JP7853211B2 - Fluorene derivatives and methods for producing the same - Google Patents

Description

This invention relates to fluorene derivatives and methods for producing the same.

In recent years, fluorene derivatives such as 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene have shown promise as raw materials for producing polymers (e.g., epoxy resins, polyesters, polyethers, polycarbonates, etc.) with excellent heat resistance, transparency, and high refractive index, and are expected to be used as raw materials for optical lenses, films, plastic optical fibers, optical disc substrates, heat-resistant resins, and engineering plastics (Patent Document 1). Furthermore, various fluorene derivatives such as 9,9-bis[6-(2-hydroxyethoxy)-2-naphthyl]fluorene (Patent Document 2) and 9,9-bis[4-(2-hydroxyethoxy)phenyl]-2,7-diphenylfluorene (Patent Document 3) have been developed, and the development of novel fluorene derivatives and their manufacturing methods is desired to further enhance the functionality of materials.

Patent No. 4140975 Japanese Patent Publication No. 2014-28806 International Publication No. 2019/151264

The present invention aims to provide novel fluorene derivatives and methods for producing the same.

The inventors have found that the above problems can be solved by the present invention having the following aspects.
《Aspect 1》
A fluorene derivative represented by the following formula (1).

(In the formula, Z is a polycyclic aromatic hydrocarbon in which three or more benzene rings are bonded; _L1 is an alkylene group having 1 to 15 carbon atoms; _{R1 and R2} are hydrocarbon groups having 1 to 20 carbon atoms; _m1 is an integer from 0 to 5; _n1 is an integer from 0 to 10; and _n2 is an integer from 0 to 4.)
Appearance 2
The fluorene derivative according to embodiment 1, wherein Z in formula (1) is phenanthrene.
《Aspect 3》
The fluorene derivative according to embodiment 1 or 2, wherein the fluorene derivative represented by formula (1) is a fluorene derivative represented by the following formula (2).

(In the formula, _R3 , R4 _{, and R5} are hydrocarbon groups having 1 to 20 carbon atoms, _n3 is an integer from 0 to 4, _n4 is 0 or 1, _n5 is an integer from 0 to 3, _{and R2} , _L1 , _m1 , and _n2 are the same as in formula (1) above.)
《Aspect 4》
The fluorene derivative according to any one of embodiments 1 to 3, wherein the fluorene derivative represented by formula (1) is a fluorene derivative represented by the following formula (3).

《Aspect 5》
The fluorene derivative according to any one of embodiments 1 to 3, wherein the fluorene derivative represented by formula (1) is a fluorene derivative represented by the following formula (4).

《Aspect 6》
A fluorene derivative according to any one of embodiments 1 to 5, wherein the HPLC purity is 90 area percent or more.
《Aspect 7》
A fluorene derivative according to any one of embodiments 1 to 6, wherein the refractive index is 1.7 or higher.
《Appearance 8》
A method for producing a fluorene derivative, comprising reacting fluorenones represented by the following formula (5) with alcohols represented by the following formula (6) in a reaction solvent in the presence of an acid catalyst to obtain a fluorene derivative represented by the following formula (7).

(In the formula, _R² and _n² are the same as in formula (1) above.)

(In the formula, Z, _R1 , and _n1 are the same as in formula (1) above.)

(In the formula, Z, _R1 , _R2 , _n1 , and _n2 are the same as in formula (1) above.)
《Aspect 9》
A method for producing a fluorene derivative, comprising reacting the fluorene derivative represented by formula (7) described in embodiment 8 with ethylene carbonate in the presence of a base to obtain a fluorene derivative represented by the following formula (8).

(In the formula, _m1 is an integer from 1 to 5, and Z, _L1 , R1 _, R2, _n1 , _{and n2} are the same as in formula (1) above.)

According to the present invention, it is possible to provide a novel fluorene derivative with high purity and a method for producing the same.

This figure shows the NMR chart of the fluorene derivative obtained in Example 1. This figure shows the NMR chart of the fluorene derivative obtained in Example 2.

Fluorene derivatives
The novel fluorene derivative in the present invention is represented by the following formula (1).

(In the formula, Z is a polycyclic aromatic hydrocarbon in which three or more benzene rings are bonded; _L1 is an alkylene group having 1 to 15 carbon atoms; _{R1 and R2} are hydrocarbon groups having 1 to 20 carbon atoms; _m1 is an integer from 0 to 5; _n1 is an integer from 0 to 10; and _n2 is an integer from 0 to 4.)
In formula (1), Z is a polycyclic aromatic hydrocarbon having three or more benzene rings bonded together, preferably a polycyclic aromatic hydrocarbon having three benzene rings bonded together, more preferably anthracene, phenanthrene, or phenalene, and most preferably phenanthrene.

In formula (1), _L1 is an alkylene group having 1 to 15 carbon atoms, preferably an alkylene group having 1 to 12 carbon atoms, more preferably an alkylene group having 1 to 4 carbon atoms, and particularly preferably an ethylene group.

In formula (1), _R1 and _R2 are each hydrocarbon groups having 1 to 20 carbon atoms. Examples of hydrocarbon groups include alkyl groups, cycloalkyl groups, aryl groups, and aralkyl groups. Specific examples of alkyl groups include _C1-6 alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, and t-butyl groups; _C1-4 alkyl groups are more preferred; _C1-3 alkyl groups are even more preferred; among these, methyl and ethyl groups are particularly preferred.

Furthermore, as specific examples of cycloalkyl groups, _C5-8 cycloalkyl groups such as cyclopentyl groups and cyclohexyl groups are preferred, and _C5-6 cycloalkyl groups are more preferred.

Furthermore, preferred examples of aryl groups include phenyl groups, alkylphenyl groups (mono- or dimethylphenyl groups, tolyl groups, 2-methylphenyl groups, xylyl groups, etc.), and naphthyl groups, with phenyl groups being more preferred.

Furthermore, preferred examples of aralkyl groups include _C6-10 aryl- _C1-4 alkyl groups such as benzyl and phenethyl groups.

In formula (1), _m1 is an integer between 0 and 5, preferably 0 or 1, and more preferably 1.

In equation (1), _n1 is an integer between 0 and 10, preferably between 0 and 2, and more preferably 0.

In formula (1), _n² is an integer between 0 and 4, preferably 0 or 1, and more preferably 0.

Furthermore, among the fluorene derivatives represented by formula (1), the fluorene derivative represented by the following formula (2) is preferred.

(In the formula, _R3 , R4 _{, and R5} are hydrocarbon groups having 1 to 20 carbon atoms, _n3 is an integer from 0 to 4, _n4 is 0 or 1, _n5 is an integer from 0 to 3, _{and R2} , _L1 , _m1 , and _n2 are the same as in formula (1) above.)
In formula (2), _R3 , _R4 , and _R5 are each hydrocarbon groups having 1 to 20 carbon atoms, and are specifically the same as _R1 in formula (1) described above.

In equation (2), n ₃ is an integer between 0 and 4, preferably between 0 and 2, and more preferably 0.

In formula (2), n ₄ is either 0 or 1, and is preferably 0.

In equation (2), n ₅ is an integer between 0 and 3, preferably between 0 and 2, and more preferably 0.

In equation (2), _L1 , _m1 , and _R2 are the same as _L1 , _m1 , and _R2 in equation (1) described above.

As specific examples of fluorene derivatives represented by formula (2), 9,9-bis(9-hydroxy-3-phenanthryl)fluorene represented by the following formula (3) and 9,9-bis[9-(2-hydroxyethoxy)-3-phenanthryl]fluorene represented by the following formula (4) are preferred, and 9,9-bis[9-(2-hydroxyethoxy)-3-phenanthryl]fluorene represented by the following formula (4) is particularly preferred.

The fluorene derivative of the present invention preferably has an HPLC purity of 90 area% or more, more preferably 95 area% or more, and even more preferably 98 area% or more, as measured by HPLC.

The fluorene derivative of the present invention preferably has a refractive index of 1.70 or higher, more preferably 1.72 or higher, and even more preferably 1.74 or higher. The refractive index was determined by dissolving a compound containing the fluorene derivative in dimethyl sulfoxide to prepare solutions of predetermined concentrations, measuring the D-line refractive index at 25°C using an ATAGO DR-M2 Abbe refractometer, and extrapolating the measurement results for each concentration to a concentration of 100% to obtain the refractive index (nD) of the compound.
Method for producing fluorene derivatives
The fluorene derivative of the present invention can be produced by reacting fluorenones represented by the following formula (5) with alcohols represented by the following formula (6) in a reaction solvent in the presence of an acid catalyst, thereby producing a fluorene derivative represented by the following formula (7) (hereinafter, this may be abbreviated as step 1).

(In the formula, _R² and _n² are the same as in formula (1) above.)

(In the formula, Z, _R1 , and _n1 are the same as in formula (1) above.)

(In the formula, Z, _R1 , _R2 , _n1 , and _n2 are the same as in formula (1) above.)
Furthermore, a fluorene derivative represented by formula (7) can be reacted with ethylene carbonate in the presence of a base to produce a fluorene derivative represented by the following formula (8) (hereinafter sometimes referred to as step 2).

(In the formula, _m1 is an integer from 1 to 5, and Z, _L1 , R1 _, R2, _n1 , _{and n2} are the same as in formula (1) above.)
Specific examples of fluorenones represented by formula (5) include fluorenone, 1,8-difluorofluorenone, 2,7-difluorofluorenone, 3,6-difluorofluorenone, 4,5-difluorofluorenone, 1,8-dichlorofluorenone, 2,7-dichlorofluorenone, 3,6-dichlorofluorenone, 4,5-dichlorofluorenone, 1,8-diiodofluorenone, 2,7-diiodofluorenone, 3,6-diiodofluorenone, 4,5-diiodofluorenone, 1,8-dibromofluorenone, 2,7-dibromofluorenone, 3,6-dibromofluorenone, and 4,5-dibromofluorenone, with fluorenone and 2,7-dibromofluorenone being more preferred, and fluorenone being particularly preferred. These may be used individually or mixed in groups of two or more, and can be arbitrarily selected depending on the purpose.

Specific examples of alcohols represented by formula (6) include 1-phenanthol, 2-phenanthol, 3-phenanthol, 4-phenanthol, 9-phenanthol, 1-anthol, 2-anthol, 3-anthol, 4-anthol, and 9-anthol, with 2-phenanthol and 9-phenanthol being more preferred, and 9-phenanthol being particularly preferred. These may be used individually or mixed in combination of two or more, and can be arbitrarily selected depending on the purpose.

Examples of acid catalysts used in step 1 of the present invention include sulfuric acid, thiolic acid, montmorillonite, and heteropoly acid. Among these, heteropoly acid is particularly preferred because it generates fewer impurities derived from the acid catalyst and facilitates the acquisition of the fluorene derivative of the present invention. A description of the heteropoly acid preferably used in the present invention is provided in Japanese Patent Publication No. 4140975.

The amount of heteropoly acid used is not particularly limited, but it is preferably 0.0001 to 1 mole, more preferably 0.0005 to 0.1 moles, and even more preferably 0.001 to 0.01 moles per mole of fluorenone.

In step 1 of the present invention, the reaction rate can be improved and the generation of impurities can be suppressed by using a compound having a thiol group (hereinafter sometimes abbreviated as SH group) in combination with the heteropoly acid described above. Examples of thiol compounds used in combination in the present invention include mercaptocarboxylic acids, alkanethiols, and salts thereof.

Examples of mercaptocarboxylic acids include α-mercaptopropionic acid, β-mercaptopropionic acid, thioacetic acid, thioglycolic acid, thiooxalic acid, mercaptosuccinic acid, and mercaptobenzoic acid. Examples of alkanethiols include methanethiol, ethanethiol, 1-propanethiol, 2-propanethiol, 1-butanethiol, 2-butanethiol, 1-pentanethiol, 2-pentanethiol, 1-hexanethiol, 1-heptanethiol, 2-heptanethiol, 1-octanthiol, 2-octanthiol, 1-nonanthiol, 1-decanethiol, 1-undecanethiol, and 1-dodecanethiol, as well as _C1-16 alkyl mercaptans. Among such compounds having an SH group, 1-octanthiol and 1-dodecanethiol are preferred. Such compounds having an SH group may be used alone or in combination of two or more.

The method for carrying out the reaction in step 1 is not particularly limited, but it can usually be carried out by charging fluorenones represented by formula (5), alcohols represented by formula (6), and heteropoly acids and/or thiol compounds into a reaction apparatus and heating and stirring in air or under an inert gas atmosphere such as nitrogen or argon, in the presence of aromatic hydrocarbons such as toluene or xylene and esters such as ethyl acetate, γ-butyrolactone, or ethylene carbonate as inert solvents. In this case, by carrying out the reaction under dehydration conditions, such as removing water in the reaction system, including catalyst-containing water and reaction product water, the reaction proceeds faster than without dehydration, the formation of by-products is suppressed, and the target product can be obtained in a higher yield. The method of dehydration is not particularly limited, but examples include dehydration by adding a dehydrating agent, dehydration by reduced pressure, and dehydration by azeotrope with a solvent at atmospheric pressure or reduced pressure.

The reaction solvent used in step 1 is not particularly limited, but examples include aromatic hydrocarbon solvents such as toluene and xylene, halogenated aromatic hydrocarbon solvents such as chlorobenzene and dichlorobenzene, aliphatic hydrocarbon solvents such as pentane, hexane, and heptane, halogenated aliphatic hydrocarbon solvents such as dichloromethane and 1,2-dichloroethane, aliphatic and cyclic ether solvents such as diethyl ether, di-iso-propyl ether, methyl-t-butyl ether, diphenyl ether, tetrahydrofuran, and dioxane, ester solvents such as ethyl acetate, butyl acetate, γ-butyrolactone, and ethylene carbonate, nitrile solvents such as acetonitrile, propionitrile, butyronitrile, and benzonitrile, and amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and 1-methyl-2-pyrrolidinone. Preferably, the solvent is an aromatic hydrocarbon solvent or an ester solvent, more preferably a mixed solvent of toluene, xylene, chlorobenzene, or dichlorobenzene with ethyl acetate, butyl acetate, γ-butyrolactone, or ethylene carbonate, and even more preferably a mixed solvent of toluene and γ-butyrolactone. These reaction solvents may be used alone or in combination of two or more.

Furthermore, while the amount used is not particularly limited, from an economic standpoint, it is preferably 0.1 times or more by weight, more preferably 0.5 to 100 times by weight, and even more preferably 1 to 20 times by weight relative to fluorenones.

The reaction temperature in step 1 varies depending on the type of raw materials and solvent used, but is preferably 50 to 200°C, more preferably 70 to 150°C, and even more preferably 90 to 130°C. If the reaction temperature is too high, it may lead to an increase in by-reactants, resulting in a decrease in yield and deterioration of color. If the reaction temperature is too low, the reaction may not proceed quickly.

The reaction can be tracked using analytical methods such as liquid chromatography.

The internal pressure during the reaction in step 1 is preferably 101.3 kPa or less, and more preferably 60.0 kPa or less. It is preferable to carry out the reaction while discharging the by-product water from the system at this internal pressure, as this allows the reaction to proceed more efficiently and reduces the amount of by-products generated.

After the reaction in step 1, the solid acid used may be removed by filtration or neutralized as needed. Examples of bases used for neutralization include alkali metal or alkaline earth metal hydroxides such as sodium hydroxide, potassium hydroxide, and calcium hydroxide; alkali metal or alkaline earth metal carbonates (bicarbonates) such as potassium carbonate, calcium carbonate, sodium carbonate, and sodium carbonate; and amines. Separation and purification may also be performed by separation methods such as filtration, concentration, extraction, crystallization, recrystallization, reprecipitation, activated carbon treatment, column chromatography, or a combination thereof.

Furthermore, in step 2 of the present invention, the fluorene derivative represented by formula (7) obtained in step 1 can be reacted with ethylene carbonate in the presence of a base to produce the fluorene derivative represented by formula (8).

The molar ratio of the fluorenone derivative represented by formula (7) to ethylene carbonate is preferably 1:1.8 to 1:3.0, more preferably 1:2 to 1:2.7, and even more preferably 1:2.1 to 1:2.5. If the amount of ethylene carbonate used is less than 1:1.8, the reaction time may be prolonged. In addition, the yield and purity may decrease due to the fluorenone derivative represented by formula (7) remaining unreacted or due to the large amount of by-products resulting from the reaction of 1 mole of the fluorenone derivative represented by formula (7) with 1 mole of ethylene carbonate. If the amount of ethylene carbonate used is more than 1:3.0, the yield and purity may decrease due to the large amount of by-products resulting from the reaction of 1 mole of the fluorenone derivative represented by formula (7) with 3 or more moles of ethylene carbonate.

Examples of bases used in step 2 of the present invention include potassium hydroxide, sodium hydroxide, barium hydroxide, magnesium oxide, sodium carbonate, and potassium carbonate, with potassium hydroxide, sodium hydroxide, and potassium carbonate being preferred, and potassium carbonate being more preferred.

The amount of base used in step 2 of the present invention is not particularly limited, but preferably 0.01 to 0.5 moles, and more preferably 0.05 to 0.3 moles, per mole of the fluorenone derivative represented by formula (7). If the amount of base used is too small, the reaction may not proceed or may be delayed. If the amount of catalyst is too large, it may lead to an increase in by-products, resulting in a decrease in yield and purity, and may cause discoloration.

The reaction solvent used in step 2 of the present invention is not particularly limited, but examples include aromatic hydrocarbon solvents such as toluene and xylene, halogenated aromatic hydrocarbon solvents such as chlorobenzene and dichlorobenzene, aliphatic hydrocarbon solvents such as pentane, hexane, and heptane, halogenated aliphatic hydrocarbon solvents such as dichloromethane and 1,2-dichloroethane, aliphatic and cyclic ether solvents such as diethyl ether, di-iso-propyl ether, methyl-t-butyl ether, diphenyl ether, tetrahydrofuran, and dioxane, ester solvents such as ethyl acetate, butyl acetate, γ-butyrolactone, and ethylene carbonate, nitrile solvents such as acetonitrile, propionitrile, butyronitrile, and benzonitrile, and amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and 1-methyl-2-pyrrolidinone. Preferably, the solvent is an aromatic hydrocarbon solvent or an amide solvent, more preferably a mixed solvent of toluene, xylene, chlorobenzene, or dichlorobenzene and ethyl acetate, butyl acetate, γ-butyrolactone, or ethylene carbonate, and even more preferably toluene or dimethylformamide. These reaction solvents may be used individually, or two or more may be used in combination.

Furthermore, while the amount used is not particularly limited, from an economic standpoint, it is preferably 0.1 times or more by weight, more preferably 0.5 to 100 times by weight, and even more preferably 1 to 20 times by weight, relative to the fluorenone derivative.

The reaction temperature in step 2 varies depending on the type of raw materials and solvent used, but is preferably 50 to 200°C, more preferably 70 to 150°C, and even more preferably 90 to 130°C. If the reaction temperature is too high, it may lead to an increase in by-reactants, resulting in a decrease in yield and deterioration of color. If the reaction temperature is too low, the reaction may not proceed quickly.

The reaction can be tracked using analytical methods such as liquid chromatography.

After the reaction in step 2, the mixture may be separated and purified by separation methods such as filtration, concentration, extraction, crystallization, recrystallization, reprecipitation, activated carbon treatment or a similar metal removal treatment, column chromatography, or a combination thereof.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the essence of the invention.

In the examples, various measurements were performed as follows.
(1) HPLC measurement A Hitachi high-performance liquid chromatograph L-2350 was used, and measurements were taken under the conditions shown in Table 1. In the examples, unless otherwise specified, the percentages are area percentage values corrected for the solvent in HPLC.

(2) NMR measurement The compounds obtained in the examples were dissolved in DMSO-d6 and measured using a JEOL JNM-AL400 (400 MHz) NMR analyzer.
(3) Refractive index (nD)
The compounds obtained in the examples were dissolved in dimethyl sulfoxide to prepare solutions of predetermined concentrations. The refractive index of each solution at each concentration was measured at 25°C using an ATAGO DR-M2 Abbe refractometer, specifically the D-line refractive index. The refractive index (nD) of the compounds obtained in the examples was defined as the value obtained by extrapolating the measurement results for each concentration to 100% concentration.
[Example 1]
Under a nitrogen atmosphere, 5.00 g of fluorenone, 11.86 g of 9-phenanthrol, 0.04 g of 1-octanethol, 0.57 g of phosphotungstic acid, 50 ml of toluene, and 2.44 g of ethylene carbonate were added to a flask equipped with a stirrer, condenser, and thermometer, and the mixture was reacted at 100°C and 50 kPa for 14 hours. After cooling the reaction mixture, it was transferred to a separatory funnel, neutralized with an aqueous NaOH solution, and washed with distilled water until neutral. Then, hexane was added to the organic layer and recrystallized. The obtained crystals were collected, recrystallized with toluene, and dried under reduced pressure for 4 hours to obtain crystals of 9,9-bis(9-hydroxy-3-phenanthryl)fluorene (hereinafter sometimes abbreviated as BPhF). (Purity: 95%, yield: 4.5 g). The NMR chart of the obtained BPhF is shown in Figure 1.
[Example 2]
Under a nitrogen atmosphere, 5.00 g of fluorenone, 10.78 g of 9-phenanthol, 0.20 g of 1-octanthiol, 0.09 g of phosphotungstic acid, 20 ml of toluene, and 5 ml of γ-butyrolactone were added to a flask equipped with a stirrer, condenser, and thermometer, and the reaction was carried out at 100°C and 50 kPa for 10 hours. After cooling the reaction mixture, 100 ml of toluene was added, the reaction mixture was transferred to a separatory funnel, and neutralization washing was performed by adding NaOH aqueous solution. Then, it was washed with distilled water until neutral. HPLC analysis of the organic layer after washing confirmed that BPhF was 78%, phenanthol was 6%, fluorenone was 9%, and other unknown components were 7%. This organic layer, ethylene carbonate: 4.62 g, and potassium carbonate: 0.35 g were placed in a flask equipped with a stirrer, condenser, and thermometer under a nitrogen atmosphere, and the reaction mixture was bubbling with nitrogen for 10 minutes. The reaction was then carried out at 110°C for 18 hours. After cooling the reaction mixture, 300 ml of toluene was added, and the reaction mixture was transferred to a separatory funnel. After washing with an aqueous NaOH solution, it was washed with distilled water until neutral. Then, hexane was added to the organic layer and recrystallization was performed. The obtained crystals were collected, dissolved in toluene, and then recrystallized with hexane. The crystals were dried under reduced pressure for 4 hours to obtain crystals of 9,9-bis[9-(2-hydroxyethoxy)-3-phenanthryl]fluorene (hereinafter sometimes abbreviated as BPhEF) (purity: 96%, yield: 4.8 g). The NMR chart of the obtained BPhEF is shown in Figure 2. The refractive index of BPhEF was 1.745.
[Comparative Example 1]
Under a nitrogen atmosphere, 9.00 g of 9-phenantrol, 6.28 g of ethylene carbonate, 0.32 g of potassium carbonate, and 20 ml of dimethylformamide were added to a flask equipped with a stirrer, condenser, and thermometer, and the reaction was carried out at 120°C for 9 hours. After cooling the reaction mixture, 200 ml of toluene was added, and the reaction mixture was transferred to a separatory funnel. After washing with an aqueous NaOH solution, it was washed with distilled water until neutral. Then, hexane was added to the organic layer and recrystallization was performed. The obtained crystals were dried under reduced pressure for 4 hours to obtain crystals of 9-phenantoxyethanol (purity: 99%, 9.3 g).

Under a nitrogen atmosphere, 1.40 g of fluorenone, 4.07 g of 9-phenantoxyethanol, 0.12 g of 1-octanthiol, 0.03 g of phosphotungstic acid, 20 ml of toluene, and 5 ml of γ-butyrolactone were added to a flask equipped with a stirrer, condenser, and thermometer, and the reaction was carried out at 100°C and 50 kPa for 5 hours. HPLC analysis of the reaction solution confirmed that 9-phenantoxyethanol was 26%, fluorenone was 40%, and other unknown components accounted for 34%. After a further 5 hours of reaction, HPLC analysis of the reaction solution showed no change in composition, and the target product, BPhEF, could not be obtained.

The novel fluorene derivatives obtained in this invention are suitable as monomers for forming resins that constitute optical components such as optical lenses and optical films.

Claims (4)

A fluorene derivative represented by the following formula (4) .
The fluorene derivative according to claim 1 , wherein the HPLC purity is 90 area percent or more. A fluorene derivative according to claim 2 or claim 1 , wherein the refractive index is 1.7 or higher. A method for producing a fluorene derivative, comprising: reacting fluorenones represented by formula (5) below with alcohols represented by formula (6) below in a reaction solvent in the presence of an acid catalyst to obtain a fluorene derivative represented by formula (7) below; and then reacting the fluorene derivative represented by formula (7) below with ethylene carbonate in the presence of a base to obtain a fluorene derivative represented by formula (4) below .
(In the formula, _R² is a hydrocarbon group having 1 to 20 carbon atoms, and _n² is an integer of 0. )
(In the formula, Z is phenanthrene, _R1 is a hydrocarbon group having 1 to 20 carbon atoms, and _n1 is an integer of 0. )