阅读说明：本技术 一种反式-4-取代环己基烯烃液晶的绿色环保合成方法 (Environment-friendly synthesis method of trans-4-substituted cyclohexyl olefin liquid crystal ) 是由 冯小琼 段迎春 辛晓强 高仁孝 于 2019-11-13 设计创作，主要内容包括：本发明公开了一种反式-4-取代环己基烯烃液晶的绿色环保合成方法,属于液晶材料合成方法技术领域,包括以下步骤：以非水溶性溶剂为反应溶剂,以溴代烷基三苯基膦盐与碱为原料,通过wittig反应制得叶立德试剂体系；向所述叶立德试剂体系中加入式(Ⅰ)化合物,反应制得式(Ⅱ)化合物粗品溶液；式(Ⅱ)化合物粗品溶液后处理,制得式(Ⅱ)化合物；本发明反应溶剂可完全回收套用,不产生有生物毒性的高浓四氢呋喃废水,利于工业化大生产。(The invention discloses a green and environment-friendly synthesis method of trans-4-substituted cyclohexyl olefin liquid crystal, belonging to the technical field of liquid crystal material synthesis methods and comprising the following steps: preparing a ylide reagent system by a wittig reaction by taking a water-insoluble solvent as a reaction solvent and taking bromoalkyl triphenylphosphine salt and alkali as raw materials; adding a compound shown in the formula (I) into the ylide reagent system, and reacting to obtain a crude product solution of a compound shown in the formula (II); carrying out aftertreatment on the crude product solution of the compound shown in the formula (II) to prepare the compound shown in the formula (II); the reaction solvent can be completely recycled, high-concentration tetrahydrofuran wastewater with biotoxicity is not generated, and industrial mass production is facilitated.)

1. A green and environment-friendly synthesis method of trans-4-substituted cyclohexyl olefin liquid crystal is characterized by comprising the following steps:

preparing a ylide reagent system by a wittig reaction by taking a water-insoluble solvent as a reaction solvent and taking bromoalkyl triphenylphosphine salt and alkali as raw materials; adding a compound shown in the formula (I) into the ylide reagent system, and reacting to obtain a crude product solution of a compound shown in the formula (II); carrying out aftertreatment on the crude product solution of the compound shown in the formula (II) to prepare the compound shown in the formula (II);

the synthesis reaction equation is as follows:

wherein n is any integer between 0 and 8;

a is R,

2. The environment-friendly synthesis method of trans-4-substituted cyclohexyl olefin liquid crystal as claimed in claim 1, characterized in that the crude compound solution of formula (II) is prepared by the following steps:

dissolving bromoalkyl triphenylphosphine salt and alkali in a water-insoluble solvent I, reacting for 1-3 h at 0-108 ℃, adding a compound of formula (I)/water-insoluble solvent II solution at-10-30 ℃, and reacting for 2h at-10-5 ℃ to prepare a crude compound solution of formula (II);

the compounds of formula (I): bromoalkyltriphenylphosphine salts: the molar ratio of the alkali is 1: 1.1-1.5: 1.05-1.45; bromoalkyltriphenylphosphine salts: the dosage ratio of the water-insoluble solvent I is 1g: 2-10 mL; water-insoluble solvent i: the volume ratio of the water-insoluble solvent II is 0.6-15: 1.

3. The green and environment-friendly synthesis method of the trans-4-substituted cyclohexyl olefin liquid crystal according to claim 2, characterized in that the alkyl group in the bromoalkyltriphenylphosphine salt refers to a straight-chain alkyl group with 1-5 carbon atoms.

4. The environmentally friendly method of synthesizing trans-4-substituted cyclohexyl olefin liquid crystal according to claim 2, wherein the base is sodium methoxide, potassium isopropoxide, sodium tert-butoxide or potassium tert-butoxide.

5. The method for synthesizing trans-4-substituted cyclohexyl olefin liquid crystal in green environment according to claim 2, wherein the water-insoluble solvent I and the water-insoluble solvent II are the same and are n-heptane, n-hexane, methylcyclohexane or toluene.

6. The method for green and environment-friendly synthesis of trans-4-substituted cyclohexyl olefin liquid crystal according to claim 5, wherein when the water-insoluble solvent I is n-heptane, n-hexane or methylcyclohexane, the crude solution of the compound of formula (II) is prepared by the following steps:

washing the crude compound solution of the formula (II), filtering, separating the organic phase from the filtrate, washing the organic phase with water, drying, passing through a silica gel column, concentrating the column passing solution, and recovering the solvent to obtain the concentrate, namely the compound of the formula (II).

7. The method for environmentally friendly synthesizing trans-4-substituted cyclohexyl olefin liquid crystal according to claim 5, wherein when the water insoluble solvent I is toluene, the crude solution of the compound of formula (II) is prepared by the following steps:

washing the crude solution of the compound shown in the formula (II) with water, concentrating and recovering toluene, adding an extracting agent into the concentrate, filtering, drying the filtrate, passing through a silica gel column, and concentrating the column passing liquid to obtain the compound shown in the formula (II).

8. The green and environment-friendly synthesis method of trans-4-substituted cyclohexyl olefin liquid crystal according to claim 7, characterized in that the extractant is n-heptane, n-hexane or methylcyclohexane.

Technical Field

The invention belongs to the technical field of liquid crystal material synthesis methods, and particularly relates to a green and environment-friendly synthesis method of trans-4-substituted cyclohexyl olefin liquid crystal.

Background

The trans-4-substituted cyclohexyl olefin single crystal is liquid crystal containing a cyclohexane skeleton, has the properties of low viscosity, good intersolubility, good optical stability and the like, is mainly applied to reducing the concentration of liquid crystal in a mixed liquid crystal formula and improving the miscibility of mixed crystals so as to realize the quick response of the mixed liquid crystal. The liquid crystal monomer becomes the main component of liquid crystal materials such as high-grade TN-LCD, STN-LCD, TFT-LCD and the like. The liquid crystal is synthesized by wittig reaction of trans-4-substituted cyclohexyl formaldehyde, the reaction selectivity is good, but the process has the main problem of generating a large amount of high COD (chemical oxygen demand) and high-salt wastewater. In the Wittig reaction, tetrahydrofuran is used as a solvent at present, potassium tert-butoxide is used as an alkali, and the post-treatment step of the reaction is to add a non-polar solvent and wash the solvent to generate a large amount of high-COD wastewater, wherein the wastewater mainly contains tetrahydrofuran, tert-butanol, triphenyl phosphine oxide and inorganic salts. Tetrahydrofuran is very poorly biodegradable and is almost impossible to remove by biodegradation. Tetrahydrofuran and the by-product tert-butyl alcohol have close boiling points, and the tert-butyl alcohol in tetrahydrofuran is difficult to completely remove. At present, various methods for recovering tetrahydrofuran are that waste liquid containing tetrahydrofuran is distilled and concentrated for many times, the content of tetrahydrofuran is gradually increased, and then reagent is used for dehydration, filtration and rectification. Large equipment investment and large energy consumption. Today, the environmental protection situation is becoming more severe, and the standard discharge of sewage in industrial enterprises has become a hard index for the survival of the enterprises. The difficulty of sewage treatment is high, the cost is high, the sewage is not easy to be qualified and reach the standard, and the survival and the development of enterprises are gradually restricted. Therefore, the organic synthesis process must cut off the pollution source from the source, improve the synthesis process, lead the solvent which can generate pollution, recycle the auxiliary materials in the process, and achieve zero emission or little emission.

Disclosure of Invention

In order to solve the problem of high-concentration wastewater, the invention provides a green and environment-friendly synthesis method of trans-4-substituted cyclohexyl olefin liquid crystal.

The invention aims to provide a green and environment-friendly synthesis method of trans-4-substituted cyclohexyl olefin liquid crystal, which comprises the following steps:

preparing a ylide reagent system by a wittig reaction by taking a water-insoluble solvent as a reaction solvent and taking bromoalkyl triphenylphosphine salt and alkali as raw materials; adding a compound shown in the formula (I) into the ylide reagent system, and reacting to obtain a crude product solution of a compound shown in the formula (II); carrying out aftertreatment on the crude product solution of the compound shown in the formula (II) to prepare the compound shown in the formula (II);

the synthesis reaction equation is as follows:

wherein n is any integer between 0 and 8;

a is R,

R is a straight-chain alkyl group with 1-8 carbon atoms; r₁And R₂Is a hydrogen atom or a fluorine atom.

Preferably, the crude solution of the compound of formula (ii) is prepared by the following steps:

dissolving bromoalkyl triphenylphosphine salt and alkali in a water-insoluble solvent I, reacting for 1-3 h at 0-108 ℃, adding a compound of formula (I)/water-insoluble solvent II solution at-10-30 ℃, and reacting for 2h at-10-5 ℃ to prepare a crude compound solution of formula (II);

the compounds of formula (I): bromoalkyltriphenylphosphine salts: the molar ratio of the alkali is 1: 1.1-1.5: 1.05-1.45; bromoalkyltriphenylphosphine salts: the dosage ratio of the water-insoluble solvent I is 1g: 2-10 mL; water-insoluble solvent i: the volume ratio of the water-insoluble solvent II is 0.6-15: 1.

Preferably, the alkyl in the bromoalkyl triphenylphosphine salt refers to a straight-chain alkyl group with 1-5 carbon atoms.

Preferably, the base is sodium methoxide, potassium isopropoxide, sodium tert-butoxide or potassium tert-butoxide.

Preferably, the water-insoluble solvent I and the water-insoluble solvent II are the same and are n-heptane, n-hexane, methylcyclohexane or toluene.

Preferably, when the water-insoluble solvent I is n-heptane, n-hexane or methylcyclohexane, the crude solution of the compound of formula (II) is prepared by the following steps:

washing the crude compound solution of the formula (II), filtering, separating the organic phase from the filtrate, washing the organic phase with water, drying, passing through a silica gel column, concentrating the column passing solution, and recovering the solvent to obtain the concentrate, namely the compound of the formula (II).

Preferably, when the water-insoluble solvent I is toluene, the crude solution of the compound of formula (II) is prepared by the following steps:

washing the crude solution of the compound shown in the formula (II) with water, concentrating and recovering toluene, adding an extracting agent into the concentrate, filtering, drying the filtrate, passing through a silica gel column, and concentrating the column passing liquid to obtain the compound shown in the formula (II).

Preferably, the extractant is n-heptane, n-hexane or methylcyclohexane.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, a non-water-soluble solvent is used as a wittig reaction solvent, and the solvent can be reused after drying and dewatering, so that the raw material cost is reduced and zero emission of the solvent is realized; the byproduct triphenylphosphine oxide is removed by filtration, so that the phenomenon that the product and the byproduct brought by tetrahydrofuran are put into water can be avoided, the recovered solvent only contains a small amount of alcohols, the solvent can be reused by treatment, no high-concentration tetrahydrofuran wastewater is generated, and the industrial mass production is facilitated.

Drawings

FIG. 1 is a mass spectrum of trans-4- (4-propylcyclohexyl) cyclohexylethylene prepared in example 1;

FIG. 2 is a mass spectrum of trans-4- (4-pentylcyclohexyl) cyclohexyl ethylene prepared in example 2;

FIG. 3 is a mass spectrum of trans-4- [4- (4-methylphenyl) cyclohexyl) ] cyclohexylbutene prepared in example 3;

FIG. 4 is a mass spectrum of trans-4- (2, 3-difluoro-4-ethoxy) phenyl-cyclohexylethylene prepared in example 4.

Detailed Description

In order to make the technical solutions of the present invention better understood and implemented by those skilled in the art, the present invention is further described below with reference to the following specific embodiments and the accompanying drawings, but the embodiments are not meant to limit the present invention.