CN112812781B - Liquid crystal compound based on bipiperazine benzoxazole and preparation method thereof - Google Patents
Liquid crystal compound based on bipiperazine benzoxazole and preparation method thereof Download PDFInfo
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- C09K19/06—Non-steroidal liquid crystal compounds
- C09K19/34—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring
- C09K19/3441—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having nitrogen as hetero atom
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- C07D263/52—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings condensed with carbocyclic rings or ring systems
- C07D263/54—Benzoxazoles; Hydrogenated benzoxazoles
- C07D263/56—Benzoxazoles; Hydrogenated benzoxazoles with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached in position 2
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Abstract
The invention disclosesA liquid crystal compound based on bipiperazine benzoxazole belongs to the technical field of organic synthesis, and has a structure shown as a formula (I), wherein F m Represents that hydrogen on the benzene ring is substituted by fluorine atoms, m represents the substitution number of the fluorine atoms, and the value of m is 1-4; m represents-NO 2 、‑Cl、‑CH 3 Or H; r represents a C2-16 linear alkyl group. The liquid crystal compound provided by the invention takes the bipiperazine-benzoxazole as a crystallization unit, takes the alkyl chain as a flexible group, takes fluorine atoms as lateral substituents, introduces different substituents into the end group, has a liquid crystal state, shows a smectic phase, can be used for special liquid crystal materials, and meanwhile, the preparation method of the bipiperazine-benzoxazole liquid crystal compound is simple to operate, and has high product yield and purity. The structure shown in the following formula (I):
Description
Technical Field
The invention belongs to the technical field of organic synthesis, and particularly relates to a liquid crystal compound based on bipiperazine benzoxazoles and a preparation method thereof.
Background
In the research field of liquid crystal materials, the hetero-ring liquid crystal material changes the positive and negative charge centers of liquid crystal molecules due to hetero atoms, so that the molecules generate new dipole-dipole acting force. F. N, O atoms have large electronegativity and electron-rich structures, and can change the molecular shape and dipole moment of liquid crystal molecules by introducing the atoms into the liquid crystal molecules, thereby changing the phase state of the liquid crystal material. Benzoxazoles have a planar rigid structure containing N, O polar heteroatoms, which can alter the dipole moment of the molecule, inducing the molecule to produce a liquid crystal phase. For many years, the research of benzoxazole liquid crystal compounds only takes benzoxazole as a crystallization unit, and the influence of the length of an alkyl chain on the liquid crystal property of the benzoxazole liquid crystal compounds is researched, but no report of researching the liquid crystal property of the benzoxazole liquid crystal compounds by taking the benzoxazole as a terminal group substituent group is seen.
In addition, the lateral fluorine-containing liquid crystal material is more and more paid attention to by students due to the advantages of low viscosity, high stability, high voltage retention rate and the like, but the preparation method of the compound is rarely reported.
Disclosure of Invention
In order to solve the problems, the invention provides a liquid crystal compound based on bipiperazine benzoxazole and a preparation method thereof. The compound takes alkyl chain as flexible group, piperazine-benzoxazole is respectively introduced at two end groups of the compound as crystallization unit, fluorine atom is taken as lateral substituent, and benzoxazole is taken as end group to introduce different substituent (-CH) 3 、-NO 2 -Cl, H), has a liquid crystalline state, exhibits a smectic phase, and can be used for specialty liquid crystal materials.
The first object of the invention is to provide a liquid crystal compound based on bipiperazine benzoxazole, which has a structure shown as a formula (I),
in the formula (I),
F m represents that hydrogen on the benzene ring is substituted by fluorine atoms, m represents the substitution number of the fluorine atoms, and the value of m is 1-4;
m represents-NO 2 、-Cl、-CH 3 Or H;
r represents a C2-16 linear alkyl group.
Preferably, the value of m is 1 or 2.
Preferably, R represents a C4-8 linear alkyl group.
Preferably, the liquid crystal compound includes any one of the following compounds:
the second object of the invention is to provide a preparation method of a liquid crystal compound based on bipiperazine benzoxazole, which comprises the following preparation steps:
s1, under the protection of nitrogen or inert gas, adding a compound of a formula (II) and piperazine serving as raw materials, alkali serving as an acid binding agent and Pd serving as a catalyst into a certain amount of solvent, and reacting for 4-10 hours at 60-100 ℃ to obtain a compound of a formula (III);
s2, taking a compound of the formula (III) and X-R-X as raw materials, taking alkali as an acid binding agent, uniformly dispersing in a solvent, and reacting at 60-100 ℃ for 4-10 hours to prepare a compound of the formula (IV);
s3, dispersing a compound of a formula (IV) and a compound of a formula (V) serving as raw materials into a solvent, reacting for 4-10 hours at 40-80 ℃, adding an epoxidation reagent, and continuing to react for 4-8 hours to obtain the liquid crystal compound based on the fluorine piperazine benzoxazole, wherein the liquid crystal compound is shown in the formula (I);
the preparation route is as follows:
in the formula (II), the formula (III), the formula (IV), the formula (V), the formula (I) and X-R-X,
F m represents that hydrogen on the benzene ring is substituted by fluorine atoms, m represents the substitution number of the fluorine atoms, and the values of the m are 1-4;
m represents-NO 2 、-Cl、-CH 3 Or H;
r represents a C2-16 linear alkyl group;
x represents Br or I.
Preferably, in S1, the Pd catalyst is tetrakis (triphenylphosphine) palladium, palladium acetate, or tris dibenzylideneacetone dipalladium; the molar ratio of the compound of the formula (II) to the Pd catalyst is 1:0.001-0.02.
Preferably, the acid binding agent comprises one or more of potassium carbonate, sodium tert-butoxide and potassium tert-butoxide.
Preferably, in S1, the molar ratio of the compound of formula (ii) to the acid-binding agent is 1:1 to 2; in S2, the molar ratio of the compound of formula (III) to the acid-binding agent is 1:2 to 4.
Preferably, the epoxidation reagent is 2, 3-dichloro-5, 6-dicyanobenzoquinone, iodobenzene acetate or lead tetraacetate; the molar ratio of the compound of formula (iv), the compound of formula (v) and the epoxidizing agent is 1: 1:2-4.
Preferably, the solvent is one or more of DMF, chloroform, dichloroethane and chloroform.
Compared with the prior art, the invention has the beneficial effects that:
the compound provided by the invention takes alkyl chain as a flexible group, piperazine-benzoxazole is respectively introduced into two end groups of the compound as a crystallization unit, fluorine atoms are taken as lateral substituents, and different substituents (-CH) are introduced into the compound by taking benzoxazole as a terminal group 3 、-NO 2 -Cl and H) has liquid crystal state, shows smectic phase, can be used for special liquid crystal materials, and can be used for synthesizing the bipiperazine benzoxazole liquid crystal compound, and has simple operation and high product yield and purity. The smectic phase liquid crystal of the compound is used for display, and after being driven, the electric signal is removed, the display content can still be kept, and the compound has a memory effect.
Drawings
FIG. 1 is a differential scanning calorimeter graph of a liquid crystal compound prepared in example 1 of the present invention.
Detailed Description
In order that those skilled in the art will better understand the technical solution of the present invention, the present invention will be further described with reference to the specific examples and the accompanying drawings, but the examples are not intended to be limiting.
The experimental methods and the detection methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.
The compound provided by the invention takes alkyl chain as a flexible group, piperazine-benzoxazole is respectively introduced into two end groups of the compound as a crystallization unit, fluorine atoms are taken as lateral substituents, and different substituents (-CH) are introduced into the compound by taking benzoxazole as a terminal group 3 、-NO 2 -Cl and H) has liquid crystal state, shows smectic phase, can be used for special liquid crystal materials, and can be used for synthesizing the bipiperazine benzoxazole liquid crystal compound, and has simple operation and high product yield and purity.
The invention provides a liquid crystal compound based on bipiperazine benzoxazole, which has a structure shown as a formula (I),
in the formula (I),
F m represents that hydrogen on the benzene ring is substituted by fluorine atoms, m represents the substitution number of the fluorine atoms, and the value of m is 1-4;
m represents-NO 2 、-Cl、-CH 3 Or H;
r represents a C2-16 linear alkyl group.
Specific examples of the present invention based on the bipiperazine benzoxazole liquid crystal compounds are shown below:
in the following, we provide specific synthetic methods for preparing the above compounds.
Example 1
A liquid crystal compound based on bipiperazine benzoxazole has a structure shown in the following formula (Ia),
the preparation method of the liquid crystal compound based on the bipiperazine benzoxazole shown in the formula (Ia) specifically comprises the following steps:
(1) Preparation of 2-fluoro-4-piperazine-benzaldehyde:
under the protection of nitrogen, 8.6g of piperazine, 20g of 2-fluoro-4-bromo-benzaldehyde, 20.7g of potassium carbonate and 0.9g of tribenzylideneacetone dipalladium are added into DMF, stirred, heated to 80 ℃ for 8 hours, poured into water after reaction, filtered and pumped to obtain 18.7g of 2-fluoro-4-piperazine-benzaldehyde, wherein the yield is 90% and the purity is 96.8%;
the reaction equation is as follows:
(2) Preparation of 4,4' bis- [ (1, 4-bipiperazine) -2-fluorobenzaldehyde ] yl-butane:
18g of 2-fluoro-4-piperazine-benzaldehyde, 9.7g of 1, 4-dibromobutane and 37.2g of potassium carbonate are added into 200ml of DMF under the protection of nitrogen, after 4h of reaction, stirring is carried out, the temperature is raised to 80 ℃, after 8h of reaction, the mixture is poured into water, filtration and toluene ethanol recrystallization are carried out, thus obtaining 18g of 4,4' -bis- [ (1, 4-bipiperazine) -2-fluorobenzaldehyde ] yl-butane, and the yield is: 85.1 percent and the purity is 97.6 percent;
the reaction equation is as follows:
(3) Preparation of 1, 4-bis {4- (4- (benzo [ d ] oxazol) -3-fluorobenzene) -piperazine) } yl-butane, i.e. formula (Ia):
18g of 4,4' -bis- [ (-1, 4-bipiperazine) -2-fluorobenzaldehyde ] base-butane and 8.4g of 2-aminophenol are added into 300ml of dichloroethane, the temperature is raised to 80 ℃, the reaction is carried out for 6 hours, 26.0g of 2, 3-dichloro-5, 6-dicyanobenzoquinone is added, after the reaction is completed, 300ml of water is added, water is washed, liquid separation is carried out, concentration and recrystallization are carried out, and 15.1g of 1, 4-bis {4- (4- (benzo [ d ] oxazole) -3-fluorobenzene) -piperazine) } base-butane is obtained, namely the bipiperazine benzoxazole liquid crystal compound shown in the formula (Ia) with the yield of 61 percent and the purity of 99.1 percent;
the reaction equation is as follows:
1, 4-bis {4- (4- (benzo [ d ] oxazol) -3-fluorobenzene) -piperazine) } yl-butane obtained in this example
The performance characterization is carried out by adopting a DSC-60 type differential scanning calorimeter, the result is shown in figure 1, and the figure 1 shows that the prepared 1, 4-bis {4- (4- (benzo [ d ] oxazole) -3-fluorobenzene) -piperazine) } base-butane has liquid crystal phase in the heating and cooling processes, and the liquid crystal phase interval is the melting point: 69 ℃; clearing point: 83 ℃.1H-NMR (400 MHz, CDCl3, TMS) delta (ppm) 7.78 (m, 2H), 7.38 (m, 2H), 7.56 (d, J=8.8 Hz, 1H), 6.78 (S, 1H), 6.57 (d, J=8.8 Hz, 1H), 3.46 (m, 8H), 3.01 (m, 2H), 1.75 (m, 2H).
Example 2
A liquid crystal compound based on bipiperazine benzoxazole has a structure shown in the following formula (Ib),
the preparation method of the liquid crystal compound based on the bipiperazine benzoxazole shown in the formula (Ib) specifically comprises the following steps:
(1) Preparation of 2, 3-difluoro-4-piperazine-benzaldehyde:
under the protection of nitrogen, 8.6g of piperazine, 22g of 2, 3-difluoro-4-bromo-benzaldehyde, 27.6g of potassium carbonate and 0.9g of dibenzylideneacetone dipalladium are added into DMF, stirred, heated to 80 ℃, reacted for 8 hours, poured into water, filtered and pumped to dryness to prepare 20.8g of 2, 3-difluoro-4-piperazine-benzaldehyde, wherein the yield is 92% and the purity is 97.3%;
the reaction equation is as follows:
(2) Preparation of 4,4' bis- [ (1, 4-bipiperazine) -2, 3-difluorobenzaldehyde ] yl-butane:
under the protection of nitrogen, 20.8g of 2, 3-difluoro-4-piperazine-benzaldehyde, 10.0g of 1, 4-dibromobutane and 25.7g of potassium carbonate are added into 200ml of DMF, after 4h of reaction, stirring and heating to 80 ℃, after 6h of reaction, pouring into water, filtering, and recrystallizing ethanol toluene to prepare 20g of 4,4' -bis- [ (1, 4-bipiperazine) -2, 3-difluorobenzaldehyde ] base-butane, and the yield is: 86.3% and purity 97.3%;
the reaction equation is as follows:
(3) Preparation of 1, 4-bis {4- (4- (5-methylbenzo [ d ] oxazole) -2, 3-difluorobenzene) -piperazine) } yl-butane, formula (Ib):
adding 10.7g of 4,4' -bis- [ (1, 4-bipiperazine) -2, 3-difluorobenzaldehyde ] yl-butane and 10.9 g of 2-amino-5-methylphenol into 300ml of dichloroethane, heating to 70 ℃, reacting for 8 hours, adding 17.9g of 2, 3-dichloro-5, 6-dicyanobenzoquinone, continuing to react, adding 300ml of water after the reaction is completed, washing with water, separating liquid, concentrating, and recrystallizing to obtain 18.3g of 1, 4-bis {4- (4- (5-methylbenzo [ d ] oxazole) -2, 3-difluorobenzene) -piperazine) } yl-butane, namely the liquid crystal compound of the bipiperazine benzoxazole shown in the formula (Ib), wherein the yield is 65%, and the purity is 98.7%;1H-NMR (400 MHz, CDCl3, TMS) delta (ppm) 7.68 (d, J=8.8 Hz, 1H), 7.56 (S, 1H), 7.25 (d, J=8.8 Hz, 1H), 6.55 (S, 2H), 3.44 (m, 8H), 3.00 (m, 2H), 1.76 (m, 2H).
The reaction equation is as follows:
example 3
A liquid crystal compound based on bipiperazine benzoxazole has a structure shown in the following formula (if),
the preparation method of the liquid crystal compound based on the bipiperazine benzoxazole shown in the formula (if) specifically comprises the following steps:
(1) Preparation of 2, 5-difluoro-4-piperazine-benzaldehyde:
under the protection of nitrogen, 8.6g of piperazine, 22g of 2, 5-difluoro-4-bromo-benzaldehyde, 13.8g of potassium carbonate and 1.8g of dibenzylideneacetone dipalladium are added into DMF, stirred, heated to 80 ℃, reacted for 8 hours, poured into water, filtered and pumped to dryness to prepare 19.9g of 2, 3-difluoro-4-piperazine-benzaldehyde, wherein the yield is 92% and the purity is 98.2%;
the reaction equation is as follows:
(2) Preparation of 4,4' bis- [ (1, 4-bipiperazine) -2, 5-difluorobenzaldehyde ] yl-hexane:
under the protection of nitrogen, 19.9g of 2, 5-difluoro-4-piperazine-benzaldehyde, 9.7g of 1, 6-dibromohexane and 24.3g of potassium carbonate are added into 200ml of DMF, after 4h of reaction, stirring and heating are carried out, the temperature is raised to 80 ℃, after 8h of reaction, the mixture is poured into water and filtered, and ethanol toluene is recrystallized to prepare 21.1g of 4,4' -bis- [ (1, 4-bipiperazine) -2, 5-difluorobenzaldehyde ] base-hexane, and the yield is: 89.8% and 97.7% purity;
the reaction equation is as follows:
(3) Preparation of 1, 4-bis {4- (4- (5-nitrobenzo [ d ] oxazol) -2, 5-difluorobenzene) -piperazine) } yl-hexane, formula (If):
adding 21.1g of 4,4' -bis- [ (1, 4-bipiperazine) -2, 5-difluorobenzaldehyde ] yl-hexane and 10.7g of 2-nitro-5-methylphenol into 300ml of dichloroethane, heating to 80 ℃, reacting for 6 hours, adding 26.6g of 2, 3-dichloro-5, 6-dicyanobenzoquinone, continuing to react, adding 300ml of water after the reaction is completed, washing with water, separating liquid, concentrating, and recrystallizing to obtain 17.6g of 1, 4-bis {4- (4- (5-nitrobenzo [ d ] oxazole) -2, 5-difluorobenzene) -piperazine) } yl-hexane, namely the bipiperazine benzoxazole liquid crystal compound shown in the formula (if), wherein the yield is 58%, and the purity is 98.7%;1H-NMR (400 MHz, CDCl3, TMS) delta (ppm) 8.28 (d, J=8.8 Hz, 1H), 8.10 (S, 1H), 8.05 (d, J=8.8 Hz, 1H), 7.35 (d, J=8.8 Hz, 1H), 6.56 (d, J=8.8 Hz, 1H), 3.46 (m, 8H), 3.02 (m, 2H), 1.28-1.35 (m, 4H).
The reaction equation is as follows:
example 4
A liquid crystal compound based on bipiperazine benzoxazole has a structure shown in the following formula (Ig),
the preparation method of the liquid crystal compound based on the bipiperazine benzoxazole shown in the formula (Ig) specifically comprises the following steps:
(1) Preparation of 2, 3-difluoro-4-piperazine-benzaldehyde:
under the protection of nitrogen, 8.6g of piperazine, 22g of 2, 3-difluoro-4-bromo-benzaldehyde, 25.6g of potassium carbonate and 1.8g of dibenzylideneacetone dipalladium are added into DMF, stirred, heated to 80 ℃, reacted for 8 hours, poured into water, filtered and pumped to dryness to prepare 19.5g of 2, 3-difluoro-4-piperazine-benzaldehyde, wherein the yield is 90 percent and the purity is 98.4 percent;
the reaction equation is as follows:
(2) Preparation of 4,4' bis- [ (1, 4-bipiperazine) -2, 3-difluorobenzaldehyde ] yl-hexane:
under the protection of nitrogen, 19.5g of 2, 3-difluoro-4-piperazine-benzaldehyde, 10.5g of 1, 6-dibromohexane and 17.8g of potassium carbonate are added into 200ml of DMF, after 4h of reaction, stirring and heating to 80 ℃, after 8h of reaction, pouring into water, filtering, and recrystallizing ethanol toluene to prepare 19.3g of 4,4' -bis- [ (1, 4-bipiperazine) -2, 3-difluorobenzaldehyde ] base-hexane, and the yield is: 84.2% and purity 98.3%;
the reaction equation is as follows:
(3) Preparation of 1, 4-bis {4- (4- (5-chlorobenzo [ d ] oxazol) -2, 3-difluorobenzene) -piperazine) } yl-hexane, formula (Ig):
adding 19.3g of 4,4' -bis- [ (1, 4-piperazine) -2, 3-difluorobenzaldehyde ] yl-hexane and 12.4g of 2-chloro-5-methylphenol into 300ml of dichloroethane, heating to 80 ℃, reacting for 6 hours, adding 24.6g of 2, 3-dichloro-5, 6-dicyanobenzoquinone, continuing to react, adding 300ml of water after the reaction is completed, washing with water, separating liquid, concentrating and recrystallizing to obtain 17.6g of 1, 4-bis {4- (4- (5-chlorobenzo [ d ] oxazole) -2, 3-difluorobenzene) -piperazine) } yl-hexane, namely the liquid crystal compound of the bipiperazine benzoxazole shown in the formula (I g), wherein the yield is 51 percent and the purity is 98.6 percent; 1H-NMR (400 MHz, CDCl3, TMS) delta (ppm) 7.80 (S, 1H), 7.71 (d, J=8.8 Hz, 1H), 7.50 (d, J=8.8 Hz, 1H), 7.36 (d, J=8.8 Hz, 1H), 6.55 (d, J=8.8 Hz, 1H), 3.44 (m, 8H), 3.04 (m, 2H), 1.29-1.36 (m, 4H).
The reaction equation is as follows:
。
the compound provided by the invention takes alkyl chain as a flexible group, piperazine-benzoxazole is respectively introduced into two end groups of the compound as a crystallization unit, fluorine atoms are taken as lateral substituents, and different substituents (-CH) are introduced into the compound by taking benzoxazole as a terminal group 3 、-NO 2 -Cl, H), has a liquid crystalline state, exhibits a smectic phase, can be used for special liquid crystal materials, and is simultaneously synthesizedThe bipiperazine benzoxazole liquid crystal compound is simple to operate and high in product yield and purity. The smectic phase liquid crystal of the compound is used for display, and after being driven, the electric signal is removed, the display content can still be kept, and the compound has a memory effect.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that such modifications and variations of this invention be included herein within the scope of the appended claims and their equivalents.
Claims (10)
1. A liquid crystal compound based on bipiperazine benzoxazole is characterized by having a structure shown as a formula (I),
in the formula (I),
F m represents that hydrogen on the benzene ring is substituted by fluorine atoms, m represents the substitution number of the fluorine atoms, and the value of m is 1-4;
m represents-NO 2 、-Cl、-CH 3 Or H;
r represents a C2-16 linear alkyl group.
2. The liquid crystal compound based on the bipiperazine-based benzoxazole as recited in claim 1, wherein the value of m is 1 or 2.
3. The liquid crystal compound based on the bipiperazine-based benzoxazole as recited in claim 1, wherein said R represents a C4-8 linear alkyl group.
4. The liquid crystal compound based on the bipiperazine-based benzoxazole as recited in claim 1, wherein said liquid crystal compound comprises any one of the following compounds:
5. a method for preparing a liquid crystal compound based on a bispiperazine benzoxazole as claimed in claim 1, comprising the following steps:
s1, under the protection of nitrogen or inert gas, adding a compound of a formula (II) and piperazine serving as raw materials, alkali serving as an acid binding agent and Pd serving as a catalyst into a certain amount of solvent, and reacting for 4-10 hours at 60-100 ℃ to obtain a compound of a formula (III);
s2, taking a compound of the formula (III) and X-R-X as raw materials, taking alkali as an acid binding agent, uniformly dispersing in a solvent, and reacting at 60-100 ℃ for 4-10 hours to prepare a compound of the formula (IV);
s3, dispersing a compound of a formula (IV) and a compound of a formula (V) serving as raw materials into a solvent, reacting for 4-10 hours at 40-80 ℃, adding an epoxidation reagent, and continuing to react for 4-8 hours to obtain the liquid crystal compound based on the bispiperazine benzoxazole, wherein the liquid crystal compound is shown in the formula (I);
the preparation route is as follows:
in the formula (II), the formula (III), the formula (IV), the formula (V), the formula (I) and X-R-X,
F m represents that hydrogen on the benzene ring is substituted by fluorine atoms, m represents the substitution number of the fluorine atoms, and the value of m is 1-4;
m represents-NO 2 、-Cl、-CH 3 Or H;
r represents a C2-16 linear alkyl group;
x represents Br or I.
6. The method for preparing a liquid crystal compound based on a bispiperazine benzoxazole as claimed in claim 5, wherein in S1, said Pd catalyst is tetrakis (triphenylphosphine) palladium, palladium acetate or tris dibenzylideneacetone dipalladium; the molar ratio of the compound of the formula (II) to the Pd catalyst is 1:0.001-0.02.
7. The method for preparing a liquid crystal compound based on a bispiperazine benzoxazole as claimed in claim 5, wherein said acid binding agent comprises one or more of potassium carbonate, sodium tert-butoxide and potassium tert-butoxide.
8. The method for preparing a liquid crystal compound based on a bispiperazine-based benzoxazole as recited in claim 7, wherein in S1, the molar ratio of said compound of formula (ii) to said acid-binding agent is 1:1 to 2; in S2, the molar ratio of the compound of formula (III) to the acid-binding agent is 1:2 to 4.
9. The method for preparing a liquid crystal compound based on a bispiperazine-based benzoxazole as recited in claim 5, wherein said epoxidizing agent is 2, 3-dichloro-5, 6-dicyanobenzoquinone, iodobenzene acetate or lead tetraacetate; the molar ratio of the compound of formula (iv), the compound of formula (v) and the epoxidizing agent is 1: 1:2-4.
10. The method for preparing a liquid crystal compound based on a bispiperazine benzoxazole as claimed in claim 5, wherein said solvent is one or more of DMF, chloroform, dichloroethane and chloroform.
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| CN103304506A (en) * | 2013-06-07 | 2013-09-18 | 陕西师范大学 | Method for preparing fluorine-containing benzoxazole liquid crystal compound |
| CN111944539A (en) * | 2020-07-31 | 2020-11-17 | 西安瑞联新材料股份有限公司 | Fluropiperazine-based benzoxazole liquid crystal compound and preparation method thereof |
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