DE2751662A1 - (1,4)-Dihydro-qnthraquinone, prepd. from tetrahydro-anthraquinone - or dihydroanthraqhydroquinone by oxidising in an aq. solvent - Google Patents

Abstract

is prepd. by oxidising 1,4,4a, 9a-tetrahydroanthraquinone or 1,4-dihydroanthrahydroquinone with O2 in an aq. solvent. Process comprises conducting the oxidn. reaction under such conditions that the pH of the aq. solvent is 8-12 and the reaction temp. is 70 degrees C. Quinone type redox catalyst is used. Adjustment of the pH is conducted using alkali hydroxide alkali carbonate, ammonia, diethylamine, triethylamine and the like. The redox catalysts include e.g. 1,4-naphthoquinone-2-sulphonic acid salt, 1,2-naphthoquinone-4-sulphonic acid salt and like water-soluble quinone cpds. The catalyst may be of oxidn. type or redn. type used in amt. 0.01-0.1 mole per mole of the starting material. The prod. is used as starting material for agricultural chemicals and dyes, and is itself used as agricultural chemical. The prepn. has shortened reaction time and content of by product is reduced, compared with prior art process.

Description

Process for the preparation of 1,4-dihydroanthraquinones

Summary 1,4-Dihydroanthraquinones are manufactured by Oxidation of 1,4,4a, 9a-tetrahydroanthraquinone or 1,4-dihydroanthrahydroquinone or a derivative thereof with an inert substituent by means of molecular Oxygen in an aqueous medium at a reaction temperature below 70 OC and at a pH of 8.5 to 12.

The invention relates to a process for the preparation of 1,4-dihydroanthraquinones. In particular, the invention relates to a process for the preparation of 1,4-dihydroanthraquinones by oxidation of 1,4,4a, 9a-tetrahydroanthraquinone or 1,4-dihydroanthralihydroquinone or a derivative with an inert substituent.

1, 4-Dihydroanthr achinone are important starting smater yes 1 ien for Manufacture of agrochemicals, dyes and other fine chemicals and them are also useful as agrochemicals themselves.

It is known to use 1,4-dihydroanthraquinones (1,4-DHAQ) according to various Method to make: (1) 1,4,4a, 9a-Tetrahydroanthraquinone (THAQ) is dissolved in ethanol oxidized with ferric chloride; (2) THAQ is made with ferric chloride in the presence one Wetting agent oxidized (Chemical Abstracts, 56, 7237e (1962)); (3) THAQ will oxidized with potassium bromate (Chemical Abstracts, 52, 12830b (1958)); (4) THAQ will with gaseous oxygen in an aqueous medium at pH 4 to 8 and preferably at pH 6 to 7 and at a temperature of 85 to 100 OC and preferably 90 to 95 OC oxidized (GB-PS 896 911 of March 23, 1962) In the process (1) and (2) expensive ferric chloride is used, so that high costs are incurred. The multiplying (3) is only suitable for the laboratory scale but not for industrial implementation. The method (4) is superior to the other methods in industrial practice. However, the reaction rate is quite slow and the reaction takes 4 hours and the purity of the 1,4-DHAQ obtained is also low, at 96% or less.

The inventors have various methods for producing 1,4-DHAQ high purity from THAQ. It was found that with an increase of the pH value compared to the pH value of the procedure (4) and in the event of a decrease the temperature during the oxidation of the THAQ with molecular oxygen in aqueous Medium the reaction is accelerated and the reaction time is shortened significantly will.

Furthermore, surprisingly, the amount of by-product formed Anthraquinone decreased.

It is an object of the present invention to provide a high speed one ongoing process for the production of 1,4-dihydroanthraquinones of high purity to create in which no expensive oxidizing agents have to be used.

According to the invention, this object is achieved by adding 1,4,4a, 9a-tetrahydroanthraquinone or 1,4-dihydroanthrahydroquinone or a derivative thereof with a inert Substituents with molecular oxygen in an aqueous medium at a reaction temperature is oxidized below 70 ° C. and at a pH in the range from 8.5 to 12, and indeed if necessary. in the presence of a quinone type redox catalyst.

1,4-Dihydroanthraquinones with inert substituents are described below designated 1,4-DHAQs. As substituents, for. B. alkyl groups, such as C1-8 alkyl groups; or halogen atoms such as chlorine or bromine; Haloalkyl groups or phenyl groups in Question. Unsubstituted 1,4-dihydroanthraquinone is referred to below as 1,4-DHAQ designated. 1,4,4a, 9a-Tetrahydroanthraquinones with inert substituents are im hereinafter referred to as THAQs.

The abovementioned substituents are possible.

Unsubstituted 1,4,4a, 9a-tetrahydroanthraquinone is combined with THAQ designated. 1,4-Dihydroanthrahydroquinones with inert substituents are described below designated 1,4-DHAHQs. The abovementioned substituents are possible. Unsubstituted 1,4-dihydroanthrahydroquinone is referred to below as 1,4-DHAHQ. To simplify the description, it mainly refers to 1,4-DHAQ, THAQ and 1,4-DHAHQ, as derivatives with inert substituents are essentially the same Show response characteristics.

A first aspect of the invention is in the manufacture of 1,4-DRAQs by oxidation of THAQs or 1,4-D s with molecular oxygen in an aqueous one Medium at a heating temperature below 70 ° C and a pH of 8.5 to 12 seen. A second aspect of the invention is in the production of 1,4-DHAQs by oxidation of TRANS or 1,4-DHAHQs with molecular oxygen in an aqueous one Medium at a reaction temperature below 70 C and a pH of 8.5 to 12 seen in the presence of a quinone-type redox catalyst First the first variant of the method according to the invention is to be explained. That as Starting material used THAQ or THAQs can be easily obtained as an addition compound of naphthoquinone and a diene by Diels-Alder reaction. They come in GB-PS 896 911 in question. Suitable dienes are butadiene, alkyl-substituted Butadienes such as isoprene, 2,3-dimethylbutadiene, 2-butylbutadiene; halogen-substituted Butadienes such as 2-chlorobutadiene, 2-bromobutadiene; phenyl-substituted butadienes, such as 2-phenylbutadiene; Cyclopentadienes and pentadienes. 1,4-dihydroanthrahydroquinones can be easily obtained by treating those obtained by Diels-Alder reaction Addition compounds with a catalytic amount of a base, e.g. B. an alkali metal hydroxide or ammonia or with an acid such as chloroacetic acid in an aqueous medium or in an organic medium. The starting material can be THAQs or 1,4-DHAHQs insert. When using 1,4-DHAHQs, the rate of reaction is relative greater. However, THAQs is commonly used to complete the isomerization stage eliminate. It is preferable to pulverize the raw material and shape it of a finely divided powder.

Water is usually used as the aqueous medium.

You can also dissolve a small amount of a salt in the water or an inert organic solvent, e.g. B. add an alcohol to the water. In some cases, such an addition is advantageous because it causes the reaction is accelerated. For economic reasons one uses the molecular oxygen usually in the form of air.

The following is a description of the typical process sequence. A reaction vessel equipped with a stirrer and a gas inlet tube is connected to an aqueous medium charged and the pH with a pH modifier 8.5 to 12 set. Then it will THAQs or 1,4-DHAHQs as Starting material dispersed in the aqueous medium. The concentration of the starting material is adjusted to about 1 to 20% by weight. It is also possible to use the starting material First disperse in an aqueous medium and then adjust the pH with a pH modifier set to 8.5 to 12. If the starting material at the previous stage is obtained in the form of an aqueous slurry, this can be done without prior separation can be used. The starting material used is THAQs or 1,4-DHAHQs not completely soluble so that a slurry is formed. Now will Air through the gas inlet pipe at the reaction temperature of 10 to 70 OC and preferably 30 to 60 ° C. introduced into the aqueous slurry. During the Reaction, the mixture is stirred to ensure intimate contact between the gaseous, bring about liquid and solid components. At the beginning is the reaction mixture white or purple white and it then takes a dark purple color due to the quinhydron at. Thereafter, as the oxidation progresses, it turns yellow. if the 1,4-DHAQs is essentially converted, so the reaction is over and so is it the typical yellow crystals are formed. Air becomes even more during a few more Minutes initiated. The reaction is complete and normal in less than 3 hours for 10 to 120 minutes, and most of the starting material lies during the reaction and the product in the form of a suspension. Thus it is used to bring about a smooth reaction favorable to stir the suspension with high shear stress and / or add a surfactant. The reaction product is filtered off and washed with water and dried under nitrogen.

The melting point and the infrared spectrum of the 1,4-DHAHQ obtained are identical to the melting point and infrared spectrum of a conventional one 1,4-DHAQs obtained with ferric chloride. The infrared spectrum of the source material, namely the THAQs or 1,4-DHAHQs is considerably different from the infrared spectrum of the product.

Therefore, the product can be easily identified.

The filtrate can be used again after the pH has been adjusted. The method according to the invention can also be applied to 1,4,4a, 9a-tetrahydroanthraquinone or without substituents or 1,4-dihydroanthrahydroquinone with or without a substituent be applied.

Suitable as pH modifiers are those agents which are listed under the The reaction conditions are inert towards the starting material and the product, and able to adjust the pH to 8.5 to 12. Suitable pH modifiers are Alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; Alkali metal carbonates, such as sodium carbonates, potassium carbonates; Ammonia and alkylamines, such as diethylamine, Triethylamine etc. You can to maintain the pH during the reaction, add a buffer, e.g. B. a mixture of boric acid and potassium chloride or a phosphate. It is preferred to keep the pH in the range of 8.5-12. if the pH is below this range, d. H. in the range of 8.5 to 7 so is the rate of reaction small amount. If the pH is above 12, the 1,4-DHAQs formed as product will expand oxidizes and it forms anthraquinones (hereinafter referred to as AQ), so that that 1,4-DHAQs is contaminated with AQ. If the pH is above 13, it will 1,4-DHAQs are essentially completely converted to AQ.

The reaction temperature is below 70 ° C. and preferably 0 in the range from 30 to 60 C. At a temperature below 10 OC, the amount of des AQ formed is less than 0.1% by weight. However, the reaction speed is also the same very low. At a temperature above 70 OC, AQ is formed in considerable quantities, so that the purity of the product is low. At a temperature of 30 to 60 OC, the reaction rate is high and the rate of formation of AQ is beneficial small amount.

The second variant of the method according to the invention is explained below will. A redox catalyst of the quinone type is used here. It can are water-soluble quinones, such as 1,4-naphthoquinone-2-sulfonate, 1,2-naphthoquinone-4-sulfonate, Anthraquinone disulfonate etc. The salt-forming cation components can be alkali metals be like sodium, potassium, and ammonium. When using a quinone redox catalyst you can either use it in oxidized form (quinone type) or in reduced form (Hydroquinone type). The amount of the quinone redox catalyst is preferably less than 1 mole and especially 0.01 to 0.1 mole per mole of the starting material in the solution.

If the amount of redox catalyst is less, so is it Effectiveness not sufficient. On the other hand, there is a larger amount of the redox catalyst not economical.

If the quinone-type redox catalyst is used, the Reaction time under the same conditions of pH, reaction temperature and the concentration as in the first variant of the method to half to 1/3 shortened. In addition, the formation of AQ can be caused by the addition of the redox catalyst of the quinone type are inhibited.

It is also preferred to set the pH in the range from 8.5 to 12 to keep. The reaction temperature is below 70 ° C. and preferably above 5 OC and especially 0 in the range from 30 to 60 C. As with the first variant of the method Here, too, the lowering of the reaction temperature leads to an effective reduction the formation of AQ to less than 0.5% by weight. A very low reaction temperature however, is from the standpoint of flexibility (energy expenditure) and required Apparatus not advantageous. At very low temperatures, the product cost elevated. The reaction temperature is optimally in the range from 30 to 60 ° C.

The quinone type redox catalyst is usually the slurry added before reaction, d. H. before the introduction of molecular oxygen. if the filtrate is returned to the 1,4-DHAQ after the reaction is complete is used, it is sufficient to replace part of the catalytic converter. Otherwise are to choose the same conditions in this process variant as in the first Process variant, in particular the conditions with regard to the starting materials, namely THAQs and 1,4-DHAHQs and with regard to the aqueous medium, the molecular one Oxygen and the pH modifier.

The first process variant has compared to conventional processes the advantage that the reaction rate is increased and the purity of the as 1,4-DHAQs formed by the product are improved. The second variant of the procedure has compared to the first variant of the process the advantage that the reaction rate is increased even further, so that the response time is reduced to half to 1/3 and that the purity of 1,4-DHAQ is increased even further.

In the following, the invention is explained in more detail with the aid of exemplary embodiments explained.

Example 1 A reactor equipped with a stirrer is set at 100 Parts by weight of water charged in which 2.12 parts by weight were dissolved and 2.12 parts by weight THAQ are added to the solution with stirring. The mix is in the form of a Slurry with pH 11.3. The mixture is heated to 50 OC and air becomes introduced into the mixture with careful stirring. As the reaction progresses the white color of the slurry changes to a purple color and finally to the dark purple color of quinhydron (adduct of 1,4-DHAHQ and 1,4-DHAQ); then the reaction mixture takes a yellow one coloring and finally the specific yellow slurry of 1,4-DHAQ is obtained. Thereafter, the color of the slurry does not change any further. Now the The introduction of air is interrupted and the reaction is ended.

The reaction time is 1 hour and the pH is at the end of the reaction 10.3.

The reaction product is filtered off and washed with water and dried under a stream of nitrogen. 2.06 parts by weight of yellow crystals are obtained of raw 1,4-DHAQ.

The yield is 98 mol%. The product has a melting point from 204 to 208 C. High speed liquid chromatography shows that the Product contains 2.1 wt% AQ. The product is recrystallized from o-xylene.

Pure 1,4-DHAQ with a melting point of 208.5 to 209.5 is obtained 0C. This melting point is identical to the melting point of a conventional one Method obtained product. Further, the infrared spectrum confirms that it is is a 1,4-DHAQ. The mixed melting point of the product with one by oxidation 1,4-DHAQ obtained with ferric chloride shows no difference in melting point.

Example 2 The procedure of Example 1 is followed, wherein 1,4-DHAHQ is used instead of THAQ. 2.05 parts by weight of crude 1,4-DHAQ are obtained. The infrared spectrum confirms that it is 1,4-DHAQ. The high-speed liquid chromatography shows that the product contains 2.0 wt% AQ.

Example 3 The procedure of Example 1 is repeated using 2.40 parts by weight of 2,3-dimethyl-1,4,4a, 9a-tetrahydroanthraquinone instead of THAQ begins. 2.33 parts by weight of the product with a melting point of 199 are obtained until 202 OC. The infrared spectrum confirms that it is 2,3-dimethyl-1,4-dihydroanthraquinone acts. The 2,3-dimethyl-anthraquinone content is 2.2% by weight.

EXAMPLE 4 0.2 mole of boric acid and 0.2 mole of potassium chloride are placed in a reactor. as well as sodium hydroxide and water for the preparation of a buffer solution of pH 9. 2.12 Parts by weight of THAQ are added to 100 parts by weight of the buffer solution and air becomes introduced into the mixture at 50 ° C. for 2 h with stirring. The reaction mixture is worked up according to Example 1. 2.05 parts by weight of the product are obtained with a melting point of 204 to 208 OC, as in Example 1. The infrared spectrum confirms that it is 1,4-DHAQ. The AQ content is 2.2% by weight.

Comparative Example 1 2.12 parts by weight of THAQ make 100 parts by weight a buffer solution with pH 7 (0.2 moles of potassium hydrogen phosphate, sodium hydroxide and Water) and air is added to the mixture at 50 ° C. for 2 h with stirring initiated. The reaction mixture is worked up as in Example 1. The infrared spectrum confirms that the product is essentially unreacted starting material. This product is then oxidized with air for a further 4 hours. However, this arises not the specific yellow slurry of 1,4-DHAQ showing completeness the response.

The infrared spectrum shows that essentially unreacted Material is present.

Comparative Example 2 2.12 parts by weight of THAQ become 100 parts by weight an aqueous solution of sodium hydroxide of pH 13 and air is added at 50 OC passed into the mixture for 1 h with stirring. The reaction mixture will worked up according to example 1. 2.05 parts by weight of yellow-orange are obtained -colored Crystals. The high speed liquid chromatography shows that the content of AQ is 62% by weight.

Example 5 The procedure of Example 1 is repeated using Introduces air for 2 h at 30 ° C. 2.06 parts by weight of the product are obtained with a melting point of 204 to 208 OC. This product is identical to example 1. It contains 2.0% by weight of AQ.

Example 6 Pour into a reaction vessel equipped with a stirrer one 4.24 parts by weight of sodium carbonate, dissolved in 100 parts by weight of water, and 8.48 parts by weight of THAQ. The mixture is stirred and the pH is adjusted by adding In-NaOH (aqueous solution) adjusted to 11.6. The mixture is then set to 50 C is heated and air is introduced with stirring.

After about 60 minutes, the dark purple color of the suspension strikes to a specific yellow coloration of the 1,4-DHAQ slurry. Then will more air is passed in and the reaction is started after 80 minutes, calculated from the beginning implementation on, stopped. The reaction mixture is worked up as in Example 1. 8.19 parts by weight of the product are obtained in the form of yellow crystals.

The product has a melting point of 204 to 208 OC.

The high speed liquid chromatography shows that the content of AQ is 2.2% by weight. The infrared spectrum confirms that it is 1,4-DHAQ acts.

Comparative example 3 The procedure in the example is used 1, but introducing air at 80 ° C. for 1 hour. Yellow-orange is obtained colored crystals. High speed liquid chromatography shows that the AQ content is 40% by weight.

Example 7 Pour into a reaction vessel equipped with a stirrer one 4.24 parts by weight of sodium carbonate, dissolved in 100 parts by weight of water and then 8.48 parts by weight of THAQ. The mixture is stirred and 0.26 part by weight of sodium 1,4-naphthoquinone-2-sulfonate (hereinafter referred to as NQSNa) are added, whereupon the pH with a aqueous In-NaOH is adjusted to 11.3. The mixture is warmed to 50 ° C and air is introduced with stirring. After about 30 minutes the dark purple color changes Slurry into a specifically yellow-colored slurry of 1,4-DHAQ µm.

After that, the coloration does not change any more. The reaction will be after 45 min, calculated from the start of the reaction, stopped.

The reaction mixture is worked up as in Example 1.

8.24 parts by weight of yellow crystals with a melting point are obtained from 206 to 208.5 ° C. High speed liquid chromatography shows that the AQ content is 1.1% by weight. The infrared spectrum confirms that it is is 1,4-DHAQ.

Example 8 The procedure of Example 7 is followed, wherein however, air is introduced at 20 OC. After 1 hour the dark purple slurry turns to a yellowish slurry. After 2 hours the specific yellow slurry lies of 1,4-DHAQ and the introduction of air is interrupted.

The reaction mixture is then worked up as in Example 1. Man receives 8.22 parts by weight of yellow crystals with a melting point of 206 to 208.5 OC. The high speed liquid chromatography shows that the content of AQ is 1.0 % By weight. The procedure is repeated, but using 1,4-DHAHQ as the starting material instead of THAQ.

The same results are achieved here. The infrared spectrum the compound shows that they are identical to conventional products.

Claims (4)

PATENT CLAIMS 1. Process for the preparation of 1,4-dihydroanthaquinones by oxidation of 1,4,4a, 9a-tetrahydroanthraquinone or 1,4-dihydroanthrahydroquinone, which, if necessary, can carry inert substituents with molecular oxygen, thereby characterized in that the oxidation at a temperature below 70 OC and at a pH: on 8.5 to 12 in an aqueous medium. 2. The method according to claim 1, characterized in that the reaction temperature is in the range from 10 to 70 ° C. 3. The method according to claim 2, characterized in that the reaction temperature is in the range of 30 to 60 OC. 4. The method according to any one of claims 1 to 3, characterized in that that the oxidation is carried out in the presence of a quinone type redox catalyst.