JPH044309B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for preparing 3,4,5,6-tetrachlorophthalonitrile in a benzonitrile medium from 190°C.
This invention relates to a method for producing 3,4,5,6-tetrafluorophthalonitrile by reacting it with a fluorinating agent, particularly potassium fluoride, in a temperature range of 400°C, a so-called halogen exchange reaction.

The so-called halogen exchange reaction, in which a halogen atom is exchanged with a fluorine atom by reacting potassium fluoride with an aromatic halide, has been known for a long time. In general, dimethyl sulfoxide (DMSO), sulfolane (TMSO ₂ ), N
-dimethylformamide (DMF), N-methyl-
Aprotic polar solvents such as 2-pyrrolidone (NMP) and dimethylsulfone (DMSO ₂ ) are mainly used, and the halogen exchange reaction is carried out at a temperature below the boiling point of the solvent [for example, Ishikawa, Journal of the Society of Organic Synthetic Chemistry, Vol. Volume 25, page 808 (1967), M. Hudlicky,
Chemistry of Organic Fluorine Compounds,
No. 112 (1976) John Wiley & Sons Publishing, etc.].

However, aromatic halides that can be halogen-exchanged by the above method are, for example, 2,6-dichlorobenzonitrile to 2,6-
As in the example of synthesizing difluorobenzonitrile, this is usually limited to aromatic halides with a small number of halogen substituents, and it is often difficult to perform complete halogen exchange with polyhalides with larger numbers of halogen substituents. Even if it is possible, the yield is poor.

That is, the above method is not suitable for producing 3,4,5,6-tetrafluorophthalonitrile from 3,4,5,6-tetrachlorophthalonitrile, which is a polyhalogen, as in the present invention. In fact, a method for producing 3,4,5,6-tetrafluorophthalonitrile by halogen exchange of polyhalide or 3,4,5,6-tetrachlorophthalonitrile using a common solvent was proposed by Ishikawa et al. , Industrial Chemistry Journal, Volume 73, Page 447 (1970)
3, all of which are satisfactory.
The yield of 4,5,6-tetrafluorophthalonitrile was not obtained. Additionally, if the solvents commonly used in the above methods are heated to high temperatures or used for long periods of time to improve yields, decomposition reactions of the solvent or side reactions between the solvent and raw materials or products may occur. In the end, the yield cannot be improved. It also has the disadvantage that it is not easy to use industrially in terms of solvent recovery and reuse. In order to avoid the disadvantage that these solvents cannot be used at high temperatures, it is common to use an autoclave without a solvent and conduct the reaction at a high temperature of 200 to 500℃. An example of halogen exchange of 3,4,5,6-tetrafluorophthalonitrile from 4,5,6-tetrachlorophthalonitrile is also described, for example, by Ueda et al., Bull.Chem.Soc.Japan Vol. 40, Vol.
688 and British Patent No. 1026290 (1966). However, since no solvent is used,
It is difficult to control the temperature due to the exothermic reaction, and a large amount of carbide adheres to the container after the reaction is completed, making it difficult to implement industrially.

As a result of intensive research into industrially possible methods to improve the above-mentioned drawbacks, the inventors of the present invention discovered that using a benzonitrile solvent, spontaneous generation occurs at a temperature above the boiling point of benzonitrile, that is, in the temperature range of 190 to 400°C. 3,4,5,6-tetrachlorophthalonitrile is reacted with a fluorinating agent, in particular potassium fluoride, to exchange halogen under pressure.
The present invention was completed by discovering that 5,6-tetrafluorophthalonitrile can be easily produced in good yield.

The invention will be explained in more detail below.

The solvent benzonitrile used in the present invention is thermally stable even at high temperatures during the halogen exchange reaction, and there is no side reaction between the solvent and the raw material or product as seen in other solvents, so it can be used at 190 to 400°C It can be used in a high temperature range, therefore, the reaction rate can be increased and the yield can also be improved. In addition, the use of this solvent has the advantage of being able to easily control the temperature and prevent the formation of a large amount of char, unlike a manufacturing method without a solvent, making it possible to obtain the desired product in high yield during industrial implementation. I can do it.

The solvent benzonitrile used in the present invention differs from commonly used aprotic polar solvents in that it has a very low ability to dissolve inorganic salts below its boiling point. In the commonly used halogen exchange reaction, it is necessary to use a solvent that has the ability to dissolve the fluoride salt, which is the fluorinating agent. For this reason, it is generally an aprotic polar solvent that has a high ability to dissolve inorganic salts.
DMSO, TMSO ₂ , DMF, NMP, DMSO ₂ and the like have been used, and it has been considered disadvantageous to use benzonitrile, which has a low ability to dissolve inorganic salts, as in the present invention. In fact GCFinger et al., J. Amer. Chem. Soc.
As described in Vol. 78, p. 6034 (1956), using benzonitrile as a solvent and potassium fluoride as a fluorinating agent, 2,4-dinitrochlorobenzene was
-There are examples of halogen exchange to dinitrofluorobenzene, but the yield is low because the reaction temperature is low at 150-170°C. Also, G.Fulle, J.Chem.Soc., No.
As described on page 6264 in 1965, we are considering a solvent for halogen exchange of hexachlorobenzene using potassium fluoride as a fluorinating agent, but unlike other solvents, benzonitrile is used as a solvent.175 There are also known cases where no halogen exchange occurred even after 18 hours of reaction at °C.

According to research conducted by the present inventors, when benzonitrile is used at a temperature above its boiling point, the solubility of fluorinating agents such as potassium fluoride increases rapidly;
We have found that it is good to carry out the reaction at a temperature of ~400°C, preferably between 230 and 360°C. The reason why the yield of 3,4,5,6-tetrafluorophthalonitrile was dramatically increased in the present invention was that by using benzonitrile as a solvent, the solubility of the fluorinating agent could be increased as well as the temperature effect. It can be said.

In general, halogen exchange of polyhalides is difficult REBamks et al., Chem & Ind. 1964, No. 835.
Although the halogen exchange rate is low as described in Ishikawa, Nikka-shi, Vol. 86, p. 90, it is easy to increase the halogen exchange rate in the present invention, and generally aromatic compounds Attractive −CN group, −
Halogens at the meta position, such as NO ₂ groups, are said to be difficult to replace, but halogens at the meta position can also be replaced.

Fluorination agents used in halogen exchange reactions generally include cesium fluoride, potassium fluoride,
Alkali fluorides such as sodium fluoride and alkaline earth metal fluoride salts such as calcium fluoride are used. In some cases, transition metal fluorides such as antimony fluoride may also be used.

In the present invention, any commonly used fluorinating agent can be used. Among these, particularly preferred is potassium fluoride, which is easy to handle and practically commercially available.

The fluorinating agent is required in an amount at least equivalent to the chlorine atom substituted by the fluorine atom in the raw material 3,4,5,6-tetrachlorophthalonitrile, and in the case of potassium fluoride per chlorine atom, A range of 1 to 2 moles is suitable.

In the present invention, it is preferable to carry out the reaction under naturally occurring pressure, but the reaction may also be carried out under a higher pressure, particularly using an inert gas, nitrogen, or the like.

The reaction time varies depending on the reaction temperature, but is suitably in the range of about 2 hours to 48 hours.

The raw material 3,4,5,6-tetrachlorophthalonitrile is used in an amount of about 5 to 50 parts per 100 parts by weight of the solvent.
It is preferable to add it to the reaction system in an amount within the range of 50%.

It is generally said that it is preferable to carry out the halogen exchange reaction under anhydrous conditions as much as possible in order to increase the reaction rate and avoid side reactions.

Commonly used DMSO, _TMSO2 , DMF,
Aprotic polar solvents such as NMP and _DMSO2 are highly hygroscopic and contain a considerable amount of water.
Therefore, prior to the reaction, it is necessary to add benzene, toluene, etc. to remove water by distillation as an azeotrope. In the present invention, this operation is not required in principle since benzonitrile has no hygroscopicity. However, since potassium fluoride used as a fluorinating agent has high hygroscopicity, in some cases it is preferable to add benzene, toluene, etc. to remove water by distillation in advance as an azeotrope.

In the present invention, it is advantageous to further include a phase transfer catalyst in the reaction system. That is, the presence of a phase transfer catalyst has the advantage of increasing the reaction rate and shortening the reaction time.

As a phase transfer catalyst, crown compounds such as dibenzo-18-crown-6-ether, molecular weight
300 to 600 polyethylene glycol, etc. can be used.

The amount of this phase transfer catalyst added is 1
0.01 mol to 0.25 mol based on the mole is suitable.

3,4,5,6-tetrafluorophthalonitrile obtained by the present invention is a compound useful as a synthetic intermediate for agricultural chemicals, medicines, dyes, and the like.

Benzonitrile, the solvent of the present invention, can be easily separated from the product by distillation and can be reused as a solvent in the next reaction.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto.

Example 1 200 g of benzonitrile, 80.0 g (0.301 mol) of 3,4,5,6-tetrachlorophthalonitrile, and 83.9 g (1.444 mol) of finely dried potassium fluoride were placed in a 500 c.c. stainless steel container autoclave. After charging and replacing the air in the reaction vessel with nitrogen gas, the mixture was heated and stirred at 230°C for 10 hours. After the reaction was completed, the mixture was cooled to room temperature, and suspended potassium chloride and unreacted potassium fluoride were removed by filtration. When the benzonitrile solution of the mother liquor was analyzed using a gas chromatograph using a packing material of SE52 1 m and a column bath temperature of 60°C, it was found that 3,4,5,6- 87.7 mol% of tetrafluorophthalonitrile was obtained.

By removing the benzonitrile by distillation under reduced pressure, crystals of 3,4,5,6-tetrafluorophthalonitrile (M.P 86-87°C) solidified at room temperature were obtained.

Example 2 Dibenzo-18-crown-6-ether 5.8g
(0.016 mol) was dissolved in benzonitrile in the same manner as in Example 1, and the mixture was charged into a 500 c.c. autoclave and heated and stirred at 200° C. for 5 hours. After the reaction was completed, the mother liquor obtained in the same manner as in Example 1 was analyzed by gas chromatography, and it was found that 3, 4, 5,
3 for 6-tetrachlorophthalonitrile,
4,5,6-tetrafluorophthalonitrile 80.8
The mole percent was obtained.

Example 3 A 500 c.c. autoclave was charged in the same manner as in Example 1, except that the reaction temperature and reaction time were changed, and the mixture was heated and stirred at 270° C. for 16 hours. After the reaction was completed, the mother liquor obtained in the same manner as in Example 1 was analyzed by gas chromatography.
85.3 mol% of 6-tetrafluorophthalonitrile was obtained.

Comparative Example 1 200 g of tetramethylene sulfone, 80.0 g of 3,4,5,6-tetrachlorophthalonitrile, and 83.9 g of ultrafine dried potassium fluoride were placed in a 500 c.c. glass flask, and the mixture was heated at 230°C under normal pressure for 10 min. The reaction was carried out by heating for an hour. After the reaction was completed, a large amount of tar was produced in the reaction solution. Next, Example 1
When the mother liquor was analyzed in the same manner as above, it was found that 59.4 mol% of 3,4,5,6-tetrafluorophthalonitrile was produced based on the charged 3,4,5,6-tetrachlorophthalonitrile.

Comparative Example 2 The same procedure as in Example 1 was repeated except that 200 g of dimethylformamide was used as the solvent instead of benzonitrile, and the mixture was charged into an autoclave and heated and stirred at 170° C. for 1 hour. The initial reaction pressure was 2 kg/cm ² ·G, but the internal pressure after the reaction had increased to 7 kg/cm ² ·G. After the reaction was completed, a large amount of tar-like substances were produced in the reaction solution, and analysis in the same manner as in Example 1 revealed that 3,4,5,6-tetrachlorophthalonitrile was present in the reaction solution. 4,5,6
-18.2 mol% of tetrafluorophthalonitrile was obtained.

Claims (1)

[Claims] 1. Characterized by reacting 3,4,5,6-tetrachlorophthalonitrile with a fluorinating agent under spontaneous pressure in a benzonitrile medium at a temperature in the range of 190 to 400°C. Method for producing 3,4,5,6-tetrafluorophthalonitrile. 2. The method according to claim 1, wherein the fluorinating agent is at least one selected from the group consisting of fluoride salts of alkali metals and alkaline earth metals. 3. The method according to claim 1 or 2, wherein the fluorinating agent is potassium fluoride. 4 characterized in that 3,4,5,6-tetrachlorophthalonitrile is reacted under spontaneous pressure with a fluorinating agent in the presence of a phase transfer catalyst in a benzonitrile medium at a temperature in the range 190-400°C. 3, 4,
Method for producing 5,6-tetrafluorophthalonitrile. 5. The method according to claim 4, wherein the fluorinating agent is at least one selected from the group consisting of fluoride salts of alkali metals and alkaline earth metals. 6. The method according to claim 4 or 5, wherein the fluorinating agent is potassium fluoride.