DE1023468B - Process for promoting the reducing effect of metal alcoholates on reducible aromatic nitrogen compounds - Google Patents

Description

Process for promoting the reducing effect of metal alcoholates on reducible aromatic nitrogen compounds Addition to patent 925 293 Die The invention relates to a further embodiment of the method according to patent 925 293 for Promotion of the reducing effect of metal alcoholates on reducible aromatic compounds Nitrogen compounds, which nitrogen in a reducible form in a higher Oxidation stage as the hydrazo stage directly on a carbon. substance atom of the aromatic Core bound included.

In general, the reduction of nitrobenzene and the like is carried out aromatic nitro compounds using metal alcoholates by heating with alcoholic Caustic alkali, e.g. B. sodium hydroxide and a lower alcohol, generally methanol, at the boiling point of the mixture by refluxing at normal pressure. Under these conditions, the alkali metal alcoholates are not sufficiently strong Reducing agent to take the reduction beyond the azoxy level. Like in the German patent specification 925 293 and in German patent application A 17211 IVd / lSq (German Auslegeschrift 1018873), this reduction can be promoted, so that reduction products of a lower oxidation level than the azoxy level arise, when adding naphthoquinoid compounds to the reaction mixture; especially naphthoquinones or their addition products, e.g. B. with bisulfites, heavy metal salts, or the corresponding dioxynaphthalene compounds added.

According to the present invention, the reduction becomes reducible aromatic nitrogen compounds by means of a metal alcoholate to the reaction mixture one or more condensed polynuclear compounds added as reduction promoters, which contain at least 9, preferably 10 ring carbon atoms and which contain a benzoquinone or benzohydroquinone condensed with a cycloaliphatic ring with at least two saturated carbon atoms in the aliphatic-cyclic nucleus are. These reduction promoters are specifically 1. Benzoquinones or benzohydroquinones, in which two adjacent carbon atoms des Quinone nucleus with the exception of those to which oxygen is bound, respectively to the terminal carbon atoms of a chain of at least 3, preferably 4 carbon atoms are bonded, of which at least two are saturated carbon atoms while the others may be unsaturated. These condensed polynuclear Compounds can be free of other substituents or in the benzene nucleus except the oxygen atoms and the cycloalkane radical contain additional substituents, z. B. halogen, hydroxyl, nitro, mercapto, amino, cyano, sulfo, carboxyl, Alkyl, alkoxy groups, etc .; 2. Addition compounds of such benzoquinones, e.g. B. with hydroquinones, bisulfites, heavy metal salts, sulfiding agents, and 3. functional derivatives and tautomeric forms of such benzoquinones that are capable of to isomerize such benzoquinones e.g. B. imides, oximes, semicarbazones and hydrazones.

This includes the said class of condensed polynuclear Compounds the following substances: indanedione- (4,7) 5,8-dihydro-naphthoquinone- (1,4) 5,6,7,8-Tetrahydro-naphthoquinone- (1,4) 4-nitroso-5,7,8-tetrahydro-anphthol- (1) 5,6,7,8-tetrahydro-naphthoquinone- (1,4 ) bis-chloroimide 2-chloro-5,6,7,8-tetrahydro-naphthoquinone- (1,4) 3-chloro-2-phenylamino-5,6,7,8-tetrahdro-anphthoquinone- (L, 4) 2,3-dichloro-5,6,7,8-tetrahydro-naphthoquinone- (1,4) 2,3-dimethyl-5,6,7,8-tetrahydro-naphthoquinone- (1,4) 5,6,7,8-tetrahydro-naphthoquinone- (1,4) sodium bisulfite addition product of 5,6,7,8-tetrahydro-naphthoquinone- (1,4) (cf. Example 4 of US Pat. No. 2,645,636) 6 -Chlor-5, 8-dihydro-naphthoquinone- ( 4) 5,8-dihydro-1,4-dioxynaphthalene 5,6, 7,8-tetrahydro-1 2-dioxynaphthalene 5,6,7,8-tetrahydro-1 , 4-dioxy-naphthalene 1, 4-diacetoxy-5, 6,7,8-tetrahydro-naphthalene 2-amino-5,6,7 , 8-tetrahydro-1 4-dioxynaphthalene 6-chloro-5, 8-dihydro-1, 4-dioxynaphthalene 5, 8-dihydro-2-methyl-1, 4-dioxynaphthalene 5, 8-dihydro-5, 8-endoethylene-1,, 4-dioxynaphthalene 5, 8-Dihydro-2, 6, 7-trimethyl-1, 4dioxy-naphthalene According to the invention, preferably Compounds used are those in which the benzoquinone and benzohydroquinone contain the carbonyl or hydroxyl radicals in the p-position, such as 1,4-benzoquinones and -Benzohydroquinones; Substances in which the condensed cycloaliphatic radical has 4 carbon atoms and the quinone nucleus is also unsubstituted are particularly preferred.

It has been found that these condensed compounds are highly effective Reduction promoter in the reduction of aromatic nitrogen compounds above-mentioned type by metal alcoholates, in particular alkali metal alcoholates, represent. As it turned out, even the addition of a small one has an effect Amount of a compound of the type mentioned and in particular of one with a cycloaliphatic Ring condensed 1,4-benzoquinone or the corresponding hydroquinone a modification the response, which has a number of advantages.

For example, compared to a reduction that is below the same conditions, but in the absence of such a reduction promoter is carried out, the reduction speed is increased and! or products of a obtained higher reduction level without significant loss of the overall yield Reduction products from a certain amount of starting material. In the reduction aromatic nitro compounds enables the addition of a reduction promoter mentioned type to the metal alcoholate reaction mixture the direct formation of azo compounds, without the use of vigorous working conditions, e.g. B. high temperatures and pressures, is required. It is the same with the addition of the reduction promoter possible according to the invention to the reaction mixture, hydrazo compounds from nitro, Azoxy and azo compounds using metal alcoholates without applying vigorous To establish working conditions. Due to their presence, the reduction promoters suppress almost completely side reactions leading to the formation of gaseous hydrogen during lead to reduction. The safety of work is therefore significantly increased and a loss of reducing agents is reduced to a minimum.

The addition of a reduction promoter of the type mentioned to the reduction medium allows the use of milder reaction conditions or the use of less Amount of reducing agent. For example, when reducing an aromatic Nitro compound with sodium hydroxide and methyl alcohol the presence of a reduction promoter of the type mentioned in the reaction mixture the use of a smaller amount Sodium hydroxide, which reduces operating costs. The result is surprising because the related alkyl-substituted benzoquinones do not have any similar reduction-promoting agents Show effect. For example, 2,3,5,6-tetramethyl-benzoquinone- (1 4) and 2,3-Dimethyl-benzoquinone- (1,4) which might be expected not only because of their similar chemical composition, but also because of the similarity Their oxidation-reduction potentials have a similar reduction-promoting effect like naphthoquinone- (1,4), have only a very minor influence on the reduction reaction.

In practicing the present invention, the reducible aromatic nitrogen compound of the reducing effect of a metal alcoholate reducing agent subjected to one or more of the above in a reaction mixture Reduction promoters were added. In the preferred embodiment in practice, in which the reducible aromatic nitrogen compound with a caustic alkali and an alcohol, preferably sodium hydroxide and methanol, at the boiling point of Reaction mixture is heated, the reduction promoter is preferably with the Alcohol mixed and after adding the caustic alkali and heating the to be reduced Nitrogen compound added to the heated mixture. The reduction promoter can however, the reaction mixture in different ways and at different times be admitted.

The reduction promoter can be used in various amounts. It was found that even small amounts of the condensed polynuclear compounds are effective as a reduction promoter. In general, amounts between 1! Soo to 1/1 mole per mole of reducible aromatic nitrogen compound is used. the smallest amount required to achieve a good reduction-promoting effect depends on the type of reducible aromatic nitrogen compound that benzoquinoid compound used and the reaction conditions. In general the reduction-promoting effect achieved is greater when a greater one is used Amount of reduction promoter and becomes smaller when the amount used is reduced provided that the other reaction conditions are constant. amounts of more than 1110 moles of reduction promoter per mole of reducible aromatic nitrogen compound are generally not advantageous even though they are also optionally used can, since the additional advantages achieved thereby are not of great importance are in order to avoid the increased costs caused by such a large amount of reduction promoters, balance.

The specified parts are parts by weight if they are not parts by volume are specified.

Example 1 part 1. 60 parts of methanol and 0.95 part of 5,6,7,8-tetrahydro-naphthoquinone- (1,4) are placed in a flask equipped with a reflux condenser, a stirrer, a Is equipped with a dropping funnel and a thermometer; then 74.5 parts are solid Sodium hydroxide was added and the mixture was heated to reflux. The heated one 123 parts of nitrobenzene are added to the mixture over the course of one hour, and the reaction mass then boiled under reflux for 22 hours at normal pressure. During the addition of the Nitrobeuzols and the subsequent reflux period develop only a small one Amount of gaseous hydrogen. The mixture is then mixed with 300 parts of water diluted and distilled to remove unreacted methanol, until the temperature has reached 110 ". The residue is left to stand and separates into an upper oil phase, which contains the reduction product, and a lower one aqueous phase. The aqueous phase, which is essentially sodium hydroxide and sodium formate contains, is withdrawn at about 100 ". The oil phase is treated with dilute hydrochloric acid boiled and then left to stand. The oil phase that forms is withdrawn, filtered hot and dried over calcium chloride at about 100 ". The yield on Product consisting essentially of a mixture of about 97 0 azobenzene and about 30! O azoxybenzene and a hardening point of 65.1 "has, is about 98% of theory, calculated on the nitrobenzene used.

Part 2. The procedure of Part 1 of this example is repeated where no 5,6,7,8-tetrahydro-naphthoquinone- (1,4) is added, but otherwise exactly the same conditions are observed. A big one is developing Amount of hydrogen, and the product consists essentially of azoxybenzene (hardening point 33.5 "). The yield is about 98% of theory.

Part 3. The procedure of Part 1 of this example is repeated where instead of 5,6,7,8-tetrahydronaphthoquinone (1 1.0 part of 2,3,5,6-tetramethyl-benzoquinone- (1,4) is used, but otherwise complies with the same conditions. The product mainly consists from a mixture of about 92% azoxybenzene and about 8% azobenzene (hardening point 31.2 "). The yield is about 98% of theory.

Part 4. The procedure of Part 1 of this example is repeated where instead of 5,6,7,8-tetrahydro-naphthoquinone- (1,4) 1.0 part 1,2,3,4,5,6,7,8- Ochtahydro-anthraquinone is used, but otherwise the same conditions are observed will. The product consists essentially of a mixture of about 86 01 azoxybenzene and about 14% azobenzene. The yield is about 98% of theory.

Example 2 The procedure of Example 1, Part 1 is repeated, however, in addition to the 5,6,7,8-tetrahydro-naphthoquinone- (1,4) and methanol 0.9 parts of sodium bisulfite are added to the flask and the mixture becomes ll2 Heated under reflux for an hour to obtain the sodium bisulfite addition product of 5,6,7,8-tetrahydro-naphthoquinone- (1,4) to form, and then cooled to room temperature before adding the sodium hydroxide admits. The product consists essentially of a mixture of about 820% azobenzene and 18010 azoxybenzene (hardening point 59.40). The yield is about 9801o Theory.

Example 3 The procedure of Example 1, Part 1, is repeated except that 2.0 parts used 5,6,7,8-tetrahydronaphthoquinone- (1,4) will. The isolated oil phase is stirred with hot water, whereupon the aqueous The mixture was cooled to room temperature and filtered and the filter cake was dried will. It essentially consists of a mixture of about 800 /, azobenzene and about 20010 hydrazobenzene. The yield is about 98% of theory.

Example 4 43 parts of methanol and 1 part of one of those in the table I mentioned reduction conveyor is in a with a reflux condenser, a stirrer, a flask fitted with a dropping funnel and thermometer.

Table I A. 5,8-Dihydro-1,4-dioxynaphthalene B. 5,6,7,8-Tetrahydro-1 , 4-dioxy-naphthalene C. 1,4-Dioxy-naphthalene 56 parts of solid sodium hydroxide then added with cooling and the resulting mixture to reflux temperature heated. Then 85 parts of nitrobenzene are added over 112 hours while the mass is kept at 95 °, and the reaction mass for 22 hours at normal pressure boiled under reflux (about 90 to 1000), taking into account the addition time of the Nitrobenzene. The mixture is then diluted to 3000 parts by volume with water, cooled to about 10 °, then filtered and the filter cake dried, either in a vacuum dryer at a temperature below 50 ° or by standing Room temperature (25 to 30 ").

The proportions of hydrazobenzene, azobenzene, azoxybenzene and aniline obtained in this way are given in Table II. Table II % of the theoretical yield, calculated on the nitrobenzene used Promoter hydrazobenzene azobenzene azoybenzene aniline None (control reaction) .. - 0 to 5 95 to 100 - A ......................... 4 95 - 1 B ......................... 3.5 95 - 1.4 C ......................... 3.5 95 - 1.5 The process can also be used in the reduction of other aromatic nitrogen compounds which contain nitrogen in a reducible form as a nucleus substituent of a benzene nucleus, e.g. B. o-nitrotoluene, m-nitrotoluene, o-nitrochlorobenzene, m-nitrochlorobenzene, p-nitrophenetol, p-nitrobenzoic acid, o-nitrobenzenesulfonic acid and their reduction products.

In view of the widespread use of hydrazobenzene and its o-substituted derivatives, such as o, o'-dichlorohydrazobenzene, o, o'-hydrazotoluene, o, o'-hydrazoanisole, o, o'-diethoxy-hydrazobenzene, as intermediate products in the production of benzidine and its derivatives, the method of the present invention is from of particular value as a means of reducing the cost of manufacturing such hydrazo compounds from the corresponding reducible aromatic nitrogen compounds, such as nitrobenzene and its o-substituted derivatives and reduction products therefrom.

The reduction of aromatic nitro compounds to azoxy compounds (1), of azoxy compounds to azo compounds (2) and of azo compounds to hydrazo compounds (3) proceeds according to the following equations, in which R denotes an aromatic nucleus: When carrying out the reduction using sodium hydroxide and methanol, it is advantageous to use these reagents in amounts greater than the theoretically required amounts. More methanol than the theoretically required amount is necessary if it also serves as a solvent, and a further excess counteracts the diluting effect of the water formed according to equations (1) and (2), which could otherwise delay the reaction. An excess of sodium hydroxide is also desirable as it increases the rate of the reaction.

It is possible to reduce a certain reducible aromatic To carry nitrogen compound up to the different stages, depending on the applied Amounts of sodium hydroxide and methanol and according to the nature and amount of the particular used conveyor. In this way you can get nitrobenzene in a single reaction mixture reduce to hydrazobenzene. However, it is also possible to use nitrobenzene up to To reduce azoxy and / or azobenzene, as shown in the examples above, and then to isolate the obtained azoxybenzene and iodine azobenzene or below renewed addition of sodium hydroxide and methanol to reduce hydrazobenzene.

The temperature at which the reaction is carried out can also can be varied, albeit in the case of reduction with the aid of alcoholic caustic alkali Temperatures at or near the boiling point of the reaction mixture at normal pressure, generally about 90 to 105c, are preferred. At lower temperatures the reaction is slower under otherwise similar conditions and can take too long Take time to get the same results as the preferred ones Temperatures. Conversely, higher reaction temperatures result in a short reaction time, but require the use of closed reaction vessels. Temperatures that are essential above 110 'are, though not always, less desirable because even in the presence of the reduction promoters they lead to the formation of considerable quantities gaseous hydrogen and primary amines result in a loss of yield brings with it the desired reaction products.

While it is preferred for an economical and easy way of working becomes, as a solvent or diluent for the reaction mixture, an excess to use on the alcohol used for the alcoholate is not the invention limited to this. Other solvents and diluents can also be used will; z. B. the reaction can be carried out with amounts of sodium hydroxide and methanol which only slightly exceed the theoretical amount if the reaction medium a sufficient amount of xylene or another inert solvent or diluent contains, such as benzene, toluene, moco- and dichlorobenzene, that a stirrable reaction mass is obtained. Furthermore, you can also unimpeded the fact that it is easier is to use an excess of the alcohol as a solvent or diluent, which acts as a reducing agent, other alcohols are used; also mixtures of alcohols can be used, especially if the boiling point is desired to modify any reaction mixture.

For the sake of convenience and economy, the procedure is generally carried out so that there is a metal alcoholate in the reaction mixture forms, e.g. B. by reacting caustic alkali with the alcohol. If necessary, can however, metal alcoholates produced earlier can also serve as reducing agents; whereby the diluting effect of the water produced as a by-product in the reaction caustic alkali with the alcohol is avoided.

Sodium hydroxide and methanol are used in the examples In view of their low cost and the fact that they are easily available. However, the invention is not limited to the use of these special substances, other types of alkali, e.g. B. potassium hydroxide, and other alcohols, e.g. B. ethyl alcohol and the various propyl, butyl and higher alcohols can be used.

Instead of the sodium bisulfite used in Example 2, for the preparation of the addition products with that with a cycloaliphatic ring condensed benzoquinone also other compounds can be used. For example one can get appropriate amounts of the various other bisulfites and other compounds according to US Pat. No. 2,645,636 or sodium hydrosulfide or others sulfiding compounds, as listed in German Patent 947,708 are.

The reduction products can be applied to any of the reaction mixtures Way to be isolated. Except for the cases where the reaction mixture an insoluble residue due to the presence of the reducing promoter in the Contains reaction mixture, the isolation of the reduction products can be done in the usual way Way. For example, you can cool them to the reduction product crystallize, and then filter and rinse the cake with water for removal the alcohol of the sodium formate obtained as a by-product of the reduction and Wash sodium hydroxide. In general, it is preferred to use the methanol from a steam distillation to subject, the aqueous methanol, which is obtained here, can after fractionated Distillation come for reuse and then the remaining hot, aqueous Cool mass to crystallize out the reduction product, which is then separated and as usual. is washed with water. When the product is in the hot mixture When it is melted, as in the case of azoxy and azobenzenes, it is easier to mass to separate into an aqueous and an oil phase, after which the latter is easily isolated as shown in the examples.

In general, the reduction promoters are of the type mentioned above soluble in the aqueous und'or alcoholic layer and become out with this the reduction product removed. If the use of the reduction conveyor is a provides a small amount of an insoluble by-product, this can be done by filtering the hot mixture prior to phase separation or otherwise removed.

Claims (6)

PATENT CLAIMS: 1. Further training of the method of promotion the reducing effect of metal alcohols on reducible aromatic nitrogen compounds according to patent 925 293, in which the nitrogen is in a higher oxidation state than of the hydrazo stage bonded directly to a carbon atom of the aromatic nucleus is, characterized in that the reaction mixture is a condensed Mehrkerl ige compound added which contains at least 9 ring carbon atoms and the a benzoquinone or benzohydroquinone condensed with a cycloaliphatic ring with at least two saturated carbon atoms in the cycloaliphatic ring, or a derivative, adduct or tautomeric form thereof. 2. The method according to claim 1, characterized in that one small amount of condensed polynuclear compound that acts as a reaction promoter is used with a lower alcohol, particularly methyl alcohol, and a Alkali metal hydroxide, especially sodium hydroxide, mixes and the to be reduced heated aromatic nitrogen compound with the reduction mixture thus obtained. 3. The method according to claim 1 and 2, characterized in that one a condensed polynuclear compound is used as a reduction promoter, the 10 Contains ring carbon atoms. 4. The method according to claim 1 to 3, characterized in that one a condensed polynuclear Compound used 'the oxo or oxy substituents contains in p-quinoid position to one another, preferably a hydrogenated naphthoquinone- (1,4) or naphthohydroquinone- (1,4). 5. The method according to claim 1 to 4, characterized in that one as a starting material a reducible aromatic nitrogen compound, preferably a nitrogen derivative of benzene or an ortho-substituted derivative of benzene, in particular nitrobenzene, o-nitrotoluene or their reduction products are used. 6. The method according to claim 1 to 5, characterized in that one as the reducible aromatic nitrogen compound, a mononuclear azoxy or azo compound used.