BONRATH WERNER (CH)
NETSCHER THOMAS (CH)
SCHÜTZ JAN (CH)
LOHRI BRUNO (CH)
| US3796732A | 1974-03-12 | |||
| US3987068A | 1976-10-19 |
DATABASE WPI Week 197549, Derwent World Patents Index; AN 1975-80890W, XP002730356
TAKIZAWA, Y. ET AL.: "Novel oxidative coupling of monophenols in the system of cupric chloride-oxygen-alcohol", THE JOURNAL OF ORGANIC CHEMISTRY, vol. 50, no. 22, 1985, pages 4383 - 4386, XP055143011, ISSN: 0022-3263, DOI: 10.1021/jo00222a038
DATABASE WPI Week 199120, Derwent World Patents Index; AN 1991-144823, XP002730353
DATABASE WPI Week 200670, Derwent World Patents Index; AN 2006-673648, XP002730355
SHIMIZU, M. ET AL.: "SYNTHESIS OF ALKYL SUBSTUTED P-BENZOQUINONES FROM THE CORRESPONDINGPHENOLS USING MOLECULAR OXYGEN CATALYZED BY COPPER(II) CHLORIDE-AMINE HYDROCHLORIDE SYSTEMS", BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, vol. 65, no. 6, 1992, pages 1522 - 1526, XP001005330, ISSN: 0009-2673
HIRAI, G. ET AL.: "Synthetic Study of Zoanthamine Alkaloids: The C-ring Model Possessing Three Consecutive Quaternary Carbons", CHEMISTRY LETTERS, no. 2, 1999, pages 141 - 142, XP055143016
TAKAKI, K. ET AL.: "Selective oxidation of phenols to hydroxybenzaldehydes and benzoquinones with dioxygen catalyzed by polymer-supported copper", BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, vol. 75, no. 2, 2002, pages 311 - 317, XP009180422, ISSN: 0009-2673
TAKEHIRA, K. ET AL.: "Novel oxidation of phenols by a copper(II) complex catalyst/oxygen system", STUDIES IN SURFACE SCIENCE AND CATALYSIS, vol. 66, 1991, pages 279 - 284, XP009180425, ISSN: 0167-2991
See also references of EP 3140273A1
| Claims 1. A process for the production of 2,6-dimethylbenzoquinone, wherein 2,6- dimethylphenol is oxidised by O2 in the presence of at least 0.4 mol-eq, based on the mol of 2,6-dimethylphenol, of at least one copper salt. 2. Process according to claim 1 , wherein the at least copper salt is a Cu(l) and/or Cu(ll) salt. 3. Process according to claim 1 , wherein the at least copper salt is a Cu(ll) salt. 4. Process according to claim 1 , wherein the copper salt is CuC . 5. Process according to any of the preceding claims, wherein the at least copper salt is used in an amount of 0.4 to 2 mol-eq. 6. Process according to any of the preceding claims, wherein the process is carried out at a temperature of from 50°C to 95°C, preferably from 60°C to 85°C, more preferably from 70 to 85°C, most preferably from 70 to 80°C. 7. Process according to any of the preceding claims, wherein the process is carried out at in an inert solvent (or mixture of solvents). 8. Process according to claim 7, wherein the solvent (or mixtures of solvents) is chosen from the group consisting of alkylene carbonates and glycol ethers. 9. Process according to any of the preceding claims, wherein the process is carried with a gas containing O2 gas. 10. Process according to claim 7, wherein the gas is air. 11. Process according to any of the preceding claims 1 - 8, wherein the process is carried with pure O2. Process according to any of the preceding claims 1 - 8, wherein the pure 02 gas or the 02-containing gas is induced directly into the liquid reaction mixture. |
The present invention relates to an improved process for the production of 2,6- dimethylbenzoquinone (2,6-DMQ).
2,6-dimethylbenzoquinone (2,6-DMQ), which is the compound of formula (A),
is an important and widely used compound in organic synthesis. 2,6-DMQ is used for example in the synthesis of Vitamin E.
Many processes for the production of 2,6-DMQ are known from the prior art. But many of them do have the issues with the yield and the selectivity of 2,6,-DMQ. Es- pecially the forming of side products during the reaction (i.e. dimer forming) is a problem.
In JP 2006-249036 a method for the manufacture of 2,3,5-trimehtlyhydroquinone is disclosed. As a reaction step in this process 2,6-dimethylphenol is oxidised with 0 2 in the presence of a Cu(l) or Cu(ll) compound. The amount of the Cu compound is between 0.01 to 0.02 mol-equivalent (mol-eq). This process still produces significant amounts of side-products.
Therefore the goal of the present invention was to find a process for the production of 2,6-DMQ, wherein an excellent yield and selectivity is achieved. Surprisingly, it was found out that the 2,6-dimethylphenol (2,6-DMP), which is the compound (B)
can be oxidised with O2 in the presence of a high amount of a copper salt (as a catalyst) in better selectivity.
It is surprising that the increase of the amount of the catalyst has a positive impact on the selectivity.
Therefore, the present invention relates to a process (I) for the production of 2,6- dimethylbenzoquinone, wherein 2,6-dimethylphenol is oxidised by O2 in the presence of at least 0.4 mol-eq, based on the mol of 2,6-dimethylphenol, of at least one copper salt.
The increased amount of at least one copper salt (in comparison the Japanese patent application 2006-249036) leads to a process with an excellent yield and selectivity of 2,6-dimethylbenzoquinone. That means that the amount of side products (dimer formation) is surprisingly decreased dramatically.
The copper salt is preferably at least one Cu(l) salt and/or at least one Cu(ll) salt, more preferred at least one Cu(ll) salt. Most preferred is CuC^ (this salt usually has crystal water= CuCl 2 x2H 2 0, so the this form is also covered by the term CuCI 2 ). Therefore the present invention also relates to a process (II), which is a process (I), wherein the at least one copper salt is a Cu(l) salt and/or Cu(ll) salt.
Therefore the present invention also relates to a process (ΙΓ), which is process (I), wherein the at least one copper salt is a Cu(ll) salt. Therefore the present invention also relates to a process (II"), which is process (I), wherein the copper salt is CuC .
The at least one copper salt (preferably Cu(ll) salt, more preferably CuCI 2 ) is used in amount of at least 0.4 mol-eq, based on the mol of 2,6-dimethylphenol.
Preferred is a process, wherein 0.4 to 2 mol-eq, more preferably up to 1 .8 mol-eq, of at least one copper salt is used.
Therefore the present invention also relates to a process (III), which is process (I), (II), (II') or (II"), wherein the at least one copper salt is used in an amount of at least 0.4 mol-eq, based on the mol of 2,6-dimethylphenol.
Therefore the present invention also relates to a process (I II'), which is process (I), (II), (ΙΓ) or (II"), wherein the at least one copper salt is used in an amount of 0.4 to 2 mol-%, based on the mol of 2,6-dimethylphenol.
Therefore the present invention also relates to a process (III"), which is process (I), (II), (ΙΓ) or (II"), wherein the at least one salt compound is used in amount of 0.4 to 1 .8 mol-eq, based on the mol of 2,6-dimethylphenol.
The copper salt (catalyst) can be reused.
The process according to the present invention is usually carried out at a temperature of from 50°C to 95°C, preferably from 60°C to 85°C, more preferably from 70 to 85°C, most preferably from 70 to 80°C.
Therefore the present invention also relates to a process (IV), which is process (I), (II), (ΙΓ), (II"), (III), (III * ) or (III"), wherein the process is carried out at a temperature of from 50°C to 95°C.
Therefore the present invention also relates to a process (IV), which is process (I), (II), (ΙΙ'), (II"), (III), (III') or (III"), wherein the process is carried out at a temperature of from 60°C to 85°C. Therefore the present invention also relates to a process (IV"), which is process (I), (II), (ΙΓ), (II"), (III), (III') or (III"), wherein the process is carried out at a temperature of from 70 to 85°C. Therefore the present invention also relates to a process (IV"), which is process (I), (II), (ΙΙ'), (II"), (III), (III') or (III"), wherein the process is carried out at a temperature of from 70 to 80°C.
The process according to the present invention is usually carried out in an inert sol- vent (or mixture of solvents), the solvent can be non-polar or polar. The solvent (or the mixture of solvents) has to be liquid at the reaction conditions (temperature, pressure) of the process according to the present invention. Suitable solvents are alkylene carbonates and glycol ethers.
Preferred solvents are ethylene carbonates and methyl diethylene glycol (MDG).
Therefore the present invention also relates to a process (V), which is process (I), (II), (ΙΙ'), (II"), (III), (III'), (III"), (IV), (IV), (IV") or (IV"), wherein the process is carried out in an inert solvent (or mixture of solvents). Therefore the present invention also relates to a process (V), which is process (I), (II), (ΙΙ'), (II"), (III), (III'), (III"), (IV), (IV), (IV") or (IV"), wherein the process is carried out at in at least one solvent chosen from the group consisting of alkylene carbonates and glycol ethers. Therefore the present invention also relates to a process (V"), which is process (I), (II), (ΙΙ'), (II"), (III), (III'), (III"), (IV), (IV), (IV") or (IV"), wherein the process is carried out at in at least one solvent chosen from the group consisting of ethylene carbonates and methyl diethylene glycol (MDG). The oxidation process according to the present invention can be carried out with pure O2 gas as well as with a gas mixture containing O2 gas (such as air). Preferred is pure 0 2 gas. Therefore the present invention also relates to a process (VI), which is process (I), (II), (ΙΙ'), (II"), (III), (III'), (III"), (IV), (IV), (IV"), (IV"), (V), (V) or (V), wherein the process is carried with gas mixture containing O 2 gas. Therefore the present invention also relates to a process (VI'), which is process (VI), wherein the gas is air.
Therefore the present invention also relates to a process (VI"), which is process (I), (II), (ΙΙ'), (II"), (III), (III'), (III"), (IV), (IV), (IV), (V), (V) or (V"), wherein the process is carried with pure O 2 .
In a preferred embodiment O 2 or air is induced directly into the liquid reaction mixture.
The flow rate of the oxygen can vary. The flow rate is dependent on the size of the reaction apparatus.
Therefore the present invention also relates to a process (VII), which is process (I), (II), (ΙΙ'), (II"), (III), (III'), (III"), (IV), (IV), (IV"), (IV"), (V), (V), (V) (VI), (VI') or (VI"), wherein (Vcontaining gas is induced directly into the liquid reaction mixture.
The so obtained 2,6-DMQ can be isolated using commonly known methods or it can be used without isolation for further reactions.
2,6-DMQ can be used as starting material in organic synthesis. For example, 2,6- DMQ can be used to form 2,3,5-trimethylhydroquinone (TMHQ), which is then reacted with (all-rac)-isophytol to obtain (all-rac)-a-tocopherol.
The following examples serve to illustrate the invention. The temperature is given in degree Celsius. Examples
Example 1 A solution of 4.10 g of CuC½ x 2H 2 0 in 8.4 ml of methyl diethyl glycol (MDG) was added into a flask. The solution was heated to 75°C and O2 was introduced (30 ml/min) into the solution and the solution was stirred.
A solution of 2.49 g (20 mmol) of 2,6-DMP in 8.4 ml of MDG was added slowly to the catalyst solution. The addition time of the DMP was about 3 hours.
The amount of CUCI2 x 2H 2 0 was 1 .2 mol-eq (in regard to the starting material). After the addition of the 2,6-DMP, the reaction mixture was stirred for another hour. Afterwards the obtained product (2,6-DMQ) was isolated.
The yield was 81 % and the conversion was >99.9% and the selectivity was 81 %.
Example 2
The procedure as described in Example 1 was repeated, but the O2 flow was in- creased to 60 ml/min.
The yield was 84% and the conversion was >99.9 % and the selectivity was 84%.
Example 3 (Comparison Example) The procedure as described in Example 1 was repeated, but the amount of CuC x 2H 2 0 was reduced to 0.68 g. which are 0.2 mol-eq.
The yield was 49% and the conversion was >99.9 % and the selectivity was 49%. It can be seen that a low amount of CuCI 2 x 2H 2 O results in lower selectivity.