JPS6317048B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing aromatic polycarboxylic acid esters. The present invention relates to a novel method for producing aromatic polycarboxylic acid esters, which involves reacting alcohols and replacing halogen atoms with carboxylic acid esters.

Aromatic polycarboxylic acids, like trimellitic anhydride, are used as plasticizers, heat-resistant paints, and as raw materials for polyamide-imide resins that have excellent heat resistance and mechanical and electrical properties. Similarly, pyromellitic acid has excellent heat resistance. It is used as a curing agent for epoxy resins to improve its properties, and as a raw material for polyimide resins with excellent mechanical properties and heat resistance, each of which occupies an important position, and in recent years has seen a lot of demand.

Conventionally, as a manufacturing method of aromatic polycarboxylic acid,
What is used industrially is the oxidation of polyalkyl aromatic compounds by gas phase or liquid phase methods.
These methods have problems such as isomers being produced as by-products during raw material synthesis, and oxidized by-products produced during oxidation, which require purification operations to remove them.

On the other hand, recently, a method of introducing a carboxyl group by substitution with a halogen without oxidizing the alkyl group has been carried out using various transition metal catalysts. The reaction involves adding carbon monoxide, a base, and an alcohol to a monohalogenated aromatic compound, such as iodobenzene, in the presence of a catalyst to obtain a benzoic acid ester. Furthermore, regarding the introduction of a carboxylic acid or its ester into a halogenated aromatic compound in which a halogen atom or a carboxylic acid ester is substituted at the para-position of the halogen, regarding the carboxylic acid substitution of para-dibromobenzene,
L.Cassar(J.Organo metal.Chem121C55,
(1976)) and RF
It has been reported by Heck (J.Org.Chem.39(23)318 (1974)). However, when introducing a carboxylic acid into a polysubstituted aromatic compound, unlike in the case of para-substituted halogenated benzenes, interactions occur between substituents at the ortho or meta positions, resulting in a change in reactivity. The catalyst was susceptible to deterioration, and substitution of halogen with carboxyl group was difficult. Therefore, no examples of halogenated aromatic compounds having three or more non-alkyl substituents on the aromatic ring have been reported.

The present inventors have developed a method for producing aromatic polycarboxylic acids that does not have the problems of conventionally known methods.
As a result of intensive research into a significantly improved method, the method of the present invention was discovered.

That is, the method of the present invention involves reacting a halogen-substituted aromatic compound with carbon monoxide, a base, and an alcohol in the presence of a palladium-containing catalyst to form an aromatic polycarboxylic acid ester that introduces a carboxylic acid ester into the halogen position. This is the manufacturing method.

The halogen-substituted aromatic compound used in the method of the present invention has the general formula () (In the formula, X represents a halogen atom, Y represents a halogen atom, and -COOR (here, R is hydrogen, an alkyl, or an aryl group). m is an integer from 2 to 5.)
A compound represented by, for example, 1, 2,
4-triiodobenzene, 1,2,4-tribromobenzene, 1,2,4,5-tetrabromobenzene, 2-iodoterephthalic acid, 2-iodoterephthalic acid dimethyl ester, 2-bromoterephthalic acid, 2, 5-dibromoterephthalic acid, 2,5-
Dibromoterephthalic acid dimethyl ester, 5-iodo-1,2,4-trimellitic acid trimethyl ester, 5-bromo-1,2,4-trimellitic acid trimethyl ester, 5-chloro-1,2,4
-Compounds such as trimellitic acid trimethyl ester.

The catalyst used in the method of the invention is also a palladium-containing catalyst.

These metals may be used themselves, various inorganic acid salts, organic acid salts, or complexes thereof, or supported on a carrier such as carbon, polymer, alumina, silica, etc. . Particularly preferred is the case where a palladium salt and an organic phosphine, an organic phosphite, or pyridine are used together, and in this case, if tolphenylphosphine or the like is used in excess of the amount required for complex formation, deterioration of the catalyst is prevented, and the reaction is smooth and smooth. Proceed under mild conditions.

The carbonylation reaction in the present invention proceeds at normal pressure or increased pressure of carbon monoxide, but the reaction is very slow at normal pressure, and the reaction proceeds quickly under increased pressure, improving the yield. The reaction is carried out under pressure of 2 to 300 atmospheres. Any base can be used as long as it can neutralize the hydrogen halide produced by carbonylation. For example, metal hydroxides such as sodium hydroxide, potassium hydroxide, calcium hydroxide, aluminum hydroxide, lithium hydroxide, weak acids such as sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, lithium carbonate, and sodium acetate. salts, metal alkoxides such as sodium methylate and sodium ethylate, sodium hydride, alkyl amines represented by NHR ₂ or NR ₃ (R represents methyl, ethyl, propyl, or butyl group), organic compounds such as pyridine, quinoline, etc. They are amines. For example, if a hydroxide such as potassium hydroxide is used as a base, the product will be obtained as a carboxylic acid salt after carbonylation, and if a trialkylamine such as triethylamine is used as a base and the required amount of alcohol is coexisting, the product will be obtained as a carboxylic acid salt. , obtained as an ester of carboxylic acid. The alcohol used is preferably an aliphatic alcohol, and methanol and ethanol are often used.

If the halogen-substituted aromatic compound as a starting material is liquid, the reaction will proceed even without a solvent, but if it is solid, water or various organic solvents are required. and paraffins such as pentane, hexane, and cyclohexane, ethers such as tetrahydrofuran and diethyl ether, alcohols such as methanol and ethanol, and other polar organic solvents such as dimethylformamide, dimethylsulfoxide, and hexamethylphosphoramide. .

The reaction proceeds between room temperature and 300℃,
Particularly preferably from 50 to 50 in terms of reaction rate and selectivity.
The temperature is 150℃.

The advantages of the present invention are that in the synthesis reaction of aromatic polycarboxylic acid esters from halogen-substituted aromatic compounds, the reaction is rapid, has a high yield, is selective, and produces significantly less by-products such as isomers. , the deterioration of the catalyst can be prevented.

The present invention will be explained below using examples.

Example 1 Dissolve 5 g of 1,2,4-tribromobenzene in 50 ml of benzene, add 5 g of methanol and 10
g of tri-n-butylamine, 50 mg of palladium acetate, and 0.50 g of triphenylphosphine were added, and the mixture was placed in an autoclave. Carbon monoxide was then pressurized to 10 atm, and the autoclave was heated to 110°C with stirring. After 6 hours, the mixture was cooled and the contents were taken out. The reaction mixture was washed three times with 20 ml of 15% aqueous hydrochloric acid to remove the amine hydrobromide salt and excess amine, and the benzene layer was washed with saturated aqueous sodium bicarbonate and water to remove hydrogen chloride. Benzene was distilled off from this solution under reduced pressure, the solution was dissolved in ethanol, and the insoluble catalyst was filtered off. The ethanol solution of the filtrate was concentrated to obtain 3.4 g of trimellitic acid trimethyl ester. Yield 86%.

Example 2 1,2,4,5-tetrabromobenzene 5.0g
was dissolved in 50 ml of toluene, 7.0 g of ethanol, 10 g of sodium carbonate, 60 mg of palladium acetate and 0.60 g of triphenylphosphine were added thereto, and the mixture was placed in an autoclave. Add 20 carbon monoxide to this
Press the autoclave up to atmospheric pressure, and while stirring the autoclave.
It was heated to 120°C, cooled after 8 hours, and the contents were taken out. The reaction mixture was treated in the same manner as in Example 1 to obtain 3.6 g of pyromellitic acid tetraethyl ester.
was obtained, yield 78%.

Example 3 Dissolve 5.0 g of 2,5-dibromo-terephthalic acid dimethyl ester in 50 ml of methanol, and add
3.2 g triethylamine, 0.10 g dichlorbis-triphenylphosphine palladium () and
0.37 g of triphenylphosphine was added and placed in an autoclave. This was heated to 120° C. with stirring, cooled after 6 hours, and the contents were taken out.
Methanol was distilled off from this solution under reduced pressure, and again
Dissolve in 50ml benzene. The resulting solution was treated in the same manner as in Example 1 to obtain 4.2 g of pyromellitic acid tetramethyl-ester. Yield 96%.

Example 4 1.0 g of 5-bromo-1,2,4-trimellitic acid trimethyl ester was dissolved in 10 ml of tetrahydrofuran, and 0.5 g of methanol and 0.34 g of it were dissolved in 10 ml of tetrahydrofuran.
of triethylamine and 30 mg of dichlorbis(tri-n-butylphosphine)palladium ()
was added and placed in an autoclave. The reaction was carried out in the same manner as in Example 3 to obtain 0.48 g of pyromellitic acid tetramethyl ester. Yield 52%.

Example 5 2-iodo-terephthalic acid dimethyl ester
2.0g and 1.0g tripropylamine and 60mg
of diiodobistriphenylphosphine-palladium () was added to 20 ml of methanol and placed in an autoclave. Thereafter, this was reacted in the same manner as in Example 3 and isolated to obtain 1.5 g of trimellitic acid trimethyl ester. Yield 94%.

Example 6 2.0 g of 5-iodo-1,2,4-trimellitic acid trimethyl ester, 0.84 g of tripropylamine, 50 mg of diiodobistriethylphosphine impardium () and 1.0 g of methanol are dissolved in 10 ml of dimethylformamide. In addition, the reaction was carried out in the same manner as in Example 3, and 1.5 g of pyromellitic acid tetramethyl ester was obtained. yield
92%.

Example 7 2.0 g of 5-chloro-1,2,4-trimellitic acid trimethyl ester, 1.4 g of tri-n-butylamine, 30 mg of palladium acetate, and 70 mg of triphenylphosphine were added to 20 ml of methanol and placed in an autoclave. Ta. While stirring this
It was heated to 140°C, cooled after 24 hours, and the contents were taken out. This was isolated in the same manner as in Example 3,
0.73 g of pyromellitic acid tetramethyl ester was obtained. Yield 34%.

Example 8 2.0 g of 3-iodo-phthalic acid dimethyl ester
30 mg of palladium acetate and 0.60 g of pyridine were added to 20 ml of methanol and placed in an autoclave. This was then reacted and isolated in the same manner as in Example 3 to obtain 1.2 g of 1,2,3-benzenetricarboxylic acid trimethyl ester. Yield 75%.

Example 9 1,2,4,5-tetrabromobenzene 5.0g
and 10 g of tri-n-butylamine and 0.10 g of dibrombistrifhenylphosphine palladium () were added to 50 ml of methanol and placed in an autoclave. Carbon monoxide was pressurized to 30 atm, and the autoclave was heated to 100°C while stirring.
After a period of time, it was cooled and the contents were taken out. The reaction mixture was then isolated in the same manner as in Example 3 to obtain 2.6 g of pyromellitic acid tetramethyl ester. Yield 66
%.

Comparative Example 1 3.7g of methyl parabromobenzoate, 3.5g of tri-n-butylamine, 1.6g of n-butanol,
56 mg of palladium acetate and 130 mg of triphenylphosphine are stirred at 100° C. for 24 hours in carbon monoxide at normal pressure. After cooling, the reaction mixture was washed twice with 15% aqueous hydrochloric acid and then with saturated sodium bicarbonate and water to remove the amine and halogen acid. This was distilled under reduced pressure to obtain 3.1 g of methyl terephthalate n-butyl diester. Yield 77%.

Comparative Example 2 In the method carried out in Comparative Example 1, 3.7 g of methyl ortho-bromobenzoate was used instead of methyl para-bromobenzoate, and the reaction was carried out in the same manner as in Comparative Example 1 except for the reaction, and the resulting ester was transferred to a silica gel column. IR,
As identified by NMR gas chromatography, methyl phthalate-n-butyl diester was obtained in a yield of 2%.

Claims (1)

[Claims] 1 General formula (1), (In the formula, X represents a halogen atom, Y represents a halogen atom, and -COOR (here, R represents hydrogen, an alkyl, or an aryl group). m is an integer from 2 to 5.)
A method for producing an aromatic polycarboxylic acid ester, which comprises reacting a halogen-substituted aromatic compound represented by the formula with carbon monoxide, a base, and an alcohol in the presence of a palladium-containing catalyst.