JPH0448783B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing 4,4'-difluorobenzophenone, which is important as a monomer for heat-resistant polymers and as an intermediate for agricultural chemicals, medicines, and the like.

[Conventional technology]

4,4'-difluorobenzophenone has recently attracted particular attention as a monomer for aromatic polyetherketone polymers with good heat resistance and chemical resistance, and there is a demand for the development of an inexpensive manufacturing method. . Conventionally, the following method has been proposed as a method for producing 4,4'-difluorobenzophenone.

(1) 4,4'-diaminodiphenylmethane is diazinated in anhydrous hydrogen fluoride or a concentrated aqueous solution of hydrogen fluoride, and then the diazonium salt is decomposed and fluorinated in the presence of nitrous acid, and the methylene group is converted to a ketone group. (2) 1,1-bis(4-fluorophenyl)-2,
A method for treating 2,2-trichloroethanol with an alkali (Japanese Unexamined Patent Publication No. 57-154139) (3) A method for reacting 4,4 dichlorobenzophenone with an alkali fluoride (Japanese Unexamined Patent Publication No. 57-169441) ( 4) A method of conducting a Friedel-Crafts type reaction between 4-fluorobenzoyl chloride and benzene fluoride in anhydrous hydrogen fluoride in the presence of boron trifluoride (Japanese Unexamined Patent Publication No. 124731/1982) (5) 1. 1-bis(4-fluorophenyl)-2,
Methods of oxidizing 2-dichloroethylene with nitric acid (Japanese Patent Application Laid-Open No. 126829/1982) However, these methods require the use of large amounts of anhydrous hydrogen fluoride, which is dangerous and difficult to handle (method (1)). ) and (4)), it is necessary to produce diazonium fluoride, which is unstable and has a risk of explosion (method (1)), and complicated steps are required to produce the raw material compound (method (1)). 2),
(3) and (5)), the reaction must be carried out at high temperatures for a long time, the yield is not very high, and it is difficult to separate raw materials, products, and side reactants (method (3)) For these reasons, there were problems in implementing any of them industrially.

On the other hand, a method for producing benzophenone by reacting unsubstituted diphenylmethane with cerium salt was known (L.Syper, Tetrahedron
Letters, 1966, p. 4493), but the yield is
The percentage was low at 76%.

However, nothing was known about 4,4'-difluorodiphenylmethane, which is a fluorine substituted product, and nothing was known about the effects of fluorine.

[Means and effects of the invention]

Therefore, the present inventors investigated a method for producing 4,4'-difluorobenzophenone from 4,4'-difluorodiphenylmethane in high yield, and as a result, they completed the present invention. That is, the present invention provides a method for producing 4,4'-difluorobenzophenone, which is characterized by reacting 4,4'-difluorodiphenylmethane with a tetravalent cerium compound.

As described above, the present invention provides that when 4,4'-difluorodiphenylmethane in which the 4,4' position is substituted with fluorine is oxidized with a tetravalent cerium () compound, the fluorine is eliminated. It has been discovered that 4,4'-difluorobenzophenone can be produced in high yield and high selectivity, not only having no adverse effect on the reaction, but also having a positive effect on the reaction. This was difficult to predict from the reaction of diphenylmethane in which fluorine was not substituted.

The tetravalent cerium compounds used in the present invention are salts with inorganic acids such as cerium sulfate (), cerium hydrogen sulfate (), cerium nitrate (), and cerium iodate (); salts with organic acids such as cerium acetate (); salts; cerium hydroxide (); cerium oxide (); cerium sulfate () ammonium;
Examples include double salts such as cerium () ammonium nitrate and cerium () magnesium nitrate.

Such tetravalent cerium compounds may be used alone or in combination. Also pure 4
It may be a mixture with a cerium compound having other valences instead of a cerium compound having a valence number.

By the reaction of the present invention, a tetravalent cerium compound is reduced to a trivalent cerium compound, but these trivalent cerium compounds can be reduced by electrolytic oxidation or the like.
It is easily oxidized and the original tetravalent cerium compound is regenerated.

In carrying out the reaction of the present invention, it is preferable to use the tetravalent cerium compound in an equimolar amount or more relative to 4,4'-difluorodiphenylmethane, but of course, even if it is less than that amount, I do not care. The reaction is usually carried out in a solvent, such as organic acids such as acetic acid and propionic acid; inorganic acids such as nitric acid, sulfuric acid, and perchloric acid;
Ethers such as tetrahydrofuran and dioxane; nitriles such as acetonitrile, propionitrile and benzonitrile; ketones such as acetone and methyl ethyl ketone; water, and mixtures thereof are used.

The reaction temperature and time vary depending on the type of tetravalent cerium compound and solvent used, but are usually 10~
300℃, 1 minute to 50 hours, preferably
The temperature ranges from 30 to 200°C and from 5 minutes to 20 hours. Further, the reaction is usually carried out under normal pressure, but may of course be carried out under increased pressure or reduced pressure.

〔Effect of the invention〕

It has been found that according to the method of the present invention, 4,4'-difluorobenzophenone can be produced from 4,4'-difluorodiphenylmethane in high yield and high selectivity.

〔Example〕

EXAMPLES Hereinafter, the present invention will be further explained with reference to Examples, but the present invention is not limited to these Examples.

Example 1 4.1 g of 4,4′-difluorodiphenylmethane,
Pour 40ml of 3.5N nitric acid aqueous solution into a flask and heat to approximately 90℃.
Heat to. A solution of 80 mmol of cerium () ammonium nitrate dissolved in 80 ml of 3.5N nitric acid was added dropwise to the solution over 4 hours with stirring. Reaction temperature is 85~
It was kept at 95°C. After the dropwise addition, the mixture was further stirred at this temperature, cooled, and extracted with ether. The ether layer was washed with an aqueous alkaline solution and water, dried, and analyzed. As a result, the reaction rate of 4,4'-difluorodiphenylmethane was 96%, the yield of 4,4'-difluorobenzophenone was 90%, and the selectivity was 96%. It was found that it was generated in 94% of cases.

Example 2 4.1 g of 4,4′-difluorodiphenylmethane,
50 ml of a 50% acetic acid aqueous solution was placed in a flask, and 30 ml of an aqueous solution containing 22 g of cerium () ammonium nitrate was added at once with stirring. 80 under stirring
After reacting at °C for 2 hours, the mixture was poured into saturated saline and extracted with ether. The organic layer was washed with an aqueous alkaline solution and water, dried, and the organic solvent was distilled off to obtain 4,4'-difluorobenzophenone in a yield of 92% and selectivity of 95%.

Example 3 4.1 g of 4,4'-difluorodiphenylmethane,
Pour 50ml of 1N sulfuric acid aqueous solution into a flask, and add 50ml of 1N sulfuric acid aqueous solution containing 50mmol of cerium sulfate to the flask.
was added with stirring. After reacting at 80° C. for 3 hours with stirring, saturated brine was added and ether extraction was performed. The ether layer was washed with an alkaline aqueous solution and water, and after drying, the ether was distilled off, resulting in 4,4'-
Difluorobenzophenone yield 93%, selectivity 95
Obtained in %.

Claims (1)

[Claims] 1. A method for producing 4,4'-difluorobenzophenone, which comprises reacting 4,4'-difluorodiphenylmethane with a cerium compound.