JPH075504B2 - Method for producing 3,5-dialkyl-4-hydroxy aromatic carbonyl compound - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention oxidizes alkyl-substituted phenols to give 3,5-
The present invention relates to a production method for producing a dialkyl-4-hydroxy aromatic carbonyl compound.

Technical Background of the Invention and Problems Thereof When an alkyl-substituted phenol represented by the following formula [I] is oxidized under a specific condition, an oxidative coupling reaction results in the following formula [II] and the following formula [III]. It is known that various biphenols and diphenoquinones represented by the following formula [IV] are produced. At this time, as a by-product, 3,5-dialkyl-4 represented by the following formula [V] is produced.
-A hydroxy aromatic carbonyl compound (hereinafter sometimes referred to as an aromatic carbonyl compound) has been obtained.

In the above formula, R ₁ and R ₂ are an alkyl group having 1 to 6 carbon atoms, and R ₃ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

The aromatic carbonyl compound represented by the above formula [V] is expected to be used as a polymer raw material, but as described above, when an alkyl-substituted phenol is oxidized under normal conditions, a biphenol and a diphenoquinone are obtained. Are mainly produced, and very little aromatic carbonyl compound is produced.

Therefore, by oxidation of alkyl-substituted phenols,
Attempts have been made to selectively produce an aromatic carbonyl compound represented by the above formula [V] in a high yield. For example, Journal of Org. Chem. 30 , 989 (1965) describes alkyl-substituted phenols. The oxidation reaction of
-Dichloro-5,6-dicyano-p-benzoquinone (DDQ)
It has been reported that aromatic aldehydes can be obtained by carrying out the reaction with. However, in this method, a special oxidant such as DDQ is used, and there is a problem that an aromatic carbonyl compound cannot be industrially produced.

Bull.of.Chem.Soc.of Japan 52 , (2) 631 (197
9) includes the oxidation reaction of alkyl-substituted phenols with silver,
It has been reported that an aromatic carbonyl compound can be obtained in a yield of 60 to 80% by using an acetate of a metal such as palladium or copper as a catalyst. However, even in this method, an expensive precious metal salt is used as a catalyst,
Moreover, there is a problem that the yield of the aromatic carbonyl compound is not necessarily high.

The present inventors have conducted diligent studies to oxidize alkyl-substituted phenols to produce aromatic carbonyl compounds in high yield, and found that in the reaction for producing biphenols and diphenoquinones by oxidation of alkyl-substituted phenols, The inventors have found that an aromatic carbonyl compound can be obtained in a high yield by using the solvent system described in 1. above and completed the present invention.

OBJECT OF THE INVENTION The present invention is intended to solve the problems associated with the prior art as described above, and to obtain a 3,5-dialkyl-4-hydroxyaromatic carbonyl compound from an alkyl-substituted phenol in a high yield. It is intended to provide a way to obtain.

SUMMARY OF THE INVENTION The method for producing a 3,5-dialkyl-4-hydroxyaromatic carbonyl compound according to the present invention is a method for producing a 2,4,6-trialkylphenol represented by the following formula [I] in the presence of a metal salt catalyst and a solvent. It is oxidized below and is represented by the following formula [V]:
In producing a 5-dialkyl-4-hydroxyaromatic carbonyl compound, manganese, iron, copper, as a catalyst,
It is characterized in that a salt of at least one metal selected from the group consisting of cerium, vanadium, molybdenum and palladium is used, and a mixture of an alcohol and a compound having an amide bond is used as a solvent. According to the present invention, since a specific metal salt catalyst is used as a catalyst and a mixture of an alcohol and a compound having an amide bond is used as a solvent, 2,4,6-trialkylphenols are oxidized, From this phenol, a 3,5-dialkyl-4-hydroxyaromatic carbonyl compound is produced with high yield and high selectivity.

In the above reaction, the 3,5-dialkyl-4-hydroxyaromatic carbonyl compound cannot be produced in high yield and high selectivity without using the catalyst and solvent system specified in the present invention.

Detailed Description of the Invention Hereinafter, the method for producing a 3,5-dialkyl-4-hydroxyaromatic carbonyl compound according to the present invention will be specifically described including Examples.

The alkyl-substituted phenols used as a raw material in the present invention are represented by the following general formula [I].

(In the formula, R ₁ and R ₂ may be the same or different and each is an alkyl group having 1 to 4 carbon atoms, and R ₃ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.) Specific examples of the alkyl-substituted phenols represented by the above general formula [I] include 2,4,6-trimethylphenol, 2,6-diethyl-4-methylphenol, and 2,6-diisopropyl-4-methyl. Phenol, 2,6-di-n-propyl-methylphenol, 2,6-di-tert-butyl-
4-methylphenol (BHT), 2,6-di-tert-amyl-4-methylphenol, 2,6-di-cyclohexyl-
4-methylphenol, 2,4,6-triethylphenol, 2-ethyl-4,6-dimethylphenol, 2-isopropyl-2,6-dimethylphenol, 2,6-diphenyl-4-methylphenol, 2, 4,6-triethylphenol, 2,6-dimethyl-4-ethylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,6-dimethyl-4-n-propylphenol and the like are exemplified. .

Metal Salt Catalyst In the present invention, the alkyl-substituted phenols as described above are oxidized in the liquid phase in the presence of a metal salt catalyst and a solvent to obtain a 3,5-dialkyl-4-hydroxyaromatic carbonyl compound. As the metal salt catalyst used at this time, a salt of at least one metal selected from the group consisting of manganese, iron, copper, cerium, vanadium, molybdenum and palladium is used.

The types of metal salts include halides of the above metals, basic halohydroxides, carboxylates, hydrochlorides, nitrates, sulfates, carbonates, basic carbonates, hydroxides, chlorates, and acetylacetone. Examples include salt.

Specific examples of halides include manganese chloride, iron chloride, cerium chloride, vanadyl chloride, molybdenum chloride,
Examples include palladium chloride, copper chloride, manganese bromide, iron bromide, copper bromide, copper iodide and the like.

Specific examples of the carboxylate include manganese acetate, iron acetate, copper acetate, molybdenum acetate, cerium acetate, palladium acetate, iron benzoate, copper benzoate, vanadyl oxalate, manganese oxalate and the like.

As nitrates, specifically manganese nitrate, cerium nitrate,
Examples thereof include palladium nitrate and copper nitrate, and examples of sulfates include manganese sulfate, iron sulfate, vanadyl sulfate, palladium sulfate, and copper sulfate.

Examples of the basic carbonate include CuCO ₃ —Cu (OH) ₂ , and examples of the chlorate include Cu (ClO ₃ ) ₂ . Other acetylacetone salts include manganese acetylacetonate, iron acetylacetonate, palladium acetylacetonate, molybdenum acetylacetonate, molybdenum acetylacetonate, and the like. In addition,
These compounds are preferably used in a dry state, but those having water of crystallization or those having absorbed moisture can be sufficiently used. Further, the above compounds may be used in combination of plural kinds.

Among the above metal salt catalysts, halides, nitrates, acetates,
Preference is given to using sulfates and acetylacetone salts.

The above metal salt catalyst is usually used in an amount of 0.005 to 1 part by mole relative to 1 part by mole of the starting phenol.

Solvent In the present invention, a mixture of an alcohol and a compound having an amide bond is used as a solvent in the oxidation reaction of alkyl-substituted phenols using the above metal salt catalyst.

Examples of alcohols used in the present invention include aliphatic alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol and hexanol, alicyclic alcohols such as cyclohexanol and cycloheptanol, and benzyl alcohol. , Aromatic alcohols such as phenethyl alcohol,
Are used.

The compound having an amide bond used with the above alcohols in the present invention includes not only so-called amide compounds, but also urea compounds (-NHCONH-) or imide compounds (-CONHCO-).

A compound having an amide bond in this molecule is easy to handle.
It is preferably a liquid at a temperature of 100 to 200 ° C., and is preferably one which is not easily oxidized in the presence of oxygen.

As the solvent satisfying all such conditions, it is preferable that all nitrogen atoms contained in the amide bond are substituted with a substituent other than hydrogen, that is, a so-called tertiary amine. In this case, the N-substituent is preferably a lower aliphatic hydrocarbon group, an alicyclic hydrocarbon group or an aromatic hydrocarbon group.

Specific examples of the compound having an amide bond in the molecule as described above include the following compounds.

N, N-dimethylformamide, N, N-diethylformamide, N, N-dipropylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylpropioamide, formpiperidine, formpyrrolidine , Acetylpiperidine, acetylpyrrolidine, formanilide, N-methylacetanilide, acetylpyridine, N-methylformtoluide, acetotoluide, dimethylbenzamide, tetramethylurea, N, N-dimethyltolylurea, succinimide, glutarimide, phthalimide and the like.

Of these, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, tetramethylurea and the like are particularly preferable.

As described above, in the present invention, a mixture of alcohols and a compound having an amide bond is used as a solvent, and the alcohols (A) and the compound (B) having an amide bond are:
A / B is used in a weight ratio of 1 to 30, preferably 2 to 20.

Alcohols (A) and amide bond-containing compounds (B)
And a weight ratio A / B of less than 2 is represented by the bis (3,5-dialkyl-4hydroxyphenyl) alkanes and the above general formulas [III] and [IV] in which the alkanes are further oxidized. It is not preferable because a large amount of the compound is generated. On the other hand, when the weight ratio A / B exceeds 30, the production rate of aromatic aldehydes decreases, and it takes a long time to complete the reaction. Further, it is not preferable to use an excessive amount of alcohol because it is uneconomical.

The mixed solvent of such an alcohol and a compound having an amide bond in the molecule is usually 0.1 to 100 parts by mole, preferably 5 to 50 parts by mole with respect to 1 part by mole of the starting alkyl-substituted phenol. Used.

Reaction Conditions The oxidation reaction of alkyl-substituted phenols is carried out using the catalyst and solvent as described above, the reaction temperature is usually 0 to 200 ° C., preferably 30 to 150 ° C., and the reaction time varies greatly depending on the reaction temperature. However, it is usually about 0.5 to 10 hours.

The above-mentioned oxidation reaction of alkyl-substituted phenols is carried out in the presence of oxygen. As oxygen introduced into the reaction system, pure oxygen, air or an oxygen-containing gas obtained by diluting oxygen with an inert gas such as nitrogen is used.

The above reaction is usually performed under normal pressure or increased pressure. When the reaction is carried out under normal pressure, oxygen is introduced into the reaction system by bubbling pure oxygen or an oxygen-containing gas into the reaction solution, while when the reaction is carried out under pressure, pure oxygen or oxygen-containing gas is introduced. Oxygen can be introduced into the reaction system by, for example, injecting a gas into the reaction system.

The oxidation reaction of the alkyl-substituted phenols according to the present invention,
It can be carried out either continuously or batchwise.

Specific examples of 3,5-dialkyl-4-hydroxy aromatic carbonyl compounds obtained by the oxidation reaction of alkyl-substituted phenols according to the present invention include 3,5-dimethyl-4-hydroxybenzaldehyde and 3,5-diethyl-4-hydroxy. Benzaldehyde, 3,5-diisopropyl-4-hydroxybenzaldehyde, 3,5-di-n-propyl-4-
Hydroxybenzaldehyde, 3,5-di-ter-butyl-
3,5-dialkyl-4-hydroxybenzaldehydes such as 4-hydroxybenzaldehyde, 3,5-di-tert-amyl-4-hydroxybenzaldehyde, 3,5-
3,5-Dicycloalkyl-4-hydroxybenzaldehydes such as dicyclohexyl-4-hydroxybenzaldehyde, 3,5-dimethyl-4-hydroxyacetophenone, 3,5-diethyl-4-hydroxyacetophenone, 3,5-diisopropyl- 4-hydroxyacetophenone, 3,5-di-tert-butyl-4-hydroxyacetophenone, 3,5-dimethyl-4-hydroxyphenylethylketone, 3,5-di-tert-butyl-4-hydroxyphenylethylketone, etc. 3,5-dialkyl-4-hydroxyphenylalkylketones can be exemplified.

In the present invention, after the reaction is completed, the product 3,5-dialkyl-4-hydroxyaromatic carbonyl compound can be separated from the reaction mixture as follows. That is, after removing alcohols and compounds having an amide bond, which are solvents, from the reaction mixture by distillation or the like, water and an organic solvent that is incompatible with water are added to the reaction mixture as an extractant, and the aqueous phase and the oil phase are separated. Two phases,
The product 3,5-dialkyl-4-hydroxyaromatic carbonyl compound is separated into an oil phase and the catalyst into an aqueous phase by an extractant. This extraction operation is usually performed at 0 to 95 ° C, preferably 20 to 90 ° C. The organic solvent as an extractant includes aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, mesitylene, propylbenzene, and cymene, ketones such as methylisobutylketone and diisopropylketone, chlorobenzene, dichlorobenzene, and chloroform. , Halogenated hydrocarbons such as carbon tetrachloride, and cyclic ethers such as tetrahydrofuran can be used.

Water and an organic solvent as the extractant are usually added in an amount of 10 to 10 parts by weight based on 1 part by weight of the reaction mixture into which the extractant is converted.
The amount of 100 parts by weight and the organic solvent is usually used in the amount of 10 to 100 parts by weight.

The catalyst extracted in the aqueous phase can be recovered from the aqueous phase and reused if necessary.

On the other hand, the 3,5-dialkyl-4-hydroxyaromatic carbonyl compound extracted in the oil phase can be precipitated from the oil phase by cooling the oil phase. The aromatic carbonyl compound precipitated from the oil phase can be increased in purity by repeating recrystallization as necessary. Further, the unreacted raw material phenols can be recovered by distilling the crystallization mother liquor after the aromatic carbonyl compound is deposited, and can be reused.

Effects of the Invention According to the present invention, a specific metal salt catalyst is used as a catalyst,
Further, since a mixture of alcohols and a compound having an amide bond is used as a solvent to oxidize 2,4,6-trialkylphenols, the yield of these phenols is 3,5- A dialkyl-4-hydroxyaromatic carbonyl compound is produced.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 1.0 g of cuprous chloride (CuCl) and 10 g of 2,4,6-trimethylphenol were placed in a flask (reactor) into which 30 g of N, N-dimethylformamide and 150 g of methanol were introduced, and the mixture was heated to the reflux temperature of methanol. The temperature was raised. Air was bubbled into the solution while controlling the flow rate of 150 ml / min while stirring at a speed of 500 rpm. The gas containing the solvent discharged from the flask and the produced water was degassed after cooling and then returned to the reactor to continue the reaction.

After reacting for 8 hours, the reaction solution was analyzed by gas chromatography (filler OV-17). As a result, the conversion of 2,4,6-trimethylphenol was 100 mol% and the selectivity of the product was shown in Table 1. It was the street.

Next, the solvent methanol and N, N-dimethylformamide were distilled off from the reaction mixture, 100 ml of acetic acid water and 100 ml of methyl isobutyl ketone were added to the reaction mixture as an extract, and the oil phase and water were added at 60 ° C. Separated into phases, the catalyst dissolved in the reaction mixture was separated into the aqueous phase. Further, the oil phase was washed with 400 ml of water and then methyl isobutyl ketone was removed by distillation to give 3,5-dimethyl-4-
Crude crystals of hydroxybenzaldehyde were obtained. Next, by crystallization with toluene, the purity of 99% or more of 3,
7.3 g of 5-dimethyl-4-hydroxybenzaldehyde was obtained.

Example 2 Example 1 was repeated except that isopropanol was used instead of methanol and the reaction was carried out at the reflux temperature of isopropanol.

The results are shown in Table 2.

Example 3 The procedure of Example 1 was repeated, except that tertiary butanol was used instead of methanol and the reaction was carried out at a temperature of 80 ° C. for 6 hours.

The results are shown in Table 2.

Example 4 Example 1 was repeated except that cyclohexanol was used instead of methanol and the reaction was carried out at 80 ° C.
Same as.

The results are shown in Table 2.

Example 5 The procedure of Example 1 was repeated, except that n-octyl alcohol was used instead of methanol and the reaction was carried out at 80 ° C.

The results are shown in Table 2.

Example 6 Table 2 shows the results of the same reaction as in Example 1 except that the amount of N, N-dimethylformamide was changed to 10 g.

Example 7 In Example 1, 10 g of N, N-dimethylformamide,
The procedure of Example 1 was repeated, except that the reaction was carried out with 30 g of memethanol.

The results are shown in Table 2.

Example 8 Same as Example 1 except that 3.0 g of ferrous manganese acetate was used instead of cuprous chloride.

The results are shown in Table 2.

Example 9 The procedure of Example 1 was repeated except that 2,6 di-tert-butyl-methyl 4-methylphenol was used instead of 2,4,6-trimethylphenol in Example 1.

The results are shown in Table 2.

Example 10 The procedure of Example 1 was repeated, except that 2,6 di-tertiary-butyl 4-methylphenol was used instead of 2,4,6-trimethylphenol in Example 1. Raw material conversion rate is 100% and selectivity is 30% with 3,5-di-tert.
-Butyl-4-hydroxy-acetophenone was formed.

The results are shown in Table 2.

Comparative Example 1 Example 1 was repeated except that the reaction was carried out for 3 hours under reflux of triene instead of methanol.

The results are shown in Table 2.

Comparative Example 2 The procedure of Example 1 was repeated, except that the reaction was carried out at 100 ° C. for 2 hours without using methanol and using a single solvent of N, N-dimethylformamide.

The results are shown in Table 2.

Comparative Example 3 The procedure of Example 1 was repeated, except that the reaction was carried out for 5 hours at the reflux temperature of methanol using a single solvent of methanol without using dimethylformamide.

The results are shown in Table 2.

Comparative Example 4 The procedure of Example 1 was repeated, except that 2,4-dimethylphenol was used instead of 2,4,6 trimethylphenol in Example 1.

The results are shown in Table 2.

Comparative Example 5 In Example 1, except that P-cresol was used instead of 2,4,6-trimethylphenol to carry out the reaction.
Same as Example 1.

The results are shown in Table 2.

Claims (4)

[Claims] 1. A 3,5-dialkyl-formula represented by the following general formula [V] is obtained by oxidizing a 2,4,6-trialkylphenol represented by the following formula [I] in the presence of a metal salt catalyst and a solvent. In producing a 4-hydroxyaromatic carbonyl compound, a salt of at least one metal selected from the group consisting of manganese, iron, copper, cerium, vanadium, molybdenum, and palladium is used as a catalyst, and alcohols and amides are used as solvents. A method for producing a 3,5-dialkyl-4-hydroxyaromatic carbonyl compound, which comprises using a mixture with a compound having a bond: (In the formula, R ₁ and R ₂ are an alkyl group having 1 to 6 carbon atoms, and R ₃ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.) 2. The method according to claim 1, wherein the alcohols are methanol and ethanol. 3. A compound having an amide bond is N, N-dimethylformamide, N, N-diethylformamide, N, N-
The method according to claim 1, which is dimethylacetamide or tetramethylurea. 4. The method according to claim 1, wherein the weight ratio (A / B) of the alcohol (A) and the compound (B) having an amide bond is 1 to 30.