JP3506768B2 - Method for synthesizing triphenylene compounds - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a triphenylene ring, which is a typical mother nucleus of discotic liquid crystals.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been widely used in word processors, personal computers, televisions, etc., and industrial activities related to the development of materials and devices related thereto have been actively carried out. Liquid crystal compounds, which are the basis of liquid crystal display materials, have been actively researched and developed, and many compounds have been developed. These compounds are not limited to display devices, and their applications are being studied for the development of various applications. In addition to the rod-shaped liquid crystal compounds that are well known and widely used in the past, disk-shaped liquid crystal compounds, so-called discotic liquid crystal compounds, have recently been drawing attention.

Typical examples of discotic liquid crystal compounds include C.I. Report of Destrade et al., Mo
l. Cryst. Liq. cryst. Volume 71, 111
As described on page (1981), for example, benzene derivatives, triphenylene derivatives, truxene derivatives, phthalocyanine derivatives and the like can be mentioned. Generally, these are used as the central nucleus of the molecule, and a straight chain alkyl group or alkoxy group is used. , A substituted benzoyloxy group is radially substituted as a side chain. Among them, the triphenylene derivative is an attractive compound that easily forms a discotic nematic phase advantageous for forming an optically functional element.

2, 3, which is the object of the synthesis method of the present invention
The 6,7,10,11-hexaalkoxy-substituted triphenylene compound is an important synthetic intermediate used in most of the mother nuclei of triphenylene-based liquid crystals reported so far. The synthesis method is described in Macromol. chem. R
rapid Communication. , 4th and 8th
It is described on page 12 (1983), and is obtained as a hexakismethoxy substitution product by the oxidative trimerization reaction of 1,2-dimethoxybenzene, but one step thereof requires 10 days. More preferred method is Advanced
Materials. There is a synthetic method described in Volume 2, page 40 (1990). However, even in this method, when the ferric chloride is mixed with concentrated sulfuric acid or 70 vol% diluted sulfuric acid, or when 1,2-dimethoxybenzene is post-added, the reaction mixture often overflows from the vessel due to vigorous foaming. In addition, there is a drawback in operability and work efficiency that it takes 24 hours to complete the reaction.

[0005]

Therefore, an object of the present invention is to provide a method for efficiently synthesizing a triphenylene ring useful as a mother nucleus of a discotic liquid crystal.

[0006]

The above object is characterized in that concentrated sulfuric acid is added to a mixture containing at least 1,2-dialkoxybenzene and an aqueous ferric chloride solution. Method for synthesizing 7,10,11-hexaalkoxy-substituted triphenylene, or 1,2-dialkoxybenzene is reacted in the presence of at least concentrated sulfuric acid and ferric sulfate. ，
It was achieved by the development of a synthetic method for 7,10,11-hexaalkoxy-substituted triphenylene.

The present invention will be described in detail below. The method according to claim 1 is an AdvancedMaterial.
s. Basically, a reaction reagent similar to the synthetic method described in Volume 2, p. 40 (1990), namely ferric chloride, concentrated sulfuric acid,
1,2-dialkoxybenzene is used. However, due to the large amount of hydrochloric acid gas, which is probably generated by the anion exchange accompanying the dissolution of iron chloride in concentrated sulfuric acid, no matter which method described in the literature, that is, mixing of the three or mixing them in any order, It was also found that it is extremely difficult to proceed the reaction under mild conditions because the viscosity of the suspension increases and the stirring efficiency significantly decreases. That is, the hydrochloric acid gas caused a rapid increase in the volume of the contents and often overflowed from the container. This is a very big problem on a scale that is manufactured industrially.

[0008] Accordingly, the present inventors have also hydrochloric gas is generated, a result of intensive studies on a method that does not lead to the increase in volume of the contents, rather than the 70 vol% dilute sulfuric acid, the coexistence of 1,2-dialkoxy benzene It was found that the reaction can be allowed to proceed extremely gently by gradually adding concentrated sulfuric acid to the aqueous solution of ferric chloride. It was found that the reaction proceeded with higher efficiency and the target product was obtained in good yield. In addition, ferric chloride, when an anhydrous salt is used, generates a lot of heat when dissolved, so hydrated salt (hexahydrate is commercially available)
Is preferably used.

On the other hand, the method described in claim 2 is a large amount which is considered to be generated by anion exchange accompanying dissolution of ferric chloride in concentrated sulfuric acid in the oxidative trimerization reaction of 1,2-dialkoxybenzene. The ferric sulfate is used to suppress the hydrochloric acid gas, and the characteristic feature is that the reaction proceeds under mild conditions at room temperature and the target product is preferentially obtained in a short time of about 6 hours. . In this reaction, ferric ion oxidizes the raw material 1,2-dialkoxybenzene, trimerizes, and is itself reduced to ferrous ion. It is considered that the reaction proceeds by undergoing a complex formation similar to the typical color reaction due to the change and coordination of iron ion to phenol. In addition, according to the reaction trace by high performance liquid chromatography, this reaction was shortly after the mixture of both 1,2-dialkoxybenzene and ferric sulfate, and the final production amount was -5%.
Since 0% has already been produced, it is speculated that the oxidation reaction itself proceeds very fast.

The two alkoxy groups of 1,2-dialkoxybenzene may be the same as or different from each other, and may be unsubstituted or substituted. The alkyl part of the alkoxy group may be linear or branched, and the number of atoms forming the main chain is preferably 1 to 22, more preferably 1 to 1
0 is preferred. For example, methoxy group, ethoxy group, n-
Propoxy, isopropoxy, n- butoxy group, Bae Nchiruokishi group, hexyloxy group, heptyloxy group, octyloxy group, 2-ethyl hexyloxy group,
Examples thereof include nonyloxy group and decyloxy group.

As the substituent of the substituted alkoxy group, a halogen atom (fluorine, chlorine, bromine, iodine), a hydroxyl group, a cyano group, a nitro group, an amino group, a formyl group, a carbamoyl group, a sulfamoyl group, a carboxy group, a sulfo group, Examples thereof include an alkoxy group, an oxirane group, an aryloxy group, an aryl group, a heterocyclic group, an alkenyl group, an alkynyl group, an acyl group, an acyloxy group, an acylamino group, an alkylthio group and an arylthio group. Examples of the substituted alkoxy group include 2-chloroethoxy group, 4-hydroxybutoxy group, 2-cyanoethoxy group, 2-nitroethoxy group, 2-piperidinoethoxy group, 3-oxopropyloxy group, 2-carbamoyl. Ethoxy group, 4-sulfamoylbutoxy group, 3-carboxypropyloxy group, 2
-Sulfoethoxy group, 2-methoxyethoxy group, 2-ethoxyethoxy group, 2-butoxyethoxy group, 2-benzyloxyethoxy group, 2-oxiranylethoxy group,
3-phenoxypropyloxy group, phenethyloxy group, 2- (2-pyridyl) ethoxy group, 3-butenyloxy group, propargyloxy group, 4-oxopentyloxy group, 3-benzoylpropyloxy group, 2-acetylaminoethoxy Group, 2-ethylthioethoxy group, 4-phenylthiobutoxy group and the like.

Examples of the divalent group in which adjacent alkoxy groups are linked to each other include an alkylenedioxy group and a phenylenedioxy group, examples of which include ethylenedioxy group and cyclohexane-1,2-dioxy group. Group, hexane-3,4-dioxy group, 1,2-phenylenedioxy group and the like.

The preferred substituents are not limited because they vary depending on the use, but in view of the yield by this synthetic method, an unsubstituted alkoxy group is preferred.
A methoxy group, an ethoxy group, and an ethylenedioxy group having a small number of carbon atoms are preferable.

The synthetic conditions for adding concentrated sulfuric acid will be described on the scale when 1.0 mol of 1,2-dialkoxybenzene is used. The order in which concentrated sulfuric acid, 1,2-dialkoxybenzene and iron chloride are mixed is important, and concentrated sulfuric acid is gradually added in the presence of a mixture of an aqueous solution of ferric chloride and 1,2-dialkoxybenzene. In addition to. When iron chloride is present as a solid, when it comes into contact with sulfuric acid, anion is immediately exchanged to generate hydrochloric acid gas.
Since this occurs from the surface of the iron chloride crystal, in the suspension containing the crystal, the gas is not exhausted immediately and the volume of the suspension expands. Moreover, when 1,2-dialkoxybenzene coexists there, the oxidation reaction probably occurs concurrently at the interface, so that the dissolution of iron chloride or iron sulfate is promoted, and as a result, anion exchange is also promoted, so that hydrochloric acid is added. It is speculated that gas will be generated more violently.
In this respect, the dissolution of iron chloride is very preferable for this reaction, and the coexistence of 1,2-dialkoxybenzene enables the oxidation reaction to be carried out in parallel. It seems that it is contributing to the generation of gas.

The amount of water used is preferably 0.5 to 1.5 liters, but when ferric chloride hexahydrate is used, the reaction can be carried out in an amount including the water of crystallization. . The reaction temperature is preferably 20 to 60 ° C, but 1,2-
Depending on the solubility of dialkoxybenzene, it may be diluted with a hydrophilic inert solvent such as water or sulfolane. But,
The reaction tends to slow down as the amount of solvent diluted increases,
It is preferably 2 liters or less including water. Concentrated sulfuric acid is 1.5
It is preferably -4 liters, more preferably 2-2.5 liters. The ferric sulfate is preferably 3.0 to 6.0 mol, more preferably 4.0 to 5.0 mol. The reaction time is preferably 10 to 40 hours, more preferably 15 to 30 hours.

Regarding the synthesis conditions in the presence of concentrated sulfuric acid and ferric sulfate, 1,2-dialkoxybenzene was 1.
The scale when 0 mol is used will be described. Concentrated sulfuric acid,
The order of mixing 1,2-dialkoxybenzene and iron sulfate is as follows: iron sulfate is suspended and mixed in a solvent amount of concentrated sulfuric acid, and then 1,2-dialkoxybenzene is mixed in order to facilitate the operation of stirring. Preference is given to adding alkoxybenzene. The coexistence of water is preferred for this reaction, presumably to promote dissolution of the iron sulfate. The amount of water is 0.5 ~
Addition of 1.5 liters is preferable, but when ferric sulfate hexahydrate is used, the reaction proceeds even with only the water of crystallization. The reaction temperature is preferably 20 to 60 ° C, but 1,2-
It is preferable to dilute with a hydrophilic inert solvent such as water or sulfolane depending on the solubility of dialkoxybenzene. However, the reaction tends to be delayed as the amount of solvent diluted increases, and it is preferably 2 liters or less including water. Concentrated sulfuric acid is preferably 1.5 to 4 liters, more preferably 2 to 2.5 liters. The ferric sulfate is preferably 3.0 to 6.0 mol, more preferably 4.0 to 5.0 mol. The reaction time is preferably 2 to 24 hours, more preferably 4 to 10 hours. Specific examples of 2,3,6,7,10,11-hexaalkoxytriphenylene obtained by the synthesis method of the present invention are shown below.

[0017]

[Chemical 1]

[0018]

[Chemical 2]

[0019]

[Chemical 3]

[0020]

[Chemical 4]

[0021]

EXAMPLE An example of synthesizing a triphenylene ring using the synthetic method according to claim 1 of the present invention will be shown below. Example 1 Synthesis of 2,3,6,7,10,11-hexamethoxytriphenylene (C-1) 135 ml of warm water was placed in a 2-liter three-necked flask, and 230 g of ferric chloride hexahydrate was completely added. After dissolving,
30 g of 2-dimethoxybenzene (veratrol) was added. Next, while vigorously stirring with a mechanical stirrer, 490 ml of concentrated sulfuric acid was gradually added over 2 hours at room temperature. After 24 hours, gradually add 2 liters of ice water,
After 1 hour, the reaction mixture was filtered through a glass filter to obtain 23 g (77%) of the objective crystal. (Example 2) Next, a synthesis example of a triphenylene ring using the synthesis method according to claim 2 of the present invention will be shown. Synthesis of 2,3,6,7,10,11-hexamethoxytriphenylene (C-1) 135 ml of ice water was put into a 2-liter three-neck flask cooled with ice, and stirred vigorously with a mechanical stirrer at room temperature under concentrated sulfuric acid. 490 ml was added slowly. Further, ferric sulfate / n-hydrate (generally referred to as 6-9 hydrate) 27
After adding 5 g, 30 g of 1,2-dimethoxybenzene (veratrol) was gradually added at an internal temperature of 45 ° C. Four
After the lapse of time, 2 liters of ice water was gradually added under ice cooling, and after another hour, the reaction mixture was filtered with a glass filter,
10 g (33%) of the desired crystal was obtained. (Comparative Example) 1 liter of ice water in a 2-liter three-necked flask cooled with ice.
35 ml was added, and 490 ml of concentrated sulfuric acid was gradually added at room temperature while vigorously stirring with a mechanical stirrer. Further, 150 g of ferric chloride) was gradually added, but immediately after the addition, vigorous foaming and heat generation were accompanied. After the addition was completed in 1 hour, 30 g of 1,2-dimethoxybenzene (veratrol) was gradually added at an internal temperature of 45 ° C., but immediately after the addition of 5 g, the content was colored blue-blue. Began to increase in volume and gradually overflowed.

[0022]

EFFECTS OF THE INVENTION According to the method described in claim 1, oxidative trimerization proceeds in a very safe and short time without generation of hydrochloric acid gas, and the desired product is obtained in good yield. be able to.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References NAARMAN, H et al. , A High Yield Easy method for the Preparation of Alkoxy-Substituted Triphenylenes, SYNTHE SIS, June 6, 1994, No. 5, p. 447-448 (58) Fields surveyed (Int.Cl. ⁷ , DB name) C07C 41/30 C07C 43/21 C07B 61/00 300 BEILSTEIN (STN)

Claims (2)

(57) [Claims] 1. Concentrated sulfuric acid is added to a mixture in which at least 1,2-dialkoxybenzene and an aqueous ferric chloride solution are present, 2,3,6,7,10,1.
Method for synthesizing 1-hexaalkoxy-substituted triphenylene 2. A 2,3,6,7,10,11-hexaalkoxy-substituted triphenylene, characterized in that 1,2-dialkoxybenzene is reacted in the presence of at least concentrated sulfuric acid and ferric sulfate. Synthesis method