CH635058A5 - Process for the preparation of isoviolanthrone - Google Patents

Description

The invention relates to a process for the preparation of isoviolanthrone by a one-pot process from 3-bromobenzanthrone.

The production of isoviolanthrone is e.g. known from DE-PS 431775 and 448 262 or US-PS 3 446 810 and 2153 312. The synthesis is carried out by fusing 3,3'-dibenzanthronyl sulfide, which is obtained from 3-bromobenzanthrone by reaction with sodium sulfide, e.g. according to US-PS 1712646, is obtained in alcoholic potassium hydroxide.

US Pat. No. 2,153,312 describes a process in which 3-bromobenzanthrone in alcohol is first reacted with sodium sulfide to give 3,3'-dibenzanthronyl sulfide and then the reaction product is melted into the reaction mixture to give the isoviolanthrone directly after the addition of potassium hydroxide. Alcohol, i.e. Ethanol called. If the first stage is carried out under the conditions mentioned, the information in Examples 3 and 4 of US Pat. No. 2153312 is confirmed; the conversion to the dianthronyl sulfide takes approximately 20 hours. Another disadvantage of this process is that the isoviolanthrone obtained is very difficult to filter. Because of the long reaction time in the first stage and because of the poor filtration properties of the isoviolanthrone obtained, the process is not suitable for industrial implementation.

It was found that high-quality isoviolanthrone can be obtained in a high space-time yield using a one-pot process by reacting 3-bromobenzanthrone with sodium sulfide in the heat and immediately following cyclization of the reaction product (ie without isolation of the reaction product) in the presence of potassium hydroxide in solvents at 110 obtained up to 150 ° C, if one carries out the reaction with the sodium sulfide and the cyclization in n-butanol as the reaction medium.

The process according to the invention gives an isoviolanthrone which is very suitable for all purposes and is very easy to filter. The process according to the invention also has the advantage that, compared to the processes of the prior art, only half the amount of potassium hydroxide is required for the same yield. From an ecological point of view, this is a great advantage.

The process according to the invention is generally carried out in such a way that the 3-bromobenzanthrone is preferably suspended in 2 to 10 times, particularly preferably 2.2 to 4 times the amount of n-butanol, the sodium sulfide is added and the mixture is generally added 80 to 130 ° C, preferably to 100 to 110 ° C, heated. The reaction is usually complete after 4 hours at 100 to 110 ° C. After cooling, preferably to 80 ° C., the potassium hydroxide is added to the mixture and the mixture is heated to 110 to 150 ° C., preferably to 120 to 130 ° C. The ring closure to isoviolanthrone is usually after 3 to 6 hours, e.g. at 125 to 130 ° C after 4 hours, ended.

The amount of potassium hydroxide can generally be 1.15 to 3 times based on 3-bromobenzanthrone. Since a product which is practically as good as that of 3 times the amount of potassium hydroxide is obtained with just 1.20 to 1.4 times the amount, preferably 1.20 to 1.4 times, in particular 1.25 times, the amount of potassium hydroxide used on 3-bromobenzanthrone.

After the reaction has ended, the melt is generally worked up in a customary manner: after cooling to 80 ° C., it can be diluted with a little water and first stirred at 90 to 70 ° C. The mixture can then be diluted with water and the n-butanol removed by steam distillation. The isoviolanthrone can be filtered, washed neutral with water and optionally dried.

A purer product is thus obtained with a higher yield of isoviolanthrone than in the prior art method.

An even purer isoviolanthrone can be obtained if 5 to 20% by weight, based on the 3-bromobenzanthrone used, of a water-soluble reducing agent, preferably sodium dithionite, is added to the aqueous butanol suspension before the butanol is distilled off and then worked up as indicated above. This generally gives an isoviolanthrone with a purity of about 90%. However, the yield is somewhat lower than in the workup described above.

The highest yield of isoviolanthrone which can be used for practically all vat dyes can be obtained if the reaction product in the dilute alkaline suspension is oxidized before or advantageously during the distillation of the butanol. The oxidation is advantageously carried out at temperatures between 40 and 80 ° C. Oxidizing agents are e.g. Atmospheric oxygen or m-nitrobenzenesulfonic acid. The aqueous suspension can then be worked up in a conventional manner.

The n-butanol recovered by steam distillation can be reused for the reaction after the water has been removed.

Compared to the prior art, the process according to the invention has the advantage of a high space-time yield with at the same time significantly less use of potassium hydroxide and a higher to the same yield.

The particular suitability of n-butanol over the ethanol known from US Pat. No. 2,153,312 was surprising and was not to be expected. If you replace the ethanol with isobutanol or isopropanol, you get significantly less favorable results than with ethanol. With n-propanol, practically the same result is obtained as with ethanol.

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The method is further explained by means of exemplary embodiments. The parts and percentages relate to the weight.

example 1

60 parts of 3-bromobenzanthrone (purity 90%) are suspended in 150 parts of n-butanol and 17 parts of 60% sodium sulfide are added. The mixture is heated at 105 to 110 ° C. for 4 hours, then cooled to 80 ° C. and at 75 ° C. Parts of potassium hydroxide are added and the mixture is then heated for 6 hours to 125 to 130 ° C., cooled to 80 ° C., mixed with 40 parts of water and stirred for 2 hours at 80 ° C. It is then diluted with 600 parts of water, 18 parts of m-nitrobenzenesulfonic acid m Sodium is added and the n-butanol is removed by steam distillation The remaining isoviolanthrone suspension is filtered, the filter cake is washed neutral and dried at 100 ° C. Yield: 45 parts of isoviolanthrone with a purity of 79%.

The same result is achieved if air is introduced into the aqueous suspension during steam distillation or before steam distillation.

Example 2

60 parts of 3-bromobenzanthrone with a purity of 90% are stirred in 150 parts of n-butanol and 17

Share 60% sodium sulfide. The mixture is heated to 105 to 110 ° C for 4 hours, then cooled to 80 ° C and mixed with 75 parts of caustic potash. The mixture is then heated to 125 to 130 ° C. for 6 hours, cooled to 80 ° C., 35 s parts of water are added and the mixture is stirred at 80 ° C. for 2 hours. It is then diluted with 600 parts of water and the n-butanol contained is removed by steam distillation. The remaining isoviolanthrone suspension is filtered, the filter material is washed neutral and dried at 100 ° C. Aus-lo loot: 39 parts of isoviolanthrone with a purity of 83%.

Example 3

60 parts of 3-bromobenzanthrone (purity 90%) are suspended in 150 parts of n-butanol, and 17 parts of 15 60% sodium sulfide are added. The mixture is heated to 105-110 ° C for 4 hours, then cooled to 80 ° C and mixed with 75 parts of caustic potash. The mixture is then heated to 125 to 130 ° C. for 6 hours, cooled to 80 ° C., 35 parts of water are added and the mixture is stirred at 80 ° C. for 2 hours. After 20 dilution with 600 parts of water, 10 parts of sodium dithionite are added and the n-butanol is removed by steam distillation. The remaining isoviolane-thren suspension is filtered, the filter material washed neutral and dried at 100 ° C.

2s yield: 31 parts of isoviolanthrone (purity: 89%).

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Claims (6)

635058 1. A process for the preparation of isoviolanthrone by reacting 3-bromobenzanthrone with sodium sulfide in the heat and immediately following cyclization of the reaction product, without intermediate isolation of the reaction product, in the presence of potassium hydroxide in solvents at 110 to 150 ° C, characterized in that the reaction with sodium sulfide and the cyclization in n-butanol as the reaction medium. 2. The method according to claim 1, characterized in that one uses 2 to 10 times the amount by weight of n-butanol, based on 3-bromobenzanthrone. 2nd PATENT CLAIMS 3. The method according to claim 1, characterized in that one uses 2.2 to 4 times the amount by weight of n-butanol, based on 3-bromobenzanthrone. 4. The method according to any one of claims 1 to 3, characterized in that one uses the 1.2 to 1.4 times the amount of potassium hydroxide, based on 3-bromobenzanthrone. 5. The method according to any one of claims 1 to 4, characterized in that 5 to the aqueous-butanolic suspension before distilling off the n-butanol 20% by weight, based on 3-bromobenzanthrone, of a water-soluble reducing agent is added, then the butanol is removed and the process product is separated from the aqueous suspension. 6. The method according to any one of claims 1 to 5, characterized in that the reaction product is oxidized in the alkaline suspension before or during the distillation of the butanol.