification and salt formation processes.

Polyphosphoric acid is both in the process according to the invention used as a condensing agent and as a reaction medium. The polyphosphoric acid is therefore present in a considerable excess. It is not necessary to have one certain molecular ratio to the amounts of o-phenylenediamine and stilbene dicarboxylic acid compounds to be observed. Satisfactory results are obtained when the weight of the polyphosphoric acid about five to twenty times the weight of the stilbene dicarboxylic acid compound amounts to. It is best to use a weight ratio of approximately 10: 1. Instead of preformed polyphosphoric acid, which is commercially available, may use you can also make this connection in situ. For example, you can use a Use a mixture of orthophosphoric acid with sufficient phosphoric anhydride, so that the mixture has a P, 0, content of 82 to 85 percent by weight by heating and stirring results.

The reaction can most easily be carried out at atmospheric pressure The use of high pressure equipment is essential in the process of the invention not mandatory.

The reaction temperature can generally be 125 to 225 ° C, preferably 140 to 200 ° C. In general, a reaction time is from one to eight Hours in practice are sufficient. Of course, the response time is longer, though lower temperatures can be used. The esters react as starting materials faster than the corresponding free acid and than the salts. The alkali salts react the slowest. While the esters take 1 hour or less to fully react need, you generally have to have a reaction time when using the free acid rate from about 3 to 5 hours. The salts can in some cases 8 require up to 20 hours of reaction time.

It is preferred to use 4,4'-stilbenedicarboxylic acid itself, since the Free acid generally more economical than the low molecular weight mono- and Dialkyl ester is to be produced and better yields than the mono- and dialkali and as the ammonium salts supplies. However, if the reaction happens quickly should, a low molecular weight 4,4'-stilbene dicarboxylic acid dialkyl ester, for example 4,4'-stilbene dicarboxylic acid diethyl ester can be used.

According to Swiss patent specification 243 782, 2,5-di- [benzimidazyl- (2)] - furan is used by reacting furan-2,5-dicarboxylic acid with o-phenylenediamine at elevated temperature made with boric acid as a catalyst. The method used there can be do not apply to the reaction of 4,4'-stilbenecarboxylic acid with o-phenylenediamine, because the resulting mixture solidifies after a short time, whereby itself no further reaction takes place when the temperature is increased. In contrast is the process according to the invention by using polyphosphoric acid Progress made that this is not just a satisfactory reaction catalyst is, but also serves as a reaction medium in excess.

The following examples illustrate the invention. All parts are parts by weight.

Example 1 13.4 parts of finely powdered 4,4'-stubendicarboxylic acid and 11.0 parts of o-phenylenediamine were added to 150 parts of polyphosphoric acid (commercially available Product) added at 100 ° C. With good stirring, the mixture was left for 5 hours heated at 150 to 160 ° C. After that, those at the beginning of the heating appeared in the mixture suspended, finely divided white particles of 4,4'-stilbene dicarboxylic acid disappeared and replaced by yellow colored particles of 4,4'-bis- [benzimidazolyl- (2)] stilbene to have become. The reaction mixture was then poured into 700 parts of ice water with vigorous Stir poured. The insoluble, solid yellow mass was filtered and washed well with cold Water washed. The solid cake was suspended in 700 parts of water and 30 Parts of 35% aqueous sodium hydroxide solution, sufficient to make the mixture on each To make case alkaline added. The insoluble solid was filtered again, washed with water and then in a mixture of 400 parts of 95% ethanol and 15 parts of 35% aqueous sodium hydroxide solution dissolved. The solution obtained was heated to approximately 65 ° C and used to remove small amounts of insoluble Filtered material. The filtrate was poured into 31% of water. The 4,4'-bis- [benzimidazolyl- (2)] - stilbene fell here the end. The product was filtered, washed well with water and dried at 70 ° C. This gave 13.0 parts of purified 4,4'-bis- [benzimidazolyl- (2)] - stilbene as yellow, solid substance with a melting point above 300 ° C. From the filtrate were by acidification with hydrochloric acid, 3.5 parts of unreacted 4,4'-stilbenedicarboxylic acid isolated.

The chemical and physical properties of the product obtained would be the same as that of a 4,4'-bis- [benzimidazolyl- (2)] stilbene that through Cyclization of 4,4'-stilbene-di- [carbox- (o-aminoanilide)]. example 2.25 parts of 4,4'-stilbenedicarboxylic acid diethyl ester and 2, 0 parts of o-phenylenediamine hydrochloride were heated with 20 parts of polyphosphoric acid at 140 to 150 ° C for 30 minutes. the The reaction mixture was diluted with a large amount of ice water and the insoluble Product filtered and, as described in Example 1, purified. One received so 2.0 parts of 4,4'-bis [benzimidazolyl- (2)] stilbene.

Similar results were obtained using the above Process described instead of 4,4'-stilbenedicarboxylic acid diethyl ester equivalents Quantities of dimethyl 4,4'-stubendicarboxylate or monoethyl 4,4'-stubendicarboxylate used. Example 3 34.4 parts of the dipotassium salt of 4,4'-stilbene dicarboxylic acid and 24 parts of o-phenylenediamine in 400 parts of polyphosphoric acid were added for 5 hours heated to 150 to 155 ° C. The reaction product was isolated and used in the example 1 described way cleaned. 8.0 parts of 4,4'-bis- [benzinv.dazolyl- (2)] - stilbene were obtained in this way. Similar Results were obtained if, instead of the dipotassium salt, equivalent amounts the monosodium salt or the diammonium salt of 4,4'-stilbene dicarboxylic acid was used.

EXAMPLE 4 620 parts of phosphorus pentoxide were slowly added to 415 parts of 85% orthophosphoric acid over the course of one hour. The mixture was heated to 165 ° C. for 30 minutes with stirring, then cooled to 130 ° C. and 102.5 parts of 4,4'-stilbene dicarboxylic acid were added. The mixture was stirred until a uniformly smooth slurry was obtained. Then 84 parts of o-phenylenediamine was slowly added over about 30 to 45 minutes. During the addition, the temperature of the reaction mixture rose to 170 to 175 ° C. This temperature was maintained for 2 hours by supplying heat from the outside. The mixture was heated to 180 to 185 ° C. for a further period of 2 hours and then finally to 190 to 195 ° C. for 30 minutes. The reaction mixture was then poured into 2,000 to 2,500 parts of ice water and stirred until a uniformly smooth slurry was obtained received. It was then filtered and the precipitate consisting of 4,4'-bis- [benzimidazolyl- (2)] - stub washed with water.

The procedure described above became another four Times repeated. The total amount of the reaction product of 4,4'-bis- [benzimidazolyl- (2)] - stilbene The five batches were cleaned as follows: The solid mass was divided into 25,000 parts Stir in water to form an evenly smooth slurry. Then were 565 parts of a 50% aqueous sodium hydroxide solution are added to the mixture alkaline to phenolphthalein. The mixture was heated to 85 to 90 ° C heated and stirred for 1 hour. It was then filtered and washed with water. In this way, 600 parts of purified 4,4'-bis- [benzimidazolyl- (2)] stilbene were obtained. the end 75 parts of 4,4'-stilbene dicarboxylic acid were added to the filtrate by acidification with 300 parts concentrated hydrochloric acid, stirring at 85 ° C for 30 minutes and filtration obtained.

Claims (2)

PATENT CLAIMS: 1. Process for the production of 4,4'-bis- [benzimidazolyl- (2)] - stilbene, characterized in that one is in a reaction medium of polyphosphoric acid about 125 to 225 ° C, preferably 140 to 200 ° C, o-phenylenediamine with 4,4'-stubendicarboxylic acid or a low molecular weight alkyl ester with 1 to 4 carbon atoms in the alkyl radical or one Brings alkali or an ammonium salt of said dicarboxylic acid to the reaction. 2. The method according to claim 1, characterized in that the molar ratio of o-Phenylenediamine to stilbene compound is approximately 2: 1 and that polyphosphoric acid is used in approximately 5 to 20 times the weight of the room connection. Publications considered: Swiss patent specification No. 243 782.