JPH02111624A - Freeze-dried potassium fluoride for fluorination - Google Patents

Abstract

PURPOSE:To enable high performance of fluorination of a variety of organic compounds by specifying the specific surface area. CONSTITUTION:Freeze-dried potassium is adjusted in its specific surface area to more than 0.3m<2>/g, preferably 0.4 to 0.8m<2>/g to prepare potassium fluoride for fluorination. The potassium fluoride has high fluorination ability to complete the fluorination of organic compounds in a short time with reduced formation of by-products and substitute the active group to be eliminated in the organic compounds with fluorine atoms readily in high selectivity and yield.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to freeze-dried potassium fluoride which has a high fluorination ability and is used for fluorination of various organic compounds.

[Problems to be solved by conventional technology and invention] Conventionally, G
,C,Finger et al., ,J,Ao+,C.
hen+, Soc+ 78+6034 (1956), organic compounds containing active halogen atoms are treated in aprotic polar solvents such as dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, dimethylsulfone, sulfolane, etc., such as potassium fluoride. A method has been proposed to obtain a fluorine compound by reacting with an alkali metal fluoride and using a halogen exchange method, but since the reaction is slow, it is necessary to carry out the reaction at high temperature for a long time.

As a result, side reaction products were produced, and the yield was still unsatisfactory as an industrial production method of 40-707.

In order to solve these problems, various methods have been proposed for changing the shape of potassium fluoride to increase its activity. For example, industrial potassium fluoride is roasted before use;
Method for making fine particles by grinding in a mortar etc.
-7529), a wet grinding method in a solvent (Japanese Unexamined Patent Publication No. 6
1-50945) and a method of dry grinding using a machine such as an atomizer (Japanese Patent Application Laid-open No. 10737-1983), but in these methods, the obtained potassium fluoride easily absorbs moisture. Variations in fluorination ability occur,
It was difficult to handle industrially and in large quantities. Also,
A method using potassium fluoride by spray drying (Japanese Patent Application Laid-open No. 58-65226) is also known, but this method requires special equipment to obtain spray-dried potassium fluoride. Spray-dried potassium fluoride is produced with different reactivity in the fluorination reaction depending on the manufacturing conditions, and special techniques are required to always achieve uniform performance.

In fact, when fluorination reactions are carried out using spray-dried potassium fluoride produced by domestic and foreign manufacturers, there is a large difference in reactivity, which causes great difficulties in industrially producing organic fluorine compounds. was.

On the other hand, a method using freeze-dried potassium fluoride has been proposed, but although this has properties as a strong base, it is reported that it has no fluorination ability at all (N, Ishikawa et al. + Chew.

Lett, +dan80.1089; 1 bid,,■8
0.1327; J, FIuor.

Chem, +18.213 (1981)).

Therefore, there has been a long-awaited demand for potassium fluoride which is always uniform and has a high fluorination ability.

[Means to solve the problem]

The inventors of the present invention solved the problems of the conventional technology and conducted intensive studies to develop potassium fluoride that is always uniform and has a high fluorination ability. By doing so, it was possible to produce freeze-dried potassium fluoride in the form of fine particles with a large specific surface area, and the present invention was completed based on the discovery that this product has an extremely high fluorination ability.

The potassium fluoride having high fluorination ability of the present invention is characterized by having a specific surface area of 0.3 nf/g or more. Its specific surface area is preferably 0.4 to 0.8 M/g.

The specific surface area of potassium fluoride varies slightly depending on the measurement method, but the specific surface area referred to in this specification is
It refers to what was measured in a He-N- (29.5% SZ) mixed gas system using tritics Flow 5orbII (Kinsetsu Seisakusho).

The potassium fluoride of the present invention, which has a high fluorination ability, is porous, has a specific surface area larger than that of roasted industrial potassium fluoride, and is a fine powder crystal with an average particle size smaller than that of industrial potassium fluoride. , has the ability to easily replace active leaving groups of organic compounds with fluorine atoms.

The potassium fluoride of the present invention can be obtained by a conventional freeze-drying process. That is, after freezing an aqueous solution of potassium fluoride, it is freeze-dried at room temperature and under reduced pressure. The lower the concentration of the potassium fluoride aqueous solution used, the more finely particulate potassium fluoride can be produced.Usually, a potassium fluoride aqueous solution of less than a saturated aqueous solution, preferably less than 40% by weight, more preferably less than 20% by weight, is freeze-dried. By doing so, freeze-dried potassium fluoride having a large specific surface area and extremely high fluorination ability can be produced. Furthermore, potassium fluoride prepared from an aqueous potassium fluoride solution containing less than 5% by weight has an even larger specific surface area and high fluorination ability, but also has the difficulty of having to evaporate a large amount of water. Therefore, the concentration of the potassium fluoride aqueous solution may be selected depending on the use and purpose.

One of the reasons why the potassium fluoride of the present invention has a high fluorination ability is that the specific surface area of the particles is extremely large and the diameter of the particles is extremely small compared to roasted potassium fluoride. can give.

(See Table 1 in Examples below) When the freeze-dried potassium fluoride of the present invention is used, the active leaving group of an organic compound can be easily converted to a fluorine atom.fftf
I can. The fluorination method itself can be carried out in the same manner as when conventional potassium fluoride is employed.

The organic compound to be fluorinated with potassium fluoride of the present invention includes, for example, a nitro group, a cyano group, an aldehyde group or a derivative thereof, an alkyl group or an aromatic substituted carboxyl group, a carboxylic acid group at the ortho or para position, Examples include esters thereof or halides thereof, sulfonic acid groups or halides thereof, trifluoromethyl groups, halogenated methyl group-substituted aromatic compounds, and halogen-substituted aromatic compounds having other electron-withdrawing groups.

Further, the leaving group may be any group that is generally recognized as a leaving group. Examples include a halogen atom, a methanesulfonyl group, a benzenesulfonyl group which may be unsubstituted or substituted with a halogen atom, an alkyl group, etc., and a trifluoromethanesulfonyl group.

[Operation and effect of the invention]

The potassium fluoride of the present invention obtained by freeze-drying an aqueous solution of potassium fluoride has a high fluorination ability, so the fluorination reaction can be completed in a short time, and the generation of side reaction products can be suppressed. It is possible to easily substitute an active de-11iI group of an organic compound with a fluorine atom with high yield and selectivity.

〔Example〕

Next, the present invention will be specifically explained with reference to examples.
The present invention is not limited in any way by the following examples.

Example 1 25 g of industrial potassium fluoride manufactured by Morita Chemical was placed in an IL eggplant type flask and dissolved in 500-g water. This was frozen to completely turn into ice, and then freeze-dried at room temperature for 3 days using a Tokyo Rikakikai Freeze Dryer FD-1 to obtain a cotton-like white powder.

Example 2 15 g of industrial potassium fluoride manufactured by Morita Chemical was dissolved in 22 g of water and frozen at -70°C. This product was freeze-dried at room temperature for 6 days to obtain a white powder.

Examples 3 to 5 Using industrial potassium fluoride manufactured by Morita Chemical, 1% by weight, 10
A 20% by weight aqueous solution was prepared and freeze-dried in the same manner as in Example 1 to obtain a white powder.

Example 6 Industrial potassium fluoride manufactured by Hashimoto Chemical was freeze-dried in the same manner as in Example 1 to obtain a cotton-like white powder.

Reference Example 1 Freeze-dried potassium fluoride prepared in Example 1 8.7 g
(0,15aol), tetraphenylphosphonium.

Promide 2.1 g (0,005a+ol), sulfolane 60 g, 4-chloronitrobenzene (PCNB)
A mixture of 15.8 g (0.1 mol) was heated to a liquid temperature of 180
Stirred at °C for 5 hours. Analysis by gas chromatography (total area method) revealed that 4-fluoronitrobenzene (PFNB) was 99% and the raw material PCNB was 1%. 4-fluoronitrobenzene by distillation 12.0
g (85% yield) was obtained.

Reference Example 2.3 A reaction was carried out in the same manner as in Reference Example 1 using the freeze-dried potassium fluoride prepared in Examples 2 and 5.

The reaction was monitored by gas chromatography at regular intervals, and the results shown in Figure 1 were obtained.

Reference Example 4 In place of the freeze-dried potassium fluoride of Example 1, the same reaction was carried out using the freeze-dried potassium fluoride prepared in Example 6. When analyzed by gas chromatography, 99% of PFNB was detected, and 1% of PCNB remained. This shows that the activity of freeze-dried potassium fluoride does not depend on the origin of the industrial potassium fluoride used as a raw material.

Reference Example 5 Freeze-dried potassium fluoride prepared in Example 1 8.7 g
(0,15+5ol), dimethyl sulfoxide (D
NSO) 48.4g, 4-chloronitrobenzene 15.
A mixture of 8 g (0,1n+ol) was stirred and refluxed.
The reaction was allowed to proceed for 5 hours. PF by gas chromatography
The production rate of NB was 99%.

Reference Example 6 Freeze-dried potassium fluoride prepared in Example 2 1.16
g (20+u+ol), polyethylene glycol (molecule 1400) 1.0 g, acetonitrile 10ml
After stirring at room temperature for 1 hour, 1.41 g of benzoyl chloride
(10 mmol) was added thereto, and the mixture was further stirred at room temperature for 2 hours. Gas chromatography analysis of the reaction mixture revealed that benzoyl fluoride was quantitatively produced.

Comparative Example 1 In place of the freeze-dried potassium fluoride of Reference Example 1, industrial potassium fluoride manufactured by Morita Chemical was used to carry out the same reaction. When analyzed by gas chromatography, 45% of PFNB was detected, and 55% of PCNB remained.

Comparative Example 2 In place of the freeze-dried potassium fluoride in Reference Example 5, industrial potassium fluoride manufactured by Morita Chemical was used to carry out the same reaction. When analyzed by gas chromatography, 65% of PFNB was detected, and 35% of PCNB remained.

Test Examples Table 1 shows the results of comparing the freeze-dried potassium fluoride prepared in Examples 1 to 5 with commercially available industrial potassium fluoride.

Particle size is Coulter Counter TA-n (manufactured by Nikaki)
Using a 3% NH, 5CN-acetone solution as an electrolyte, the particle size distribution was measured to determine the average particle size.

Table I Comparison time (h) of KF Reaction in sulfolane Figure 1 *Ishikawa: 39th Comprehensive Organic Synthetic Chemistry Research Presentation Lecture, p.
73 (1981)

[Brief explanation of the drawing]

FIG. 1 shows the time course of the reaction between 4-chloronitrobenzene and potassium fluoride in sulfolane conducted in Reference Examples 1, 2.4, and Comparative Example 1. The horizontal axis shows the reaction time (h), and the vertical axis shows the production rate (%) of 4-fluoronitrobenzene. FIG. 2 shows the time course of the reaction between 4-chloronitrobenzene and potassium fluoride in dimethyl sulfoxide conducted in Reference Example 5 and Comparative Example 2. The horizontal axis shows the reaction time (h), and the vertical axis shows the production rate (%) of 4-fluoronitrobenzene. Time (h) Figure 2 of the reaction in DMSO

Claims (1)

[Claims] 1) Freeze-dried potassium fluoride for fluorination, characterized by having a specific surface area of 0.3 m^2/g or more.