GB2142018A

GB2142018A - Method for producing 2,6-difluorobenzonitrile

Info

Publication number: GB2142018A
Application number: GB08415348A
Authority: GB
Inventors: Yasuhiro Tsujii; Shigeo Murai; Tatsuo Isogai; Keiichilo Ito; Sadao Tsukada
Original assignee: Ishihara Sangyo Kaisha Ltd
Current assignee: Ishihara Sangyo Kaisha Ltd
Priority date: 1983-06-23
Filing date: 1984-06-15
Publication date: 1985-01-09
Also published as: JPH0216746B2; JPS604159A; GB2142018B; DE3422936C2; FR2549048B1; CH660361A5; DE3422936A1; GB8415348D0; FR2549048A1

Abstract

A method for producing 2,6-difluorobenzonitrile by reacting 2,6-dichlorobenzonitrile with potassium fluoride, characterized in that the reaction of 2,6-dichlorobenzonitrile with potassium fluoride is conducted in the absence of a solvent at a temperature of from 200 to 450 DEG C under pressure.

Description

SPECIFICATION Method for producing 2,6-Difluorobenzonitrile The present invention relates to a method for producing 2,6-difluorobenzonitrile by reacting 2,6dichlorobenzonitrile with potassium fluoride. The 2,6-difluorobenzonitrile is useful as an intermediate for various agricultural chemicals, medicines or dyestuffs.

Heretofore, methods for producing 2,6-difluorobenzonitrile by substituting fluorine atoms for the chlorine atoms of 2,6-dichlorobenzonitrile, have been disclosed, for instance, in J. Chem.

Soc., Chem. Comm., 1965, pages 430-431, and in the Journal of Organic Synthetic Chemistry Association, Vol. 27, page 1 75 (1969). In these methods, the reactions are required to be conducted in the presence of a solvent such as dimethyl sulfone or dimethyl sulfoxide.

Due to the decomposition of the solvent, there will be a substantial amount of decomposition products which are hardly separable and make the work-up difficult. Further, it is necessary to employ a great amount of such a solvent, but presently it is practically very difficult to recover the solvent. Thus, these methods are economically disadvantageous. Under the circumstances, it has been desired to develop an industrially advantageous method which can be substituted for the conventional methods.

The present inventors have conducted extensive researches to overcome the difficulties in the above-mentioned methods, and have found that the desired product can be obtained in good yield by conducting the reaction under pressure even without a solvent. On the basis of this discovery, a novel and industrially advantageous method has now been invented. Namely, the present invention provides a method for producing 2,6-difluorobenzonitrile by reacting 2,6dichlorobenzonitrile with potassium fluoride, characterized in that the reaction of 2,6-dichlorobenzonitrile with potassium fluoride is conducted in the absence of a solvent at a temperature of from 200 to 450"C under pressure.

Now, the present invention will be described in detail with reference to the preferred embodiments.

The method of the present invention may be conducted by feeding 2,6-dichlorobenzonitrile and potassium fluoride into a closed container such as an autoclave, and heating and stirring the mixture.

The potassium fluoride to be used in the present invention, may be a usual commerical product or a finely pulverized product. It is usually used in an amount of from 0.8 to 2.0 times, preferably from 1 to 1.5 times, more preferably from 1.2 to 1.5 times, the theoretical molar amount required for the reaction with 2,6-dichlorobenzonitrile, i.e. the theoretical molar amount required for substituting fluorine atoms for the chlorine atoms of the 2,6-dichlorobenzonitrile.

The reaction temperature is usually from 200 to 450"C, preferably from 250 to 400"C, more preferably from 300 to 400"C, most preferably from 330 to 350"C. The reaction time is usually from 0.5 to 20 hours. The pressure in the closed reactor may be a spontaneous pressure due to the heating under the closed condition, and it is usually from about 3 to about 25 kg/cm2.

Further, the air in the closed reactor may be substituted by an inert gas to prevent oxidation, or the pressure may be raised to a level higher than the above-mentioned pressure range to prevent polymerization.

From the reaction product thus obtained, 2,6-difluorobenzonitrile as the desired product can be obtained in high purity and in good yield with or without subjecting the reaction product to usual separation or purification treatment. Further, a partially fluorinated product remaining in the reaction products may be recovered by a proper separation method such as distillation and recycled for reuse.

Now, the present invention will be described in further detail with reference to Examples.

However, it should be understood that the invention is by no means restricted to these specific Examples.

EXAMPLE 1 Into a 500 ml autoclave equipped with a pressure gauge, a stirrer and a thermometer, 111.8 g of 2,6-dichlorobenzonitrile (purity: 96%) and 108.8 g of potassium fluoride were fed, and the autoclave was closed. Then, the air in the autoclave was substituted by dry nitrogen gas. The temperature was gradually raised under stirring to an internal temperature of 350 C, and then the reaction was continued for 3 hours. During the reaction, the maximum pressure was 14.3 kg/cm2. After the completion of the reaction, the autoclave was cooled, and the product was collected at a temperature around 200"C by means of a distillation recovery apparatus which was preliminarily fitted on the autoclave, whereby 73.0 g of an oily product (boiling point: 81-83"C/13 mmHg) was obtained.

This oily product was analyzed by gas chromatography, whereby the content of 2,6difluorobenzonitrile was 99% (yield: 83%).

EXAMPLES 2 to 7: In the same manner as in Example 1, reactions were conducted under the conditions specified in the following Table. The results thereby obtained are also shown in the Table. Table

Amount of Amount of composition of the Yield of Potassium Example 2,6-dichloro- Temperature Time Pressure the oily product (wt.%) by the desired fluoride No. benzonitrile product gas chromatography product (96% purity) (g) ( C) (hr) (g) (%) Spontaneous 2,6-difluorobenzo2 111.8 108.8 350 1 (max 74.2 nitrile: 82 70 23.0 kg/cm) Others: 8 2,6-difluorobenzo3 137.6 89.3 350 5 (max" 90.2 nitrile: 83 70 23.5 kg/cm) Others: 7 2,6-difluorobenzo4 77.4 75.3 300 17.5 " 47.5 nitrile: 97 77 (max 21.5 kg/cm) Others: 3 2,6-difluorobenzo5 118.8 108.8 400 1 " 68.3 nitrile: 99 78 (max 24.5 kg/cm) Others: 1 2,6-difluorobenzo6 124.3 100.7 330 5 " 85.0 nitrile: 98.8 87.2 (max 22.5 kg/cm) Others: 1.2 2,6-difluorobenzo7 124.3 100.7 300 5 (max" 89.6 nitrile: 96.6 89.6 21.5 kg/cm) Others: 3.4

Claims

1. A method for producing 2,6-difluorobenzonitrile by reacting 2,6-dichlorobenzonitrile with potassium fluoride, characterized in that the reaction of 2,6-dichlorobenzonitrile with potassium fluoride is conducted in the absence of a solvent at a temperature of from 200 to 450"C under pressure.

2. The method according to Claim 1, wherein the reaction temperature is from 250 to 400C.

3. The method according to Claim 1, wherein the reaction temperature is from 300 to 4aO"C.

4. The method according to Claim 1, wherein the reaction temperature is from 330 to 350 C.

5. The method according to Claim 1, wherein potassium fluoride is used in a molar amount of from 0.8 to 2.0 times the theoretical molar amount required for the reaction with 2,6dichlorobenzonitrile.

6. The method according to Claim 1, wherein potassium fluoride is used in a molar amount of from 1 to 1.5 times the theoretical molar amount required for the reaction with 2,6dichlorobenzonitrile.

7. The method according to Claim 1, wherein potassium fluoride is used in a molar amount of from 1.2 to 1.5 times the theoretical molar amount required for the reaction with 2,6dichlorobenzonitrile.

8. The method according to Claim 1, wherein the reaction is conducted under pressure of from about 3 to about 25 kg/cm2.

9. A method for producing 2,6-difluorobenzonitrile, substantially as described in the Examples.