CH653987A5 - METHOD FOR PRODUCING MONOAMINOVIOLANTHRON. - Google Patents

Description

The invention relates to a process for the preparation of monoaminoviolanthrone and to the monoaminoviolanthrone obtained according to the process.

Monoaminoviolanthrone according to «THE CHEMISTRY OF SYNTHETIC DYES AND PIGMENTS - American Chemical Society No. 127 (1955) p. 453-457 »by reducing the corresponding mononitroviolanthrones with sodium sulfide, or with metal powder in sulfuric acid or by vatting. However, all of these methods have disadvantages. For example, the reduction with sodium sulfide is not entirely harmless due to the sulfide content, and as far as the reduction with metal powders is concerned, this is an expensive process since the metals are difficult to regenerate and also pollute the waste water; Finally, the linking method does not represent a selective reduction method of the nitro group, but simultaneously reduces the carbonyl group, so that the latter have to be oxidized again in a separate work process.

It has now surprisingly been found that monoaminoviolanthrone can advantageously be obtained by reducing mononitro-violanthrone if the reduction is carried out with formaldehyde in the presence of a catalyst.

This process eliminates all of the disadvantages mentioned above and is also an economically interesting process due to its ease of implementation.

The invention accordingly relates to a new process for the preparation of monoaminoviolanthrone by reducing the corresponding mononitroviolant horn by reacting mononitroviolanthrone with formaldehyde in the presence of alkaline compounds and a catalyst in an aqueous-alcoholic solution.

Formaldehyde can be used in gaseous form or, preferably, in the form of its aqueous solution. Substances which give off formaldehyde under the reaction conditions can also be used, e.g. Paraformaldehyde, trioxane, poly-oxymethylene such as tetraoxymethylene, hexamethylene triamine. The aqueous formaldehyde solutions advantageously contain 30 to 55 percent by weight, preferably 35 to 45 percent by weight, of formaldehyde. Formaldehyde can be reacted with the mononi troviolanthrone in a stoichiometric amount or in excess, advantageously in an amount of 3 to 20, in particular 3 to 5, mol of formaldehyde based on 1 mol of mononitro-5 violanthrone.

The reaction is advantageously carried out in the presence of an alkaline compound in an amount of 4 to 20, preferably 6 to 10 equivalents of alkaline compound, based on 1 mol of mononitroviolanthrone. Preferred io alkaline compounds are sodium and potassium compounds, especially hydroxides, carbonates or mixtures. Examples of suitable alkaline compounds are: potassium hydroxide, potassium carbonate, sodium carbonate and in particular sodium hydroxide.

15 The reaction is carried out in an aqueous-alcoholic solution. A water: alcohol ratio of 1: 2 to 1: 6 is advantageous. Monohydric and polyhydric alcohols are suitable as alcohols. For example, methanol, ethanol, isopropanol and glycol are mentioned. A preferred solution is an aqueous ethanolic one.

According to the invention, quinone compounds, especially naphthoquinone compounds, are used as catalysts. The preferred catalyst is 2,3-dichloro-naphtho-quinone-1,4. The amounts used vary between 0.3 25% by weight and 5.0% by weight, based on the nitroviolanthrone compound. .

The reaction is conveniently carried out at a temperature of 30 to 100 ° C, preferably 75 to 85 ° C.

Mononitroviolanthrone or monoaminoviolan-30 thron is to be understood here to mean a compound (x = 1) or a mixture of compounds which corresponds to the following formulas:

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respectively.

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as well as the corresponding iso compounds.

55 The monoaminoviolanthrone obtained according to the invention is a valuable starting product for the production of dyes.

The following example illustrates the invention; Parts mean parts by weight.

60

example

50 parts of nitroviolanthrone and 0.6 part of 2,3-dichloro-naphthoquinone-1,4 are dissolved in 300 parts by volume of ethanol and 150 parts by volume of 50% aqueous sodium hydride.

65 oxide solution heated to 78-80 ° C. At this temperature, 37% aqueous formaldehyde solution is added dropwise according to consumption. The formaldehyde consumption can be measured by measuring the relative redox potential changes

controlled or the addition regulated. Duration about 11 II to 2 hours. Then the resulting amino violant throne is completely precipitated by adding water,

3,653,987

filtered off, washed with water and dried in vacuo at 80 ° C. About 45 g (95% theoretical yield) of aminoviolanthrone are obtained.

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Claims (8)

653 987 1. A process for the preparation of monoaminoviolanthrone by reduction of the corresponding mononitroviolane throne, characterized in that mononitroviolane throne is reacted with formaldehyde in the presence of alkaline compounds and a catalyst in an aqueous-alcoholic solution. 2. The method according to claim 1, characterized in that the reduction is carried out in an aqueous ethanol solution. 2nd PATENT CLAIMS 3. The method according to claim 2, characterized in that the aqueous ethanolic solution contains 1 part by volume of water and 2 to 6 parts by volume of ethanol. 4. The method according to claim 1, characterized in that sodium hydroxide is used as the alkaline compound. 5. The method according to claim 1, characterized in that a quinone compound is used as catalyst. 6. The method according to claim 5, characterized in that the catalyst used is 2,3-dichloronaphthoquinone-1,4. 7. The method according to claim 1, characterized in that one carries out the reduction at a temperature of 75-85 ° C. 8. The monoaminoviolanthrone obtained according to the process of claims 1 to 7.