TRANSHEXAHYDROTEREPHTALIC ACID ESTER DERIVATIVES

Abstract: Novel transhexahydroterephthalic acid ester derivatives represented by the general formula (I): are usable as a liquid crystal or an additive to liquid crystal compositions. The compound (I) can lower the melting point and raise the clear point of a liquid crystal composition, thus the liquid crystal range of the composition would broaden.

Description: This invention relates to transhexahydroterephthalic acid ester derivatives, and more particularly to transhexahydroterephthalic acid ester derivatives usable as liquid crystals and as an additive to liquid crystal compositions. Nematic liquid crystal substances are widely utilized as electro-optical display elements and the like for their characteristics of changing the optical properties markedly under the influence of an electric field. In order to actually utilize these substances for an industrial purpose, they should meet several requirements which include: colorless and transparent properties; electrical, optical and chemical stability; wide liquid crystal range desirably from -5°C to +65°C; and low viscosity desirably lower than 50 cp. Although great many liquid crystal substances have been known to date, none of them can satisfy the above-mentioned requirements as a single substance. Therefore, it has been the conventional practice to use for liquid crystal display elements a composition containing two or three or more liquid crystal substances. In order to impart satisfactory contrast on application of a given voltage, the liquid crystal is required to have predetermined dielectric anisotropy. However, in a case where a conventional high temperature liquid crystal is added to a liquid crystal composition for the purpose of broadening its liquid crystal range, difficulties are encountered in that the properties of the liquid crystal composition are deteriorated by an increase of viscosity or degradation of dielectric anisotropy. Chemical Abstacts, vol . 98, no. 4, abstract no. 25872x discloses the synthesis and the mesomorphic properties of homologous series of di (4'-alkylphenyl) trans-cyclohexane-1 ,4-dicarboxylates in which the alkyl group is C₁ to D₁₂. The compounds are prepared by esterification of trans-1 ,4-cyclohexanedicarboxylic acid or dicarbonyl chloride with 4-alkylphenols. Chemical Abstracts, vol . 94 no. 3, abstract no. 23244n describes trans-cyclohexanedicarboxylates and terephthalates which are prepared by treating the corresponding diacid chlorides with phenols which are substituted by a lower alkyl or lower alkoxy group. The compounds are used as liquid crystals. Chemical Abstracts, vol . 92, no. 3, abstract no. 22180k discloses the synthesis and mesomorphic properties of trans-1 ,4-cyclohexanebis (4-n-alkoxybenzenes) which are prepared by esterification of trans-1 ,4-cyclohexanedicarbonyl chloride with 4-alkoxyphenols. The two ester residues of the compounds of the above mentioned three publications are identical to each other, in other words, they are all symetrical relative to the cyclohexane ring. Chemical Abstracts, vol . 103, no. 8, abstract no. 6297lw describes 4'-alkoxyphenyl-4' '-cyanophenyl-1 ,4-cyclohexane-dicarboxylates and their reentrant phases. It is object of the invention to provide liquid crystal substances which broden the liquid crystal range, decrease the melting point and raise the clear point when blended into the liquid crystal composition. This object is solved according to the invention by a transhexahydroterephthalic acid ester derivative represented by the general formula (I): wherein A is a group of in which R₁ denotes an alkyl group having 1 to 6 carbon atoms, or a group of in which R₂ denotes an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, B is a group of in which R₃ denotes a halogen atom, a cyano group, an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and R₄ denotes a hydrogen atom or a halogen atom, or a group of in which R₅ denotes an alkyl group having 1 to 6 carbon atoms, except for a case where R₁ and R₃ are concurrently alkyl groups having the same number of carbon atoms and R₄ is a hydrogen atom. Further, it has been found that, among the compounds (I), the compounds represented by the following formula (I') have the above-mentioned effects while lowering the threshold value (Vth) or the liquid crystal composition. wherein R₆ is a halogen atom or a cyano group, R₇ is a hydrogen atom, a halogen atom or a cyano group, and A has the same meaning as defined hereinbefore. The transhexahydroterephthalic acid ester derivatives according to the present invention can be prepared by a known process, reacting a transhexahydroterephthalic acid or its derivative with a substituted phenol and/or a substituted cyclohexenol successively or concurrently. Examples of transhexahydroterephthalic acid derivatives include acid halides, activated esters and the like. The solvent to be used for the reaction may be an organic solvent such as toluene, benzene, ether and the like. When the group A and/or the group B in the transhexahydroterephthalic acid ester derivatives according to the invention is a substituted cyclohexyl group, it is preferred to be of a trans-form. Although the transhexahydroterephthalic acid ester of the invention is a liquid crystal by itself, it is preferred to use it as a liquid crystal composition containing other liquid crystal substance or substances. When added to a liquid crystal composition, the compound (I) according to the invention can lower the melting point and raise the clear point of the composition. Especially, the compound (I′) according to the invention is further capable of lowering the threshold value, Vth, of the composition. Accordingly, the compound of the invention is usable for broadening the liquid crystal range. Now, the invention is illustrated more particularly by the following examples. Example l Synthesis of transhexahydroterephthalic acid 4-n-propylphenyl-4′-fluorophenyldiester: (i) After adding l0 g of transhexahydroterephthalic acid dichloride to 50 ml of toluene, a mixture of 4.2 g of pyridine and 6.5 g of n-propylphenol was dropped thereinto over a time period of 40 minutes at l00°C while stirring. Further, a solution of 4.2 g of pyridine in l0 g of water was carefully added thereto, and, after cooling down to 20°C, the resulting mixture was filtered and the mother liquor was extracted with sodium bicarbonate water. The extract was acidified by addition of hydrochloric acid, followed by filtration of the precipitate and recrystallization with toluene to obtain 3.3 g of hexahydroterephthalic acid 4-n-propylmonoester. (ii) The monoester obtained in (i) was formed into acid chloride by ordinary procedures, and recrystalized (3.3 g) in ether. 3 g of this acid chloride was added to l5 ml of toluene containing 0.8 g of pyridine and l.l g of 4-fluorophenol, while stirring for l hour at l00°C for reaction. After cooling, the reaction product was washed with dilute hydrochloric acid, and then washed with water until the wash liquid became neutral, and dried with sodium sulfuric anhydride. After distilling out toluene, the residue was recrystalized in alcohol for two times and then dried to obtain 3.2 g of hexahydroterephthalic acid 4-n-propylphenyl-4′-fluorophenyldiester. Mesomatic range (M.R.) 83.5 → l50.9°C Example 2 The following compounds were obtained in the same manner as in Example l, using a substituted phenol or a substituted transcyclohexanol corresponding to transhexahydroterephthalic acid chloride. (l) Hexahydroterephthalic acid 4-n-propylphenyl-3′,4′-difluorophenyldiester M.R. 72.8 → ll3.2°C (2) Hexahydroterephthalic acid 4-n-propylphenyl-4′-cyanophenyldiester M.R. l02.8 → 2l2.5°C (3) Hexahydroterephthalic acid 4-n-propylphenyl-3′-fluoro-4′-cyanophenyldiester M.R. 82.2 → l72.5°C (4) Hexahydroterephthalic acid 4-n-butylphenyl-4′-fluorophenyldiester M.R. 77.2 → l38.l°C (5) Hexahydroterephthalic acid 4-n-butylphenyl-3′,4′-difluorophenyldiester M.R. 62.2 → 99.5°C (6) Hexahydroterephthalic acid 4-n-butylphenyl-4′-cyanophenyldiester M.R. 92.l → l90.l°C (7) Hexahydroterephthalic acid 4-n-butylphenyl-3′-fluoro-4′-cyanophenyldiester M.R. 95.4 → l55.4°C (8) Hexahydroterephthalic acid 4-n-propylphenyl-4′-hexylphenyldiester M.R. 75.8 (crystal) → ll7.5(S)→l53.l(N)°C (9) Hexahydroterephthalic acid 4-n-propylcyclohexyl-4′-fluorophenyldiester M.R. 98.6 → l38.9°C (l0) Hexahydroterephthalic acid 4-n-propylphenyl-4′-n-butylphenyldieste M.R. 93.4 → l60.8°C (ll) Hexahydroterephthalic acid 4-n-propylphenyl-4′-methoxyphenyldiester M.R. l02.3 → 203.8°C M.R. l3l.9 → l6l.2°C (l2) Hexahydroterephthalic acid 4-n-propylphenyl-4′-propylcyclohexyldiester M.R. 94.6 → l54.7°C (l3) Hexahydroterephthalic acid 4-n-butylphenyl-4′-methylphenyldiester M.R. 82.6 → l64.8°C (l4) Hexahydroterephthalic acid 4-n-butylphenyl-4′-chlorophenyldiester M.R. 88.4 → l64.8°C Example 3 The following liquid crystal compositions were prepared, followed by measurement of N → I temperature and Vth. The results are shown in Table l. Compositions: Basic Composition A A mixture of equivalent amounts of 4-n-propylcyclohexanecarboxylic acid 4′-ethoxyphenylester, 4-n-butylcyclohexanecarboxylic acid 4′-ethoxyphenyl ester and 4-n-pentylcyclohexanecarboxylic acid 4-methoxyphenyl ester. Basic Composition B (comparative composition) 50 parts of Basic Composition A, 9 parts of n-propylcyclohexanecarboxylic acid 4′-cyanophenyl ester, 8 parts of n-butylcyclohexanecarboxylic acid 4′-cyanophenyl ester, 8 parts of 4-n-pentylcyclohexanecarboxylic acid 4′-cyanophenyl ester, and 5 parts of 4-propylbenzoic acid 4′-cyanophenyl ester. Inventive Composition l 92 parts of Basic Composition B, 4 parts of hexahydroterephthalic acid 4-n-propylphenyl-4′-fluorophenyl diester, and 4 parts of hexahydroterephthalic acid 4-butylphenyl-4′-fluorophenyl diester. Inventive Composition 2 92 parts of Basic Composition B, 4 parts of hexahydroterephthalic acid 4-n-propylphenyl-4′-fluorophenyl diester, and 4 parts of hexahydroterephthalic acid 4-n-butylphenyl-4′-fluorophenyl diester. Inventive Composition 3 92 parts of Basic Composition B, 4 parts of hexahydroterephthalic acid 4-n-propylphenyl-4′-cyanophenyl diester, and 4 parts of hexahydroterephthalic acid 4-butylphenyl-4′-cyanophenyl diester. Inventive Composition 4 92 parts of Basic Composition B, 4 parts of hexahydroterephthalic acid 4-n-propylphenyl-3′-fluoro-4′-cyanophenyl diester, and 4 parts of hexahydroterephthalic acid 4-butylphenyl-3'-fluoro-4′-cyanophenyl diester.

Claims: A transhexahydroterephthalic acid ester derivative represented by the general formula (I): wherein A is a group of in which R₁ denotes an alkyl group having 1 to 6 carbon atoms, or a group of in which R₂ denotes an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, B is a group of in which R₃ denotes a halogen atom, a cyano group, an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and R₄ denotes a hydrogen atom or a halogen atom, or a group of in which R₅ denotes an alkyl group having 1 to 6 carbon atoms, except for a case where R₁ and R₃ are concurrently alkyl groups having the same number of carbon atoms and R₄ is a hydrogen atom. A transhexahydroterephthalic acid ester derivative according to Claim 1, wherein A in formula (I) is a group of in which R₁ has the same meaning as defined above, and B is a group of in which R₃, denotes an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and R₁ and R₃, are not identical.

Inventors: SATO, HISATO
Applicants: SATO, HISATO
Application year: 1987
Main classification: C07C69
IPC codes: C09K19, C07C255, C07C253, C07C67, C07C69