JPS58189151A - Preparation of 3-chloro-2,6-difluorobenzonitrile - Google Patents

Abstract

NEW MATERIAL:3-Chloro-2,6-difluorobenzonitrile. USE:A raw material of 2,6-difluorobenzonitrile useful as a synthetic raw material of agricultural chemicals, pharmaceuticals, etc. PROCESS:The objective 3-chloro-2,6-difluorobenzonitrile can be prepared by reacting 2,3,6-trichlorobenzonitrile (TCBN) with potassium fluoride in the presence of an aprotic polar solvent (e.g. N-methyl-2-pyrrolidone) at 130-250 deg.C, preferably 150-200 deg.C. The amount of the solvent is 2-30pts.wt., preferably 3-10pts.wt. per 1pt.wt. of TCBN, and that of potassium fluoride is 1-2 times, preferably 1-1.5 times the stoichiometric amount to substitute the 6-position chlorine atoms and fluorine atoms of TCBN.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an industrially advantageous method for producing 8-chloro-2,6-cyfluoropenzonitrile (hereinafter referred to as CDFBN). CDFBN is a new compound that can be fermented into crystalline 2,6-cyfluorobenzonitrile (hereinafter referred to as DFBN), which is useful as an intermediate raw material for agricultural chemicals and medicines. When we were looking to find a production method, we discovered that by reacting 2,8°6-trichlorobenzonitrile (hereinafter referred to as TCBN) with potassium fluoride in the presence of a specific solvent, the desired CDFBN could be obtained in high yield. I gained knowledge of what can be done.

That is, the present invention provides, in the presence of an aprotic polar solvent,
2,8.6-)! It is characterized in that 8-chloro-2,6-cyfluoropenzonitrile is produced by reacting Jchlorobenzonitrile and potassium fluoride. 8-
This is a method for producing chloro-2,6-cyfluorobenzonitrile.

2.8.6-) Lichloropenzonitrile, the starting material of the process of the present invention, can be prepared by, for example, 4-methylbenzenesulfonic acid in the presence of 1 sulfuric acid and iodine at 50 to 150°C by blowing chlorine gas. .

2.8.5-) Dichloro-4-methylbenzenesulfonic acid is produced, which is desulfonated with hot steam to produce 2,8. It is possible to obtain trichlorotoluene by reacting it with air and ammonia gas in the gas phase at 800-600 DEG C. in the presence of a vanadium-iron catalyst (ammoxidation).

According to the method of the present invention, '
l' CB N and potassium fluoride are added and reacted under heating to obtain CDFBN.

Examples of the aprotic polar solvent include cyclic amide solvents, dimethyl sulfoxide, dimethyl sulfone, and sulfolane, and industrially preferred are cyclic amide solvents. Examples of the cyclic amide solvent used in this fluorination reaction include un-pyrrolidone, N-cyclohexyl-2-pyrrolidone, and 1,8-dimethyl-2-imidazolidinone. The amount of solvent to be used is 2-80 times that of TCBN, preferably 8-1O, although it cannot be generally specified.
It is twice (weight). As potassium fluoride, either ordinary commercial products or ultrafine particles can be used, and the amount used is the stoichiometric amount for replacing the chlorine atom at the 2.6-position of T Ck3 N with a fluorine atom. 1 to 2 times, preferably 1 to 1.5 times. Generally the reaction temperature is 180-250
The time is 1-10 hours.

When this fluorination reaction product is subjected to conventional separation operations such as filtration, liquid separation, and distillation, CDFBN can be obtained in high yield. Further, the solvent can be easily recovered from the aqueous layer obtained by adding water to the fluorination reaction product and separating the liquid.

CDI obtained by the method of the present invention? BN is produced at 50-250°C in an autoclave in the presence of a platinum oxide or palladium catalyst and a hydrogen chloride promoter such as triethylamine, trimethylamine, pyridine, picoline, etc. under a hydrogen pressure of 5-250°C.
When reduced by hydrogen gas at 50 Kp/cII, useful FBN can be obtained in high yield.

The method of the present invention provides the following advantages.

(1) The starting material TCBN can be easily produced industrially. ■■ Reaction conditions such as reaction temperature and reaction time are moderate, and side reactions hardly occur.

The target C1) FBN can be obtained in high yield (31
The amount of potassium fluoride used as a raw material is approximately the stoichiometric amount for the reaction, and the solvent can be easily recovered by a simple method.

Example 2.8.6-) 210.6j of dichlorobenzonitrile was dissolved in 100j' of N-methyl-2-pyrrolidone, 18.91i of potassium fluoride was added thereto, and 18.91i of potassium fluoride was added while stirring.
The reaction was carried out at a temperature of 90° C. for 4 hours.

The reaction mixture was filtered to remove potassium fluoride and potassium chloride, and then water was added to the r solution to separate the solution.

The oil layer was distilled to obtain 165 g (yield 95%) of 3-chloro-2,6-difluorobenzonitrile having a boiling point of 95° C./l 1 mHjl. In addition, the aqueous layer was distilled to obtain N-methyl-
981 2-pyrrolidone (recovery rate 98%) was recovered.

In addition, 17 g of 3-chloro-2,6-difluorobenzonitrile obtained in reaction E was added to 80% water, and a palladium-carbon catalyst (element weight ratio; Pd:C=2:
100) 0.0851i+ and triethylamine 1
241 was added, and while hydrogen gas was blown in to maintain the hydrogen pressure in the system at 101 t, the reaction was carried out at 100C in an autoclave for 8 hours. Separate the catalyst, add a small amount of diluted hydrochloric acid to the liquid F, adjust the pH to 5, separate the oil layer, and distill.

18.6Ii (yield 98%) of 2.6-cyfluoropenzonitrile was obtained. The aqueous layer was made alkaline with a small amount of caustic soda aqueous solution to obtain triethylamine 117 (recovery rate 9).
1%) was recovered.

Comparative Example In the above example, i! ,,8.6-t! 2,6-cyclobenzonitrile 1 instead of J chlorobenzonitrile
The reaction was carried out in the same manner except that 7.2y was used, and the purification treatment was performed to obtain 2.6-difluorobenzonitrile 951 (yield: 68
%) was obtained.

Patent applicant: Ishihara Sangyo Co., Ltd.

Claims (1)

[Claims] A method for producing 2,8.6-tobenzonitrile in the presence of an aprotic polar solvent.