Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
1998-10-30
2002-09-03
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S076000, C560S086000, C560S146000, C560S231000, C560S109000, C560S001000, C560S130000, C568S341000, C568S763000
Reexamination Certificate
active
06444841
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a hydroquinone diester derivative with high purity and the method for producing the same.
BACKGROUND OF THE INVENTION
A hydroquinone diester derivative (e.g., a trimethylhydroquinone diester, trimethylhydroquinone produced by hydrolyzing a trimethylhydroquinone diester) is useful as an intermediate of a medicine, and it is also one of the industrially important compounds as a raw material for vitamin E; an antioxidant for resins, higher fatty acids, higher alcohols, or fat and oils; and a polymerization inhibitor for polymerizable monomers.
Japanese Patent Application Laid-Open No. 7632/1972 (JP-A-47-7632) discloses a method for producing a trimethylhydroquinone diester by reacting 2,6,6-trimethylcyclohex-2-ene-1,4, -dione (ketoisophorone, KIP) with an acylating agent in the presence of an acid catalyst (e.g., a protonic acid catalyst or a Lewis acid catalyst).
In this method, however, a purified trimethylhydroquinone diester is obtained by, after neutralization and extraction, removing the acid catalyst from the reaction product by filtration, condensing the extract under reduced pressure, and recrystallizing the condensed extract with the use of hexane. Therefore, its purification process is complicated, and the yield is low. Moreover, when hexane is employed as a solvent for recrystallization, the purity of a trimethylhydroquinone diester can be improved only to a limited extent probably because the by-produces have poor solubility in hexane. Probably due to such reasons, in the reference mentioned above, the melting point of a trimethylhydroquinone dimethyl ester is disclosed to be in a wide range of 97 to 107° C. Moreover, since hexane has a low boiling point and the solubility in hexane of the object compound is considerably low, a large amount of hexane is required for recrystallization. Therefore, the purification process in this method is industrially disadvantageous.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a hydroquinone diester derivative with high purity and a method for producing the same.
It is another object of the present invention to provide a method for producing a hydroquinone diester derivative with high purity in a high yield by simple operations.
A further object of the present invention is to provide a method for producing a hydroquinone diester derivative with high purity from the product formed by the esterification of 2,6,6-trimethylcyclohex-2-ene-1,4-dione (ketoisophorone, KIP) with an acylating agent and the transition reaction in a high yield by a simple operation.
The inventors of the present invention did intensive investigation, found that a trimethylhydroquinone diester with high purity can be obtained in a high yield by subjecting the reaction product of 2,6,6-trimethylcyclohex-2-ene-1,4-dione (KIP) with an acylating agent to a crystallization process, and achieved the present invention.
The hydroquinone diester derivative of the present invention is shown by the following formula (1):
wherein R
1
represents an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group, and each R
2
is the same or different and represents an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group, and comprises 0.001 to 2% by weight of a catechol diester derivative shown by the following formula (2):
wherein R
1
and R
2
are the same as defined above.
In the method of the present invention, in the presence of a catalyst, a cyclohex-2-ene-1,4-dione derivative (e.g., 2,6,6-trisubstituted cyclohex-2-ene-1,4-dione) shown by the following formula (3):
wherein R
2
has the same meaning mentioned above; is allowed to react with an acylating agent, and the reaction product is purif ied by crystallization to produce a hydroquinone dies ter derivative shown by the formula (1). The hydroquinone diester derivative (1) obtained in such manner contains about 0 to 2% by weight of a catechol diester derivative shown by the formula (2). The solvent for crystallization is usually a polar solvent, particularly a mixed solvent of an organic carboxylic acid corresponding to the above-mentioned acylating agent (in particular, acetic acid or the like), and water.
DETAILED DESCRIPTION OF THE INVENTION
As for R
1
and R
2
of the formulae (1) to (3), examples of an alkyl group include C
1-10
alkyl groups (e.g., C
1-8
alkyl groups such as methyl, ethyl, butyl, isobutyl, t-butyl, pentyl and hexyl). Examples of a cycloalkyl group include C
3-10
cycloalkyl groups (e.g., cyclohexyl group). Examples of an aryl group include C
6-12
aryl groups (e.g., phenyl group, substituted phenyl groups such as p-methylphenyl group). Examples of a heterocyclic group include aromatic or non-aromatic 5- or 6-membered heterocyclic groups having at least one heteroatom selected from the group consisting of nitrogen, oxygen and sulfur (e.g., furyl group, thienyl group, nicotinyl group and pyridyl group). In the compounds shown by the formulae (1) to (3), the species of the substituents R
1
and R
2
may be the same or different.
In the above hydroquinone diester derivative (1) and the catechol diester derivative (2), as a preferred R
1
, there may be exemplified C
1-8
alkyl groups, particularly C
1-6
alkyl groups (e.g., C
1-4
alkyl groups such as methyl group and ethyl group). As a preferred R
2
, there may be mentioned methyl group.
The features of the present invention reside in that a hydroquinone diester derivative (1) is highly pure, and that the content of a catechol diester derivative (2) produced as a by-product during the reaction is significantly low. Usually, the content of the catechol diester derivative (2) is substantially 2% by weight or less (i.e., an inevitable amount to 2% by weight). To be concrete, the content of the catechol diester derivative (2) as an impurity is about 0.001 to 2% by weight (e.g., about 0.001 to 1.5% by weight), preferably about 0.001 to 1% by weight, and more preferably about 0.001 to 0.8% by weight.
Such hydroquinone diester derivative (1) with high purity can be produced by reacting a cyclohex-2-ene-1,4-dione derivative shown by the formula (3) with an acylating agent in the presence of a catalyst and purifying the reaction product by crystallization. In this method, a hydroquinone diester derivative (1) containing substantially about 0% by weight (i.e., about 0 to 2% by weight) of the catechol diester derivative (2) can be also obtained.
As a compound shown by the formula (3), usually, there may be used 2,6,6-tri-C
1-4
alkylcyclohex-2-ene-1,4-diones, particularly, 2,6,6-trimethylcyclohex-2-ene-1,4-dione (ketoisophorone, KIP).
As a catalyst, a protonic acid or a Lewis acid may be employed. As a protonic acid, there may be exemplified inorganic acids (e.g., sulfuric acid, hydrochloric acid, phosphoric acid, fluoroboric acid and hydrof luoric acid), organic acids (e.g., sulfonic acids such as p-toluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid and ethanesulfonic acid; halocarboxylic acids or halogen-containing carboxylic acids such as chloroacetic acid, trichloroacetic acid and trifluoroacetic acid; and picric acid), and super strong acids with a Hammett's acidity function H
0
of smaller than −11.93 (e.g., H
2
SO
4
—SO
3
, HF—NbF
5
, HF—TaF
5
, SbF
5
, HF—SbF
5
, SbF
5
—FSO
3
H, FSO
3
H—TaF
5
, SbF
5
—CF
3
SO
3
H). As a Lewis acid, there may be exemplified BF
3
, BF
3
OEt
2
, AlCl
3
, FeCl
3
, ZnCl
2
, TiCl
4
and SnCl
2
.
The amount of the catalyst may be an effective amount according to reaction conditions. For example, the amount may be about 0.001 to 100 parts by weight, preferably about 0.01 to 10 parts by weight, and more preferably about 0.1 to 5 parts by weight relative to 100 parts by weight of a substrate shown by the formula (3) (e.g., KIP).
The catalyst may be used as a solid catalyst (in particular, a solid acid catalyst). As a solid acid catalyst, there may be exemplified strong acidic ion-exchange resins (e.g., non-porous or porous ion-exchange resins containing a sulfonic acid group), super
Shibata Hikaru
Takahashi Ikuo
Birch & Stewart Kolasch & Birch, LLP
Daicel Chemical Industries Ltd.
Killos Paul J.
Oh Taylor V.
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