JPH0153264B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing 4-hydroxy-2,4,6-trimethyl-2,5-cyclohexadien-1-one in high yield by oxidizing 2,4,6-trimethylphenol. 4-hydroxy-2,4,6-trimethyl-
2,5-cyclohexadien-1-one easily undergoes a rearrangement reaction in the presence of a base, resulting in 2,3,6-
Produces trimethylhydroquinone. This 2,
3,6-trimethylhydroquinone is not only used as an antioxidant and polymerization inhibitor, but is also very useful as a raw material for producing vitamin E. 4-hydroxy-2,4,6-trimethyl-
Various methods for producing 2,5-cyclohexadien-1-one have been proposed, including a method in which 2,4,6-trimethylphenol is oxidized with molecular oxygen in an organic solvent using a sarcomine catalyst (e.g. Ger. Offen. 2747497) and a method of oxidizing 2,4,6-trimethylphenol with molecular oxygen in an alkaline aqueous solution (for example, JP-A-50-4044). However, in either method, 2,4,6-trimethylphenol must be of high purity, require expensive reagents, or have sufficiently high selectivity to the desired product. The drawback was that it was difficult to say. The present inventors have conducted various studies in order to overcome the shortcomings of the conventional method for producing 4-hydroxy-2,4,6-trimethyl-2,5-cyclohexadien-1-one, and as a result2,4 When oxidizing ,6-trimethylphenol, the objective 4
-Hydroxy-2,4,6-trimethyl-2,5
It was discovered that the selectivity to -cyclohexadien-1-one was dramatically improved, and the present invention was completed based on this finding. That is, the present invention provides 2,4,6-trimethylphenol with the general formula (In the formula, R ₁ to R ₅ represent a hydrogen atom or a lower alkyl group, and they may be the same or different from each other.)
1 or 2 of (excluding 6-trimethylphenol)
4-, which is characterized by being oxidized in the presence of more than one species.
Hydroxy-2,4,6-trimethyl-2,5-
A method for producing cyclohexadien-1-one is provided. In the method of the present invention, 2,4,6-trimethylphenol used as a raw material may be synthesized by any method. The oxidation reaction of the present invention can be carried out in the presence or absence of a liquid medium, regardless of the reaction method, but is preferably carried out in a liquid medium. Examples of this liquid medium include water, methanol,
Ethanol, n-propanol, i-propanol, n-butanol, i-butanol, t-butanol, carbon tetrachloride, chloroform, acetonitrile, dimethylacetamide, dimethylformamide, acetone, methyl ethyl ketone, cyclohexane, benzene, toluene, etc. Solutions of water and the organic liquid medium described above may also be used. The oxidation reaction can be carried out, for example, by contacting 2,4,6-trimethylphenol dissolved or suspended in a liquid medium with molecular oxygen or a molecular oxygen-containing gas, or by contacting 2,4,6-trimethylphenol dissolved or suspended in a liquid medium. ,6-
This is carried out by dropping hydrogen peroxide into trimethylphenol. In this case, the molecular oxygen or molecular oxygen-containing gas is, for example, at normal pressure to 80
Kg/cm ² G and hydrogen peroxide e.g.
It is used as a hydrogen peroxide solution of about % by weight. This oxidation reaction is preferably carried out under alkaline conditions. The alkaline conditions are not particularly limited, but are preferably adjusted by adding an alkali metal or a compound thereof, or an alkaline earth metal or a compound thereof. The reaction temperature for the oxidation reaction is sufficient if the target 4-hydroxy-2,4,6-trimethyl-2,5-cyclohexadien-1-one is produced but does not decompose or change. 0~80℃
A range of is preferred. If the reaction temperature is less than 0°C, the reaction will not substantially proceed, and if it exceeds 80°C, the selectivity of the target compound will decrease. Also, the reaction time is 10 minutes ~
A range of 5 hours is preferred. used as an additive in the method of the present invention,
Examples of the phenol compound represented by the above general formula include 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 2,3,6-trimethylphenol,
Examples include 2,6-di-tert-butyl-4-methylphenol and 2,4,6-tri-tert-butylphenol. 2 of these compounds
It is also possible to use more than one species in combination. This compound is added not only as a separate additive using purified 2,4,6-trimethylphenol, but also as one of the by-products when it is synthesized into 2,4,6-trimethylphenol. It may also be used in a contained form. In the present invention, the amount of the phenol compound represented by the above general formula added is generally in the range of 0.001 to 100 mol, preferably 0.05 to 10.0 mol, more preferably 0.05 to 10.0 mol, per 1 mol of 2,4,6-trimethylphenol. It ranges from 0.1 to 5.0 moles. In this case, if the amount added is less than 0.001 mol, no substantial effect will be observed, and if it is more than 100 mol, it will not be economical due to an increase in the amount of reaction liquid and an increase in by-products due to oxidation of the additive. This is not preferable because it causes loss. Thus, according to the method of the present invention, 2, 4, 6
- The yield of 4-hydroxy-2,4,6-trimethyl-2,5-cyclohexadien-1-one by oxidation of trimethylphenol can be dramatically improved. Next, the present invention will be explained in more detail based on examples. In each example, parts indicate parts by weight, and % indicates mol%. Compositional analysis of reaction products
This was done by gas chromatography. Examples 1 to 3 and Comparative Examples 1 to 3 100ml of water was placed in a 200ml stainless steel autoclave equipped with a gas inlet, a thermometer, and a stirrer.
part, 3.5 parts of sodium hydroxide and the amounts of 2,4,6-trimethylphenol (hereinafter referred to as
(abbreviated as TMP) and 2,6-xylenol, an oxygen pressure of 30 kg/cm ² G was applied, and the internal temperature was kept at 30°C.
The reaction was carried out for 4.5 hours while stirring vigorously.
After the reaction was completed, the reaction product was taken out and analyzed. The results are shown in Table 1. Note that HTCD in the table indicates 4-hydroxy-2,4,6-trimethyl-2,5-cyclohexadien-1-one.

[Table] Example 4 TMP7.5 in the same autoclave as Example 1
parts, 100 parts of water, 3.5 parts of sodium hydroxide and 2.6 parts
- 7.5 parts of di-tert-butyl-4-methylphenol was added, an oxygen pressure of 30 kg/cm ² G was applied, and the internal temperature was raised to 30°C.
The reaction was carried out for 4.5 hours while stirring vigorously.
When the reaction product was taken out and analyzed, it was found that the TMP conversion rate was 72.2% and the HTCD selectivity was 64.5%. Examples 5 and 6 100 parts of water was added to the same autoclave as in Example 1.
3.5 parts of sodium hydroxide and the amounts of TMP, 2,6-xylenol and 2,6-di-tert-butylphenol shown in Table 2 below were charged, and 30Kg/cm ² G
of oxygen pressure was applied, the internal temperature was maintained at 30°C, and the mixture was reacted for 4.5 hours with vigorous stirring. The reaction products were extracted and analyzed, and the results are shown in Table 2.

[Table] Example 7 TMP10.5 in the same autoclave as Example 1
part, 2,6-xylenol 3.0 parts, 2,6-di-
Add 1.5 parts of tert-butylphenol, 100 parts of water, and 3.5 parts of sodium hydroxide, apply oxygen pressure of 80 kg/cm ² G, keep the internal temperature at 30°C, and stir vigorously.
The reaction was allowed to proceed for 3.5 hours. When the reaction product was taken out and analyzed, the TMP conversion rate was 99.0% and the HTCD selectivity was found to be 99.0%.
It was 67.7%. Examples 8 and 9 and Comparative Examples 4 and 5 1.5 parts of TMP, 0.35 parts of NaOH, 30 parts of water, and 0.2 to 0.3 parts of the additives shown in Table 3 below were charged, and the reaction solution was kept at 50°C. Oxygen was bubbled for 3 hours at normal pressure. The results of extracting and analyzing the reaction products are shown in the third column.
Shown in the table.

【table】

Claims (1)

[Claims] 1 2,4,6-trimethylphenol expressed by the general formula (In the formula, R ₁ to R ₅ represent a hydrogen atom or a lower alkyl group, and they may be the same or different from each other.)
1 or 2 of (excluding 6-trimethylphenol)
4-, which is characterized by being oxidized in the presence of more than one species.
Hydroxy-2,4,6-trimethyl-2,5-
A method for producing cyclohexadien-1-one.