Method for producing aromatic compound using heterogeneous noble metal catalyst

Abstract

To provide a technique for synthesizing aromatic compound such as indole by dehydrogenation reaction that is low in manufacturing cost, and a green technique that is low in environmental impact.SOLUTION: Provided is a method for producing aromatic compound, which comprises dehydrogenating cyclohexadienes or cyclohexenes in the presence of a solvent and molecular oxygen using a heterogeneous noble metal catalyst in which one or more of the noble metals selected from the group consisting of ruthenium, iridium, palladium, platinum and rhodium are supported on a carbon carrier.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing aromatic compounds using a heterogeneous noble metal catalyst, the method comprising the steps of: (a) preparing a cyclohexadienes or cyclohexenes as a raw material; [Background technology]

[0002] Aromatic compounds such as indole are known as pharmaceuticals, such as fragrances and antibacterial agents, and as synthetic intermediates thereof.

[0003] Various methods have been proposed for synthesizing such indoles. One of them is a method in which a dihydroindole derivative is dehydrogenated using manganese dioxide as a catalyst and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (also called DDQ) as an oxidizing agent in a stoichiometric amount or more (Non-Patent Documents 1 to 3).

[0004] However, this method requires the use of a large amount of DDQ, which is a dangerous oxidant, beyond the stoichiometric amount, and therefore poses a high environmental burden as well as a high safety issue.

[0005] In addition to the above, a method that does not use DDQ as an oxidant is to use oxygen gas as an oxidant and [Ru(phd) 3 ](PF 6 ) 2 There is a method for synthesizing indole by dehydrogenating a dihydroindole derivative in a solvent such as methanol or acetonitrile using a Ru complex catalyst such as the following (Non-Patent Document 4).

[0006] However, this method uses a homogeneous catalyst complex as the catalyst, and therefore the catalyst must be separated after the reaction, making it a high-cost method for industrial use. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] U. Pindur et al., Tetrahedron, 1992 , 17, 3515-3526 [Non-Patent Document 2] C. Bailly et al., Bioorganic & Medicinal Chemistry, 2001, 9, 1533-1541 [Non-Patent Document 3] WENoland et al., Journal of Heterocyclic Chemistry, 2009, 46, 1154-1176 [Non-Patent Document 4] SSStahl et al., Organic Letters, 2019, 21, 1176-1181 Summary of the Invention [Problem to be solved by the invention]

[0008] Given this background, there is a demand for a technology for synthesizing aromatic compounds such as indole through dehydrogenation that has low production costs and is also a green technology that has a low environmental impact. [Means for solving the problem]

[0009] As a result of intensive research conducted by the present inventors to solve the above problems, they have found that by using a heterogeneous precious metal catalyst in which a specific precious metal is supported on a carbon support, among other heterogeneous catalysts which can be recovered and reused, the dehydrogenation reaction of cyclohexadienes or cyclohexenes proceeds efficiently in the presence of a solvent and molecular oxygen, and aromatic compounds can be obtained in good yields.

[0010] The present inventors have also found that a dehydrogenation reaction can be carried out successively in the same reaction vessel in which cyclohexadienes or cyclohexenes, which are the raw materials for the above reaction, are synthesized, and have completed the present invention.

[0011] That is, the present invention provides a method for producing an aromatic compound, which comprises subjecting cyclohexadienes or cyclohexenes to a dehydrogenation reaction in the presence of a solvent and molecular oxygen using a heterogeneous precious metal catalyst in which one or more precious metals selected from the group consisting of ruthenium, iridium, palladium, platinum and rhodium are supported on a carbon support.

[0012] The present invention also relates to a method for producing an aromatic compound, which comprises adding a conjugated diene and a dienophile in a reaction vessel via a Diels-Alder reaction to obtain cyclohexadienes or cyclohexenes, and then dehydrogenating the cyclohexadienes or cyclohexenes in the same reaction vessel in the presence of a solvent and molecular oxygen using a heterogeneous precious metal catalyst in which one or more precious metals selected from the group consisting of ruthenium, iridium, palladium, platinum and rhodium are supported on a carbon support.

[0013] Furthermore, the present invention is an aromatic compound represented by any one of the following chemical formulas: [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] Effect of the Invention

[0014] In the method for producing an aromatic compound of the present invention, the aromatization reaction of cyclohexadienes or cyclohexenes proceeds with good selectivity and yield even under mild conditions.

[0015] Furthermore, the process for producing an aromatic compound of the present invention is industrially advantageous since the dehydrogenation reaction can be carried out successively in the same reaction vessel in which the cyclohexadienes or cyclohexenes, which are the raw materials for the above reaction, are synthesized. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The method for producing an aromatic compound of the present invention (hereinafter referred to as the "method of the present invention") involves dehydrogenating cyclohexadienes or cyclohexenes in the presence of a solvent and molecular oxygen using a heterogeneous precious metal catalyst in which a precious metal selected from the group consisting of ruthenium, iridium, palladium, platinum and rhodium is supported on a carbon support.

[0017] (substrate) The substrate used in the method of the present invention is a cyclohexadienes or cyclohexenes, and is not particularly limited as long as it is an aromatic compound by dehydrogenation. Examples of such cyclohexadienes or cyclohexenes include those having a heterocycle, such as cyclohexadienes or cyclohexenes containing a nitrogen atom that become carbazole, indole, etc. by dehydrogenation, cyclohexadienes or cyclohexenes containing an oxygen atom that become benzofuran, etc. by dehydrogenation, and cyclohexadienes or cyclohexenes containing a sulfur atom that become benzothiophene, etc. by dehydrogenation. In the method of the present invention, it is preferable to use cyclohexadienes or cyclohexenes having a heterocycle, preferably cyclohexadienes or cyclohexenes having a heterocycle adjacent to a cyclohexadiene structure or cyclohexene structure, as a substrate, since it is possible to synthesize indole or its derivatives, which are known as pharmaceuticals such as perfumes and antibacterial agents, or their synthetic intermediates. Among these substrates, from the viewpoint of yield and the like, cyclohexadienes having a heterocycle are preferred, and cyclohexadienes having a heterocycle adjacent to a cyclohexadiene structure are more preferred.

[0018] (solvent) The solvent used in the method of the present invention is not particularly limited, but examples thereof include water, toluene, dioxane, t-butyl alcohol, dimethylformamide, etc. Among these solvents, water, toluene, dioxane, and t-butyl alcohol are preferred from the viewpoint of yield, and toluene and dioxane are more preferred. These solvents may be used alone or in combination.

[0019] (Molecular oxygen) The molecular oxygen used in the method of the present invention may be any gas containing molecular oxygen, such as oxygen, air, or a mixture of oxygen and argon. These may be supplied to the system by, for example, replacing the atmosphere or attaching a balloon filled with the gas. The amount of molecular oxygen present in the method of the present invention is not particularly limited, and may be, for example, 0.1 to 10,000, preferably 1 or more, assuming that the amount of oxygen required for the substrate is 1.

[0020] (Heterogeneous precious metal catalyst) The heterogeneous precious metal catalyst used in the method of the present invention is a catalyst in which one or more precious metals selected from the group consisting of ruthenium, iridium, palladium, platinum and rhodium are supported on a carbon support. The carbon support is not particularly limited, but examples thereof include activated carbon, carbon nanotubes, graphite, graphene, etc. Among these carbon supports, activated carbon is preferred because it has a large specific surface area and can improve the dispersibility of the supported precious metal. Among the precious metals, one or more of ruthenium, iridium, palladium, and platinum are preferred, and one or more of ruthenium, iridium, and platinum are preferred because they provide a high yield, ruthenium and / or iridium are preferred because they provide a higher yield, and ruthenium is particularly preferred because they provide a high yield. These heterogeneous precious metal catalysts can be prepared according to known methods.

[0021] Among the above-mentioned heterogeneous precious metal catalysts, those in which the precious metal is supported on activated carbon are preferred, and (a) the precious metal is contained in an amount of 1 to 20 wt %, preferably 5 to 15 wt %, calculated as the metal relative to the activated carbon. If the amount of precious metal is too small, the reactivity may decrease, and if the amount is too large, the activity may not be commensurate with the amount used. Also, if the amount of precious metal is too large, the precious metals on the catalyst may aggregate, which may reduce the surface area of ​​the entire precious metal particles and reduce activity.

[0022] (b) Activated carbon with a specific surface area (BET value) of 500 to 2,000 m 2 / g, preferably 800 to 1,500 m2 / g. If the specific surface area of ​​the activated carbon is too small, the dispersibility of the precious metal may decrease, resulting in a decrease in reactivity, whereas if the specific surface area is too large, the reactivity may decrease in the method of the present invention.

[0023] Among the above-mentioned heterogeneous precious metal catalysts, those in which ruthenium is supported on activated carbon are preferred, and those having the following properties (a) and (b) are particularly preferred. (a) The activated carbon contains ruthenium in an amount of 1 to 20 wt %, preferably 5 to 15 wt %, calculated as ruthenium metal. If the amount of ruthenium is too small, the reactivity may decrease, and if it is too much, the activity may not be commensurate with the amount used. Also, if the amount of ruthenium is too much, the ruthenium particles on the catalyst may aggregate, which may reduce the surface area of ​​the entire ruthenium particles and reduce the activity.

[0024] (b) Activated carbon with a specific surface area (BET value) of 500 to 2,000 m 2 / g, preferably 800 to 1,500 m 2 / g. If the specific surface area of ​​the activated carbon is too small, the dispersibility of ruthenium may decrease, resulting in a decrease in reactivity, whereas if the specific surface area is too large, the reactivity may decrease in the method of the present invention.

[0025] The heterogeneous precious metal catalyst having ruthenium supported on activated carbon having the above-mentioned properties may be prepared according to a known method, or may be prepared, for example, from 5% Ru carbon powder (hydrated product) [Type A] (ruthenium content: 5 wt%, specific surface area: 900 m 2 / g), [K type] (ruthenium content: 5 wt%, specific surface area: 1100 m 2 / g), [R type] (ruthenium content: 5 wt%, specific surface area: 1200 m 2 / g), [B type] (ruthenium content: 5 wt%, specific surface area value: 900 m 2 Commercially available products such as 1,2-dichlorophenyl ether (1,2-dichlorophenyl ether) and 1,2-dichlorophenyl ether (1,2-dichlorophenyl ether) (both manufactured by N.E. Chemcat Corporation) can also be used.

[0026] These heterogeneous noble metal catalysts may be present in the system during the process of the present invention, for example, in an amount of 1 to 50 mol %, preferably 3 to 20 mol %, based on the substrate. Such heterogeneous noble metal catalysts are easy to separate after the reaction and to reuse the separated catalyst.

[0027] (Dehydrogenation reaction) In the method of the present invention, the dehydrogenation reaction is carried out by using a heterogeneous precious metal catalyst in the presence of a solvent and molecular oxygen. The reaction conditions are not particularly limited, and the reaction may be carried out by appropriately controlling conditions such as the reaction temperature, reaction time, and atmosphere.

[0028] (Reaction temperature) The reaction temperature in the method of the present invention is not particularly limited as long as the dehydrogenation reaction proceeds, but is preferably 40 to 200°C, and more preferably 50 to 150°C.

[0029] (Reaction time) The reaction time in the method of the present invention is not particularly limited, but is, for example, 1 to 48 hours, and preferably 6 to 26 hours. It is preferable to stir the mixture during the reaction.

[0030] (atmosphere) The reaction atmosphere in the method of the present invention is not particularly limited as long as it allows the dehydrogenation reaction to proceed with a heterogeneous precious metal catalyst. For example, the reaction is preferably carried out in an inert atmosphere such as argon or nitrogen, and argon is particularly preferred.

[0031] (Reaction vessel) The vessel used in the method of the present invention is not particularly limited, and may be a test tube, a flask, a batch reactor, or the like, whichever is appropriate for the scale of the reaction.

[0032] According to the method of the present invention described above, cyclohexadienes or cyclohexenes are dehydrogenated to obtain aromatic compounds. After the dehydrogenation reaction, the mixture may be cooled, filtered, or purified according to a conventional method. It is possible to confirm whether an aromatic compound has been obtained by a known method such as NMR.

[0033] After the process of the present invention is completed, the heterogeneous precious metal catalyst can be recovered by filtration, centrifugation or the like and reused.

[0034] Furthermore, before carrying out the method of the present invention, a Diels-Alder reaction may be carried out in a reaction vessel according to a known method to add-polymerize a conjugated diene and a dienophile (alkene or alkyne) to obtain cyclohexadienes or cyclohexenes, and then the method of the present invention may be carried out in the same reaction vessel, thereby enabling the production of aromatic compounds in one pot.

[0035] Examples of preferred cyclohexadienes or cyclohexenes in the method of the present invention and aromatic compounds obtained by dehydrogenating them are shown in Table 1 below. Note that all of these aromatic compounds have a heterocycle, which is a cyclohexadienes having a cyclohexadiene structure adjacent thereto, or a cyclohexenes having a cyclohexene structure adjacent thereto. Among these, cyclohexadienes and aromatic compounds obtained by dehydrogenating them are particularly preferred.

[0036] [Table 1] *In the above chemical formula, R and R 1 ~R 6 are each independently a group selected from the group consisting of hydrogen, a methoxy group, an acetyl group, a nitro group, a nitrile group, a halogen group, a phenyl group, a benzyl group, a carboxylic acid derivative having 1 to 20 carbon atoms, and an alkyl or alkane group having 1 to 20 carbon atoms which may have a fused ring or the above-mentioned substituent. EXAMPLES

[0037] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. 1 H and 13 C NMR was performed using a JEOL JNM ECA-500 ( 1 H NMR, 500 MHz; 13 C NMR, 125 MHz) or JEOL JNM ECZ-400 ( 1 H NMR, 400 MHz; 13 C NMR, 100 MHz. NMR chemical shifts were measured using CDCl. 3 Absorption of trace amounts of unlabeled substance in 1 H NMR: δ = 0.00; 13 C NMR: δ = 77.0) was used as an internal standard and the results are expressed in ppm. High-resolution mass spectra were measured using a Shimazu hybrid IT-TOF mass spectrometer.

[0038] Example 1 Precious metals considerations: The dehydrogenation reaction shown in the following formula was carried out. First, N-benzyl-6,7-dihydroindole-4,5-dicarboxylate dimethyl (65 mg, 0.2 mmol) and 10% catalyst 10 mol% were added to distilled water (1 mL) and stirred at 100 ° C. for 24 hours under an argon atmosphere. The reaction solution was allowed to cool to room temperature and filtered through a membrane filter (Millipore, Millex-LH: 0.20 mm). The catalyst in the filter was washed with ethyl acetate (10 mL × 3), and the filtrate was combined with distilled water (20 mL) and extracted. The aqueous layer was further extracted with ethyl acetate (10 mL × 2), and the organic layers were combined, dried over anhydrous sodium sulfate, and filtered. The obtained filtrate was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography. The yield is shown in Table 2.

[0039] [ka]

[0040] [Table 2]

[0041] These results demonstrate that the use of heterogeneous precious metal catalysts, such as ruthenium, iridium, palladium, platinum or rhodium supported on a carbon support, enables the dehydrogenation of cyclohexadienes, producing the aromatic compound 1 in good yield.

[0042] Example 2 1-Pot reaction: The dehydrogenation reaction shown in the following formula was carried out in a one-pot system. First, dimethyl acetylenedicarboxylate (2a: 30 μL, 0.24 mmol) was added to a toluene (1 mL) solution of N-benzyl-2-vinylpyrrole (1a: 37 mg, 0.2 mmol), and the mixture was stirred at 120 °C for 24 hours under an argon atmosphere to obtain a reaction solution containing cyclohexadienes. Next, the reaction solution was allowed to cool to room temperature, and 20 mg (10 mol%) of 10% Ru carbon powder (dried product) K type (manufactured by N.E. Chemcat) was added, and the mixture was further stirred at 110 °C for 24 hours under an oxygen atmosphere. The reaction solution was allowed to cool to room temperature, and filtered with a membrane filter (Millipore, Millex-LH, 0.20 mm) using ethyl acetate (50 mL). The filtrate obtained was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography to obtain 4a (46.5 mg, 72%).

[0043] [ka]

[0044] This result demonstrated that the method of the present invention can be carried out in a one-pot system.

[0045] Example 3 Substrate diversity study: The dehydrogenation reaction represented by the following formula was carried out in a one-pot system in the same manner as in Example 2. The substrates, reaction conditions, products, etc. in this dehydrogenation reaction are shown in Table 3.

[0046] [ka]

[0047] [Table 3-1] [Table 3-2] [Table 3-3] [Table 3-4] [Table 3-5]

[0048] These results indicate that various conjugated dienes and alkynes can be added together via the Diels-Alder reaction to give cyclohexadienes or cyclohexenes, which can then be dehydrogenated to give aromatic compounds.

[0049] Example 4 Repeated use of catalyst: The dehydrogenation reaction shown in the following formula was carried out. First, N-benzyl-6,7-dihydroindole-4,5-dicarboxylate dimethyl (3a: 65 mg, 0.2 mmol) and 10% Ru carbon powder (dried product) K type (manufactured by N.E. Chemcat) 20 mg, 10 mol% were added to distilled water (1 mL) and stirred at 100 °C for 24 hours under an argon atmosphere. The reaction solution was allowed to cool to room temperature and filtered through a membrane filter (Millipore, Millex-LH, 0.20 mm). The catalyst in the filter was washed with ethyl acetate (10 mL × 3), and the filtrate was combined with distilled water (20 mL) and extracted. The aqueous layer was further extracted with ethyl acetate (10 mL × 2), and the organic layers were combined, dried over anhydrous sodium sulfate, and filtered. The filtrate was distilled under reduced pressure, and the residue was purified by silica gel column chromatography to obtain 4a (56.1 mg, 87%). The catalyst used was washed on filter paper alternately with methanol (10 mL x 5) and distilled water (10 mL x 5), dried under reduced pressure for 24 hours, recovered, and reused. The results are shown in Table 4.

[0050] [ka]

[0051] [Table 4]

[0052] It was found that the heterogeneous precious metal catalyst used in the method of the present invention can be used repeatedly. The reason why the conversion rate and yield are lower in the second and third runs is because the catalyst itself was not activated or reduced. It is believed that if these treatments were performed, the conversion rate and yield would be equivalent to those of the first run.

[0053] Example 5 Aromatization reaction: The dehydrogenation reaction represented by the following formula was carried out in the same manner as in Example 1. The substrate, reaction conditions, products, etc. in this dehydrogenation reaction are shown in Table 5.

[0054] [ka]

[0055] [Table 5]

[0056] These results demonstrated that it is possible to synthesize indoles from cyclohexadienes or cyclohexenes having various heterocycles.

[0057] Example 6 1-Pot synthesis of pyrrolocarbazoledione derivatives: The dehydrogenation reaction shown in the following formula was carried out in a one-pot system. First, dimethyl acetylenedicarboxylate (2a: 30 μL, 0.24 mmol) was added to a toluene (1 mL) solution of N-benzyl-3-vinylindole (1a: 46 mg, 0.2 mmol), and the mixture was stirred at 150 °C for 24 hours under an argon atmosphere. The reaction solution was allowed to cool to room temperature, and 20 mg (10 mol%) of 10% Ru carbon powder (dried product) K type (manufactured by N.E. Chemcat) was added, and the mixture was stirred at 110 °C for 48 hours under an oxygen atmosphere. The reaction solution was allowed to cool to room temperature, toluene was distilled off under reduced pressure, and N,N-dimethylethylenediamine (1.5 mL) and DMF (1.5 mL) were added, and the mixture was stirred at 150 °C for another 24 hours. The reaction solution was allowed to cool to room temperature and concentrated under reduced pressure. The residue was filtered with ether (50 mL) using a membrane filter (Millipore, Millex-LH, 0.20 mm). The filtrate was separated and extracted, and the organic layer was dried over anhydrous sodium sulfate and then filtered. The filtrate was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography to obtain 2-[2-(dimethylamino)ethyl]-10-benzyl-1,2,3,10-tetrahydropyrrolo[3,4-a]carbazole-1,3-dione ( 1 H NMR (400 MHz, CDCl 3): δ 8.34 (d, J = 8.0 Hz, 1H), 8.11 (d, J = 8.0 Hz, 1H), 7.70 (d, J = 8.0 Hz, 1H), 7.49-7.45 (m, 1H), 7.35-7.28 (m, 2H) 7.25-7.17 (m, 3H), 7.08 (d, J = 6.4 Hz, 2H), 6.30 (s, 2H), 3.79 (t, J = 6.8 Hz, 2H), 2.59 (t, J = 6.8 Hz, 2H), 2.28 (s, 6H); 13 C NMR (100 MHz, CDCl 3 ): δ 169.0, 168.3, 142.4, 137.8, 136.7, 130.9, 130.2, 128.6, 128.1, 127.2, 126.3, 125.3, 122.5, 120.8, 120.7, 113.9, 113.3, 110.6, 57.1, 50.0, 45.5, 35.9; HRMS: m / z [M+H] + Calcd for C 25 H 24 N 3 O 2 398.1863; Found 398.1869.47mg, 0.118mmol, 59%) was obtained in the 1-pot.

[0058] [ka]

[0059] Example 7 One-Pot Synthesis of 2-[2-(Dimethylamino)ethyl]-6-benzyl-1,2,3,6-tetrahydropyrrolo[3,4-e]indole-1,3-dione: The reaction was carried out in the same manner as in Example 6, except that the substrate was changed from N-benzyl-3-vinylindole to N-benzyl-2-vinylpyrrole. As a result, 2-[2-(dimethylamino)ethyl]-6-benzyl-1,2,3,6-tetrahydropyrrolo[3,4-e]indole-1,3-dione ( 1 H NMR (400 MHz, CDCl3 ): δ 7.59 (d, J = 8.0 Hz, 1H), 7.49 (d, J = 8.0 Hz, 1H), 7.39 (d, J = 3.2 Hz, 1H), 7.33-7.29 (m, 3H), 7.09 (dd, J = 7.2, 1.6 Hz, 1H), 7.05 (d, J = 3.2 Hz, 1H), 5.39 (s, 2H), 3.81 (t, J = 7.2 Hz, 2H), 2.61 (t, J = 7.2 Hz, 2H), 2.30 (s, 6H); 13 C NMR (100 MHz, CDCl 3 ): δ 169.9, 169.5, 140.6, 136.2, 133.7, 129.0, 128.1, 126.6, 125.0, 124.3, 123.9, 116.0, 114.2, 101.2, 57.4, 50.6, 45.5, 35.7; HRMS: m / z [M+H] + Calcd for C 21 H 22 N 3 O 2 348.1707; Found 348.1706.) was obtained in a 1-pot culture with a yield of 64%.

[0060] [ka] [Industrial Applicability]

[0061] The method of the present invention can be utilized for producing pharmaceuticals such as flavorings and antibacterial agents, and aromatic compounds such as indoles which are known as synthetic intermediates thereof.

Claims

1. A method for producing an aromatic compound, comprising the steps of: dehydrogenating cyclohexadienes or cyclohexenes in the presence of a solvent and molecular oxygen using a heterogeneous precious metal catalyst in which one or more precious metals selected from the group consisting of ruthenium, iridium, palladium, platinum and rhodium are supported on a carbon support.

2. 2. The process for producing an aromatic compound according to claim 1, wherein the solvent is one or more solvents selected from the group consisting of water, toluene, dioxane and t-butyl alcohol.

3. The method for producing an aromatic compound according to claim 1 or 2, wherein the dehydrogenation reaction is carried out at 50 to 150°C.

4. 4. The method for producing an aromatic compound according to claim 1, wherein the cyclohexadienes or cyclohexenes have a heterocycle.

5. A method for producing an aromatic compound, comprising the steps of: adding and polymerizing a conjugated diene and a dienophile in a reaction vessel by a Diels-Alder reaction to obtain cyclohexadienes or cyclohexenes; and then, in the same reaction vessel, dehydrogenating the cyclohexadienes or cyclohexenes in the presence of a solvent and molecular oxygen using a heterogeneous precious metal catalyst in which one or more precious metals selected from the group consisting of ruthenium, iridium, palladium, platinum and rhodium are supported on a carbon support.

6. 6. The process for producing an aromatic compound according to claim 5, wherein the solvent is one or more solvents selected from the group consisting of water, toluene, dioxane and t-butyl alcohol.

7. The method for producing an aromatic compound according to claim 5 or 6, wherein the dehydrogenation reaction is carried out at 50 to 150°C.

8. 8. The method for producing an aromatic compound according to claim 5, wherein the cyclohexadienes or cyclohexenes have a heterocycle.

9. An aromatic compound represented by any of the following chemical formulas. 【Chemistry 1】 【Chemistry 2】 【Chemistry 3】 【Chemistry 4】 【Chemistry 5】 【Chemistry 6】 【Chemistry 7】 【Chemistry 8】 【Chemistry 9】 【Chemistry 10】

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