JP3398339B2 - 2-sulfonic acid-4,6-dinitroresorcin and salts thereof and methods for producing them - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to novel intermediates useful in the synthesis of 4,6-diaminoresorcin, which is a monomer of polybenzobisoxazole (PBO), and a process for producing them. PBO fiber is Japanese Patent Publication Sho 61-50
As described in Japanese Patent No. 1452, strength, elastic modulus,
A resin that is superior to conventional products in various physical properties such as heat resistance and chemical resistance, and is expected to be applied to various applications such as structural materials and heat insulating materials as super fiber superior to aramid. is there. 4,6-Diaminoresorcinol is an important raw material because it becomes a monomer of PBO.

[0002]

2. Description of the Related Art As a conventional method for producing 4,6-diaminoresorcin, a method in which resorcin is acetylated and nitrated (Ber. Dtsch. Chem. Ges., 1
6,552,1883), and a method of nitrating 1,3-bis (alkyl carbonate) benzene (JP-A-2-1)
No. 36) and the like to synthesize and reduce the anterior dinitroresorcin.

However, in these methods, a process is complicated because a protecting group is introduced into the hydroxyl group of resorcin, and the protecting group eliminated in the hydrolysis step becomes an unrecoverable by-product. was there.

As a method not using a protecting group, a method using halobenzene as a raw material has been proposed, and a method of nitrating trichlorobenzene (Japanese Patent Application Laid-Open No. 2-50).
No. 0743), and a method of nitrating dihalobenzene and hydrolyzing it with an alkali (JP-A 1-238561, JP-A 7-233127, JP-A 7-316).
No. 102, Japanese Patent Laid-Open No. 8-73417) and the like are known.

However, trichlorobenzene and its nitrates are highly toxic and have the problem of causing skin irritation, and it is not preferable to use the nitrates of halobenzene for the safety of workers.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel intermediate useful for producing 4,6-diaminoresorcinol at low cost and a method for producing the same.

[0007]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that resorcin is sulfonated to give resorcin 2,4,6-trisulfonate, and further 2,4,6. Nitration of resorcinol 6-trisulfonate gives 2-sulfonic acid-4, with high regioselectivity.
The inventors have found that 6-dinitroresorcinol can be obtained, and completed the present invention.

That is, the present invention is as follows. (1) 2-sulfonic acid-4,6-dinitroresorcinol represented by the following formula and salts thereof

[Chemical 2] (In the formula, M represents hydrogen, an alkali metal, or an alkaline earth metal, and n is 1 or 2.) (2) A method for producing 2-sulfonic acid-4,6-dinitroresorcinol, which comprises the following steps. First step of producing resorcin 2,4,6-trisulfonic acid by contacting resorcin with a sulfonating agent, 2-sulfonic acid-4 by contacting resorcin 2,4,6-trisulfonic acid with a nitrating agent ，
Second step to produce 6-dinitroresorcin.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION 2-sulfonic acid according to the present invention
4,6-Dinitroresorcinol or its salt is a substance having the structure shown below.

[Chemical 3] (In the formula, M represents hydrogen, an alkali metal or an alkaline earth metal, n is 1 or 2) Here, sodium or potassium is used as the alkali metal, and magnesium, calcium or barium is used as the alkaline earth metal. .

2-sulfonic acid in the present invention-4,6-
The first step of the method for producing dinitroresorcin is a step of sulfonating resorcin to obtain resorcin 2,4,6-trisulfonate. Here, a known sulfonating agent capable of producing the substance can be used, for example, concentrated sulfuric acid, fuming sulfuric acid, sulfur trioxide, etc. are used. The reaction may be carried out in a suitable solvent, but it is industrially advantageous to carry out the reaction in excess concentrated sulfuric acid or fuming sulfuric acid without using a solvent. In order to prevent desulfonation due to hydrolysis, it is preferable to use concentrated sulfuric acid or fuming sulfuric acid at a concentration of 80 to 100% by weight, more preferably 95% by weight or more of concentrated sulfuric acid or fuming sulfuric acid, and fuming sulfuric acid is used. Is most preferred.
Since the sulfuric acid concentration is lowered by the water generated during the reaction,
The amount of concentrated sulfuric acid or fuming sulfuric acid is 6 at the end of the reaction.
It is preferred to use an amount such that it is 0% by weight or more.
More preferably, the sulfuric acid concentration is 90% by weight or more at the end of the reaction, and most preferably the sulfuric acid concentration is 100% by weight or an excess of SO ₃ is contained at the end of the reaction. The amount depends on the sulfuric acid concentration used, but when considering volumetric efficiency, etc.
It is preferably about 20 times by weight. The reaction can be carried out in any temperature range where the desired substance can be obtained, but the preferable reaction temperature is about 0 ° C to 200 ° C, and more preferably 20
It is about 100 ° C, and most preferably about 40 ° C to 90 ° C.

The second step in the present invention is a step of nitrating 2,4,6-trisulfonic acid resorcinol to obtain 2-sulfonic acid-4,6-dinitroresorcinol. Here, a known nitrating agent capable of producing the compound can be used, and examples thereof include nitric acid, fuming nitric acid, nitrates such as sodium nitrate and potassium nitrate. 2, 4, 6-
Although resorcinol trisulfonate may be isolated and nitrated, it is industrially advantageous to charge the sulfonated mass with a nitrating agent and perform nitration in one pot. The amount of the nitrating agent to be used may be about 1 to 10 mol times with respect to resorcin, and about 2 to 4 mol times is preferable in order to allow the reaction to proceed sufficiently and suppress excessive nitration.

The reaction can be carried out in any temperature range where the desired substance can be obtained. However, if the reaction temperature is too high, the reaction proceeds rapidly and an undesired side reaction occurs. Therefore, the reaction temperature is usually controlled by cooling. While being done. The preferred reaction temperature is about 0 to 80 ° C., more preferably 0.
It is about 50 ° C.

In order to isolate the substance, first, the reaction mass is neutralized with an alkali to form an alkali metal salt or an alkaline earth metal salt, which is then precipitated by salting out to obtain an alkali metal salt of sulfuric acid or an alkaline earth metal salt. Obtained as a mixture with salt. Then, the mixture is charged into a mixed solution of water: ethanol = 2: 8, heated to 50 to 80 ° C. to dissolve the target compound, and then an inorganic salt is removed by hot filtration. When the filtrate was cooled, precipitation of yellow crystals was observed, and by filtering this, an alkali metal salt or alkaline earth metal salt of 2-sulfonic acid-4,6-dinitroresorcin was obtained. Further, by desolvating the filtrate, an alkali metal salt or an alkaline earth metal salt of 2-sulfonic acid-4,6-dinitroresorcin can be obtained. To desalinate the compound, the compound is dissolved in water and then passed through a column packed with a strongly acidic cation exchange resin to remove water, thereby removing 2-sulfonic acid-
4,6-Dinitroresorcinol is obtained.

2-Sulfonic acid-4,6-dinitroresorcin can be converted to 4,6-dinitroresorcin by hydrolyzing it in an aqueous solution of mineral acid. By reducing the substance, 4,6-diaminoresorcin can be obtained. Is obtained. That is 2-
Sulfonic acid-4,6-dinitroresorcinol is useful as an intermediate for 4,6-diaminoresorcinol.

[0015]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Example 1 5.5 g of resorcin (0.5% by weight) was added to 50 g of 30% by weight fuming sulfuric acid.
(05 mol) was slowly charged and the temperature was raised to 90 ° C., the reaction mass became a dark red solution, which was analyzed by liquid chromatography (abbreviated as HPLC) to give 2,4,6-
It was confirmed that resorcinol trisulfonate was produced. HPLC analysis condition column: YMC-312A (ODS) Mobile phase: acetonitrile: water: PIC = 1000: 20
00:10 PIC = tetrabutylammonium hydroxide flow rate: 1 ml / min Detection wavelength: 254 nm Constant temperature layer: 40 ° C. 60% nitric acid 10.5 g (0.
(1 mol) was added dropwise, and violent heat was generated, and the reaction mass became a yellowish brown slurry. This nitrated trout on ice 1
After the 2,4,6-trinitroresorcinol produced as a by-product was charged into 100 g of the solution and filtered, the filtrate was cooled with ice to give 49
When 27.7 g of an aqueous sodium hydroxide solution was added dropwise, yellowish white crystals were precipitated to form a slurry. This was filtered, the filter cake was washed with 100 g of ethanol, and 2-sulfonic acid-
9.44 g of a mixture of 4,6-dinitroresorcinol sodium salt and sodium sulfate was obtained. 5.04 g of the mixture was charged into 200 g of a mixture of water 20 / ethanol 80,
When sludge was filtered at 80 ° C., hot filtered, and then allowed to stand at room temperature and cooled, precipitation of crystals was observed. This was filtered to obtain 1.07 g of yellow crystals of 2-sulfonic acid-4,6-dinitroresorcinol sodium salt. 1.07 g of the compound is added to water 2
Ion exchange resin (MD-S1368) 2 dissolved in 5 g
It was passed through a column packed with 0 ml and further washed with 30 g of water. This liquid was dehydrated with an evaporator, dried under nitrogen, washed with ethanol and filtered to give 2-sulfonic acid-4,
130 mg of crystals of 6-dinitroresorcinol were obtained. The ¹³ C-NMR spectrum of 2-sulfonic acid-4,6-dinitroresorcinol synthesized in Example 1 shows the following absorptions, and the respective absorptions correspond to carbons a to d in the structural formula shown in the following formula. Be attributed. δ = 119.4 ppm a (NO ₂ -substituted aromatic carbon) δ = 125.2 ppm b (SO ₃ H-substituted aromatic carbon) δ = 128.9 ppm c (hydrogen-bonded aromatic carbon) δ = 155.0 ppm d (OH-substituted aromatic carbon)

[Chemical 4] In addition, the following characteristic absorption bands were observed in the infrared absorption spectrum measurement. 1588 cm ^-1 NO ₂ (absorption band due to asymmetric stretching vibration) 1363 cm ^-1 NO ₂ (absorption band due to symmetrical stretching vibration) 1332 cm ^-1 SO ₂ (absorption band due to asymmetric stretching vibration) 1154 cm ^-1 SO ₂ (absorption due to symmetrical stretching vibration) band)

Example 2 Mixture of 2-sulfonic acid-4,6-dinitroresorcinol sodium salt obtained in Example 1 and sodium sulfate 9.44
4.12 g in 10 g of a mixed solution of water 20 / ethanol 80
When 0 g was charged, sludge was filtered at 80 ° C., hot filtration was performed, and the mixture was allowed to stand at room temperature and cooled, whereby precipitation of crystals was observed. This was filtered and air dried under nitrogen to obtain 1.18 g of 2-sulfonic acid-4,6-dinitroresorcinol sodium salt yellow crystal. The ¹³ C-NMR spectrum of 2-sulfonic acid-4,6-dinitroresorcinol sodium salt synthesized in Example 2 shows the following absorptions, and each absorption corresponds to carbons a to d in the structural formula shown in the following formula. Be attributed. δ = 119.4 ppm a (NO ₂ -substituted aromatic carbon) δ = 125.2 ppm b (SO ₃ H-substituted aromatic carbon) δ = 128.9 ppm c (hydrogen-bonded aromatic carbon) δ = 155.0 ppm d (OH-substituted aromatic carbon)

[Chemical 5] In addition, the following characteristic absorption bands were observed in the infrared absorption spectrum measurement. 1588 cm ^-1 NO ₂ (absorption band due to asymmetric stretching vibration) 1363 cm ^-1 NO ₂ (absorption band due to symmetrical stretching vibration) 1332 cm ^-1 SO ₂ (absorption band due to asymmetric stretching vibration) 1154 cm ^-1 SO ₂ (absorption due to symmetrical stretching vibration) Band) Elemental analysis value (%) C ₆ H ₃ N ₂ O ₉ SNa Element C H N S Na Theoretical value 23.86 1.00 9.27 10.59 7.76 Measured value 23.68 0.99 9 .24 10.80 7.89

Reference Example As a reference, an example in which 4,6-diaminoresorcinol is synthesized from 2-sulfonic acid-4,6-dinitroresorcinol sodium salt is shown below. When 250 g of a 20 wt% sulfuric acid aqueous solution was charged with 15.1 g (0.05 mol) of 2-sulfonic acid-4,6-dinitroresorcinol sodium salt and heated at 100 ° C. for 7 hours, precipitation of crystals was gradually observed. It was The reaction mass was cooled to room temperature and then filtered to obtain yellowish white crystals 8.
95 g were obtained. The crystals were recrystallized with 500 g of ethanol and then air-dried under nitrogen to obtain 7.6 g of purified dinitroresorcin. 2 g (0.01 mol) of the compound and 50 ml of n-propanol, 5% Pd / C (50% wet product) 0.12
g in an autoclave, average hydrogen pressure 2 kg / cm
² , reduction reaction was carried out at 15 ° C. for 7 hours. The reaction mass was discharged into 5 wt% hydrochloric acid water containing 0.6 g of stannous chloride, filtered to remove the catalyst, depressurized at 45 ° C. to remove the solvent, washed with acetone and dried to give a crude 4 2.1 g of crystals of 6-diaminoresorcinol hydrochloride were obtained. (2-sulfonic acid-4,6-dinitroresorcinol sodium salt yield 60.2 mol%)

[0018]

EFFECT OF THE INVENTION 2-Sulfonic Acid-4,6-
Dinitroresorcin can be hydrolyzed to obtain 4,6-dinitroresorcin, which is useful as an intermediate of 4,6-diaminoresorcin. That is, according to the present invention,
6-diaminoresorcin can be produced industrially advantageously.

Front page continued (56) References European patent application publication 1048644 (EP, A 1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C07C 309/42 C07C 303/06 C07C 303/22 C07C 215 / 80 CAPLUS (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. A 2-sulfonic acid-4,6-represented by the following formula:
Dinitroresorcin and its salts. [Chemical 1] (In the formula, M represents hydrogen, an alkali metal or an alkaline earth metal, and n is 1 or 2) 2. A 2-sulfonic acid-4 comprising the following steps:
A method for producing 6-dinitroresorcin. (1) Contacting resorcin with a sulfonating agent
First step of producing 4,6-trisulfonic acid resorcinol, (2) contacting 2,4,6-trisulfonic acid resorcinol with a nitrating agent to produce 2-sulfonic acid-4,6-dinitroresorcinol Second step.