SU39289A1 - Method for reducing dibenzatron oxidation product and methylation of the resulting substance - Google Patents

Description

According to German Patent No. 259370 (Example 3), the oxidation product of dibenzantrone can be reduced in various ways: for example, by treating dioxydibenzantrone with bisulfite or sodium sulfide in an aqueous medium, copper powder in a sulfate medium or, finally, tin chloride in an organic solvent medium. Of all the above mentioned methods, the above mentioned patent stops in relatively detail only on the first one (i.e., on the bisulfite), as the best restoration method, limited only by the mention of the possibility of using all the others.

It should be noted that, according to the literature, the bisulfite reduction method is indeed of exceptional and widespread use in the dibenzthrone range in all similar cases (see, for example, German patents No. 411013, 416208, 418639, US patents No. 1531261, 1761624, French patent number 705774 and others).

The resulting, product of dioxidibenzantrone reduction, as is known, serves as a starting material for obtaining valuable vat dyes of high strength; by itself, it is not an interesting dye due to the fragility of washing, chlorine,

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acids and alkalis. Of its derivatives, the product of methylation, the bluish-green dimethoxydibenzantron, first released in England under the name „Caledon Jade Green. However, methylation of the reduction product obtained by treating dioxydibenzantrone with bisulfite does not immediately give a dye with a bluish-green tint, characteristic of pure dimethoxydibenzantrone, but gives a shade much bluer and blunt. Therefore, the resulting methylation product has to be subjected to additional processing for the purpose of purification (see Germ. Pat. No. 417068, Examples 2, 3 and 4).

It was found by the authors (see Certificate of Authors No. 39287) that this deviation in shade depends on the side-produced purple dye, the formation of which is apparently due to the fact that some of the undereduced compound remains in the bisulfite reduction product moreover, this part gives exactly the above-mentioned violet dye at methylation simultaneously with the well-known dimethoxy compound. Therefore, the bisulfite reduction method is far from perfect.

The authors found that the completeness of the reduction, and therefore the purity and homogeneity of the methylation product of the reduced compound, is obtained only when some metals are used as a reducing agent in an excess of sulfuric acid. As such a reducing agent, aluminum B was best in the form of a powder, but zinc, copper, or combinations thereof could be used. When using aluminum

1) the degree of recovery needed is provided very quickly,

2) metal consumption is minimal,

3) the yield of the reduction product is quantitative, and finally

4) the technological implementation of the entire operation is extremely simple and does not cause any difficulties.

It is also known from the literature that the formation of the green vat dye of dimethoxydibenzantrone, released in Inglia under the name of "Caledon Jade Green," occurs both during the methylation of the oxidation product of dibenzantrone, and in the methylation of this compound after its reduction, and in English patent No. 181304 (corresponding to German Patent No. 417068) methylation is produced by dimethyl sulfate, and German Patent No. 485188 uses p-toluenesulfonic acid methyl ester.

Both of these patents definitely indicate that for the end results of methylation it does not matter whether the product of oxidation of the violantrone is taken as the starting material (see German Patent No. 259370, example L for the starting material), or the latter after its treatment with bisulfite (see German patent number 259370, example 3).

In addition, in the later German patent No. 485188, for the example of obtaining dimethoxydibenzantrone, the oxidant of the violantrone was taken as the starting material, and not its subsequent reduction. At the same time, it should be noted that a product obtained under the conditions of the above patents, according to the same patents, does not immediately have sufficient purity, i.e., it does not immediately have a shade characteristic of pure dimethoxydibenzthrone, in view of which it must be cleaned: recrystallization from sulfuric acid (example 4 of German patent No. 417068) or from nitrobenzene (example 2 of the same patent), subjected to treatment with sodium chlorate and hydrochloric acid (example 3 of the same patent), etc. All these purification methods, causing excessive rubbed These products, however, are not very effective. For example, during crystallization, a partial decomposition of the product occurs simultaneously, since crystallization is accompanied by saponification of methoxyl groups; in the treatment of MASNH- | -NS1, along with some purification, chlorination also occurs, while recrystallization from nitrobenzene reaches its goal only after repeated repetitions.

The authors found that the deviation of the shade of the methylation product obtained under the conditions of the above patents from the shade characteristic of pure dimethoxydibenzantrone depends solely on the composition of the starting material. So, first of all, it was noted that to obtain pure dimethoxydibenzantrone, it was necessary not to methylate the oxidation product of the violantrone directly, but to methylate it after a corresponding reduction, since methylation of the oxidation product directly leads to the formation of not one, but two dyes, of which one is green dimethoxydibenzantron, and the second with a new cubic violet (see certificate of authorship No. 39287).

When used as the starting material of the product of the recovery of dioxydibenzantron, the formation of the violet dye does not occur, and the reaction proceeds only in one direction, towards the formation of dimethoxydibenzantrone.

The authors have found that if the reduction product obtained by reduction with metals, in particular aluminum, in a solution of sulfuric acid (see above) is methylated, a very pure and uniform dye corresponding to blue-green dimethoxide, ibenzthrone, is formed immediately. Semi