JPH1059919A - Production of asymmetric azine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new production process of an asymmetric azine which is useful as an organic electronic material and a nematic liquid crystal material in high yield with reduced formation of by-products such as symmetric azines by adding an amine to the reaction system. SOLUTION: An asymmetric azine represented by formula I (R<1> and R<2> are each a (substituted) 1-10C alkyl, a halogen, cyano or the like) is produced by reaction of hydrazone of formula II with a benzaldehyde of formula III in the presence of an amine. The amount of the amine is preferably 0.1-20 moles, more preferably 0.5-10 moles per mole of the compound of formula II. When the amine is added, the hydrazine of formula II containing the amine is preferably allowed to react with a compound of formula III. In another case, a benzaldehyde derivative of formula IV is allowed to react with an excessive amount of hydrazine in a solvent such as ethanol to prepare hydrazine. After completion of the reaction, a solvent such as dichloromethane is added, the mixture is washed with water to remove excessive hydrazine, when necessary, the amine is added, and the compound of formula III added to effect the reaction with the hydrazone.

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 an asymmetric azine useful as an organic electronic material or a medical or agricultural chemical, particularly a nematic liquid crystal material for electro-optical liquid crystal display.

[0002]

2. Description of the Related Art Liquid crystal display elements have been used in various measuring instruments, such as watches and calculators, automobile panels, word processors, electronic organizers, printers, computers, televisions, and the like. Typical liquid crystal display methods are TN (twisted nematic) type and S type.
TN (super twisted nematic) type, DS (dynamic light scattering) type,
There are GH (guest / host) type or FLC (ferroelectric liquid crystal), etc., and the driving method is generally multiplex driving instead of conventional static driving, and moreover, simple matrix method, recently active matrix method is practical. Has been According to these display methods and driving methods, various characteristics are required as a liquid crystal material, and therefore, a large number of liquid crystal compounds have been synthesized.

[0003] Among such liquid crystal compounds, the general formula (A)

[0004]

Embedded image

The azine derivative represented by the formula (where ^Ra represents an alkyl group or an alkoxyl group) has been known for a long time, and (i) has a high maximum temperature of a liquid crystal phase. (ii) High-speed response is possible. (iii) It is easy and inexpensive to manufacture. It is an excellent liquid crystal material having such properties. However, this compound (A) has a problem that its melting point is high and its compatibility with other liquid crystal compounds is poor.

As a compound having improved this problem, Japanese Patent Application Laid-Open No. 54-87688 discloses a compound of the general formula (I)

[0007]

Embedded image

Wherein R ¹ and R ² are different from each other;
Represents an optionally substituted alkyl group or alkoxyl group having less than 10 carbon atoms, a halogen atom such as a fluorine atom, a chlorine atom or a bromine atom, or a cyano group. Asymmetric azines containing the compound represented by the formula (1) have been reported.

The compound (I) has a lower melting point than the compound (A), and is excellent in compatibility with other liquid crystal compounds. The maximum temperature of the liquid crystal phase is almost the same as that of the compound (A). Furthermore, since a polar group such as a cyano group or a halogen atom can be introduced as R ¹ or R ² , a so-called P-type liquid crystal compound can be obtained, which is effective even when a low threshold voltage is required. Has excellent properties such as

However, the compounds of the formula (I) are not without problems with regard to their preparation. JP-A-5
JP-A-4-87688 only describes a general method for producing the compound of the formula (I) and does not describe specific production examples.

[0011]

Embedded image

(Wherein R ¹ has the same meaning as in the general formula (I)).
I)

[0013]

Embedded image

(Wherein R ² has the same meaning as in formula (I)), and the compound of formula (I) is prepared by reacting a benzaldehyde derivative represented by the formula:
However, in practice, during the reaction or during the post-treatment, disproportionation occurs, and in addition to the target compound (I), the compound of the general formula (Va)

[0015]

Embedded image

(Wherein R ¹ has the same meaning as in formula (I)) or formula (Vb)

[0017]

Embedded image

(Wherein, R ² has the same meaning as in the general formula (I)). In preparing the hydrazone of (II), the symmetric azines of (Va) are often purified in the course of post-treatment. Since these symmetric azines have good crystallinity and a high melting point like the above-mentioned compound (A), it is often difficult to separate and remove them by recrystallization. Furthermore, since they have poor compatibility with other liquid crystal compounds, if they are used without separation, there is a high risk of separation and precipitation in the composition. In particular, when a cyano group or a halogen atom is used as R ¹ or R ² , the characteristics thereof are greatly reduced, which causes a serious problem.

Therefore, in order to actually use the compound of the general formula (I), it is desirable not to include a symmetric azine such as (Va) or (Vb). A manufacturing method that does not produce by-products is required.

[0020]

The problem to be solved by the present invention is to solve the above-mentioned problem by producing by-products such as symmetric azines in the production of asymmetric azines represented by the general formula (I). And a novel production method having a very low reaction yield and a high reaction yield.

[0021]

The present invention has been made in order to solve the above problems. General formula (I)

[0022]

Embedded image

Wherein R ¹ and R ² are different from each other;
Represents an optionally substituted alkyl group or alkoxyl group having less than 10 carbon atoms, a halogen atom such as a fluorine atom, a chlorine atom or a bromine atom, or a cyano group. A method for producing a compound represented by the formula (II):

[0024]

Embedded image

(Wherein, R ¹ has the same meaning as in formula (I)) and a compound represented by formula (II)
I)

[0026]

Embedded image

(Wherein R ² has the same meaning as in formula (I)). A process for producing a compound, characterized by reacting the compound in the presence of an amine. 2. 2. The method for producing a compound of the general formula (I), wherein the amine according to the above (1) is a trialkylamine. 3. The compound of the general formula (II) according to the above 1 or 2,
General formula (IV)

[0028]

Embedded image

(Wherein R ¹ has the same meaning as in the general formula (I)), and is reacted with an excess of hydrazine or a hydrate thereof. A method for producing a compound of the general formula (I), which is obtained by distilling off a solvent after adding an amine. Was found as a means for solving the above-mentioned problem.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION An example of the following method for producing an asymmetric amine of the present invention will be described. As amines, 2
A tertiary amine or a tertiary amine is preferred, and a tertiary amine is particularly preferred. Examples of the tertiary amine include trialkylamines such as triethylamine, trimethylamine and tributylamine; aromatic amines such as N, N-dimethylaniline and N, N-diethylaniline; and cyclic amines such as pyridine. And the like are particularly preferred.

The amount of the amine to be used is preferably 0.1 to 20 mol, more preferably 0.5 to 10 mol, based on the hydrazone of the formula (II). These amines may be added to the system when reacting the hydrazone of (II) with the benzaldehyde of (III). (I
The hydrazone of I) may be reacted with the benzaldehyde of (III), and this method is more preferred. That is, the general formula (IV)

[0032]

Embedded image

(Wherein, R ¹ has the same meaning as in the general formula (I)). After completion of the reaction, a solvent insoluble in water, such as dichloromethane, is added, and washing with water is repeated to remove excess hydrazine. After distilling off most of the solvent, an amine is added if necessary, and the reaction is performed by adding the benzaldehyde of (III) in a solvent such as ethanol. This reaction may be carried out under cooling or under heating, but is usually preferably carried out at around room temperature. After completion of the reaction, a solvent insoluble in water such as dichloromethane is similarly added, and washing with water is repeated. Then, the solvent is distilled off and purified by recrystallization from a solvent such as methanol. Further, if necessary, it is also preferable to purify using column chromatography with basic alumina.

Examples of the azine derivatives of the general formula (I) actually produced according to the production method of the present invention are listed in Table 1 together with their purity and phase transition temperature.

[0035]

[Table 1]

In the table, Cr represents a crystal phase, N represents a nematic phase, and I represents an isotropic liquid phase. Purity is the purity of the purified product obtained by recrystallization twice from twice (mL / g) methanol after alumina (basic) column chromatography, and is the purity of (I-1) and (I-2). The impurities in less than 100% of the compounds as in (1) are all symmetrical azine derivatives by-produced. The phase transition temperature is “° C.”.

As can be seen from Table 1, by using the production method of the present invention, 97% is obtained when both R ¹ and R ² are alkyl groups, and 100% when ^one of R ¹ and R ² is a fluorine atom.
%, The compound of the general formula (I) can be easily produced.

On the other hand, except that no amine was used, (I-4)

[0039]

Embedded image

When the compound was prepared, its purity was 8
Only 8%, which is a symmetric system (V-1)

[0041]

Embedded image

8% and (V-2)

[0043]

Embedded image

Was contained at 4%. Among these symmetrical azine derivatives, (V-2) has a serious problem that precipitation is liable to occur due to poor liquid crystallinity and poor compatibility with other liquid crystal compounds.

Therefore, by using the production method of the present invention, these symmetric azine derivatives can be completely removed or reduced, and therefore, it is very practical as a method for producing the asymmetric azine derivative of the general formula (I). You can see that there is.

[0046]

EXAMPLES Examples of the present invention are shown below to further explain the present invention. However, the present invention is not limited to these examples.

The structure of the compound was confirmed by a nuclear magnetic resonance spectrum (NMR), a mass spectrum (MS) and an infrared absorption spectrum (IR), and the purity was measured by a capillary gas chromatograph. (Example 1) 1- (4-propylbenzylidene) -2
Synthesis of-(4-methylbenzylidene) hydrazine (compound No. (I-1) in Table 1)

[0048]

Embedded image

To 120 g of hydrazine monohydrate, 30 g of 4-propylbenzaldehyde dissolved in 150 mL of ethanol was added, and the mixture was stirred at room temperature for 40 minutes. After adding 300 mL of dichloromethane, the mixture was washed three times with 200 mL of a saturated aqueous solution of sodium hydrogen carbonate. Triethylamine 15m
After adding L, the mixture was dehydrated and dried with anhydrous sodium sulfate.
The solvent was distilled off under reduced pressure, 15 mL of triethylamine was added, 120 mL of ethanol and 24.3 g of 4-methylbenzaldehyde were added, and the mixture was further stirred at room temperature for 8 hours. After adding 300 mL of dichloromethane and washing three times with 200 mL of a saturated aqueous solution of sodium hydrogen carbonate, the solvent was distilled off under reduced pressure. The residue was purified using alumina (basic) column chromatography (dichloromethane) and recrystallized twice from 100 mL of methanol to give 1-
17.9 g of (4-propylbenzylidene) -2- (4-methylbenzylidene) hydrazine was obtained. The compound was 97% pure and contained 1.5% each of 1,2-bis (4-propylbenzylidene) hydrazine and 1,2-bis (4-methylbenzylidene) hydrazine. (Comparative Example 1) 1- (4-Propylbenzylidene) -2- (4-methylbenzylidene) hydrazine was synthesized in exactly the same manner as in Example 1 except that triethylamine was used. Later purity is 86
%, Containing 6% 1,2-bis (4-propylbenzylidene) hydrazine and 8% 1,2-bis (4-methylbenzylidene) hydrazine. (Example 2) 1- (4-Fluorobenzylidene) -2
Synthesis of-(4-propylbenzylidene) hydrazine (compound No. (I-4) in Table 1)

[0050]

Embedded image

In the same manner as in Example 1 except that 4-fluorobenzaldehyde was used instead of 4-methylbenzaldehyde, 1- (4-fluorobenzylidene) -2- (4-propylbenzylidene) Hydrazine was synthesized. The purity at the end of the reaction was 94.2% and contained 5.1% of 1,2-bis (4-propylbenzylidene) hydrazine and 0.7% of 1,2-bis (4-fluorobenzylidene) hydrazine. The purity after purification by alumina (basic) column chromatography and recrystallization was 100%, and did not contain symmetric azines. Comparative Example 2 1- (4-Fluorobenzylidene) -2- (4-propylbenzylidene) hydrazine was synthesized in exactly the same manner as in Example 2 except that triethylamine was used. The purity at the end of the reaction is 60.
It contained only 0% and contained 23.2% of 1,2-bis (4-propylbenzylidene) hydrazine and 16.8% of 1,2-bis (4-fluorobenzylidene) hydrazine. This was similarly purified by alumina (basic) column chromatography and recrystallization, but the purity after purification was only 88%, 8% 1,2-bis (4-propylbenzylidene) hydrazine and 4% 1,2-bis (4-
(Fluorobenzylidene) hydrazine. (Application example) Preparation of liquid crystal composition Host liquid crystal (H)

[0052]

Embedded image

(Where "%" represents "% by weight") shows a nematic phase at 116.7 ° C. or less. This is thickness 6
The response time measured by filling in a TN cell of μm was 25.3.
m seconds. (At the time of applying a voltage at which the fall time and the rise time are equal) A liquid crystal composition comprising 80% by weight of the host liquid crystal (H) and 20% by weight of the compound (I-4) obtained in Example 2 was prepared. The maximum temperature of the nematic phase did not decrease so much as 104 ° C. When the response time was measured in the same manner, it was found that the speed was significantly increased to 18.5 ms.

When this composition was left at 0 ° C. for 24 hours, no precipitation of crystals was observed. (Comparative Application Example) In the above application example, the same amount of the compound containing the symmetric azine derivative obtained in Comparative Example 2 was added in place of the compound (I-4) obtained in Example 2, to obtain a white crystal. Remained and did not completely dissolve.

As described above, the azine derivative obtained by the production method of the present invention has a very low solubility in the symmetric azine derivative compared with the compound obtained by the conventional production method. It can be understood that the compound is very useful in preparing a liquid crystal material having a low risk of crystal precipitation and high responsiveness when mixed with a general-purpose liquid crystal composition because it is a small amount or contains no liquid at all. .

[0056]

According to the production method of the present invention, various liquid crystal compounds which are asymmetric azine derivatives can be easily produced. The obtained liquid crystal compound hardly contains a poorly soluble symmetric azine derivative, or the content thereof is extremely small as compared with that obtained by the conventional production method. When mixed, it has excellent solubility and the risk of crystal precipitation is low.

Therefore, the present invention is extremely useful as a method for manufacturing a liquid crystal material for a practical liquid crystal display requiring a wide temperature range and a high-speed response.

Claims (3)

[Claims] 1. A compound of the general formula (I) (In the formula, R ¹ and R ² are different from each other and may be an optionally substituted alkyl group or alkoxyl group having less than 10 carbon atoms, or a halogen atom such as a fluorine atom, a chlorine atom or a bromine atom, or a cyano group. Which is a compound represented by the general formula (II): (Wherein R ¹ has the same meaning as in general formula (I)) and a compound represented by general formula (III): (Wherein R ² has the same meaning as in formula (I)). A method for producing a compound, comprising reacting a compound represented by the formula (I) in the presence of an amine. 2. The method for producing a compound of the formula (I), wherein the amine according to claim 1 is a trialkylamine. 3. The compound of general formula (II) according to claim 1 or 2, wherein the compound of general formula (IV) is (Wherein, R ¹ has the same meaning as in the general formula (I)). A method for producing a compound of the general formula (I), which is obtained by distilling off a solvent after addition.