DE2058121A1 - Anthraquinones prepn - using sulphur trioxide as cyclisation agent - Google Patents

Abstract

Anthraquinones of formula (I): (where gps. R are same or different H, halogen, alkyl or hydroxy) are prepd. by cyclisation of an o-benzoylbenzoic acid of formula (II): using 100% SO3 as cyclisation agent. Corrosion is not appreciable and use of large quantities of acid or water is avoided. Pref. acids have R = H, Cl, Br 1-4C alkyl or OH, esp. o-benzoylbenzoic acid.

Description

Process for the preparation of anthraquinones The invention relates to a process for the preparation of anthraquinones by cyclizing an o-benzoylbenzoic acid in the presence of 100 percent sulfur trioxide as a cyclizing agent.

It is known that one can use benzoylbenzoic acid and substituted benzoylbenzoic acids in the presence of an excess of concentrated sulfuric acid (85 to 100 percent) or weak oleum (5 to 20 percent) and at elevated temperature in the corresponding Can transfer anthraquinones (Ullmanns Encyklopadie der technischen Chemie, 3. Volume, page 659 ff. (1953); Kirk-Othmer, Encyclopedia of Chemical Technology, 2 (1963), Page 431 ff.). Depending on the benzoylbenzoic acid to be cyclized and temperatures depending on the selected strength of the cyclizing agent from 85 to 150 OC and reaction times between one and two hours after addition the acid to be cyclized.

A major disadvantage of this cyclization method, which is simple and cheap in itself is the large amount of sulfuric acid resp.

Oleum, especially when working up, when diluted with water must be, take up a lot of space, cause corrosion and either recycled or must be destroyed.

The disposal of the resulting waste water is another problem.

These shortcomings of the process are only reduced by using them Attempted to correct amounts of condensing agent (DBP 1 004 599; US patent 2,842,562; British Patent 765 036). To do this, however, it is necessary to heat the reaction mixture to very high temperatures. The split off water in conjunction with the added acid, however, works extremely well under such conditions corrosive, moreover, begins to decompose the reaction mixture.

It is also described that when oleum is used as a condensing agent the rate of cyclization of benzoylbenzoic acid up to a content of 55 free sulfur trioxide increases steadily, while at higher concentrations it does in sulfur trioxide increases only slightly (J. Amer.

Chem. Soc. 67, 329 (1945)).

It has now been found that anthraquinones of the general formula in which the individual radicals R can be identical or different and each represent a hydrogen atom, a halogen atom, an alkyl group or a hydroxyl group, by cyclization of an o-benzoylbenzoic acid of the general formula in which R has the abovementioned meaning, in the presence of a cyclizing agent, advantageously obtained when cyclizing using 100 percent sulfur oxide as the cyclizing agent.

In the case of using o-benzoylbenzoic acid, the reaction can be represented by the following formulas: In comparison to the known processes, the process according to the invention provides anthraquinones in a simpler and more economical way in good yield, better purity and at a higher reaction rate. Sulphonation on the anthraquinone nucleus does not occur to any significant extent. The amount of cyclizing agent used is lower and the laborious work-up with larger amounts of acid or water and wastewater problems are avoided. You are also able to work up the resulting reaction mixtures anhydrous, for example using methanol or isobutanol.

Corrosion of the systems does not occur to any significant extent.

In view of the prior art, these are advantageous results surprised.

Preferred starting materials II and correspondingly preferred end materials I are those in whose formulas the individual radicals R are identical or different can and each have a hydrogen atom, a chlorine or bromine atom, a straight chain or branched alkyl group having 1 to 4 carbon atoms or a hydroxy group mean. For example, the following starting materials II are suitable: 4-chloro, 2,5-dichloro, 4,4'-dichloro, 2,2 ', 5,5'-tetrachloro, 4-bromo, 4-bromo-5'-chloro, 2-chloro-3-methyl, 2-hydroxy-5-chloro, 3,3'-dihydroxy-o-benzoylbenzoic acid and especially o-benzoylbenzoic acid.

100 percent sulfur trioxide is in solid or preferably in liquid form or used as a gas. Regarding the definition of 100 percent Sulfur trioxide is on Ullmanns Encyklopadie der technischen Chemie, Volume 15, Pages 465-467 referenced. The cyclizing agent is usually used in an amount of 0.5 to 2.5 mol per 1 mol of starting material II, preferably 0.5 to 1 mole at the Working method in the melt of the starting material and from 1 to 2.5 moles in the procedure using organic solvents.

The cyclization is generally carried out at a temperature between 80 and 2200C, carried out without pressure or under pressure, continuously or discontinuously. When working in the melt, temperatures of 160 to 2000C are below Use of organic solvents, temperatures from 100 to 17 ore preferred. When using organic solvents, all come under the reaction conditions inert solvents in question, preferably aliphatic hydrocarbons, e.g. Petroleum ether, ligroin, n-heptane, 2-ethylhexane, n-octane, nonane; and especially high-boiling, chlorinated, aliphatic or aromatic hydrocarbons, e.g.

1,1,2, 2-tetrachloroethane, 1,1, 2,2-tetrachlorethylene, mono-, di- and Trichlorobenzene. The solvent is generally used in an amount of from 85 to 400 Ges ,, based on starting material II, used. The solvents can, optionally can be used again after previous processing.

The reaction can be carried out as follows: In the procedure In the melt, the starting material II, which has been heated above the melting point, is added liquid sulfur trioxide was added in portions and then the Melt the mixture at the reaction temperature for 0.5 to 30 minutes.

If you cyclize the starting material in a solvent, the Sulfur trioxide is expediently added to the solution of the starting material, e.g. 100 ° C, which can heat up to e.g. 1500C due to the heat of reaction, and the mixture then held at the reaction temperature for 1 to 60 minutes. But you can also do that Submit sulfur trioxide in the solvent, add the starting material, the mixture Bring to reaction temperature and allow to react. You can also do the same gaseous sulfur trioxide in the melt or solution of the starting material under initiate thorough mixing and carry out the cyclization.

The end product is then made from the reaction mixture in the customary manner separated, e.g. the mixture can be cooled, e.g. to 100 to 120 ° C, water or Add steam to the mixture, reflux the resulting suspension and then Suck off the end product formed, wash with e.g. methanol and dry. In the The procedure in the organic solvent can be carried out from the mixture after cyclization and cooling, the end product can be separated off directly. The solvents can, optionally can be used again after previous processing.

With some starting materials II, e.g. with 4-chlorobenzoylbenzoic acid, the anhydrous work-up with methanol or isobutanol is preferable to the aqueous one, since in the aqueous work-up the end product, e.g. the 2-chloroanthraquinone, very much can be finely divided. In such cases it will be advantageous to follow the procedure cyclized in the melt, the reaction mixture cooled, e.g. to 64 to 120 ° C, and an alkanol such as methanol or isobutanol, preferably in an amount of 100 up to 300% by weight, based on the reaction mixture, was added. The suspension formed is then suctioned off and washed and dried the filter material.

The compounds preparable by the process of the invention are valuable starting materials for the manufacture of dyes. Regarding the use reference is made to the publications indicated.

The parts given in the examples are parts by weight.

Example 1 a) Benzoylbenzoic acid melted in 45.2 parts at 135 to 140 ° C 7.7 parts become liquid within 5 minutes without additional external heating Sulfur trioxide added with stirring; the temperature of the reaction mixture rises in the process on 185 to 19500. The mixture becomes 3 to 10 minutes after the addition of sulfur trioxide is complete fixed. After it has cooled to 700C, 80 parts of methanol are added, the mixture is stirred up, the end product is suctioned off, with methanol washed and dried.

Yield: 38.8 parts (93% of theory) of anthraquinone, melting point 286.degree.

b) In the case of the aqueous work-up, the cooled to 100.degree. C. Mixture given 100 parts of water. The mixture thus obtained is refluxed for 1/2 hour heated, the Endatoff sucked off, washed and dried.

Yield: 38.7 parts (93% of theory) of anthraquinone, melting point 283 ° C.

Example 2 In a 10006 hot solution of 22.6 parts of benzoylbenzoic acid in 40 parts of 1,1,2,2-tetrachloroethane are stirred within one minute 7.7 parts of liquid sulfur trioxide were added. The temperature of the reaction mixture increases to 145 ° C. When the addition of sulfur trioxide is complete, it is then 5 minutes stirred for a long time under reflux, the mixture cooled rapidly and the precipitated Anthraquinone sucked off, washed with methanol or isobutanol and dried.

Yield. 20.3 parts (97.5% of theory) anthraquinone, melting point 287 ° C.

If the mixture is stirred for 10 minutes instead of 5, the same yield is obtained of anthraquinone. The recovered tetrachloroethane can be used again.

Example 3 In 52 parts of molten 4-chlorobenzoylbenzoic acid at 150 ° C 19.2 parts of liquid sulfur trioxide are added with stirring within 15 minutes admitted. The temperature of the reaction mixture rises to 17500 and falls, after 2/3 of the sulfur trioxide have been added, it again drops to 160 ° C. The mixture will Stirred for 30 minutes at 160.degree. C. and then with 100 parts of water for 2 hours heated to boiling with mechanical comminution of the solidified mass. After work-up analogously to Example 1, 33.2 parts (68.5% of theory) of 2-chloroanthraquinone are obtained, Mp. 208 ° C.

Example 4 In a 10,000 hot solution of 26 parts of 4-chlorobenzoylbenzoic acid in 40 parts of 1,1,2,2-tetrachloroethane, 15.4 parts of sulfur trioxide are added with stirring admitted. The solution is brought to reflux temperature by the heat of reaction. After 1/2 hour at 148 ° C., 25.6 parts of tetrachloroethane are distilled off.

After cooling to 100 ° C., the residue is mixed with 40 parts of isobutanol added, filtered off with suction at room temperature, rubbed with methanol, washed and dried.

Yield: 20.6 parts (85 of theory) of 2-chloroanthraquinone, melting point 2080C.

Example 5 Into a 100 ° C. solution of 26 parts of 4-chlorobenzoylbenzoic acid 19.2 parts of liquid sulfur trioxide are added to 96 parts of trichlorobenzene with stirring admitted. The temperature of the solution rises to 140 OC. After 1/4 hour at 145 up to 1500C the mixture is distilled with steam, the residue is suctioned off, washed and dried.

Yield: 19.6 parts (81% of theory) of 2-chloroanthraquinone, melting point 210 until 21200.

Example 6 Into a 160 to 170 ° X hot melt of 54 parts of 2,5-dichlorobenzoylbenzoic acid 7.7 parts of liquid sulfur trioxide are added with stirring. The mixture will then stirred for 1/2 hour at this temperature. After cooling the liquid 80 parts of methanol are added to the mixture, the mixture is filtered off with suction and dried. Yield: 29 parts (57% of theory) 1,4-dichloroanthraquinone, melting point 18400.

Claims (1)

Claim Process for the preparation of anthraquinones of the general formula in which the individual radicals R can be identical or different and each represent a hydrogen atom, a halogen atom, an alkyl group or a hydroxyl group, by cyclizing an o-benzoylbenzoic acid of the general formula in which R has the aforementioned meaning, in the presence of a cyclizing agent, characterized in that cyclization is carried out using 100 percent sulfur trioxide as the cyclizing agent.