DE3715029A1 - CRYSTALLINE-LIQUID CONNECTIONS FOR MIXTURES WITH NEGATIVE DIELECTRIC ANISOTROPY AND METHOD FOR PRODUCING THE CONNECTIONS USED - Google Patents

Abstract

The invention relates to crystalline-liquid compounds for mixtures in opto-electronic components for modulating transient or rejected light as well as for coloured or black-and-white reproduction of figures, symbols and images which occurs by virtue of their dielectric and optical anisotropy. The aim is to produce new substances which can offer high negative dielectric anisotropy for wide temperature ranges, ready miscibility with other liquid crystals and ease of production and which can be used in liquid crystal mixtures for electro-optical arrangements. According to the invention, r-2-substituted-t-5-substituted-c-5-cyano-1,3-dioxanes are used as crystalline liquid compounds Cholesterinic crystalline liquid compounds or chiral smectic liquid crystals or also non-crystalline-liquid substances, particularly dyestuffs, may be added to the substances according to the invention.

Description

Field of application of the invention

The invention relates to a method for producing new crystalline liquid r-2-sub-t-5-sub-5-cyan-1,3- dioxanes of the general formula

where the substituents have the following meaning:

such as
R ² = R ³ , -OR ³ , -OCOOR ³ , -COR ³ , halogen,

-COO cholesteryl, -CN, -COOR ³ , -OOCR ³ ,

R ³ = -C _n H _{2 n +1}

With
X = -COO-, -OOC-, single bond
Y = -O-, -S-
Z = -O-, -S-
R ⁵ , R ⁶ = H, CH ₃ / CH ₃ , H / CN, H / H, CN / H, H / CN, CN
if R ² ≠ CN

R ⁸ = -C _m H _{2 m +1}
R ⁹ = -OR ³ , -CH ₂ OR ³ , -Cl, -Br, -COOR ³ , -OOCR ³ , --CN
with n = 1-16, m = 1-16, p = 0.2; q = 2-8
the number of rings being 2 to 4, which can be used in electro-optical components for the representation of numbers, characters and images and for information storage.

Characteristic of the known technical solutions

Those synthesized by the process according to the invention Substances are new. No procedure has yet been developed for them Manufacturing described.

By EIDENSCHINK (OS 33 25 727) substances mentioned have only odd numbers Middle groups and were not characterized in detail. Possibilities for their synthesis are also not specified.

Aim of the invention

The aim of the invention is to produce new crystalline liquid derivatives of r-2-Subst.-t-5-subst.-c-5- cyan-1,3-dioxans used in electro-optical devices can be.

State the nature of the invention

The object of the invention is a process for the preparation of crystalline-liquid r-2-Subst.-t-5-subst.-c-5-cyan-1,3-dioxanes. According to the invention, crystalline liquid r-2-sub-t-5-sub-c-5-cyan-1,3-dioxanes are prepared by reacting 2-sub-2-cyanopropane-1,3-diols with aldehydes in the presence of acidic catalysts such. B. HCl, H ₂ SO ₄ , p-toluenesulfonic acid, BF ₃ , AlCl ₃ , acidic ion exchangers in organic solvents such as. B. benzene, toluene, CCl ₄ , CHCl ₃ , CH ₂ Cl ₂ , 1,2-dichloroethane, gasoline in the presence of water-binding agents such as molecular sieves, Na ₂ SO ₄ , CuSO ₄ or in the absence of these, preferably with azeotropic removal of the water of reaction, where Surprisingly, preference is given to the isomer with the axial position of the nitrile function, which is the only one capable of forming crystalline-liquid phases. This isomer can be purified by simple recrystallization from methanol.

Equation 1:

The 2-Subst.-2-cyanpropan-1,3-diols are according to the invention prepared by reacting 2-Subst.-cyanoacetic acid esters or thiolesters with formaldehyde as a pure compound, as an aqueous solution (formalin), paraformaldehyde or Polyoxymethylene in the presence of basic catalysts such as e.g. B. alkali metal carbonates, hydrogen carbonates, hydroxides, -alcoholates or other salts of weak acids or amines in the presence or absence of solvents, at temperatures between -78 ° C and + 100 ° C, preferably between -20 ° C and + 35 ° C.

Equation 2:

X = O-alkyl, S-alkyl

The 2-sub-2-hydroxymethyl-cyanoacetic acid derivatives thus obtained by selective reduction of the ester or Thiolester function with complex hydrides in the 2-Subst.-2- cyanopropane-1,3-diols are converted.

Equation 3:

X = O-alkyl, S-alkyl

The selective reduction of the thiol alkyl ester function with NaBH ₄ in alcoholic solvents is successful.

Equation 4:

The selective reduction of the carboxylic ester function besides The nitrile function can be done by two methods:

• A) By reducing the carboxylic acid ester function with LiBH ₄ or Ca (BH ₄ ) ₂ in ethereal solvents such as THF or Diglyme (MM Steward, J. Org. Chem. 26, 3360 (1961)). Instead of LiBH ₄ or Ca (BH ₄ ) ₂ , mixtures of NaBH ₄ and a Li⁺ or Ca ²⁺ salt (e.g. LiBr, CaCl ₂ ) can also be used (HC Brown, S. Narasimhan, YM Choi, J. Org. Chem. 47, 4702-08).
• B) By reducing the carboxylic acid ester function with Na (OCH ₃ ) ₃ BH, the reduction being carried out with NaBH ₄ in methanol preferably at 0 ° C. to 20 ° C. or with NaBH ₄ in t-butanol or ethereal solvents such as THF or diglyme elevated temperature (preferably 50 ... 100 ° C) with the slow addition of methanol (Bull. Chem. Soc. Jpn. 57, 1948 (1984)).

The hydroxymethyl function can be used to increase the Yield during the reduction step as silyl ether, Acetate or acetal (e.g. THP ether) are protected. By acetalizing the 2-sub-2-cyanopropane 1,3-diols with suitable aldehydes were the 2,5-disubstitute 5-cyan-1,3-dioxane derivatives as above described in the correct configuration.

The conversion temperatures of substances according to the invention are in Tables 1 and 2.

Mean
K = crystalline solid N = nematic S = smectic I = isotropic - liquid

Table 1

r-2-Subst.-t-2-n-alkyl-c-5-cyan-1,3-dioxanes

Table 2

r-2-Subst.-t-5-subst.-c-5-cyan-1,3-dioxanes

example 1 Synthesis of the 2-alkylcyanoacetic acid ethyl ester (variant A)

To a sodium ethanolate solution, which by dissolving 1 gram atom (23 g) Na in 500 ml abs. Ethanol was prepared, 1 mol (113 g) of ethyl cyanoacetate was added. After adding 1 g of KJ and 1 mol of alkyl bromide, the mixture is heated to boiling under reflux for 2 h. After the reaction mixture has cooled, the NaBr which has separated out is filtered off with suction, the solvent is distilled off in vacuo on a rotary evaporator and the residue is taken up in ether and washed twice with H ₂ O. After the solvent has been distilled off, it is fractionated in vacuo.
Yield: 30-40% of theory Th.

Example 2 Synthesis of the 2-alkylcyanoacetic acid ethyl ester (variant B)

A mixture of 1 mol of freshly distilled aldehyde, 1 mol (113 g) of cyanoacetate, 500 ml of benzene or toluene and 0.1 mol (7.7 g) of ammonium acetate and 0.2 mol (12 g) of acetic acid is heated for 6 hours on a water separator . After the reaction mixture has cooled to room temperature, it is washed four times with water, dried over Na ₂ SO ₄ and the solvent is distilled in vacuo on a rotary evaporator. The residue is dissolved in 500 ml of methanol or ethanol and hydrogenated over 2 g of Pd on carbon (5 or 10%) at room temperature. When the uptake of hydrogen has ended, the catalyst is filtered off and the solvent is distilled off. The residue is fractionated in vacuo.
Yield: 70-95% of theory Th.

Example 3 Synthesis of ethyl 2- (4-ethylcyclohexyl) cyanoacetate (Variant C)

To a solution of 0.2 gram atom (1.4 g) of lithium in 1000 ml of liquid ammonia, a solution of 0.092 mol (20 g) of e-ethylcyclohexylidene-acetic acid ethyl ester and 0.4 mol (34.4 ml) of t- Butanol added dropwise in 50 ml of absolute THF. After a reaction time of 0.5 h, the excess lithium is destroyed by adding NH ₄ Cl and the NH _{3 is} distilled off. The residue is mixed with 100 ml of ether and acidified with 5% hydrochloric acid. The organic phase is separated off, washed with water, NaHCO ₃ solution and again with water. After the solvent has been distilled off, it is fractionated in vacuo.

Table 3

2-Subst. Ethyl cyanoacetate

R-CH (CN) -COOC ₂ H ₅

Example 4 Synthesis of the 2-Subst.-2-hydroxymethylcyanessigsäureethylester

1 mol of ethyl 2-sub-cyanoacetate is mixed with 120 ml of formalin, 2 g of K ₂ CO ₃ and 700 ml of methanol and stirred for 2 hours at room temperature. The reaction mixture is diluted with 2 l of water and extracted three times with a total of 500 ml of ether. After careful drying over Na ₂ SO ₃ , the solvent is distilled off on a rotary evaporator. The yield is quantitative.

Example 5 Synthesis of the 2-Subst.-2-cyanpropan-1,3-diols (variant A)

A solution of 0.1 mol of 2-subst. 2-hydroxymethylcyanoacetate in 50 ml abs. THF is stirred with a solution of 2.5 g of LiBH ₄ in 200 ml of abs. THF dropped. The resulting solution is refluxed for 3 hours. After cooling, 100 ml of methanol are carefully added dropwise and the mixture is stirred at room temperature for 0.5 h. The solvents are distilled off in vacuo on a rotary evaporator. The residue is mixed with 250 ml of water, carefully acidified with concentrated hydrochloric acid and extracted three times with ether. The combined organic phases are washed with 200 ml of 10% KOH, once with water and once with saturated NaCl solution. After drying over Na ₂ SO ₄ , the solvent is distilled off on a rotary evaporator and the residue is recrystallized from n-hexane, possibly with the addition of a little ethyl acetate.

Example 6 Synthesis of the 2-Subst.-2-cyanpropan-2,3-diols (variant B)

A solution of 0.1 mol of 2-sub-2-hydroxymethylcyanoacetate in 50 ml of THF is stirred with a solution of 3.8 g of NaBH ₄ and 9.0 g of LiBr in 400 ml of abs. THF added dropwise and heated to boiling under reflux for 3 h. The processing takes place analogously to variant A.

Example 7 Synthesis of the 2-Subst.-2-cyanpropan-1,3-diols (variant C)

To a solution of 0.1 mol of 2-subst. 2-hydroxymethylcyanoacetate in 150 ml abs. THF are added 0.11 mol (11.9 g) trimethylchlorosilane and 0.11 mol (11.1 g) triethylamine and stirred for 0.5 h at room temperature. The resulting precipitate of triethylammonium chloride is filtered off and twice with 30 ml of abs. THF washed. The solution obtained is mixed with 11 g NaBH ₄ and heated to boiling. To the boiling solution, 100 ml of abs. Methanol was slowly added dropwise with stirring. The mixture is allowed to cool to about 40 ° C. and 150 ml of 15% hydrochloric acid are added and the mixture is stirred for about 0.5 h. Most of the THF and methanol are distilled off on a rotary evaporator, the residue is diluted with water and extracted four times with ether. Further processing is carried out analogously to variant A.

Example 8 Synthesis of the 2-Subst.-2-cyanpropan-1,3-diols (variant D)

0.1 mol of 2-sub-2-hydroxymethylcyanoacetate is silylated in accordance with the instructions given under variant C. The solution of the 2-Subst.-2-trimethylsilyloxymethylcyanacetic acid ester in THF becomes a solution of 2.5 g LiBH ₄ in 100 ml abs. THF dropped and heated to boiling for 3 h. After cooling, 100 ml of methanol are added and the resulting solution is worked up further as indicated under C.

Table 4

2-Subst. 2-cyanopropane-1,3-diols

RC (CN) (CH ₂ OH) ₂

Example 9 Synthesis of r-2-Subst.-t-5-subst.-c-5-cyan-1,3-dioxanes

A mixture of 0.01 mol of 2-sub-2-cyanopropane-1,3-diol, 0.01 mol of aldehyde and 100 mg of p-toluenesulfonic acid and 150 ml of benzene is heated to boiling in a water separator for about 20 minutes. The cooled reaction mixture is washed once with NaHCO ₃ solution and twice with water, dried over Na ₂ SO ₄ and the solvent is distilled off on a rotary evaporator. The residue is recrystallized from methanol until the transition temperatures are constant.
Yield: 50 to 65% of theory. Th.

The compounds thus prepared are in Tables 1 and 2 summarized.

Example 10 Synthesis of trans-4- (t-4-alkyl-c-4-cyan-1,3-dioxan-2-r-yl) - cyclohexane carboxylic acids

0.2 mol of trans-4- (t-4-alkyl-c-4-cyan-1,3-dioxan-2-r-yl) cyclo hexane carboxylic acid methyl ester is dissolved in 2 l of methanol and after adding a solution of 100 g KOH in 100 ml water Heated under reflux for 20 min. The solvent is on Rotary evaporator distilled off and the residue with approx. 2 l of water added.

The solution is acidified against Congo red with 25% sulfuric acid and extracted three times with ethyl acetate. The organic phases are washed with saturated NaCl solution and dried over Na ₂ SO ₄ . After the solvent has been distilled off on a rotary evaporator, n-hexane is added and the product is suctioned off.

Example 11 Esterification of trans-4- (t-4-alkyl-c-4-cyan-1,3-dioxan-2-r-yl) - cyclohexane carboxylic acids (variant A)

0.01 mol of trans-4- (t-4-alkyl-c-4-cyano-1,3-dioxan-3-r-yl) cyclohexane carboxylic acid and 0.01 mol of 4-substituted phenol or 0.015 mol of 4 -Alkylcyclohexanol and 100 mg DMAP in 200 ml abs. Suspended methylene chloride and mixed at room temperature with a solution of 0.011 mol (2.27 g) dicyclohexylcarbodiimide in 30 ml methylene chloride. The mixture is stirred at room temperature for 24 h, the separated dicyclohexylurea is filtered off, the solvent is distilled off on a rotary evaporator and the residue is recrystallized from methanol.
Yield: 40 to 70% of theory. Th.

Example 12 Esterification of trans-4- (t-4-alkyl-c-4-cyan-1,3-dioxan-2-r-yl) - cyclohexane carboxylic acid (variant B)

0.002 mol of trans-4- (t-4-alkyl-c-4-cyan-1,3-dioxan-2-r-yl) cyclohexane carboxylic acid, 0.002 mol of 4-subst. Phenol or 0.003 mol of trans-4-alkylcyclohexanol and 20 mg of DMAP are suspended in 20 ml of methylene chloride and, after the addition of 0.0025 mol of 1- (3-dimethylaminopropyl) 1-ethylcarbodiimide methiodide, stirred for 24 hours at room temperature. The reaction mixture is diluted with methylene chloride and washed three times with water, once with NaHCO ₃ solution and again with water. The solvent is distilled off on a rotary evaporator and the residue is recrystallized from methanol.
Yield: 60 to 80% of theory. Th.

Claims (1)

Process for the preparation of crystalline liquid r-2-Subst.-t-5-Subst.-c-5-cyan-1,3-dioxanes of the general formula I. where the substituents have the following meaning: such as
R ² = R ³ , -OR ³ , -OCOOR ³ , -COR ³ , halogen, -COO cholesteryl, -CN, -COOR ³ , -OOCR ³ , R ³ = -C _n H _{2 n +1} With
X = -COO-, -OOC-, single bond
Y = -O-, -S-
Z = -O-, -S-
R ⁵ , R ⁶ = H, CH ₃ / CH ₃ , H / CN, H / H, CN / H, H / CN, CN,
if R ² ≠ CN R ⁸ = -C _m H _{2 m +1}
R ⁹ = -OR ³ , -CH ₃ OR ³ , -Cl, -Br, -COOR ³ , -OOCR ³ , -CN
with n = 1-16, m = 1-16 p = 0.2, q = 2-8
the number of rings being 2 to 4, characterized in that 2-sub-2-cyanopropane-1,3-diols of the general formula II from 2-sub-cyanoacetic acid esters or thiolesters of the general formula III and formaldehyde either as a pure compound or as an aqueous solution of paraformaldehyde or polyoxymethylene in the presence of basic catalysts, such as. B. alkali metal carbonates, hydrogen carbonates, hydroxides, alcoholates or other salts of weak acids or amines, at temperatures between -78 ° C and + 100 ° C, preferably between -20 ° C and + 35 ° C, and subsequent reduction of the thio - Or carboxylic acid ester group can be obtained in a known manner, with aldehydes of the general formula IV in the presence of acidic catalysts, such as. B. HCl, H ₂ SO ₄ , p-toluenesulfonic acid, BF ₃ , AlCl ₃ or acidic ion exchanger in organic solvents, such as. B. benzene, toluene, CCl ₄ , CHCl ₃ , Cl-CH ₃ -CH ₃ -Cl, in the presence of water-binding agents or in the absence of these, preferably with azeotropic removal of the water of reaction and the stereoisomerically pure form is isolated by recrystallization from methanol.