JP7746196B2 - Method for producing 9,9-bis(4-amino-3-fluorophenyl)fluorene - Google Patents

Description

The present invention relates to a method for producing 9,9-bis(4-amino-3-fluorophenyl)fluorene.

Since 9,9-bis(4-amino-3-fluorophenyl)fluorene contains electron-withdrawing fluorine atoms in its structure, polyimides, polyamides, and epoxy resins that use this compound as a starting material are expected to have lower dielectric constants and improved heat resistance, making it suitable for use in a wide range of industrial fields, including electronic information materials and composite materials.

9,9-bis(4-amino-3-fluorophenyl)fluorene is obtained by condensing 9-fluorenone and 2-fluoroaniline. However, the resulting 9,9-bis(4-amino-3-fluorophenyl)fluorene has the problem of being easily discolored.

In particular, 9,9-bis(4-amino-3-fluorophenyl)fluorene with little coloring is required for use in optical applications that require transparency, such as liquid crystal display substrates and flexible display substrates.

In Patent Document 1, the condensation reaction between 9-fluorenone and 2-fluoroaniline is carried out using 7.0 moles of 2-fluoroaniline and 1.3 moles of trifluoromethanesulfonic acid relative to the amount of 9-fluorenone.

In Patent Document 2, a condensation reaction is carried out between 9-fluorenone and 2-fluoroaniline in the presence of 15 molar amounts of 2-fluoroaniline relative to the 9-fluorenone, using 0.9 molar amounts of hydrochloric acid or 2-fluoroaniline hydrochloride relative to the 9-fluorenone, and the resulting 9,9-bis(4-amino-3-fluorophenyl)fluorene is decolorized using activated carbon.

In Patent Document 3, a condensation reaction between 9-fluorenone and 2-fluoroaniline is carried out using 8.0 moles of 2-fluoroaniline relative to 9-fluorenone and a titanium-based solid acid catalyst.

Patent Document 1 describes a method for producing 9,9-bis(4-amino-3-fluorophenyl)fluorene using trifluoromethanesulfonic acid as an acid catalyst. However, the yield is low at 45%, and there is no mention of the coloration of the resulting 9,9-bis(4-amino-3-fluorophenyl)fluorene. Furthermore, because trifluoromethanesulfonic acid is a volatile liquid, there are concerns that it may corrode equipment.

Patent Document 2 describes a method for producing 9,9-bis(4-amino-3-fluorophenyl)fluorene using hydrochloric acid as an acid catalyst. Hydrochloric acid forms a salt with 2-fluoroaniline, and some of this salt precipitates during the condensation reaction, making the mixture difficult to stir. Furthermore, using activated carbon to decolorize the resulting 9,9-bis(4-amino-3-fluorophenyl)fluorene complicates the production process, and no examples of the decolorization process are described.

The reaction in Patent Document 3 uses a titanium-based solid superacid as the acid catalyst. Trace amounts of metal dissolve from this titanium-based acid catalyst, leaving metal residue in the resulting 9,9-bis(4-amino-3-fluorophenyl)fluorene, raising concerns that this could adversely affect the physical properties of polyamides, polyimides, epoxy resins, and other products that use 9,9-bis(4-amino-3-fluorophenyl)fluorene.

Japanese Unexamined Patent Publication No. 2-261524 JP 2011-84502 A Chinese Patent No. 104926667

The object of the present invention is to provide a manufacturing method that can produce 9,9-bis(4-amino-3-fluorophenyl)fluorene with little coloration in high yield.

The method for producing 9,9-bis(4-amino-3-fluorophenyl)fluorene of the present invention includes a step of subjecting 9-fluorenone and 2-fluoroaniline, in an amount of 7.5 to 12.5 times by mole relative to the 9-fluorenone, to a condensation reaction in the presence of an aromatic sulfonic acid to obtain a reaction solution containing 9,9-bis(4-amino-3-fluorophenyl)fluorene.

The method for producing 9,9-bis(4-amino-3-fluorophenyl)fluorene of the present invention includes a step of condensing 9-fluorenone and a specific amount of 2-fluoroaniline in the presence of an aromatic sulfonic acid to obtain a reaction solution containing 9,9-bis(4-amino-3-fluorophenyl)fluorene, thereby producing 9,9-bis(4-amino-3-fluorophenyl)fluorene with low coloration in high yield. After obtaining the reaction solution containing 9,9-bis(4-amino-3-fluorophenyl)fluorene, the method simply involves performing a neutralization treatment and cooling crystallization, which are common purification steps, resulting in an industrially excellent production method that produces 9,9-bis(4-amino-3-fluorophenyl)fluorene with low coloration in high yield. When a 10 mg/mL tetrahydrofuran solution of 9,9-bis(4-amino-3-fluorophenyl)fluorene obtained by the production method of the present invention is prepared, it exhibits a light transmittance of 97% or more over the entire wavelength range from 400 to 900 nm, exhibiting low coloration, and can be used in electronic information materials, optical materials, composite materials, and other applications. Theoretically, the upper limit of light transmittance is 100%, so there is no particular limit.

FIG. 1 is a graph comparing the light transmittance of tetrahydrofuran solutions of 9,9-bis(4-amino-3-fluorophenyl)fluorene synthesized by changing the type of acid catalyst used in the condensation reaction in the Examples. FIG. 1 is a graph comparing the light transmittance of tetrahydrofuran solutions of 9,9-bis(4-amino-3-fluorophenyl)fluorene synthesized by varying the amount of 2-fluoroaniline used in the examples. FIG. 1 is a graph comparing the light transmittance of tetrahydrofuran solutions of 9,9-bis(4-amino-3-fluorophenyl)fluorene synthesized by varying the amount of p-toluenesulfonic acid used in the examples.

The present invention will be described in detail below.
The 9,9-bis(4-amino-3-fluorophenyl)fluorene produced in the present invention is produced by the condensation reaction of 9-fluorenone and 2-fluoroaniline.

The amount of 2-fluoroaniline used in the condensation reaction of the present invention is 7.5 to 12.5 times the number of moles of 9-fluorenone. By using 7.5 to 12.5 times the number of moles of 2-fluoroaniline, a 9,9-bis(4-amino-3-fluorophenyl)fluorene compound with little coloration can be produced. In particular, when a 10 mg/mL tetrahydrofuran solution of the resulting 9,9-bis(4-amino-3-fluorophenyl)fluorene is prepared, the light transmittance is 97% or higher over the entire wavelength range of 400 to 900 nm, and the compound has little coloration.

The condensation reaction of 9-fluorenone and 2-fluoroaniline is carried out in the presence of an aromatic sulfonic acid. Aromatic sulfonic acid is an acid catalyst soluble in 2-fluoroaniline, and the salt of aromatic sulfonic acid and 2-fluoroaniline also dissolves in 2-fluoroaniline. Therefore, salt precipitation does not occur during the condensation reaction, preventing stirring. On the other hand, the use of liquid, volatile sulfonic acids such as methanesulfonic acid and trifluoromethanesulfonic acid can be difficult to handle due to concerns about corrosion of equipment. Furthermore, aromatic sulfonic acids do not readily oxidize 2-fluoroaniline during the condensation reaction, making them less likely to produce colored compounds. When an oxidizing acid catalyst, such as a heteropolyacid such as phosphotungstic acid or silicotungstic acid, is used, the reaction solution turns reddish-purple. This is thought to be due to the oxidation of 2-fluoroaniline by the acid catalyst, resulting in the production of colored compounds. Consequently, the use of aromatic sulfonic acid offers the advantage of reducing the color of the resulting 9,9-bis(4-amino-3-fluorophenyl)fluorene.

Examples of aromatic sulfonic acids include p-toluenesulfonic acid, benzenesulfonic acid, m-xylene-4-sulfonic acid, p-xylene-2-sulfonic acid, 2-naphthalenesulfonic acid, and hydrates thereof. These aromatic sulfonic acids may be used in combination. More preferred are p-toluenesulfonic acid, p-toluenesulfonic acid monohydrate, and benzenesulfonic acid.

The amount of aromatic sulfonic acid is preferably 0.1 to 5.0 times the number of moles of 9-fluorenone, and more preferably 1.0 to 3.0 times. Using 0.1 or more moles of aromatic sulfonic acid allows the condensation reaction to proceed efficiently. Furthermore, using 3.0 or less moles of aromatic sulfonic acid allows for efficient use of expensive aromatic sulfonic acid.

In the condensation reaction of 9-fluorenone and 2-fluoroaniline, water is produced, but it is preferable to remove this water while carrying out the reaction. To achieve this, a method is used in which an inert gas is passed through the reaction system while entraining the produced water, or an azeotropic solvent is used to continuously remove the produced water. Nitrogen is preferably used as the inert gas. The azeotropic solvent is a solvent that is inert to the reaction system, such as cyclohexane, methylcyclohexane, benzene, toluene, or xylene. Toluene or xylene is preferably used. The amount of this azeotropic solvent used is preferably 0.5 to 10 times the mass of 9-fluorenone.

The condensation reaction is preferably carried out in an oxygen-free inert atmosphere. Specifically, it can be carried out by passing substantially oxygen-free nitrogen gas through the reaction system. If the reaction is carried out in the presence of oxygen, 2-fluoroaniline will be oxidized, producing colored substances that may discolor the 9,9-bis(4-amino-3-fluorophenyl)fluorene.

The reaction temperature is preferably 80 to 170°C, more preferably 120 to 160°C. If the reaction temperature is lower than 80°C, it will take a long time to complete the reaction, and if it is higher than 170°C, the boiling point of 2-fluoroaniline will be exceeded, and 2-fluoroaniline will be discharged from the system along with water. Furthermore, while the recovery and reuse of unreacted 2-fluoroaniline is important for reducing production costs, if 2-fluoroaniline is discharged from the system, the recovery rate of 2-fluoroaniline will decrease, leading to a worsening of the unit consumption and an increase in waste.

The reaction time depends on the reaction temperature, but is preferably 3 to 100 hours, more preferably 5 to 80 hours. The reaction end point can be set as the point in time when, in liquid chromatography analysis of the reaction solution, the total peak area of 9-fluorenone and the imine intermediate formed by condensing one molecule of 2-fluoroaniline with 9-fluorenone is preferably 5.0 area% or less, more preferably 2.0 area% or less, of the peak area obtained by subtracting the total peak area of 2-fluoroaniline and aromatic sulfonic acid from the total peak area.

After the reaction is complete, the reaction solution contains 9,9-bis(4-amino-3-fluorophenyl)fluorene, as well as excess 2-fluoroaniline, aromatic sulfonic acid, and impurities. The aromatic sulfonic acid can be removed by adding an aqueous alkaline solution to the reaction solution and washing it. This reduces the aromatic sulfonic acid content in the 9,9-bis(4-amino-3-fluorophenyl)fluorene obtained by the crystallization procedure. In other words, the aromatic sulfonic acid content in the crystallized 9,9-bis(4-amino-3-fluorophenyl)fluorene can be substantially reduced to 30 ppm or less.

After the reaction is complete, the reaction solution is preferably diluted with 2-fluoroaniline. Because the solubility of 9,9-bis(4-amino-3-fluorophenyl)fluorene in 2-fluoroaniline is 17% by mass at 100°C, a concentration below this level can prevent precipitation of 9,9-bis(4-amino-3-fluorophenyl)fluorene during the washing process with an alkaline aqueous solution. While there is essentially no lower limit to the concentration of 9,9-bis(4-amino-3-fluorophenyl)fluorene when diluting the reaction solution, for example, diluting the 9,9-bis(4-amino-3-fluorophenyl)fluorene to 5% by mass increases the amount of 2-fluoroaniline used and reduces the crystallization rate of 9,9-bis(4-amino-3-fluorophenyl)fluorene in the subsequent crystallization process, thereby reducing productivity. Therefore, a concentration of 9,9-bis(4-amino-3-fluorophenyl)fluorene in the reaction solution of 11 to 17% by mass is preferred.

As the alkaline aqueous solution, an aqueous solution of an alkali metal hydroxide, an aqueous solution of an alkali metal carbonate, an aqueous solution of an alkali metal hydrogencarbonate, or an aqueous solution of an alkali metal sulfite may be used. Examples of the aqueous solution of an alkali metal hydroxide include an aqueous solution of lithium hydroxide, an aqueous solution of sodium hydroxide, and an aqueous solution of potassium hydroxide. Examples of the aqueous solution of an alkali metal carbonate include an aqueous solution of sodium carbonate, an aqueous solution of lithium carbonate, and an aqueous solution of potassium carbonate. Examples of the aqueous solution of an alkali metal hydrogencarbonate include an aqueous solution of sodium hydrogencarbonate, and an aqueous solution of an alkali metal sulfite include an aqueous solution of sodium sulfite.

The molar amount of base in the alkaline aqueous solution is preferably in excess of the molar amount of aromatic sulfonic acid used in the reaction. More preferably, it is 1.1 to 2.0 times the molar amount of aromatic sulfonic acid.

The mass of the alkaline aqueous solution is preferably 0.25 to 4 times, and more preferably 0.5 to 2 times, the mass of the reaction liquid. By making the mass of the alkaline aqueous solution 0.5 times or more, the separability of the organic phase and the aqueous layer is improved. Furthermore, by making the mass of the alkaline aqueous solution 2 times or less, the amount of wastewater can be reduced.

Since some alkali metal ions remain in the solution after washing with an alkaline aqueous solution, it is preferable to remove the remaining alkali metal ions by washing with water. The mass of water is preferably 0.25 to 4 times, and more preferably 0.5 to 2 times, the mass of the solution after washing with an alkaline aqueous solution.

After washing with an alkaline aqueous solution, or an alkaline aqueous solution and water, the organic phase is cooled to 0-10°C, causing 9,9-bis(4-amino-3-fluorophenyl)fluorene to precipitate. This is then filtered and rinsed with a poor solvent, allowing for the production of low-coloration 9,9-bis(4-amino-3-fluorophenyl)fluorene in high yield.

The poor solvent used for washing may be an alcohol solvent, an aromatic hydrocarbon solvent, an ether solvent, an ester solvent, or an amide solvent, but an alcohol solvent is preferably used as the solvent for rinsing. Examples of the alcohol solvent include methanol, ethanol, and isopropyl alcohol.
The mass of the poor solvent used for washing is preferably 0.1 to 10 times the mass of 9-fluorenone.

The following examples provide a more detailed explanation, but the present invention is not limited to these examples. The analytical values of the 9,9-bis(4-amino-3-fluorophenyl)fluorene obtained in this specification were measured using the following methods.

(conversion rate, reaction yield, chemical purity)
The fraction (HPLC area %) of the peak area of 9-fluorenone relative to the total peak area excluding the peak areas of 2-fluoroaniline and p-toluenesulfonic acid, as measured by liquid chromatography (Shimadzu Corporation, LC-20A) under the following conditions, was measured, and the value obtained by subtracting this value from 100% was defined as the 9-fluorenone conversion rate (%). Similarly, the fraction (HPLC area %) of the peak area of 9,9-bis(4-amino-3-fluorophenyl)fluorene was measured, and this was defined as the reaction yield (%).

Furthermore, the 9,9-bis(4-amino-3-fluorophenyl)fluorene obtained after purification was measured by liquid chromatography (LC-20A manufactured by Shimadzu Corporation) under the following conditions, and the peak area fraction of 9,9-bis(4-amino-3-fluorophenyl)fluorene was taken as the chemical purity (LC area %).
Column: YMC-Pack ODS-AM 4.6φ×250mm
Column temperature: 40°C
Mobile phase: 0.1% (v/v) phosphoric acid aqueous solution was used as composition (A) and acetonitrile as composition (B), and the composition was changed in the following gradient (A/B).
Gradient Time (min) Composition (A/B)
0 60/40
10 45/55
15 20/80
25 20/80
30 10/90
40 10/90
45 40/60
60 40/60
・Flow rate: 1ml/min
・Injection volume: 10μl
Detection: UV 254 nm
Analysis time: 45 minutes. Analysis sample preparation: 0.02 g of sample was weighed and diluted with approximately 40 ml of acetonitrile. However, the analysis conditions are not limited to these as long as the same results as those based on the above analysis conditions are obtained.

(p-Toluenesulfonic acid content)
The content of p-toluenesulfonic acid in the resulting 9,9-bis(4-amino-3-fluorophenyl)fluorene was measured by liquid chromatography (Shimadzu Corporation, LC-20A) under the above conditions, except that the detection UV wavelength was changed to 225 nm.

The internal standard method was used to quantify the p-toluenesulfonic acid content. The standard sample of p-toluenesulfonic acid was p-toluenesulfonic acid monohydrate (Nacalai Tesque, Grade 1), and the internal standard was diphenyl ether (Fujifilm Wako Pure Chemical Industries, Ltd.). The diphenyl ether concentration was fixed at 134 mg/L, and acetonitrile solutions with p-toluenesulfonic acid monohydrate concentrations of 0.2, 0.6, and 1.0 mg/L were prepared, and a calibration curve was created.

For the p-toluenesulfonic acid measurement sample, a 4 mg/mL acetonitrile solution of the obtained 9,9-bis(4-amino-3-fluorophenyl)fluorene was prepared and used for measurement. However, these analytical conditions are not limited to these as long as the same analytical results as those based on the above analytical conditions are obtained.

(Light transmittance measurement)
For the light transmittance measurement sample, a 10 mg/mL tetrahydrofuran solution of the obtained 9,9-bis(4-amino-3-fluorophenyl)fluorene was prepared, and the light transmittance was measured using an ultraviolet-visible spectrophotometer (Shimadzu Corporation UV-1900) under the following conditions.
・Measurement wavelength 400-900nm
Measurement cell: Quartz cell (optical path length 1.0 cm)
- Scan speed: Medium - Sampling pitch: 1.0 nm
- Type of photometric value: Transmittance - Baseline measurement: Baseline measurement with tetrahydrofuran

Example 1
A 300 mL four-neck flask equipped with a thermometer, a condenser, and a stirrer was charged with 6.3 g (35 mmol) of 9-fluorenone, 38.9 g of 2-fluoroaniline (10 mol/9-fluorenone), and 6.7 g of p-toluenesulfonic acid monohydrate (1.0 mol/9-fluorenone). Under stirring in a nitrogen atmosphere, the liquid temperature was raised to 150°C to initiate the reaction. During the reaction, the condensation reaction was carried out by aging for 19 hours while distilling off water. After completion of the reaction, the conversion of 9-fluorenone was 100% (LC area %), and the reaction yield of 9,9-bis(4-amino-3-fluorophenyl)fluorene was 93.7%.

77.8 g of 2-fluoroaniline (20 moles per 9-fluorenone, 11% by mass concentration of 9,9-bis(4-amino-3-fluorophenyl)fluorene after dilution) was added to the resulting reaction solution. 124.2 g of a 5% by mass aqueous sodium carbonate solution (1.7 moles per p-toluenesulfonic acid monohydrate) was then added and the mixture was washed at 90°C. The aqueous layer was then removed, and 124.2 g of purified water was added and the mixture was washed at 90°C. The aqueous layer was removed, and the washed organic layer was allowed to cool, yielding a slurry containing 9,9-bis(4-amino-3-fluorophenyl)fluorene. A cake was obtained by filtering this slurry. The cake was vacuum-dried overnight at 60°C and a reduced pressure of 0.01 kPa or less, yielding 10.1 g of 9,9-bis(4-amino-3-fluorophenyl)fluorene (isolation yield 75.1% by mass based on 9-fluorenone) as a white solid. The chemical purity determined by liquid chromatography analysis was 98.9% (LC area %), and the p-toluenesulfonic acid content determined by the liquid chromatography internal standard method was less than 30 ppm.

Example 2
The reaction was carried out in the same manner as in Example 1, except that the amount of 2-fluoroaniline used was changed from 38.9 g (10 mol times/9-fluorenone) to 29.2 g (7.5 mol times/9-fluorenone). The reaction was completed in 10 hours, and the reaction yield was 93.5%. Purification was carried out in the same manner as in Example 1, except that the amount of 2-fluoroaniline used was changed from 77.8 g (20 mol times/9-fluorenone, 9,9-bis(4-amino-3-fluorophenyl)fluorene concentration after dilution: 11% by mass) to 87.5 g (23 mol times/9-fluorenone, 9,9-bis(4-amino-3-fluorophenyl)fluorene concentration after dilution: 11% by mass). As a result, 10.2 g of 9,9-bis(4-amino-3-fluorophenyl)fluorene (isolation yield: 76.0%/based on 9-fluorenone) was obtained as a white solid. The chemical purity determined by liquid chromatography analysis was 99.0% (LC area %), and the p-toluenesulfonic acid content determined by the liquid chromatography internal standard method was less than 30 ppm.

Example 3
The reaction was carried out in the same manner as in Example 1, except that 38.9 g of 2-fluoroaniline (10 mol times/9-fluorenone) was changed to 48.6 g of 2-fluoroaniline (12.5 mol times/9-fluorenone). The reaction was completed in 20 hours, and purification was carried out in the same manner as in Example 1, except that 77.8 g of 2-fluoroaniline (20 mol times/9-fluorenone, 9,9-bis(4-amino-3-fluorophenyl)fluorene concentration after dilution: 11% by mass) was changed to 68.1 g of 2-fluoroaniline (18 mol times/9-fluorenone, 9,9-bis(4-amino-3-fluorophenyl)fluorene concentration: 11% by mass). As a result, 10.6 g of 9,9-bis(4-amino-3-fluorophenyl)fluorene (isolation yield 78.9%/based on 9-fluorenone) was obtained as a white solid. The chemical purity determined by liquid chromatography analysis was 98.9% (LC area %), and the p-toluenesulfonic acid content determined by the liquid chromatography internal standard method was less than 30 ppm.

Example 4
The reaction was carried out in the same manner as in Example 1, except that 6.7 g of p-toluenesulfonic acid monohydrate (1.0 mol/9-fluorenone) was replaced with 10.0 g of p-toluenesulfonic acid monohydrate (1.5 mol/9-fluorenone). The reaction was completed in 10 hours, and the reaction yield was 94.3%. Purification was carried out in the same manner as in Example 1. As a result, 10.7 g of 9,9-bis(4-amino-3-fluorophenyl)fluorene (isolated yield 79.2% based on 9-fluorenone) was obtained as a white solid. The chemical purity determined by liquid chromatography analysis was 99.2% (LC area %), and the p-toluenesulfonic acid content determined by the liquid chromatography internal standard method was less than 30 ppm.

Example 5
A reaction was carried out in the same manner as in Example 1, except that 6.7 g of p-toluenesulfonic acid monohydrate (1.0 mol fold/9-fluorenone) was changed to 20.0 g of p-toluenesulfonic acid monohydrate (3.0 mol fold/9-fluorenone). The reaction was completed in 8 hours, and the reaction yield was 92.5%. Purification was carried out in the same manner as in Example 1, except that 124.2 g of a 5% by mass aqueous sodium carbonate solution (1.7 mol fold/p-toluenesulfonic acid monohydrate) was changed to 124.2 g of a 10% by mass aqueous sodium carbonate solution (1.1 mol fold/p-toluenesulfonic acid monohydrate). As a result, 9.3 g of 9,9-bis(4-amino-3-fluorophenyl)fluorene (isolation yield 69.4% based on 9-fluorenone) was obtained as a white solid. The chemical purity determined by liquid chromatography analysis was 99.2% (LC area %), and the p-toluenesulfonic acid content determined by the liquid chromatography internal standard method was less than 30 ppm.

(Comparative Example 1)
A reaction was carried out in the same manner as in Example 1, except that 6.7 g of p-toluenesulfonic acid monohydrate (1.0 mol/9-fluorenone) was replaced with 3.7 g of 35% hydrochloric acid (1.0 mol/9-fluorenone). The reaction was not complete even after 47 hours, at which point the reaction was terminated. Purification was carried out in the same manner as in Example 1. As a result, 7.2 g of 9,9-bis(4-amino-3-fluorophenyl)fluorene was obtained as a pale purple solid. This solid was placed in a 300 mL four-neck flask equipped with a thermometer, a condenser, and a stirrer, and 120.0 g of toluene was added. The mixture was heated to reflux and then allowed to cool, thereby recrystallizing 9,9-bis(4-amino-3-fluorophenyl)fluorene. This was then filtered to obtain a cake. The cake was dried overnight at 60°C under a reduced pressure of 0.01 kPa or less to obtain 5.6 g of 9,9-bis(4-amino-3-fluorophenyl)fluorene (isolated yield: 41.8% based on 9-fluorenone) as a pale purple solid. The chemical purity determined by liquid chromatography was 99.4% (LC area %).

(Comparative Example 2)
The reaction was carried out in the same manner as in Example 1, except that 6.7 g of p-toluenesulfonic acid monohydrate (1.0 mol/9-fluorenone) was replaced with 3.4 g of sulfuric acid (1.0 mol/9-fluorenone). The reaction was not complete even after 75 hours, at which point the reaction was terminated. Purification was carried out in the same manner as in Example 1. As a result, 6.8 g of 9,9-bis(4-amino-3-fluorophenyl)fluorene (isolation yield 50.5% based on 9-fluorenone) was obtained as a pale purple solid. The chemical purity as determined by liquid chromatography analysis was 98.1% (LC area %).

(Comparative Example 3)
A reaction was carried out in the same manner as in Example 1, except that 6.7 g of p-toluenesulfonic acid monohydrate (1.0 mol/9-fluorenone) was replaced with 1.2 g of phosphotungstic acid hydrate (0.01 mol/9-fluorenone). Immediately after the addition of phosphotungstic acid hydrate, the reaction solution turned reddish purple. The reaction was completed in 24 hours, and purification was carried out in the same manner as in Example 1. As a result, 10.2 g of 9,9-bis(4-amino-3-fluorophenyl)fluorene (isolation yield 76.1% based on 9-fluorenone) was obtained as a pale purple solid. The chemical purity determined by liquid chromatography analysis was 99.4% (LC area %).

(Comparative Example 4)
A reaction was carried out in the same manner as in Example 1, except that 6.7 g of p-toluenesulfonic acid monohydrate (1.0 mol/9-fluorenone) was replaced with 1.2 g of tungstosilicic acid hydrate (0.01 mol/9-fluorenone). Immediately after the addition of tungstosilicic acid hydrate, the reaction solution turned reddish purple. The reaction was completed in 24 hours, and purification was carried out in the same manner as in Example 1. As a result, 9.7 g of 9,9-bis(4-amino-3-fluorophenyl)fluorene (isolation yield 71.8% based on 9-fluorenone) was obtained as a pale purple solid. The chemical purity determined by liquid chromatography analysis was 99.4% (LC area %).

(Comparative Example 5)
The reaction was carried out in the same manner as in Example 1, except that the amount of 2-fluoroaniline used was changed from 38.9 g (10 mol times/9-fluorenone) to 19.4 g (5.0 mol times/9-fluorenone). The reaction was completed in 7 hours, and the reaction yield was 91.4%. Purification was carried out in the same manner as in Example 1, except that the amount of 2-fluoroaniline used was changed from 77.8 g (20 mol times/9-fluorenone, 9,9-bis(4-amino-3-fluorophenyl)fluorene concentration after dilution: 11% by mass) to 97.2 g (25 mol times/9-fluorenone, 9,9-bis(4-amino-3-fluorophenyl)fluorene concentration after dilution: 11% by mass). As a result, 10.0 g of 9,9-bis(4-amino-3-fluorophenyl)fluorene (isolation yield: 74.5%/based on 9-fluorenone) was obtained as a white solid. The chemical purity determined by liquid chromatography analysis was 99.1% (LC area %), and the p-toluenesulfonic acid content determined by the liquid chromatography internal standard method was less than 30 ppm.

(Comparative Example 6)
The reaction was carried out in the same manner as in Example 1, except that the amount of 2-fluoroaniline used was changed from 38.9 g (10 mol times/9-fluorenone) to 58.3 g (15.0 mol times/9-fluorenone). The reaction was completed in 21 hours, and the reaction yield was 93.1%. Purification was carried out in the same manner as in Example 1, except that the amount of 2-fluoroaniline used was changed from 77.8 g (20 mol times/9-fluorenone, 9,9-bis(4-amino-3-fluorophenyl)fluorene concentration 11% by mass) to 58.3 g (15 mol times/9-fluorenone, 9,9-bis(4-amino-3-fluorophenyl)fluorene concentration 11% by mass). As a result, 10.1 g of 9,9-bis(4-amino-3-fluorophenyl)fluorene (isolation yield 75.3%/based on 9-fluorenone) was obtained as a white solid. The chemical purity determined by liquid chromatography analysis was 98.8% (LC area %), and the p-toluenesulfonic acid content determined by the liquid chromatography internal standard method was less than 30 ppm.

Table 1 provides an overview of Examples 1 to 5, and Table 2 provides an overview of Comparative Examples 1 to 6. Regarding light transmittance, measurements showing a transmittance of 97% or higher across the entire wavelength range of 400 to 900 nm are marked with an ◯, and results other than this are marked with an ×. The results of light transmittance measurements for Examples 1 to 5 and Comparative Examples 1 to 6 are also shown in Figures 1 to 3.

Figure 1 compares the light transmittance at wavelengths of 400 to 900 nm of a 10 mg/mL tetrahydrofuran solution of 9,9-bis(4-amino-3-fluorophenyl)fluorene, synthesized using 10 moles of 2-fluoroaniline relative to 9-fluorenone and various acid catalysts.

Figure 2 compares the light transmittance at wavelengths of 400 to 900 nm of a 10 mg/mL tetrahydrofuran solution of 9,9-bis(4-amino-3-fluorophenyl)fluorene synthesized using 1.0 mole of p-toluenesulfonic acid relative to 9-fluorenone and 5.0 to 15 moles of 2-fluoroaniline relative to 9-fluorenone.

Figure 3 compares the light transmittance at wavelengths of 400 to 900 nm of a 10 mg/mL tetrahydrofuran solution of 9,9-bis(4-amino-3-fluorophenyl)fluorene synthesized using 10 molar equivalents of 2-fluoroaniline relative to 9-fluorenone and 1.0 to 3.0 molar equivalents of p-toluenesulfonic acid relative to 9-fluorenone.

When p-toluenesulfonic acid, which has no oxidizing power, was used, 9,9-bis(4-amino-3-fluorophenyl)fluorene was obtained in high yield with a transmittance of over 97%. On the other hand, when hydrochloric acid or sulfuric acid was used, the transmittance and yield decreased. Furthermore, when phosphotungstic acid and silicotungstic acid, which have oxidizing power, were used, the yield was high, but the transmittance was less than 97%.

According to the method for producing 9,9-bis(4-amino-3-fluorophenyl)fluorene of the present invention, 9-fluorenone and 2-fluoroaniline are subjected to a condensation reaction in the presence of an aromatic sulfonic acid to obtain a reaction solution containing 9,9-bis(4-amino-3-fluorophenyl)fluorene. Then, by performing a neutralization treatment and cooling crystallization, which are common purification processes, 9,9-bis(4-amino-3-fluorophenyl)fluorene can be obtained in high yield with little coloration. The method for producing 9,9-bis(4-amino-3-fluorophenyl)fluorene of the present invention is an industrially excellent production method.

The 9,9-bis(4-amino-3-fluorophenyl)fluorene compound obtained by the manufacturing method of the present invention can be used in electronic information materials, optical materials, composite materials, etc.

Claims (3)

A method for producing 9,9-bis(4-amino-3-fluorophenyl)fluorene, comprising the step of condensing 9-fluorenone with 7.5 to 12.5 times by mole of 2-fluoroaniline relative to the 9-fluorenone in the presence of an aromatic sulfonic acid to obtain a reaction solution containing 9,9-bis(4-amino-3-fluorophenyl)fluorene. The method for producing 9,9-bis(4-amino-3-fluorophenyl)fluorene according to claim 1, wherein the aromatic sulfonic acid is p-toluenesulfonic acid, benzenesulfonic acid, m-xylene-4-sulfonic acid, p-xylene-2-sulfonic acid, 2-naphthalenesulfonic acid, a hydrate thereof, or a mixture thereof. 3. The method for producing 9,9-bis(4-amino-3-fluorophenyl)fluorene according to claim 1 or 2, wherein the aromatic sulfonic acid is used in an amount of 1.0 to 3.0 times by mole relative to the 9-fluorenone in the condensation reaction.