JPS61172845A - Production of 4,4-difluorobenzophenone - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as a monomer for a heat- resistant polymer or an intermediate for agricultural chemical, drug, etc. easily in high yield, by reacting 4,4'-difluorodiphenylmethane as a raw material with a tetravalent cerium compound. CONSTITUTION:4,4'-Difluorodiphenylmethane is reacted with an equimolar amount or more of a cerium (IV) compound in a solvent such nitric acid, sulfuric acid, acetic acid, etc., at 10-300 deg.C for 1min-50hr at normal pressure, to give the aimed compound. A salt with an inorganic acid such as cerium (IV) sulfate, cerium (IV) hydrogensulfate, cerum (IV) nitrate, cerium (IV) iodate, etc., cerium (IV) hydroxide, cerium (IV) oxide, or a double salt such as ammonium cerium (IV) sulfate, ammonum cerium (IV) nitrate, magnesium cerium (IV) magnesium (IV), etc., may be cited as the tetravalent cerium compound.

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 having good heat resistance and chemical resistance, and there is a demand for the development of an inexpensive method for producing it. The following methods have been proposed for producing 4.4'-difluorobenzophenone.

(1) 4.4'-Diaminodiphenylmethane is diazotized in anhydrous hydrogen fluoride or a thick hydrogen fluoride aqueous solution, followed by decomposition and fluorination of the diazonium salt and oxidation of the methylene group to a ketone group in the presence of nitrous acid. (2) 1.1-bis(4
-fluorophenyl)-2゜2.2-Trichloroethanol alkali treatment method (JP-A-57-15413
9) (314,4' dichlorobenzene phenone reacted with alkali fluoride (Japanese Unexamined Patent Publication No. 57-169
(4) A method of conducting a Friedel-Kraf type reaction between 4-fluorobenzoyl chloride and fluorinated benzene in anhydrous hydrogen fluoride in the presence of boron trifluoride (JP-A-58-12)
4731) (5) 1,1-bis(4-fluorophenyl)-2゜2
- Method of oxidizing dichloroethylene with nitric acid (Japanese Unexamined Patent Publication No. 58
However, these methods require the use of large amounts of anhydrous hydrogen fluoride, which is dangerous and difficult to handle (methods (1) and (4)), and which are unstable and have the risk of explosion. diazonium fluoride must be produced (method (1)); complex steps are required to produce the raw material compound (methods (2), (3) and (5))
), they require a long reaction time at high temperatures, the yield is not very high, and separation from raw materials, products, and side reactants is difficult (method (3)), so both methods are not suitable for industrial use. There were problems in implementing it.

On the other hand, a method for producing benzophenone by reacting unsubstituted diphenylmethane with cerium (■) salt was also known (L, 5yper, Tetrahedron L).
e-tters, 1966, p. 4493).

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 (IV) compound.

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

Such tetravalent cerium compounds may be used alone or in combination. Further, instead of being a pure tetravalent compound, it may be a mixture with cerium compounds having other valences.

Through the reaction of the present invention, tetravalent cerium compounds are reduced to trivalent cerium compounds, but these trivalent cerium compounds are easily oxidized by electrolytic oxidation, etc., and the original tetravalent cerium compounds are regenerated. be done.

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 it is of course possible to use a smaller amount. . The reaction is usually carried out in a solvent, and such solvents include 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; acetonitrile, Nitriles such as 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 in the range of 10 to 300°C and 1 minute to 50 hours, preferably 30 to 200°C,
Speak in the range of 5 minutes to 20 hours. Further, the reaction is usually carried out under normal pressure, but it 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.

〔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 40 g of 3.5N nitric acid aqueous solution into a flask and heat to about 90°C.
Heat to. A solution of 80 mmol of ammonium cerium (IV) nitrate dissolved in 80 m/3.5N nitric acid was added dropwise to this solution over 4 hours with stirring. The reaction temperature is 85-9
It was kept at 5°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 9.
At 6%, the yield of 4゜4'-difluorobenzophenone was 90%.
%, with a selectivity of 94%.

Example 2 4.1 g of 4'-difluorodiphenylmethane.

50% acetic acid aqueous solution 50r11! was placed in a flask, and an aqueous solution containing 22 g of ammonium cerium (IV) nitrate (30°) 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. After washing the organic layer with an aqueous alkaline solution and water, it was dried and the organic solvent was distilled off, resulting in 4.4'-
Difluorobenzophenone yield 92%, selectivity 95%
Obtained with.

Example 3 4.1 g of 4'-difluorodiphenylmethane.

IN sulfuric acid aqueous solution 50- is put into a flask, and IN sulfuric acid aqueous solution 5Qm7 containing cerium sulfate 59n+mol is placed in the flask.
was added while 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 aqueous alkaline solution and water, dried, and then the ether was distilled off to obtain 4.4'-difluorobenzophenone in a yield of 93% and a selectivity of 95%.

Claims (1)

[Claims] 4,4'-difluorodiphenylmethane was dissolved in cerium (I
V) 4,4′- characterized by reacting with a compound
Method for producing difluorobenzophenone.