Preparation of 2,6- and 2,7-disubstituted anthraquinone derivatives

Abstract

The present invention relates to novel anthraquinone derivatives, 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexyl-anthracene-9,10-dione, preferably to be used for the preparation of hydrogen peroxide, and to a process for the preparation of these anthraquinone derivatives.

Claims

1. A compound of formula (Ia) ##STR00075##

2. A compound of formula (Ib) ##STR00076##

3. A composition, comprising a compound of formula (Ia) ##STR00077## and a compound of formula (Ib) ##STR00078##

4. The composition of claim 3, wherein at least 90 weight-% of the composition consists of the compounds of formula (Ia) and formula (Ib).

5. The composition of claim 3, wherein the molar ratio of the compound of formula (Ia) relative to the compound of formula (Ib) is in a range of from 0.2:1 to 5:1.

6. The composition of claim 3, having a solubility of at least 1.0 mol/l in a solvent mixture of which at least 99.9 weight-% consists of ortho-xylene and diisobutyl carbinol wherein the molar ratio of the ortho-xylene relative to the diisobutyl carbinol in a range of from 0.99:1 to 1.01:1, wherein said solubility refers to the molar amount of the compound of formula (Ia) plus the molar amount of the compound of formula (Ib) dissolved in 1 l of the solvent mixture at a temperature of from 20 to 23 C. and at a pressure of from 0.9 to 1.1 bar.

7. The composition of claim 3, wherein at least 90 weight-% of the compound of formula (Ia) and at least 96 weight-% of the compound of formula (Ib) are present in solid form.

8. The composition of claim 3, being at least partially dissolved in a solvent.

9. A solution, comprising a compound of formula (Ia) ##STR00079## and/or a compound of formula (Ib) ##STR00080## and a solvent.

10. A process for preparing a composition comprising a compound of formula (Ia) ##STR00081## and a compound of formula (Ib) ##STR00082## said process comprising: (i) providing a mixture comprising the compound of formula (IIa) ##STR00083## and the compound of formula (IIb) ##STR00084## and (ii) subjecting the mixture to a hydrogenation reaction.

11. The process of claim 10, wherein (i) comprises (a) providing a compound of formula (III) ##STR00085## (b) reacting the compound of formula (III) with a compound of formula (IV) ##STR00086## thereby obtaining a mixture comprising a compound of formula (Va) ##STR00087## and a compound of formula (Vb) ##STR00088## and (c) subjecting the mixture obtained in (b) to an oxidation reaction thereby obtaining a mixture comprising the compound of formula (IIa) and the compound of formula (IIb).

12. The process of claim 11, wherein the reacting (b) is carried out in a solvent.

13. The process of claim 11, further comprising: after (b) and prior to (c), (b) separating the compounds of formula (Va) and formula (Vb) from the mixture obtained in (b), thereby obtaining a mixture comprising the compounds of formula (Va) and formula (Vb).

14. The process of claim 11, wherein prior to (c), the compounds of formula (Va) and formula (Vb) are not separated from the mixture obtained in (b).

15. The process of claim 11, wherein the oxidation reaction in (c) is carried out in a solvent.

16. The process of claim 11, further comprising: after (c) and prior to (ii), (c) separating the compounds of formula (IIa) and formula (IIb) from the mixture obtained in (c), thereby obtaining a mixture comprising the compounds of formula (IIa) and formula (IIb).

17. The process of claim 11, wherein after (c) and prior to (ii), the compounds of formula (IIa) and formula (II) are not separated from the mixture obtained in (c).

18. The process of claim 10, wherein the hydrogenation reaction in (ii) is carried out in a solvent in the presence of a hydrogenation catalyst.

19. The process of claim 10, further comprising (iii) treating the mixture obtained in (ii) with an inorganic base, thereby obtaining a mixture comprising the compounds of formula (Ia) and formula (Ib).

20. The process of claim 10, further comprising crystallizing the compounds of formula (Ia) and formula (Ib) from the mixture obtained in (ii).

21. A mixture or a composition, comprising the compounds of formula (Ia) ##STR00089## and of formula (Ib) ##STR00090## obtained by the process of claim 10.

22. A process for preparing hydrogen peroxide, the process comprising: preparing hydrogen peroxide from a compound selected from the group consisting of a compound of formula (Ia), a compound of formula (Ib), and a combination thereof: ##STR00091##

23. A process for preparing hydrogen peroxide, the process comprising (I) providing a compound of formula (Ia) ##STR00092## or a compound of formula (Ib) ##STR00093## or a composition comprising the compound of formula (Ia) and the compound of formula (Ib); (II) preparing a mixture comprising the compound or the composition provided in (I) dissolved in an organic solvent, and further comprising a hydrogenation catalyst; (III) subjecting the mixture prepared in (II) to a hydrogenation reaction, thereby obtaining a mixture comprising a compound of formula (VIIa) ##STR00094## or comprising a compound of formula (VIIb) ##STR00095## or comprising the compound of formula (VIIa) and the compound formula (VIIb); (IV) subjecting the mixture obtained in (III) to an oxidation reaction in the presence of an oxygen containing gas, thereby obtaining a mixture comprising the compound of formula (Ia), or the compound of formula (Ib), or the compound of formula (Ia) and the compound of formula (Ib), and further comprising hydrogen peroxide; and (V) separating hydrogen peroxide from the mixture obtained in (IV), thereby obtaining a mixture comprising hydrogen peroxide and a mixture comprising the compound of formula (Ia), or the compound of formula (Ib), or the compound of formula (Ia) and the compound of formula (Ib).

Description

EXAMPLES

Reference Example 1: IR Measurements

(1) The IR measurements were performed on a Nicolet 6700 spectrometer. The materials were measured as film on a KBr window, wherein in case the materials were present as solid, the solid was solved in dichloromethane prior to applying on the KBr window. The samples were introduced into a high vacuum cell placed into the IR instrument. The spectra were recorded in the range of 4000 cm.sup.1 to 400 cm.sup.1 at a resolution of 4 cm.sup.1. The obtained spectra were represented by a plot having on the x axis the wavenumber (cm.sup.1) and on the y axis the absorbance (arbitrary units). For the quantitative determination of the peak heights and the ratio of the peak heights, a baseline correction was carried out.

Reference Example 2: Elemental Analysis

(2) The elemental analysis regarding carbon and hydrogen were performed on an elemental analyzer of model vario Micro cube of the company Elementar, wherein oxygen was used for combustion, and wherein the content of carbon and hydrogen were detected via conductivity measurement.

(3) The elemental analysis regarding oxygen was performed on an elemental analyzer of model EuroVector EA3000 of the firm HEKAtech, wherein soot was used for pyrolysis, and wherein the content of oxygen was detected via conductivity measurement.

(4) The measurements were carried out according to the manufacturer's instructions.

Reference Example 3: GC/MS Measurements

(5) The GC/MS measurements were performed on a gas chromatograph Agilent GC 6890 N using a detector Agilent 5975 MSD and a column Restek 13623.

(6) The measurements were carried out according to the manufacturer's instructions.

Example 1: Preparation of a Mixture of 2,6-bis(4-methylpent-3-enyl)-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9-10-dione and 2,7-bis(4-methylpent-3-enyl)-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9-10-dione (Compounds of Formula (Va) and (Vb))

(7) A round bottom flask was equipped with a reflux condenser and flushed with argon. Then, 20.0 g cyclohexa-2,5-diene-1,4-dione were provided in the round bottom flask and suspended in 200 ml toluene. The obtained suspension was heated to an internal temperature of 90 C. and 63.0 g 7-methyl-3-methylene-1,6-octadiene were added and the mixture was stirred for 7 days at 80 C. with a stirring rate of 400 r.p.m. (rounds per minute). Thereafter, the mixture was cooled to 22 C. and filtered. The solvent in the obtained solution was evaporated under reduced pressure, so that a solid was obtained. Boiling ethanol was then added until the solid was dissolved completely. The solution was cooled to 22 C. and then further cooled to 22 C. for 15 h. The obtained solid was filtered off from the mother liquor and washed with ethanol having a temperature of 22 C. until the solid was colorless. The obtained product was dried under reduced pressure. The solvent in the mother liquor was evaporated and the thus obtained solid was purified as described above.

(8) 59.0 g (84%) of the mixture of 2,6-bis(4-methylpent-3-enyl)-1,4,4a,5,8,8a,9a,10a-octahydro-anthracene-9-10-dione and 2,7-bis(4-methylpent-3-enyl)-1,4,4a,5,8,8a,9a,10a-octahydro-anthracene-9-10-dione were obtained. The obtained product had a melting point of 73.9 C. and 77 C. IR spectrum of the obtained product exhibits the following absorption bands with maximums at (KBr pellet): 428 cm.sup.1, 510 cm.sup.1, 555 cm.sup.1, 782 cm.sup.1, 835 cm.sup.1, 912 cm.sup.1, 934 cm.sup.1, 982 cm.sup.1, 1106 cm.sup.1, 1129 cm.sup.1, 1176 cm.sup.1, 122 cm.sup.1, 1244 cm.sup.1, 1280 cm.sup.1, 1375 cm.sup.1, 1443 cm.sup.1, 1706 cm.sup.1, 2855 cm.sup.1, 2917 cm.sup.1, 2966 cm.sup.1. Further, the following data were found by mass spectrometry (GC/MS) and elemental analysis (EA): GC/MS: C.sub.26H.sub.36O.sub.2 calculated (m/z): 380.27; determined (GC/MS, (m/z)): 380; EA: C.sub.26H.sub.36O.sub.2 calculated: C: 82.06 weight-%, H: 9.53 weight-%, O: 8.41 weight-%, determined: C: 81.9 weight-%, H: 9.6 weight-%, O: 8.3 weight-%.

Example 2: Preparation of a Mixture of 2,6-bis(4-methylpent-3-enyl)anthracene-9,10-dione and 2,7-bis(4-methylpent-3-enyl)anthracene-9,10-dione (Compounds of Formula (IIa) and (IIb))

(9) 10.0 g of the product obtained in Example 1 were dissolved in 200 ml of a mixture of toluene and n-butanol having a volume ratio of 3:1. The resulting solution was heated to an internal temperature of 60 C. and 1.5 g KOH were added. After KOH was solved in the solution, technical air containing 4 volume-% oxygen, was passed through the solution with a flow rate of 10 l/h for a period of 24 h and with a stirring rate of 750 r.p.m. The obtained solution was extracted with 50 ml distilled water for two times. The organic layer was separated and dried over Na.sub.2SO.sub.4. The solvent in the solution was evaporated under reduced pressure, so that a solid was obtained. Boiling ethanol was then added until the solid was dissolved completely. The solution was cooled to 22 C. and then further cooled to 22 C. for 15 h. The obtained solid was filtered off from the mother liquor and washed with ethanol having a temperature of 22 C. until the solid was colorless. The obtained product was dried under reduced pressure. The solvent in the mother liquor was evaporated and the thus obtained solid was purified as described above.

(10) 8.70 g (89%) of a mixture of 2,6-bis(4-methylpent-3-enyl)anthracene-9,10-dione and 2,7-bis(4-methylpent-3-enyl)anthracene-9,10-dione were obtained. The obtained product had a melting point of 69.8 C. and 77.9 C. IR spectrum of the obtained product exhibits the following absorption bands with maximums at (KBr pellet): 462 cm.sup.1, 550 cm.sup.1, 621 cm.sup.1, 666 cm.sup.1, 718 cm.sup.1, 743 cm.sup.1, 833 cm.sup.1, 848 cm.sup.1, 879 cm.sup.1, 932 cm.sup.1, 970 cm.sup.1, 1151 cm.sup.1, 1104 cm.sup.1, 1221 cm.sup.1, 1258 cm.sup.1, 1300 cm.sup.1, 1325 cm.sup.1, 1383 cm.sup.1, 1439 cm.sup.1, 1574 cm.sup.1, 1596 cm.sup.1, 1673 cm.sup.1, 2858 cm.sup.1, 2919 cm.sup.1, 2963 cm.sup.1, 3029 cm.sup.1, 3054 cm.sup.1, 3433 cm.sup.1. Further, the following data were found by mass spectrometry (GC/MS) and elemental analysis (EA): GC/MS: C.sub.26H.sub.28O.sub.2 calculated (m/z): 372.21 determined (m/z)): 372; EA: C.sub.26H.sub.28O.sub.2 calculated: C: 83.83 weight-%, H: 7.58 weight-%, O: 8.59 weight-% determined: C: 82.9 weight-%, H: 7.6 weight-%, O: 8.8 weight-%.

Example 3: Preparation of a Mixture of 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexylanthracene-9,10-dione (Compounds of Formula (Ia) and (Ib)) by Use of a Palladium Catalyst on Carbon

(11) A solution of 2.25 g of the product obtained in Example 2 dissolved in 150 ml ethanol was provided in an autoclave. 0.65 g of a palladium catalyst on carbon (5% Pd/C) were added. The autoclave was closed and flushed with 10 bar nitrogen for five times. The solution was cooled by air cooling having 20 C. and the solution was stirred with a stirring rate of 700 r.p.m. Thereafter, the pressure was set to 3.0 bar by introducing hydrogen gas. The pressure decreased within approximately 2 h to 1 bar and thereafter, the pressure was again set to 3 bar by introducing hydrogen gas. After approximately 5 h the pressure decreased to 1 bar and stirring was stopped. The pressure was set to atmosphere pressure and the autoclave was flushed with 10 bar nitrogen for two times. The palladium catalyst was filtered off and the solvent of the obtained solution was evaporated under reduced pressure, so that a solid was obtained. Boiling ethanol was then added until the solid was dissolved completely. The solution was cooled to 22 C. and then further cooled to 22 C. for 15 h. The obtained solid was filtered off from the mother liquor and dried under reduced pressure. The solvent in the mother liquor was evaporated and the thus obtained solid was purified as described above.

(12) 1.61 g (72%) a mixture of 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexyl-anthracene-9,10-dione were obtained. The obtained product had a melting point of 79.1 C. The IR spectrum of the obtained product exhibits the following absorption bands with maximums at (KBr pellet): 413 cm.sup.1, 553 cm.sup.1, 615 cm.sup.1, 654 cm.sup.1, 720 cm.sup.1, 750 cm.sup.1, 848 cm.sup.1, 879 cm.sup.1, 917 cm.sup.1, 934 cm.sup.1, 983 cm.sup.1, 1144 cm.sup.1, 1169 cm.sup.1, 1211 cm.sup.1, 1297 cm.sup.1, 1308 cm.sup.1, 1328 cm.sup.1, 1365 cm.sup.1, 1383 cm.sup.1, 1459 cm.sup.1, 1470 cm.sup.1, 1596 cm.sup.1, 1673 cm.sup.1, 2867 cm.sup.1, 2926 cm.sup.1, 2951 cm.sup.1, 3066 cm.sup.1, 3477 cm.sup.1. Further, the following data were found by mass spectrometry (GC/MS) and elemental analysis (EA): GC/MS: C.sub.26H.sub.32O.sub.2 calculated (m/z): 376.24; determined (m/z): 376; EA: C.sub.26H.sub.32O.sub.2 calculated: C: 82.94, H: 8.57, O: 8.50 determined: C: 82.3, H: 8.6, O: 8.9.

Results of Examples 1 to 3

(13) Examples 1 to 3 show that 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexyl-anthracene-9,10-dione are obtained by a process according to the present invention in an overall yield of 54%.

Example 4: Preparation of a Mixture of 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexylanthracene-9,10-dione (Compounds of Formula (Ia) and (Ib)) by Use of Different Catalysts and Solvents

(14) 200 mg of the mixture obtained in Example 3, catalyst (the amount used is given in Table 1 below) and 5 ml solvent (the solvent used is given in Table 1 below) were provided in an autoclave having a nominal volume of 80 ml. The pressure was set to 20.0 bar by introducing hydrogen gas and the reaction mixture was stirred for 15 h at 40 C. Thereafter, the catalyst was separated by filtration and the solvent was evaporated under reduced pressure.

(15) TABLE-US-00001 TABLE 1 Conversion (starting Selectivity (to Complex Ligand Additive Solvent material) product) 10 mol-% 10 mol-% MeOH 100% 75% [Rh(COD).sub.2][BF.sub.4].sup.(1) DTBPP.sup.(2) 17 mol % 10 mol-% 35 mol % THF 100% 60% [Ru(COD)Cl.sub.2].sub.n.sup.(1) PCy.sub.3.sup.(3) BMIMCl.sup.(4) 1 mol-% MeOH 100% 29% 2% Pd/C 1 mol-% toluene 100% 18% 2% Pd/C .sup.(1)COD = 1,5-cyclooctadiene .sup.(2)DTBPP = 1,2-bis(di-tert-butyl-phosphinomethyl)benzene .sup.(3)PCy.sub.3 = tricyclohexylphosphin .sup.(4)BMIMCl = 1-butyl-3-methylimidazolium chloride

Results of Example 4

(16) Example 4 shows that a variety of homogeneous and heterogeneous catalysts and solvents may be used to hydrogenate 2,6-bis(4-methylpent-3-enyl)anthracene-9,10-dione and 2,7-bis(4-methylpent-3-enyl)anthracene-9,10-dione even at an absolute hydrogen pressure of 20 bar.

Example 5: Preparation of a Mixture of 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexylanthracene-9,10-dione (Compounds of Formula (Ia) and (Ib)) and Subsequent Treatment with KOH

(17) 15 g of the mixture obtained in Example 3, 2.5 g of a palladium catalyst on carbon (5% Pd/C) and 200 ml ethanol were provided in an autoclave. The autoclave was closed and flushed with 1 bar nitrogen for three times. The pressure was set to 1.5 bar by introducing hydrogen gas and the reaction mixture was stirred for 140 h at 25 C. Thereafter, the catalyst was separated by filtration and the solvent was evaporated under reduced pressure. The resulting reaction mixture was analyzed by GC-MS. The conversion of the starting material was 100% and the selectivity to 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexylanthracene-9,10-dione was 81%, the rest being over-hydrogenated byproducts

(18) The resulting solution was heated to an internal temperature of 60 C. and 3.8 g KOH were added. After KOH was solved in the solution, technical air containing 4 volume-% oxygen, was passed through the solution with a flow rate of 10 l/h for a period of 4 h and with a stirring rate of 750 r.p.m. The obtained solution was extracted with 70 ml distilled water for two times. The organic layer was separated and dried over Na.sub.2SO.sub.4. The solvent in the solution was evaporated under reduced pressure, so that a solid was obtained. Boiling ethanol was then added until the solid was dissolved completely. The solution was cooled to 22 C. and then further cooled to 22 C. for 15 h. The obtained solid was filtered off from the mother liquor and washed with ethanol having a temperature of 22 C. until the solid was colorless. The obtained product was dried under reduced pressure. The solvent in the mother liquor was evaporated and the thus obtained solid was purified as described above.

(19) The resulting reaction mixture was analyzed by GC-MS, wherein the selectivity to 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexylanthracene-9,10-dione was 97%.

Results of Example 5

(20) Example 5 shows that a subsequent treatment with potassium hydroxide leads to an increased selectivity to 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexylanthracene-9,10-dione. Without the treatment with potassium hydroxide, a selectivity to 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexylanthracene-9,10-dione of 81% is achieved, wherein the subsequent treatment with potassium hydroxide increases the selectivity to 97%. This can be explained by the re-oxidation of the over-hydrogenated byproducts that are generated in the hydrogenation step even under such mild conditions described.

Example 6: Preparation of a Mixture of 2,6-bis(4-methylpent-3-enyl)anthracene-9,10-dione and 2,7-bis(4-methylpent-3-enyl)anthracene-9,10-dione (Compounds of Formula (IIa) and (IIb)) Starting from 1,4-dihydroxybenzol (Compound of Formula (VI))

(21) 0.19 g copper chloride dihydrate and 0.19 g dry lithium chloride were dissolved in 8 ml distilled water in a round bottom flask, which was equipped with a reflux condensor. 17 ml n-hexanol were added and the obtained solution was heated to an internal temperature of 60 C. 1.55 g 7-methyl-3-methylene-1,6-octadiene and 0.5 g 1,4-dihydroxybenzol were added. Thereafter, technical air was passed through the solution for 96 h, wherein the solution was stirred with a stirring rate of 900 r.p.m. Then, the organic layer was separated, heated to 70 C. and 0.25 g potassium hydroxide were added. Technical air was passed through the thus obtained mixture for 10 h. Thereafter, the obtained mixture was extracted with 30 ml distilled water and dried over Na.sub.2SO.sub.4. The solvent in the solution was evaporated under reduced pressure, so that a solid was obtained. Boiling ethanol was then added until the solid was dissolved completely. The solution was cooled to 22 C. and then further cooled to 22 C. for 15 h. The obtained solid was filtered off from the mother liquor and dried under reduced pressure, wherein a selectivity to 2,6-bis(4-methylpent-3-enyl)anthracene-9,10-dione and 2,7-bis(4-methylpent-3-enyl)anthracene-9,10-dione of 69% was achieved.

Results of Example 6

(22) Example 6 shows that 2,6-bis(4-methylpent-3-enyl)anthracene-9,10-dione and 2,7-bis(4-methylpent-3-enyl)anthracene-9,10-dione may be obtained in a one-pot process starting from 1,4-dihydroxybenzene, wherein a combination of copper chloride and lithium chloride is used as catalyst.

Example 7: Preparation of a Mixture of 2,6-bis(4-methylpent-3-enyl)-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9-10-dione and 2,7-bis(4-methylpent-3-enyl)-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9-10-dione (Compounds of Formula (IIa) and (IIb)) Starting from 1,4-dihydroxybenzene (Compound of Formula (VI))

(23) 0.49 g of a catalyst consisting of 60 weight-% copper(II) oxide, 20 weight-% zinc(II) oxide, 17.5 weight-% aluminum(III) oxide, 2.5 weight-% zirconium (IV) oxide were suspended in a mixture of 15 mL distilled water and 30 mL of 2-ethylhexanol. The obtained suspension was heated to an internal temperature of 60 C. and 4.65 g 7-methyl-3-methylene-1,6-octadiene and 1.5 g 1,4-dihydroxybenzol were added to the suspension. Thereafter, technical air was passed through the solution for 72 h, wherein the solution was stirred. The resulting reaction mixture was cooled to 22 C. and the organic layer was separated, dried over Na.sub.2SO.sub.4 and the solvent was evaporated under reduced pressure. The obtained solid was recrystallized in ethanol, wherein 5.18 g (yield: 84%) of 2,6-bis(4-methylpent-3-enyl)-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9-10-dione and 2,7-bis(4-methyl-pent-3-enyl)-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9-10-dione were obtained. The product obtained was further treated with KOH in the presence of an oxygen containing gas according to Example 2 to obtain 2,6-bis(4-methylpent-3-enyl)anthracene-9,10-dione and 2,6-bis(4-methylpent-3-enyl)anthracene-9,10-dione.

Results of Example 7

(24) Example 7 shows that 2,6-bis(4-methylpent-3-enyl)-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9-10-dione and 2,7-bis(4-methylpent-3-enyl)-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9-10-dione and further 2,6-bis(4-methylpent-3-enyl)anthracene-9,10-dione and later on 2,7-bis(4-methylpent-3-enyl)anthracene-9,10-dione may be obtained by use of different catalyst and solvents, where in 2-ethylhexanol and an heterogeneous catalyst containing copper, zinc, aluminum and zirconium is used.

Example 8: Preparation of a Mixture of 2,6-bis(4-methylpent-3-enyl)anthracene-9,10-dione and 2,7-bis(4-methylpent-3-enyl)anthracene-9,10-dione starting (Compounds of Formula (Va) and (Vb)) from 1,4-dihydroxybenzene (Compound of Formula (VI))

(25) 0.49 g of a catalyst consisting of 60 weight-% copper(II) oxide, 20 weight-% zinc(II) oxide, 17.5 weight-% aluminum(III) oxide, 2.5 weight-% zirconium (IV) oxide were suspended in a mixture of 15 mL distilled water and 30 mL of 2-ethylhexanol. The obtained suspension was heated to an internal temperature of 60 C. 4.65 g 7-methyl-3-methylene-1,6-octadiene and 1.5 g 1,4-dihydroxybenzol were added to the suspension. Thereafter, technical air was passed through the solution for 240 h, wherein the solution was stirred. The resulting reaction mixture was cooled to 22 C. and the organic layer was separated, dried over Na.sub.2SO.sub.4 and the solvent was evaporated under reduced pressure. The obtained solid was recrystallized in ethanol, wherein 4.51 g of 2,6-bis(4-methylpent-3-enyl)anthracene-9,10-dione and 2,7-bis(4-methylpent-3-enyl)anthracene-9,10-dione starting from benzene-1,4-diol were obtained.

Results of Example 7 and 8

(26) Comparison of Example 7 with Example 8 shows that an extension of the reaction time leads to an oxidation of 2,6-bis(4-methylpent-3-enyl)-1,4,4a,5,8,8a,9a,10a-octahydro-anthracene-9-10-dione and 2,7-bis(4-methylpent-3-enyl)-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9-10-dione by the technical air used, wherein 2,6-bis(4-methylpent-3-enyl)anthracene-9,10-dione and 2,7-bis(4-methylpent-3-enyl)anthracene-9,10-dione starting from benzene-1,4-diol are obtained without the use of a catalyst.

Comparative Example 1: Preparation of a Mixture of 2,6-bis(4,8-dimethylnonane-3,7-dienyl)-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9-10-dione and 2,7-bis(4,8-dimethylnonane-3,7-dienyl)-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9-10-dione

(27) A round bottom flask was equipped with a reflux condenser and flushed with argon. Then, 2.0 g cyclohexa-2,5-diene-1,4-dione were provided in the round bottom flask and suspended in 20 ml toluene. The obtained suspension was heated to an internal temperature of 80 C. and 9.0 g (6E)-7,11-dimethyl-3-methylene-1,6,10-dodecatrien were added and the mixture was stirred for 14 days at 80 C. with a stirring rate of 700 r.p.m. Thereafter, the mixture was cooled to 22 C. and filtered. The solvent in the obtained solution was evaporated under reduced pressure, so that a solid was obtained. The resulting crude product was purified by chromatography on silica using cyclohexane and ethyl acetate (volume ratio 40:1) as eluent.

(28) 6.71 g (61%) of 2,6-bis(4,8-dimethylnonane-3,7-dienyl)-1,4,4a,5,8,8a,9a,10a-octahydro-anthracene-9-10-dione and 2,7-bis(4,8-dimethylnonane-3,7-dienyl)-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9-10-dione in form of an oil were obtained. IR spectrum of the obtained product exhibits the following absorption bands with maximums at (KBr pellet): 432 cm.sup.1, 451 cm.sup.1, 551 cm.sup.1, 594 cm.sup.1, 826 cm.sup.1, 886 cm.sup.1, 921 cm.sup.1, 984 cm.sup.1, 1041 cm.sup.1, 1159 cm.sup.1, 1108 cm.sup.1, 1215 cm.sup.1, 1282 cm.sup.1, 1376 cm.sup.1, 1440 cm.sup.1, 1601 cm.sup.1, 1674 cm.sup.1, 1713 cm.sup.1, 2729 cm.sup.1, 2850 cm.sup.1, 2918 cm.sup.1, 2966 cm.sup.1, 3413 cm.sup.1. Further, the following data were found by mass spectrometry (GC/MS): C.sub.36H.sub.52O.sub.2 calculated (m/z): 516.40 determined (m/z)): 516.

Comparative Example 2: Preparation of a Mixture of 2,6-bis(4,8-dimethylnonan-3,7-dienyl)anthracene-9,10-dione and 2,7-bis(4,8-dimethylnonan-3,7-dienyl)anthracene-9,10-dione

(29) 4.0 g of the product obtained in Comparative Example 1 were dissolved in 74.5 ml of a mixture of toluene and n-butanol having a volume ratio of 3:1. The resulting solution was heated to an internal temperature of 60 C. and 0.434 g KOH were added. After KOH was solved in the solution, compressed air was passed through the solution with a stirring rate of 700 r.p.m. The obtained solution was extracted with 30 ml distilled water for two times. The organic layer was separated and dried over Na.sub.2SO.sub.4. The solvent in the solution was evaporated under reduced pressure, so that a solid was obtained. Boiling ethanol was then added until the solid was dissolved completely. The solution was cooled to 22 C. and then further cooled to 22 C. for 15 h. The obtained solid was filtered off from the mother liquor and washed with ethanol having a temperature of 22 C. until the solid was colorless. The obtained product was dried under reduced pressure. The solvent in the mother liquor was evaporated and the thus obtained solid was purified by chromatography on silica using cyclohexane and ethyl acetate (volume ratio 40:1) as eluent.

(30) 3.60 g (yield: 90%) of 2,6-bis(4,8-dimethylnonan-3,7-dienyl)anthracene-9,10-dione in form of a crystalline solid and 1.11 g 2,7-bis(4,8-dimethylnonan-3,7-dienyl)anthracene-9,10-dione in form of an oil were obtained. 2,6-bis(4,8-dimethylnonan-3,7-dienyl)anthracene-9,10-dione had a melting point of 82.4 C. IR spectrum of the obtained product exhibits the following absorption bands with maximums at (KBr pellet): 414 cm.sup.1, 452 cm.sup.1, 596 cm.sup.1, 618 cm.sup.1, 653 cm.sup.1, 718 cm.sup.1, 726 cm.sup.1, 750 cm.sup.1, 807 cm.sup.1, 881 cm.sup.1, 852 cm.sup.1, 918 cm.sup.1, 973 cm.sup.1, 1110 cm.sup.1, 1147 cm.sup.1, 1212 cm.sup.1, 1262 cm.sup.1, 1298 cm.sup.1, 1324 cm.sup.1, 1383 cm.sup.1, 1451 cm.sup.1, 1594 cm.sup.1, 1670 cm.sup.1, 2853 cm.sup.1, 2913 cm.sup.1, 2968 cm.sup.1, 3442 cm.sup.1. Further, the following data were found by mass spectrometry (GC/MS) and elemental analysis (EA): GC/MS: C.sub.36H.sub.44O.sub.2 calculated (m/z): 508.33, determined (m/z): 508; EA of 2,6-bis(4,8-dimethylnonan-3,7-dienyl)anthracene-9,10-dione C.sub.36H.sub.44O.sub.2 calculated: C: 84.99 weight-%, H: 8.72 weight-%, O: 6.29 weight-%; determined: C: 83.1 weight-%, H: 8.6 weight-%, O: 7.8 weight-%.

Comparative Example 3: Preparation of a Mixture of 2,6-(1,5-dimethyl)-nonylanthracene-9,10-dione and 2,7-(1,5-dimethyl)-nonylanthracene-9,10-dione

(31) 3.0 g of the mixture obtained in Comparative Example 2, 0.32 g Rh(COD).sub.2BF.sub.4 and 100 ml Methanol were provided in an autoclave having a nominal volume of 300 ml. The pressure was set to 20.0 bar by introducing hydrogen gas and the reaction mixture was stirred for 48 h at 40 C. Thereafter, the catalyst was separated by filtration and the solvent was evaporated under reduced pressure.

(32) 2.1 g (70%) of a mixture of 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexyl-anthracene-9,10-dione were obtained in form of a wax. IR spectrum of the obtained mixture exhibits the following absorption bands with maximums at (KBr pellet): 415 cm.sup.1, 556 cm.sup.1, 623 cm.sup.1, 655 cm.sup.1, 751 cm.sup.1, 879 cm.sup.1, 934 cm.sup.1, 983 cm.sup.1, 1146 cm.sup.1, 1171 cm.sup.1, 1211 cm.sup.1, 1308 cm.sup.1, 1328 cm.sup.1, 1365 cm.sup.1, 1459 cm.sup.1, 1470 cm.sup.1, 1675 cm.sup.1, 2867 cm.sup.1, 2951 cm.sup.1, 3066 cm.sup.1, 3469 cm.sup.1. Further, the following data were found by mass spectrometry (GC/MS) and elemental analysis (EA): GC/MS: C.sub.26H.sub.32O.sub.2 calculated (m/z): 516.40; determined (m/z): 516; EA: C.sub.26H.sub.32O.sub.2 calculated: C: 83.67 weight-%, H: 10.14 weight-%, O: 6.19 weight-%; determined: C: 83.75 weight-%, H: 10.22 weight-%, O: 6.03 weight-%.

Comparative Example 4: Preparation of 2-(3-methylbut-2-en-1-yl)-anthracene-9,10-dione

(33) 2-(3-methylbut-2-en-1-yl-anthracene-9,10-dione was prepared according to Example 8 in EP 1 178 032 A1: 850 g naphthoquinone were added to a mixture of 4 l toluene and 1.3 l n-butane and the obtained mixture was heated to 90 C. Thereafter, 990 g myrcene were added and after 5 h the mixture was cooled to 70 C. 250 ml water, 52 ml 50% NaOH and 50 ml diethyl amine were added and the resulting mixture was purged by oxygen gas at 70 C. for a period of 5 h. The aqueous layer was separated and the organic layer was washed with diluted phosphoric acid. The solvent in the organic layer was evaporated under reduced pressure and the crude product was purified by crystallization.

Comparative Example 5: Preparation of 2,3,6,7-tetramethyl-1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9,10-dione

(34) 10.0 g cyclohexa-2,5-diene-1,4-dione were suspended in 30 ml of a mixture of toluene and n-butanol having a volume ratio of 3:1. This suspension and 10.26 g 2,3-dimethylbuta-1,3-diene were provided in an autoclave having a nominal volume of 100 ml and the obtained mixture was heated to an internal temperature of 90 C. and stirred for 2 days at this temperature. Thereafter, the mixture was cooled to 22 C. and filtered. The thus obtained solution was used for the preparation of 2,3,6,7-tetramethylanthracene-9,10-dione without further purification.

Comparative Example 6: Preparation of 2,3,6,7-tetramethylanthracene-9,10-dione

(35) The solution obtained in Comparative Example 5 was set to a temperature of 60 C. and then 5.13 g KOH were added. After KOH was dissolved completely, compressed air was passed through the solution for a period of 5 h with a stirring rate of 700 r.p.m. Thereafter, the mixture was cooled to 22 C. and the solid thus created was separated by filtration and washed with cooled dichloromethane and water. The obtained solid was dried for 24 h at 70 C. in vacuum. The IR spectrum of the obtained mixture exhibits the following absorption bands with maximums at (KBr pellet): 412 cm.sup.1, 542 cm.sup.1, 655 cm.sup.1, 743 cm.sup.1, 872 cm.sup.1, 934 cm.sup.1, 1146 cm.sup.1, 1170 cm.sup.1, 1211 cm.sup.1, 1308 cm.sup.1, 1328 cm.sup.1, 1365 cm.sup.1, 1459 cm.sup.1, 1470 cm.sup.1, 1684 cm.sup.1, 2867 cm.sup.1, 3123 cm.sup.1, 3415 cm.sup.1. Further, the following data were found by mass spectrometry (GC/MS) and elemental analysis (EA): GC/MS: C.sub.18H.sub.16O.sub.2 calculated (m/z): 264.12; determined (m/z): 264; EA: C.sub.18H.sub.16O.sub.2 calculated: C: 81.79 weight-%, H: 6.10 weight-%, O: 12.11 weight-%; determined: C: 81.53 weight-%, H: 6.05 weight-%, O: 12.42 weight-%.

Example 9: Determination of the Solubility

(36) 0.06 ml of a mixture of xylene (50 volume-%) and diisobutylcarbinol (50 volume-%) were added to 1 g of the respective anthraquinone derivative at 22 C. every 60 seconds until the anthraquinone derivative was dissolved completely. The results of the solubility test are shown in Table 2 below.

(37) TABLE-US-00002 TABLE 2 Solubility Obtained from Anthraquinone derivative [mol/l] Example 2 2,7-bis(4-methylpent-3-enyl)anthracene- 0.77 9,10-dione and 2,6-bis(4- methylpent-3-enyl)anthracene-9,10-dione Example 3 2,7-diisohexylanthracene-9,10-dione and 1.61 2,6-diisohexylanthracene-9,10-dione Comparative 2,6-bis(4,8-dimethylnonan-3,7- 0.65 Example 2 dienyl)anthracene-9,10-dione and 2,7-bis(4,8-dimethylnonan- 3,7-dienyl)anthracene-9,10-dione Comparative 2,6-(1,5-dimethy)-nonylanthracene- 0.39 Example 3 9,10-dione and 2,7-(1,5- dimethy)-nonylanthracene-9,10-dione Comparative 2-(3-methylbut-2-en-1-yl)-anthracene- 0.77 Example 4 9,10-dione Comparative 2,3,6,7-tetramethylanthracene-9,10-dione insoluble Example 6 (commercially 2-ethylanthraquinone 0.27 available)

Results of Example 9

(38) As may be taken from the solubility test of the different anthraquinone derivatives, the anthraquinone derivatives having small substituents are insoluble (anthraquinone derivative obtained from Comparative Example 6) or only poorly soluble (commercially available anthraquinone derivative) in the used solvent system compared to the anthraquinone derivatives having 2 substituents, wherein these substituents have six or eleven carbon atoms. However, the anthraquinone derivative according to the present invention, which is obtained from Example 3 exhibits the highest solubility in the solvent system used.

Example 10: Preparation of Hydrogen Peroxide by Use of Anthraquinone Derivatives

(39) 5 g of the anthraquinone derivative obtained from Example 3 was dissolved in an equivolume mixture of xylene and diisobutylcarbinol at 30 C. to obtain 100 ml of an anthraquinone solution. 2 g of a palladium catalyst on alumina was added to 50 ml of the anthraquinone solution and then the solution was made to absorb the theoretical amount of hydrogen at 30 C. The obtained solution has been left untouched for 15 h to thoroughly precipitate the excess of anthrahydroquinone. After the catalyst and the precipitate have been separated by filtration under a current of nitrogen, the resulting solution was stirred under air in order to oxidize the anthrahydroquinone back to the corresponding anthraquinone. The produced hydrogen peroxide was extracted with water. After the extraction of the hydrogen peroxide was completed, 25 mL of the working solution were further submitted to subsequent hydrogenation at 30 C. as described above until a state of saturation was reached. The amount of absorbed hydrogen until the precipitation of the anthrahydroquinone that was observed corresponded to a solubility of the anthrahydroquinone obtained from the anthraquinone described in Example 3 in said equivolume mixture of xylene and diisobutylcarbinol of 1.01 mol/l.

Results of Example 10

(40) TABLE-US-00003 TABLE 3 Yield of Alkylanthrahydro- hydrogen quinone Solubility peroxide obtained from Anthraquinone derivative [mol/l] [g/l] Example 3 2,7-diisohexylanthracene- 1.01 32.4 9,10-dione and 2,6- diisohexylanthracene- 9,10-dione (Ia and Ib)

Summary of the Examples

(41) As shown in Examples 1 to 8, 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexyl-anthracene-9,10-dione may be obtained by a sustainable and atom efficient process according to the present invention. Further, Example 9 shows 2,6-diisohexylanthracene-9,10-dione and 2,7-diisohexylanthracene-9,10-dione according to the present invention exhibit the advantage that these compound have the highest solubility in the solvent system used when compared to the anthraquinone derivatives obtained according to the Comparative Examples.

CITED LITERATURE

(42) Ullmann's Encyclopedia of Industrial Chemistry, Vol. 18, chapter Hydrogen Peroxide, DOI: 10.1002/14356007.a13_443.pub2. GB 1 387 511 A1 GB 1 387 512 DE 43 39 649 A1 DE 1 051 257