JPS6236019B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is based on the general formula The present invention relates to a method for producing benzoquinones represented by the formula (wherein R ¹ , R ² , R ³ and R ⁴ are hydrogen or an alkyl group). More specifically, in the present invention, in the presence of a catalyst comprising ruthenium and an alkaline earth metal supported on a carrier, (In the formula, R ¹ , R ² , R ³ and R ⁴ are the same as above.) A benzoquinone represented by the above general formula () is produced by reacting a phenol represented by the above with hydrogen peroxide. It is about the method. Benzoquinones represented by the general formula () are widely used as fragrances, pharmaceuticals, etc., or raw materials for their production, as typified by trimethylbenzoquinone, which is a raw material for producing tocopherols. In order to produce benzoquinones represented by the above general formula () by hydrogen peroxide oxidation of phenols represented by the above general formula (), a homogeneous oxidation method using a ruthenium chloride catalyst and a heterogeneous oxidation method using a ruthenium-carbon catalyst are used. The system oxidation method (Ito, Aihara, Matsumoto, 16th Oxidation Reaction Conference Abstracts p112 1982, Kyoto) is known as a typical method. but,
In the homogeneous oxidation method using a ruthenium chloride catalyst, it is difficult to efficiently recover the catalyst. Furthermore, when a ruthenium-carbon catalyst is used, there are disadvantages such as poor selectivity for producing the desired benzoquinone and the need for complicated operations when isolating the target product. The present inventors have discovered that by adding an alkaline earth metal to ruthenium supported on a carrier, secondary reactions of benzoquinones and hydroquinones to be produced can be suppressed and benzoquinones can be produced in good yield, and the present invention has been completed. did. Examples of the phenols represented by the general formula () that are raw materials of the present invention include cresol, xylenol, trimethylphenol, and tetramethylphenol. On the other hand, hydrogen peroxide that is commercially available as an aqueous solution may be used, and a concentration of about 30% is sufficient. The present invention is carried out in the presence of a catalyst comprising ruthenium and an alkaline earth metal supported on a carrier. Examples of the ruthenium constituting the catalyst of the present invention include ruthenium chloride, ruthenium bromide, μ ₃ -oxotriruthenium complex, ruthenium phosphine complexes such as triphenylphosphine ruthenium dichloride, triphenylphosphine hydridoruthenium, and ruthenium carbonyl complexes. can be used by being supported on a carrier by the reduction-supporting method normally employed in this type of field. The amount of ruthenium supported is 0.5 to 20 wt% based on the carrier used. Examples of alkaline earth metals constituting the catalyst of the present invention include magnesium, calcium, strontium, and barium, which can be supported on a carrier by impregnation with hydroxide, acetate, chloride, etc. can. The amount of alkaline earth metal supported is 0.02 to 2 equivalents relative to ruthenium.
Supports include activated carbon, silica gel, alumina,
Supports commonly used in catalytic reactions, such as diatomaceous earth, can be used. The catalyst can be prepared by supporting the ruthenium on a carrier and then supporting an alkaline earth metal. For example, the catalyst may be prepared by supporting an alkaline earth metal on commercially available ruthenium-activated carbon. The present invention is preferably carried out in a solvent, and for example, a mixture of a carboxylic acid such as acetic acid or formic acid, or a saturated alcohol such as methanol or ethanol, and a mineral acid such as hydrochloric acid can be used. Also, the reaction is 0
The reaction proceeds at a temperature of 100°C to 100°C, but a temperature range of 20 to 60°C is preferred in order to obtain the desired product in good yield. Incidentally, the catalyst of the present invention can be used repeatedly. Hereinafter, the present invention will be explained in more detail with reference to Examples. Reference example 1 g of 5% ruthenium-carbon powder (manufactured by Nippon Engelhard Co., Ltd.) was added to a pure aqueous solution (15 ml) of barium hydroxide (31 mg) under an argon gas atmosphere.
The mixture was heated to reflux for an hour. After cooling, it was filtered, and the carbon powder was washed with pure water until the filtrate became neutral, and dried under reduced pressure at room temperature. When the catalyst thus prepared was subjected to X-ray fluorescence analysis, the characteristic spectral intensity Ba (L
α)/Ru(Kα)=0.36. Example 1 500 mg of 2,3,6-trimethylphenol and 30 mg of the catalyst prepared in Reference Example were added to 5 ml of acetic acid, and then 1 g of 30% hydrogen peroxide was added at room temperature, followed by stirring for 6 hours. After the reaction was completed, the catalyst was filtered off, and the acetic acid solution was washed with NaHCO ₃ water and extracted with ether.
After drying with MgSO ₄ and concentrating, the residue was applied to a silica gel column and flushed with dichloromethane to obtain 515 mg of trimethylbenzoquinone (yield 94
%) was obtained. The physical properties of the product [yellow needle crystals (from hexane), melting point 28°C] are based on literature values [Org.
Syn.52, 83 (1972)]. Example 2 600 mg of the catalyst prepared in Reference Example and 2,3,6-
10 g of trimethylphenol was added to 90 ml of acetic acid.
While cooling the solution with ice water, add 30% hydrogen peroxide 20
g was added dropwise over about 40 minutes, and the mixture was further stirred overnight. After the reaction, the catalyst was filtered off, the acetic acid solution was concentrated under reduced pressure to about 20 ml, diluted with ether, and NaHCO ₃
After washing with an aqueous solution, it was dried. The residue obtained by distilling off the ether was distilled under reduced pressure to obtain 8.7 g of trimethylbenzoquinone (boiling point: 64° C./0.7 torr). In addition, by treating the distillation residue with column chromatography (SiO ₂ /CH ₂ CI ₂ ), further
Obtained 0.5g of trimethylbenzoquinone. Total yield: 9.2g (84% yield). Examples 3 to 7 30 mg of Ru-Ba/C catalyst prepared by the same procedure as in the reference example except that the concentration of barium hydroxide was changed, 500 mg of 2,3,6-trimethylphenol
The reaction was carried out at room temperature using 5 ml of acetic acid and 1 g of 30% hydrogen peroxide solution. The results are shown in the table below. In addition, the results of Example 1 are also listed in the table.

[Table] Example 8 Ru prepared in the same manner as the reference example except that 46 mg of calcium hydroxide was used instead of 31 mg of barium hydroxide.
- Using 30 mg of Ca/C catalyst, in the same manner as in Example 1,
When trimethylphenol was oxidized, the yield was 84%.
I obtained trimethylbenzoquinone. Examples 9-11 Ruthenium-alkaline earth metal/carbon catalysts prepared in the same manner as in Reference Example except that 0.18 mmol (31 mg) of barium hydroxide was replaced with the same molar amount of calcium hydroxide, strontium acetate, or magnesium acetate. When 2,3,6-trimethylphenol was oxidized in the same manner as in Example 1 using 30 mg, trimethylbenzoquinone was obtained in the yield shown in the following table.

[Table] Example 12 2,3,5,6-tetramethylphenol instead of 500 mg of 2,3,6-trimethylphenol
When the reaction and treatment were carried out in the same manner as in Example 1 except that 500 mg was used, tetramethylbenzoquinone was obtained with a yield of 55%. Comparative example 2,3,6-trimethylphenol 500mg and 5
Add 30 mg of %ruthenium-carbon powder (manufactured by Nippon Engelhard) to 5 ml of acetic acid, and add 30 mg at room temperature.
% hydrogen peroxide solution was added thereto, and the mixture was stirred for 6 hours. After the reaction was completed, the catalyst was filtered off, and the acetic acid solution was washed with NaHCO ₃ water and extracted with ether. After drying with _MgSO4 , it was concentrated and the residue was applied to a silica gel column.
Elution with dichloromethane gave 419 mg of trimethylbenzoquinone (76% yield). In addition, the product [yellow needle-like crystals (from hexane), melting point
The physical properties at 28°C are the literature values [Org.Syn.52, 83
(1972)].

Claims (1)

[Claims] 1. In the presence of a catalyst consisting of ruthenium and an alkaline earth metal supported on a carrier, the general formula A general formula characterized by reacting phenols represented by hydrogen peroxide with A method for producing benzoquinones represented by [wherein,
R ¹ , R ² , R ³ and R ⁴ are hydrogen or an alkyl group. ].