DE1014549B - Process for promoting the reducing effect of a metal alcoholate on a reducible aromatic nitrogen compound - Google Patents

Description

Process for promoting the reducing effect of a metal alcoholate to a reducible aromatic nitrogen compound The invention relates to a further training of the process to promote the reducing effect of metal alcoholates on reducible aromatic nitrogen compounds that convert nitrogen into a reducible Contains form in a higher oxidation level than corresponds to the hydrazo level, and in which the nitrogen is bonded to a carbon atom of the core. This Process is the subject of German patent 925 293. In particular, concerns the invention the use of certain naphthofuran or naphthothiophene compounds as a reduction accelerator in the process according to the cited patent. In the The rule is the reduction of nitrobenzene and related nitrogen compounds with metal alcoholates by heating with alcoholic caustic alkali, e.g. B. sodium hydroxide and a lower alcohol, usually methanol, with boiling the mixture Reflux carried out at atmospheric pressure. Under these conditions the Metal alcoholates do not have a sufficiently strong reducing agent to override the reduction move up the azoxy level. As set out in German Patent 925 293, the reduction can be promoted so that a more extensive reduction stage than the azoxy stage is reached if naphthoquinoid compounds are added to the reaction mixture, in particular naphthoquinones and addition products thereof, e.g. B. with bisulfite, Heavy metal salts and the like, or the corresponding hydroxynaphthalene compounds clogs.

According to the present invention, the reduction of the reducible aromatic nitrogen compound by a metal alcoholate in the presence of naphthofuran or Naphthothiophene compounds carried out as reduction promoters.

The naphthofuran and naphthothiophene compounds are around condensed, nucleus-substituted derivatives of naphthoquinone and their addition products, Reduction products, e.g. B. dioxynaphthalene compounds, tautomers and derivatives, e.g. B. functional derivatives and core derivatives. In these addition products, reduction products etc. of the nucleus-substituted derivatives of naphthoquinone is a furan or thiophene nucleus with the quinoid benzene nucleus of the naphthalene residue (benzene nucleus of naphthoquinone or derivative which contains the oxo or oxy groups in the quinoid position) common, neighboring carbon atoms connected. They include: a) Dione, e.g. B. Quinones, b) diols, e.g. B. leuco compounds or hydroquinones, c) addition compounds such dione, e.g. B. with bisulfites or heavy metal salts, as in the USA patent No. 2,645,636 discloses d) functional derivatives of such diones or diols, e.g. B. Imides, semicarbazones, oximes, hydrazones and esters, which can be saponified by caustic potash are, as well as core derivatives of the aforementioned substances, in which one or more of the Nuclear hydrogen atoms have been replaced by other atoms or simple radicals, e.g. B. Halogen, hydroxyl, nitro, amino, carboxyl, sulfo, alkyl, alkoxy, cyano, Mercapto and other groups.

Suitable reduction promoting agents according to the present invention are furano-naphthoquinone or thiopheno-naphthoquinone compounds, as listed below, which are designated according to "The Ring Index" Patterson and Capell (1940), pp. 234, 335, 338, 427, 430 : Dinaphtho- (2, 1, 2 ', 3') - furan-dione- (8, 13) dinaphtho- (1, 2, 2 ', 3') - furan-dione- (7, 12) naphtho- ( 2, 3-b) -furan-dione- (4, 9) 2-methyl-naphtho- (2, 3-b) -furan-dione- (4, 9) benzo- (b) -naphtho- (2, 3-b) -furan-dione- (6; 11) thiophanthrene-dione- (4, 9) benzo- (b) -thiophanthrene-dione- (6, 11) 8-chloro-benzo- (b) -thiophanthrene- dione- (6, 11) 3-oxybenzo- (b) -naphtho- (2, 3-d) -furan-dione- (6, 11) 8, 13-diacetoxydinaphtho- (2, 1, 2 ', 3 ') - furan 3-methoxydinaphtho- (2, 1, 2', 3 ') - furan-dione- (8, 13) dinaphtho- (1, 2, 2', 3 ') - furan = dione- (7, 12) -sulfonic acid- (5) dinaphtho- (2, 3, 2 ', 3') - furan-tetron- (5, 7, 12, 13) dinaphtho- (2, 1, 2 ', 3' ) -thiophene-dione- (8, 13) 5-chloro-dinaplitho- (1, 2,2 ', 3') -furan-diol- (7, 12) are in the form of quinone- (1, 4) they represent posed by the formula in which X is oxygen or sulfur, R and R 'are hydrogen or identical or different substituents, e.g. B. halogen, nitro, amino, alkyl, alkoxy, etc., or together form part of a cyclic nucleus or one or more of the nuclear hydrogen atoms of the molecule can be replaced by other atoms or simple radicals as mentioned above.

Connections of this type can be made in a number of ways will; a number of them are known. For example, one obtains -Dinaphtho- (2, 1, 2 ', 3') - furandione- (7,12) by reaction of 2, 3-dichloro-naphthoquinone- (1,4) with ß-naphthol or a-naphthol, as described in vBeichte der deutsch. chem. Gesellschaft ", 80 '(1947), p. 52, and" Journal of the Chemical Society ", London, 1952, p.4699 / 4700. Thiopheno-naphthoquinone compounds of the type mentioned above by reacting phthalic anhydride with a thiophene compound, e.g. B. Thionaphthene and ring closure of the resulting o-thionaphthenoylbenzoic acid as described in German patent specification 499 745.

Hydroxy derivatives of said furan and thiofuran, e.g. B. Dinaphtho- (2, 1, 2 ', 3') - furan-diol- (8, 13) and dinaphtho- (1, 2, 2 ', 3') - furan-diol- (7, 12) by reducing the corresponding diones with a reducing agent, e.g. B. aqueous alkaline sodium hydrosulfite.

It has been found that the furano-naphthoquinone compounds of the type mentioned have a particularly strong, reduction-promoting effect. It was found that the addition of a furano-naphthoquinone compound such as dinaphtho- (2, 1, 2 ', 3') - furan-dione- (8, 13) of the formula or dinaphtho- (1, 2, 2 ', 3') - furan-dione- (7, 12) of the formula to the reaction mixture, in which nitrobenzene is subjected to the reducing action of sodium methylate, not only promotes the reduction, but also leads to high yields of hydrazobenzene as a direct reduction product.

This result is surprising because applying one is the same low amount of another anti-reducing agent, such as naphthoquinone- (1, 4) or 2,3-dichloro-naphthoquinone- (1, 4) usually do not contain large amounts of hydrazobenzene can be obtained as a direct reduction product.

In the practice of the present invention, the Reducible aromatic nitrogen compound of the reducing effect of a metal alcoholate subjected in a reaction mixture to which one or more promotes the reduction Agents of the type mentioned above are added. In a preferred embodiment, in which the reducible aromatic nitrogen compound with caustic alkali and an alcohol; preferably sodium hydroxide and methanol, to the boiling point of the Reaction mixture is heated, the reduction promoting agent is expediently with mixed with alcohol; after adding the caustic alkali and heating, the to be reduced Nitrogen compound added to the heated mixture. That which promotes reduction Means can be added to the reaction mixture in different ways and at different Times are added: The implementation of the procedure in detail takes place in the manner described in German Patent 925 293. In view, however to the level of the reduction-promoting activity of the invention. using Furano-naphthoquinone compounds can be used with smaller amounts of reduction-promoting Means as used in the patent specifications mentioned are the same Effects are achieved; also is the minimum concentration of the reduction-promoting Means lower. Furthermore, it is in view of the greater activity of the furano-naphthoquinone compounds Possible as reduction-promoting agents, reduction products of a lower oxidation level as a direct reduction product if you have similar amounts of furano-naphthoquinones used as in the cited patents, or it is possible to use a Reduction to a certain oxidation level with a smaller amount of metal alcoholate bring to.

In the examples below, parts are given as parts by weight, unless they are specifically referred to as parts by volume. Example I Part 1. 43 parts of methanol and 1 part of dinaphtho- (2, 1, 2 ', 3') - furan-dione- (8, 13) are placed in a flask equipped with a reflux condenser, a stirrer, an addition funnel and a thermometer. Then 56 parts of solid sodium hydroxide are added with cooling; the mixture is refluxed. 85 parts of nitrobenzene are then introduced over a period of half an hour, while the mass is kept at 95 °. The reaction is refluxed for about 2 1/2 hours at about 90 to 100 ° under atmospheric pressure. The mixture is diluted to 3000 parts by volume with water, cooled to 10 ° and filtered; the filter cake is dried by standing at room temperature. The yield of reduction products as a percentage of the yield based on nitrobenzene is: Hydrazobenzene ......................: 72 ° / o Azobenzene ............................ 27%. Azoxybenzene ......................... 0 ° / a Aniline ... , ........................... 10/0 Part 2. Repeating the procedure of Part 1, 1 part of naphthoquinone- (1, 4) is used instead of dinaphtho-furan-dione. This results in a much lower yield of hydrazobenzene. The percentages are: Hydrazobenzene ..................... 18.50 /, Azobenzene .......................... 80.6% Azoxybenzene ....................... 0 '/ o Aniline ........................: .... 1 0/0 Example II The procedure of Example I, Part 1, is repeated using a portion of dinaphtho- (1,2,2 ', 3') furan-dione- (7, 12) in place of dinaphtho- (2, 1 , 2 ', 3') - furan-dione- (8, 13). The yield is: Hydrazobenzene ....................... 48 "/, Azobenzene ................ ............ 510 / ö Azoxybenzene ......................... 0% Aniline ............................... 10/0 The method can also be used to reduce other aromatic nitrogen compounds which contain nitrogen as a substituent in a benzene nucleus in a reducible form, such as, for example, o-nitrotoluene, m-nitrotoluene, o-nitrochlorobenzene, m-nitrochlorobenzene, p-nitrophenetole, p-nitrobenzoic acid , o-nitrobenzenesulfonic acid and its reduction products. In view of the extensive use of hydrazobenzene and its ortho-substituted derivatives such as o, o'-dichlorohydrazobenzene, o, o'-hydrazotoluene, o, o'-hydrazoanisole, o, o'-diethoxyhydrazobenzene as intermediates for the preparation of benzidine and its Derivatives, the process according to the invention is of particular value because it makes the production of such hydrazo compounds from the corresponding reducible aromatic nitrogen compounds considerably cheaper.

Instead of the dinaphtho-furan-diones used in the above-mentioned examples can be a corresponding amount of other Furano-naphthoquinone-Verbin boys of the above Art can be used as a reduction promoting agent.

When carrying out the reduction using sodium hydroxide and methanol it is advisable to use these reagents in excess of the theoretical amount to use the required quantities. An excess of methanol over the theoretically required Amount is necessary if it serves as a solvent at the same time; another Excess is desirable as it is due to the dilution formed in the process Water, which would otherwise delay the reaction, counteracts this. An excess of Sodium hydroxide is also beneficial because it increases the rate of reaction causes.

It is possible to reduce aromatic nitrogen compounds to lead to different levels, depending on the amounts of sodium hydroxide and Methanol, as well as the specific nature and amount of the used, the reduction promotional agent. So, as explained in the examples above, it is possible Reduce nitrobenzene to hydrazobenzene in a single operation. It is but also possible to initially reduce nitrobenzene to azoxy and / or azobenzene, the resulting azoxy-benzene and / or azobenzene to isolate and with a fresh Reduce batch of sodium hydroxide and methanol to hydrazobenzene.

The temperature at which the reaction is carried out can also be used vary, albeit in the case of a reduction carried out with alcoholic caustic alkali Temperatures of the reaction mixture at or near the boiling point at atmospheric Pressure (at 98 to 105 °) are preferable. Runs at lower temperatures the reaction is slower, under otherwise similar conditions. 'She can do one thing require a long period of time to produce the same result as the preferred ones Temperatures. Conversely, higher reaction temperatures bring about a shortening of the Reaction time, but require the use of closed reaction vessels. Temperatures well above 110 ° can be used, but not appropriate, as they are even in the presence from reduction-promoting agents to the development of considerable amounts of hydrogen and lead to the formation of primary amines, resulting in a loss of yield of the desired Reduction product means.

For economical and simple operation, the solution and diluent of the reaction mixture using an excess of the To be preferred to alcohol used for the alcoholate. Other solvents can also be used and diluents are used; for example, the method with quantities of sodium hydroxide and methanol only in a slight excess over those for the reduction theoretically required amounts are carried out in a reaction medium, which contains sufficient xylene or another inert solvent or diluent, z. B. benzene, toluene, mono- and dichlorobenzene that a stirrable reaction mass is obtained. Furthermore, although simpler, can be used as solvents and diluents using an excess of the reducing agent alcohol, too other alcohols or mixtures of alcohols are used; in particular when it is desired to modify the boiling temperature of the reaction mixture. For the sake of convenience and economical operation, the method generally carried out so that a metal alcoholate in the reaction mixture, z. B. by the reaction of caustic alkali with the alcohol. However, it can also Find prepared metal alcoholate as a reducing agent use, wherein the dilution by the as a by-product of the reaction of caustic alkali with alcohol formed water is avoided.

Sodium hydroxide and methanol are made according to the examples given used because they are relatively cheap and readily available. It but can also use other alkalis, e.g. B. potassium hydroxide, and also other alcohols, z. B. Ethyl alcohol and the various propyl, butyl and higher alcohols, be used.

The reduction products can be different from the reaction mixture Way to be isolated. Except for the cases in which the reaction mixture an insoluble residue resulting from the reducing agent in the reaction mixture, contains, the isolation of the reduction products can be done in the usual way; z. B. is the reaction mixture for the purpose of crystallization of the reduction product chilled and filtered and the cake washed with water to remove the alcohol and that Sodium formate and sodium hydroxide formed as by-products of the reduction to remove. The methanol can also be removed from the reaction mixture with steam distill off; the aqueous methanol obtained can after fractional distillation can be reused. From the remaining, hot, aqueous mass can through Cooling the reduction product crystallizes out, separated and, as usual, with Water to be washed. When the product is in molten form in the hot aqueous Mixture is present, as in the case of Azoxy and azobenzenes, the mass can be separated into an aqueous phase and an oily phase and the latter can be separated without difficulty. Usually those are reduction-promoting Agents of the type indicated above in the aqueous and / or alcoholic layer soluble and are removed with this from the reduction product.

When the use of the reduction promoting agent is little If the amount of insoluble by-products is found, this can be removed by filtering the hot Mixture can be removed prior to phase separation or in any other way.

Claims (5)

PATENT CLAIMS: 1. Further training of the method of promotion the reducing effect of a metal alcoholate on a reducible aromatic Nitrogen compound in which the nitrogen is in a higher oxidation state, than corresponds to the hydrazo stage, directly to a carbon atom of the aromatic Core is bound, the reaction mixture being a naphthoquinoid compound is added, according to Patent 925 293, characterized in that the reaction mixture mixed with a naphthofuran or naphthothiophene compound, which is a condensed Nuclear substitution derivative of naphthoquinone or an addition product, a Reduction product or a derivative thereof and in which a furan or Thiophene nucleus with the quinoid nucleus of the naphthalene residue together via two adjacent, non-oxygen-substituted carbon atoms is condensed. 2. Procedure according to Claim 1, characterized in that a small amount of the as a conveyor for the reaction to be used naphthofuran or naphthothiophene compound with a lower alcohol, especially methanol, and an alkali hydroxide, especially Sodium hydroxide, mixed, heated and with the reaction mixture thus obtained the aromatic nitrogen compound is reduced. 3. The method according to claim 1 and 2, characterized in that a dinaphtho-furan-dione or a dinaphtho-furan-diol, preferably dinaphtho- (2; 1, 2 ', 3') - furan-dione- (8,13) or dinaphtho- (1, 2, 2 ', 3 ') - furan-dione- (7, 12), used as a reduction accelerator. 4. Procedure according to Claim 1 to 3, characterized in that the aromatic nitrogen compound preferably a nitrogen derivative of benzene or an ortho-substituted benzene derivative; in particular nitrobenzene, o-nitrotoluene or a reduction product thereof is used. 5. The method according to claim 1 to 4, characterized in that the aromatic Nitrogen compound a mononuclear azoxy or azo compound is used.