JPH0443067B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing compounds having heterocycles. More specifically, the present invention relates to a method for producing a compound having a benzimidazole skeleton.

Benzimidazoles are widely used as heat-resistant materials, paints, epoxy hardeners, adhesives, etc. due to their chemical properties.

Many methods have been known for a long time to synthesize benzimidazole skeletons. These are mainly produced by reaction with o-arylene diamine. o
-Arylene diamine is represented by the following formula () It is a chemical compound. R ₁ and R ₂ each represent an alkyl group or an aryl group. ) Many substances are known to react with this o-arylene diamine, including carboxylic acids such as acetic acid and benzoic acid, as well as corresponding esters, amides, anhydrides, and acid halides. It is known that benzimidazole skeletons can be produced by reactions with iminoesters, cyano compounds, and even aldehydes such as formalin, acetaldehyde, and benzaldehyde.

Among these, the reaction with aldehyde is an industrially advantageous production method for the following reasons. First, the raw materials are cheap and easily available, second, the reaction conditions are mild, and third, the reaction requires almost no additives.

For example, Tetrahedron Letter-1971 P.3541 describes the reaction of o-phenylenediamine and benzaldehyde, and states that benzimidazoles were synthesized with a yield of 19%.
Furthermore, Heterocyclic Chemistry Vol.2P.453
(1965) describes a method in which aldehydes are reacted with sodium sulfite and then reacted with o-arylene diamine. However, these methods have been unsatisfactory due to problems such as low yields and complicated post-treatment of the sodium sulfite used.

The present inventors, in the process of repeatedly studying the manufacturing method of benzimidazole from this perspective,
Surprisingly, in the reaction between aldehydes and o-allenediamines, if the reaction is carried out by adding a proton catalyst, preferably in the presence of air or oxygen, the reaction can be carried out under mild conditions and
The present invention was achieved by discovering that a benzimidazole skeleton can be synthesized with extremely high yield and with simple post-treatment.

That is, the present invention relates to a method for producing benzimidazoles, which is characterized by reacting aldehydes and o-arylene diamines while blowing air or oxygen in the presence of a mineral acid.

The aldehydes in the present invention are substances having one or more aldehyde groups (-CHO), such as formalin, acetaldehyde, propionaldehyde, benzaldehyde, acrolein, terephthalaldehyde, isophthalaldehyde, and phthalaldehyde. Furthermore, it is not limited to such a low molecular weight aldehyde, but may be a polymer having an aldehyde group. Polymers having aldehyde groups refer to linear or crosslinked polymers.

The polymerized unit having an aldehyde group is not particularly limited, but examples include polymerized units such as acrolein and formylstine. As mentioned above, the polymer having an aldehyde group may be a linear polymer or a crosslinked polymer, and it does not matter whether it is a homopolymer or a copolymer.

Other polymerized units in the copolymer may be crosslinkable polymerized units such as divinylbenzene, triallylisocyanurate, divinylpyridine, divinyltoluene, methylenebisacrylamide, and dimethacrylate, or styrene, vinyl chloride, and methacrylate. It may also be a non-crosslinked polymer unit such as methyl acid or vinyl acetate. Of course, there is nothing wrong with containing both of them.

These aldehyde group-containing polymers can be produced by polymerizing monomers having aldehyde groups or copolymerizing them with other monomers if necessary. It is also possible to adopt a method in which aldehyde groups are introduced by polymer reaction after obtaining the polymer. One of the major features of the present invention is that benzimidazoles can be produced in good yield even when using polymers, and especially when the amount of aldehydes is small compared to o-arylene diamines, this Great effect.

The o-arylene diamines referred to in the present invention are:
It is a compound having two amino groups at adjacent positions of an aryl compound, and one of the hydrogens may be substituted with another substituent. Some preferred specific examples include o-phenylenediamine, N-methyl-o-phenylenediamine, N-ethyl-o-phenylenediamine, N-phenylenediamine, and N-ethyl-o-phenylenediamine.
-phenyl-o-phenylenediamine, N-benzyl-o-phenylenediamine, and the like.

By reacting a substance having two or more aldehyde groups in one molecule with a polyamine having two or more pairs of amino groups, it is possible to produce a polymer having a benzimidazole skeleton (polybenzimidazole). It is. Further, by reacting a polymer having an aldehyde group with a polyamine having two or more sets of amino groups, it is also possible to carry out a crosslinking reaction between the polymers. Furthermore, in the reaction between a substance having two aldehyde groups and a substance having one set of amino groups, it is possible to perform a 1:2 reaction, and conversely, a substance having one aldehyde group and a substance having one set of amino groups can undergo a 1:2 reaction. In the reaction of substances with a set of amino groups,
It is also possible to carry out a 2:1 reaction opposite to the above.

Next, a specific manufacturing method of the present invention will be described.

According to the present invention, a benzimidazole skeleton can be effectively produced by allowing a mineral acid to coexist as a proton catalyst when reacting aldehydes and o-arylene diamines. Mineral acids in the present invention include hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid. The amount of the proton catalyst is preferably 0.01 to 100 mol%, more preferably 0.1 to 10 mol%, based on the number of moles of aldehyde groups in the raw material aldehyde-containing polymer.

The reaction is preferably carried out in the presence of an inert liquid. An inert liquid is one that is substantially inert to the raw materials and products and is liquid at the reaction temperature. Although it is preferable to dissolve o-arylene diamines and low molecular weight aldehydes in the inert liquid, it is not necessary to dissolve the polymer having an aldehyde group. However, it is preferred that the polymer itself, especially a crosslinked polymer, be swollen with an inert liquid. Examples of such inert liquids include aliphatic hydrocarbons such as bentane, hexane, heptane, and octane, alcohols such as methanol, ethanol, propanol, and butanol, and acetone, methyl ethyl ketone, and diethyl ketone. Ketones, ethers such as diethyl ether, methyl ethyl ether, dibutyl ether, dioxane, tetrahydrofuran, benzene, toluene,
Aromatic hydrocarbons such as xylene, esters such as ethyl formate, ethyl acetate, and butyl acetate, amides such as dimethylformamide and dimethylacetamide, aliphatic halides such as chloroform, methylene chloride, and dichloroethane, and chlorobenzene. These include aromatic halides, dimethyl sulfoxide, and polar liquids such as water. These liquids can be used alone or as a mixture of two or more liquids.

There is no particular restriction on the reaction temperature, but preferably -
The temperature is 50°C to 150°C, more preferably -0°C to 100°C. The reaction time is also not particularly limited, but is preferably 1 to 50 hours.

The preferred amount of o-arylene diamines is 0.1 to 20 times the amount of one set of amino groups per one aldehyde group, more preferably 0.5 to 20 times the amount of amino groups.
It is 3 times the mole.

Various methods can be used to coexist air or oxygen in the present invention, but the simplest and most effective method is to blow air into the reaction system through a nozzle or the like. It is also possible to use oxygen gas or oxygen gas diluted with an inert gas such as nitrogen. In such cases, it is also effective to apply pressure using an autoclave or the like. Although it is possible to carry out stirring in the air without actively blowing in the gas as described above, this is less effective in terms of the purpose of the production method of the present invention.

The amount of gas to be blown in is at least 0.5 times the mole of aldehyde, more preferably at least 1 times the mole of the aldehyde, but it is preferable to increase or decrease it as appropriate while checking the progress of the reaction. It can be said to be a law.

To give an example of a specific manufacturing method, o-arylene diamines are dissolved in an inert liquid as required, and a predetermined amount of a proton catalyst is added thereto.
A predetermined amount of aldehydes is added to this by a method such as dropping, and the mixture is stirred at a predetermined temperature for a predetermined time.
The reaction is carried out while blowing in gas as necessary.

Specific examples are shown below, but these are not intended to limit the scope of the invention.

Example 1 14.0 gr of o-phenylenediamine and 6.4 ml of 0.1N hydrochloric acid were mixed with 50 ml of methanol, and the mixture was cooled to -10°C with stirring. Divinylbenzene,
15wt% of polymerized units of formylstyrene,
10 gr of copolymer containing 85 wt% was slowly added. Stirring was continued for 30 minutes at the same temperature under stirring. Next, while blowing air through a blowing nozzle, the reaction temperature was gradually raised to 20°C. The reaction was continued at this temperature for an additional 10 hours with continued bubbling and stirring.

After the product was separated, it was thoroughly washed with water and acetone. The product had a dry weight of 14.53 gr.

When the infrared spectrum of the product was measured, it was 740,
Characteristic peaks based on the benzimidazole skeleton were observed around 1280, 1450, and 1490 cm ^-1 . In addition, when we measured the weak base capacity of the product,
It was 3.14 mmol/g.

Example 2 23.6g of N-methyl-o-phenylenediamine was used instead of o-phenylenediamine, and 50ml of a 1/1 methanol/water mixture was used instead of methanol.
A product was obtained in the same manner as in Example 1 except that .

The infrared spectrum of the product includes 740, 1320,
Characteristic absorptions were observed around 1380 and 1460 cm ^-1 , and the weak base exchange capacity was 2.89 mmol/g.

Example 3 11.8g N-methyl-o-phenylenediamine
r, 2.4 ml of 1N hydrochloric acid with dimethylformamide
The solution was dissolved in 50 ml and cooled to -5°C while stirring. This includes divinylbenzene, ethylstyrene,
The polymerized unit of formylstyrene is 20wt%, respectively.
10.0 gr of polymer consisting of 16 wt% and 64 wt% was gradually added. Next, the temperature was further raised to 50°C, and a mixed gas of 1/4 oxygen/nitrogen was blown into it through a blowing nozzle equipped with sintered glass. In this state, the reaction was continued for 15 hours under stirring to obtain a product. The product exhibited infrared characteristic absorption similar to that of the product of Example 2, and the amount of weak base was 2.35 mmol/g.

Example 4 In 50 ml of methanol, o-phenylenediamine
Mix and dissolve 5.83gr (0.055mol) and stir.
The temperature was 10℃. After adding 5 ml of 0.1N hydrochloric acid to this,
5.4 gr (0.05 mol) of benzaldehyde was added dropwise over 15 minutes. Adjust the reaction temperature while blowing air.
After the temperature was set to 20°C, the reaction was continued for 1 hour. From liquid chromatography analysis using standard samples,
The conversion rate of o-phenylenediamine is 100%, 2-
The production rate of phenylbenzimidazole was also 100%.

Claims (1)

[Claims] 1. A method for producing benzimidazoles, which comprises reacting an aldehyde with an o-arylene diamine represented by the following structural formula () while blowing air or oxygen in the presence of a mineral acid. . (In the formula, R ₁ and R ₂ each represent an alkyl group or an aryl group.)