CN1315800C - Novel LCD compound p-n-pentoxy cinnamic acid -2-fluoro-4-hydroxy- benzonitrile ester and its preparation method - Google Patents

Abstract

The invention relates to a substituted cinnamate liquid crystal compound containing fluorine atoms and cyano groups and a preparation method thereof. The structural formula of this compound is shown in the figure, and its preparation method is characterized by: introducing an alkoxy group on the 4-position of the benzene ring of cinnamic acid (3-phenylacrylic acid) through Williamson etherification reaction to generate alkoxy cinnamic acid , and then through DCC dehydration condensation to promote the condensation of alkoxycinnamic acid and 2-fluoro-4-hydroxybenzonitrile to generate the desired compound. The present invention also relates to the use of the compound. The monomer liquid crystal can be used in mixed liquid crystals, and the mixed liquid crystals can be used in liquid crystal displays.

Description

Novel liquid crystal compound——p-pentyloxycinnamic acid-2-fluoro-4-hydroxybenzonitrile ester and its preparation method

technical field

The invention relates to the technical field of organic synthesis, in particular to a substituted cinnamate organic liquid crystal compound containing a fluorine atom and a cyano group, a preparation method and an application thereof.

Background technique

In recent years, liquid crystal compounds and liquid crystal materials have become one of the hot spots in the research of applied chemistry and material chemistry, and have been widely used in electronics, optics, acoustics, bioengineering, chemical industry, etc., and the most extensive and important It is its application in electronic display. With the development of the information industry, the requirements for liquid crystal materials are constantly increasing. Although there have been many reports on liquid crystal materials, not all of them are suitable for use in display devices, because liquid crystal materials for display must meet a wide operating temperature range, low operating voltage, low viscosity, fast response, high stability requirements.

The liquid crystal compound with 2-fluoro-4-hydroxybenzonitrile as the intermediate has the advantages of both fluorine-containing liquid crystal and cyano liquid crystal, and is an important class of liquid crystal compound that satisfies the above conditions and represents the development trend of liquid crystal, while 2-fluoro- 4-Hydroxybenzonitrile has therefore become an important intermediate in the liquid crystal chemical industry. This intermediate was first synthesized by Japan's Sumitomo Chemical Co. Ltd. in 1982. Since then, hundreds of liquid crystal compounds have been synthesized using this intermediate. These compounds have the advantages of high-definition bright spots, wide liquid crystal working range, and low viscosity. They are suitable for As a component of display liquid crystal material with excellent performance.

Contents of the invention

The object of the present invention is to provide a kind of substituted cinnamate liquid crystal compound containing fluorine atom and cyano group, its structural formula is

The compound has the advantages of stable chemical properties, high clearing point and wide liquid crystal range, and is a potential component of liquid crystal display materials.

The compound is prepared by organic synthesis techniques. The key points of the method for synthesizing this compound are:

1) Take ethanol-water solution as a mixed solvent, wherein the volume percentage of ethanol is 70% to 95%; add soluble alkali metal hydroxide to make the pH of the solution reach pH>10, add halogenated n-pentane (halogen atom Including fluorine, chlorine, bromine atoms) and p-hydroxycinnamic acid, the ratio of the two substances is 2-5:1, and the mass fraction of p-hydroxycinnamic acid in the solution is 5%-30%. Under these conditions, a condensation reaction occurs between the two. The reaction temperature is 50-80°C.

2) After the condensation reaction is completed, react with the mixed solution obtained in the previous step reaction with the ethanol-water mixed solvent solution of soluble alkali metal hydroxide, remove the by-product generated in step 1) by hydrolysis reaction, and obtain pure paranormal Pentoxycinnamic acid. The ratio of the amount of soluble hydroxide used to the amount of p-hydroxycinnamic acid used in step 1) is 2 to 5: 1, the pH of the reaction system> 12, the reaction temperature is 50 to 80 ° C, and ethanol in the mixed solvent The volume percentage is 60% to 80%.

3) With DCC (N, N-dicyclohexylcarbodiimide) as a dehydrating agent, DMAP (N, N-dimethylaminopyridine) as a catalyst, and anhydrous tetrahydrofuran as a solvent, impel n-pentoxycinnamic acid and 2-Fluoro-4-hydroxybenzonitrile undergoes a dehydration condensation reaction to generate the target compound p-pentyloxycinnamate-2-fluoro-4-hydroxybenzonitrile. The ratio of the amount of DCC, p-pentyloxycinnamic acid, 2-fluoro-4-hydroxybenzonitrile and DMAP is 1～1.5:1～2:1:0.01～0.02, 2-fluoro-4-hydroxybenzene The initial mass fraction of nitrile in the solution is 5%-20%. The reaction temperature is 0-30°C.

The following experiments will help to understand the present invention, but the following experiments do not limit the content of the present invention.

Implementation 1

1) Dissolve 0.01mol of p-hydroxycinnamic acid and 0.02mol of potassium hydroxide in 40ml of 95% (volume fraction) ethanol, then add 0.03mol of n-pentane bromide dropwise at a rate of about 1ml/min, reflux for 24 hours, and then Add 14ml of 70% (volume fraction) ethanol solution of 0.02mol potassium hydroxide, and continue to reflux for 2h. Add 100ml of water, 20ml of concentrated hydrochloric acid, heat for 15min, cool and filter, wash with distilled water, dry, and then recrystallize with 95% (volume fraction) ethanol to obtain p-pentyloxycinnamic acid as white flaky crystals. 54%.

2) Add 0.01mol of p-pentyloxycinnamic acid and 20ml of anhydrous tetrahydrofuran into a three-necked flask, stir to dissolve completely, then add 0.01mol of DCC (N,N-dicyclohexylcarbodiimide), and wait until After the turbidity phenomenon, 0.01mol2-fluoro-4-hydroxybenzonitrile and a small amount of DMAP[4-(N,N-dimethylamino)pyridine] were dissolved in 20ml of anhydrous tetrahydrofuran to form a solution, which was slowly dripped into the flask. Stir at about 10°C for 24 hours. After the reaction is completed, remove the by-product N,N-dicyclohexylurea by filtration, add distilled water to the filtrate to precipitate the product, and separate it by column chromatography after drying to obtain 0.54g of pure product, with a yield of about 15 %.

Implementation 2

1) Dissolve 0.02mol of p-hydroxycinnamic acid and 0.05mol of potassium hydroxide in 100ml of 95% (volume fraction) ethanol, then add 0.03mol of n-pentane bromide, and reflux for 48h. Then add 35ml of 70% (volume fraction) ethanol solution of 0.03mol potassium hydroxide, and continue to reflux for 2h. Add 100ml of water and 40ml of concentrated hydrochloric acid, mix well, heat for 20min, cool and filter, wash with distilled water, dry, and recrystallize with 95% (volume fraction) ethanol to obtain p-pentyloxycinnamic acid as white flaky crystals , yield 49%.

2) Add 0.015mol of p-pentyloxycinnamic acid and 50ml of anhydrous tetrahydrofuran into a three-necked flask, stir to dissolve completely, then add 0.01mol of DCC (N,N-dicyclohexylcarbodiimide), and wait until After the turbidity, completely dissolve 0.015mol 2-fluoro-4-hydroxybenzonitrile and a small amount of DMAP[4-(N,N-dimethylamino)pyridine] in 35ml of anhydrous tetrahydrofuran to form a solution, and slowly drop it into the flask, Stir at about 20°C for 24 hours. After the reaction is completed, remove the by-product N,N-dicyclohexylurea by filtration, add distilled water to the filtrate to precipitate the product, and separate the pure product by column chromatography after drying. 0.86g, the yield is about 17%.

The synthesized compound was characterized by IR, ¹ H NMR to confirm its structure.

IR (infrared spectrum):

Cyano group (1, C≡N bond stretching vibration, 2230cm ^-1 )

Benzene ring (2, stretching vibration of the carbon skeleton of the benzene ring, 1602, 1571, 1512cm ^-1 )

Carbonyl (3, C=O stretching vibration, 1725cm ^-1 )

Carbon-oxygen single bond (4, COC stretching vibration, 1258, 1159cm ^-1 )

¹ HNMR (hydrogen nuclear magnetic resonance spectrum):

Proton 1: δ=6.74×10 ^-6 , s=1.0

Proton 2: δ=7.01×10 ^-6 , s=2.09

Proton 3: δ=7.78×10 ^-6 , s=2.06

Proton 4: δ=7.35×10 ^-6 , s=1.01

Proton 5: δ=7.61×10 ^-6 , s=1.0

Proton 6: δ=7.87×10 ^-6 , s=1.01

Proton 7: δ=8.05×10 ^-6 , s=0.94

Proton 8: δ=0.90×10 ^-6 , s=2.88

Proton 9: δ=1.37×10 ^-6 , s=4.25

Proton 10: δ=1.73×10 ^-6 , s=2.13

Proton 11: δ=4.03×10 ^-6 , s=2.01

It was thus confirmed that the structures of the synthesized compounds were consistent with expectations.

The liquid crystal phase transition properties of the synthesized compounds were characterized by DSC (differential calorimetry scanning) and POM (orthogonal polarizing microscope).

The phase transition behavior of the synthesized compound was found by differential calorimetry scanning analysis:

K 79.0 N 106.3 I 105.1 N 47.7 K

It is consistent with the phase transition behavior of thermotropic liquid crystals.

The synthesized sample was observed through an orthogonal polarizing microscope. At room temperature, the sample appeared as a flaky crystal under a polarizing microscope. The sample was heated at a rate of 5°C/min, and when it reached about 80°C, the sample melted into a liquid crystal state, and appeared in the field of view. A large number of droplets, many black stripes appear in the droplets, cross extinction phenomenon appears at the intersection, showing a typical stripe texture, and flowing rapidly, indicating that the sample currently exists in a nematic phase. Reheated to 108°C, the schlieren texture rapidly decreased and disappeared, and the field of view appeared black, indicating that the sample had been transformed into an isotropic liquid. When the temperature is lowered, a schlieren texture with a yellow background appears in the field of vision at 105°C, and then crystallizes and becomes crystal again at about 45°C. This shows that p-pentyloxycinnamate-2-fluoro-4-hydroxybenzonitrile is a tautotropic liquid crystal.

The above test results about liquid crystal properties show that p-pentyloxycinnamic acid-2-fluoro-4-hydroxybenzonitrile is suitable as an ideal component of liquid crystal composites used in liquid crystal displays, and is suitable for TN, STN, In liquid crystal composite materials used in liquid crystal displays such as TFT.

Claims (2)

1. a liquid crystalline cpd---to n-pentyloxy styracin-2-fluoro-4-4-hydroxy-benzonitrile ester, its structural formula is

2. a liquid crystalline cpd---the preparation method to n-pentyloxy styracin-2-fluoro-4-4-hydroxy-benzonitrile ester is characterized in that

1) under the potential of hydrogen of pH＞10,50～80 ℃ temperature, in solution, add halo Skellysolve A and p-Coumaric Acid, make both that condensation reaction take place, generate the n-pentyloxy styracin,

2) after condensation finishes, under 50～80 ℃ of conditions, remove reactions steps 1 by hydrolysis reaction with the solution of highly basic in ethanol-water mixed solvent) in the by product that generates,

3) with N, the N-dicyclohexylcarbodiimide is a dewatering agent, and N, N-Dimethylamino pyridine are catalyzer, 0～30 ℃ of reaction down, impels n-pentyloxy styracin and the paired n-pentyloxy styracin of 2-fluoro-4-4-hydroxy-benzonitrile dehydrating condensation-2-fluoro-4-4-hydroxy-benzonitrile ester.