DE2447099A1 - LIQUID CRYSTALLINE SHIP'S BASES - Google Patents

Description

RAN 6220/5

F. Hoffmann-La Roche & Co. Aktiengesellschaft, Basel / Switzerland

Liquid crystalline Schiff bases

The invention relates to new compounds of the general formula

ROCOO

where X is -CH = N- or -N = CH- and R is straight-chain alkyl with 1 to 10 carbon atoms,

Process for their production and their use in Liquid crystalline state as a dielectric in electro-optical devices.

509815 / 13U

In the liquid-crystalline state, the compounds according to the invention have a positive anisotropy of the dielectric constant (fi. "> E.j_, where £ _{/ f is} the dielectric constant along the longitudinal axis of the molecule and S j_ is the dielectric constant perpendicular thereto).

In an electric field, the nematic liquid crystals according to the invention (because of V ⁵ ″ ^ε JL) orient themselves with the direction of their greatest dielectric constant, ie with their longitudinal axes parallel to the field direction 1 ^, 91 (1968) y exploited the interaction between embedded molecules and the liquid-crystalline molecules (guest-host interaction). Another interesting application of the dielectric field orientation is that of M. Schadt and W. HeIfrich / Applied Physics Letters 1,8 , 127 (1971) 7 found rotary cell.

This electro-optical rotary cell is essentially a capacitor with transparent electrodes, the dielectric of which is made up of a nematic substance with ε "> tj. is formed. The longitudinal axes of the molecules of the liquid crystal are arranged helically between the capacitor plates in the field-free state, the helical structure being determined by the specified wall orientation of the molecules. After applying an electrical voltage to the capacitor plates, the molecules align themselves with their longitudinal axes in the direction of the field (ie perpendicular to the plate surface), so that linearly polarized light is no longer rotated in the dielectric. (The liquid crystal becomes uniaxial perpendicular to the surface of the plates). This effect is reversible and can be used to electrically control the optical transparency of the capacitor.

509815/1314

In such a "light-rotating cell" it is desirable to use compounds which have a low melting point, have a wide nematic range and a low viscosity.

It has now been found, surprisingly, that the inventive Compounds of the general formula I not only have the required large positive anisotropy of the dielectric constant but especially in the form of their Jemish among themselves or with other nematic or non-nematic Substances are liquid crystalline at relatively low temperatures, show a low viscosity and have a broad nematic range. Operation is accordingly possible with low voltage and the Response time is short. Another advantage of the invention Substances lies in the fact that they can form supercooled nematic phases, resulting in one for practical use very important, high stability in the nematic area.

Preferred compounds of the formula I are those in which X is -GH = N- and R is straight-chain alkyl having 4 to 8 carbon atoms ". Further preferred compounds of the formula I are those in which X is -N = CH- and R is n-propyl, means n-hexyl or n-heptyl ".

The compounds of general formula I can be prepared according to the invention by

a) for the preparation of a compound in which X is -CH = N-, a compound of the formula II

ROCOO V ) ^CH0

II

E098 15/1314

wherein R has the meaning mentioned above, reacts with p-aminobenzonitrile or

Td) for the preparation of a compound in which X-N = OH- is a Compound of formula III

ROCOO

wherein R has the meaning mentioned above, reacts with p-cyanobenzaldehyde.

In both embodiments of the process according to the invention, a substituted benzaldehyde is condensed with a substituted aniline. This reaction is conveniently carried out in an inert organic solvent such as alcohol such as methanol, ethanol, isopropanol, hydrocarbons such as benzene, toluene, xylene, chlorinated hydrocarbons such as chloroform, methylene chloride or ethylene chloride. The reaction temperature is between about 0 ° and 160 °, preferably between 20 ° and 130 °. The reaction is advantageously carried out at normal pressure. When working in a water-immiscible solvent, the water formed is advantageously separated off by means of a water separator. The reaction is accelerated by adding a catalytic amount (up to 5% of the aldehyde weight) of an inorganic acid such as sulfuric acid, hydrochloric acid or an organic strong acid such as methanesulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid, etc.

The p-formylphenyl carbonic acid-n-alkyl esters used as starting materials of the formula II can be prepared, for example, according to that of CG. Mitton , RL Schowen , M.Gresser and J. Shapley , J. Amer. Chem. Soc. £ 1, ² ° 36 (1969) using the example of p-formylphenyl carbonate described

509815/1314

The method can be obtained by the action of the corresponding alkyl chlorocarbonate on p-hydroxybenzaldehyde in the presence of quinoline and a solvent such as methylene chloride or chloroform. The connections can be in a vacuum, respectively. Distill under high vacuum. With the exception of R = CH., (M.p. 36 ⁰ ), they are obtained in liquid form in the distillation, but crystallize on cooling below room temperature.

The p-aminophenyl carbonic acid-n-alkyl esters used as starting materials of the formula III can be prepared, for example, according to the method described by GGSmith, DAK Jones and R.Taylor , J.Org. Chem. 28 , 3547 (1963) using the example of the ethyl p-aminophenyl carbonate obtained by catalytic reduction of the corresponding n-alkyl p-nitrophenyl carbonate with hydrogen and platinum in ethanol. The compounds can be purified by chromatography on silica gel with benzene-ethyl acetate mixtures and by distillation in a high vacuum.

The physical properties of the nematic substances according to the present invention are shown below Table illustrates:

X. R. Melting point
(M.p.) ⁰ C Clearing point
(KIp.) ⁰ C a) A. -CH = N- methyl 139.0-139.2 156.0 B. -CH = N- EthyI 133.0-133.1 139.7 C. -CH = N- n-propyl 144.2-144.5 113.2 D. -CH = N- H-butyl 68.3-68.4 105.7 E. -CH = N- n-pentyl 70.5-70.7 99.4 P. -CH = N- n-hexyl 62.5-62.7 96.4 b) G -CH = N- n-heptyl 63.6-63.9 95.1 c) H -CH = N- n-octyl 64.8-65.0 95.0 I. -CH = N- n-nonyl 62.9-63.0 94.4 J -CH = N- n-decyl 60.9-61.0 95.0

509815/13 U

κ -N = CH- methyl 145.1-146.2 L. -N = CH- EthyI 143.2-143.9 M. -N = CH- n-propyl 75.7-76.3 N -N = CH- n-butyl 91.2-91.8 O -N = CH- n-pentyl 93.4-94.3 P. -N = CH- n-hexyl 82.4-83.2 Q -N = CH- n-heptyl 75.0-75.6 R. -N = CH- n-octyl 75.4-75.9 S. -N = CH- n-nonyl 81.7-82.3 T -N = CH- n-decyl 75.6-76.3 a) monotropic b) smectic up 83.7 ° c) smectic up 93.0 ° d) smectic up 91.9 ° e) smectic up 99.5 °

163.4

l40.9 a) 117.8

110.5 104.8 102.1

99.4

99.2

98.7 d) 100.0 e)

The compounds according to the invention are preferably used in the form of their mixtures with one another, mixtures which correspond to a eutectic are particularly preferred.

Some exemplary compositions are summarized in the following table.

composition

50 % D + 50 % E

50 % D + 50 % P

50 % D + 50 % G

50 % D + 50 % H

50 % E + 50 % F

50 % E + 50 % G

50 % E + 50 % H

50 % F + 50 % G

509815/13 U

Melting point Clearing point (M.p.) ⁰ C (KIp.) ⁰ C 59.3-59.9 102.4 47.3-48.1 98.7 38.2-41.5 99.7 42.4-43.7 95.0 56.4-56.7 97.5 42.8-43.1 92.9 42.8-43.3 96.1 56.1-56.8 93.5-94.6

50 y fl / dd 50 * whether T5
Jw A 50 y } *? A. 50 y Ct Ό
yrt> A 50 y Ck * p 50 y 50? } V A 50 y YES 50 pp 6 F H £ G M g M H 6 N H 6 0 π ί Ph i Q, H 6 s λ I TH h 50 h 50 h 50 h 50 h 50 h 50 h 50 h 50 h 50

45.2-50.1 93.5-94.2

49.4-50.4 94.2-94.5

47-51 102.9

55-58 101.9

58-60 100.6

59-60 100.1 60-61 99.2

66-70 98.9

56-59 99.1

All information in

The compounds according to the invention can be used in the form of their mixtures with other nematic or non-nematic Substances are used, such as with known ship's eyes Bases of the general formula

CH = N

wherein R, straight chain alkyl having 2 to 8 carbon atoms, straight chain alkoxy with 4-7 carbon atoms or straight-chain alkanoyloxy with 2 to 8 carbon atoms means.

The compounds according to the invention can also be used in the form of their mixtures with known compounds of the formula

5 0 9 815/1314.

N = CH

where R is straight-chain alkyl having 4 to 7 carbon atoms,
or with compounds of the general formula

COO

wherein R, straight-chain alkyl with 4 to 8 carbon atoms, straight-chain alkoxy with 5 to 8 carbon atoms or straight-chain alkyl carbonate with 3 to 11 carbon atoms,
or with known compounds of the general formula

VII

where R _{2 is} straight-chain alkyl such as n-pentyl, n-hexyl or n-heptyl or straight-chain alkoxy such as n-pentyloxy, n-heptyloxy or n-hexyloxy,
be used.

509815 / 13U

The compounds of the formula VI, wherein R, straight-chain Alkyl carbonate means are new and can be converted by reacting a compound of the formula

RoOCOO (' ^X ) COCl

can be obtained with p-hydroxybenzonitrile.

Mixtures of p - [(p-n-hexylbenzylidene) amino] benzonitrile and p - [(p-cyanobenzylidene) amino] phenyl-n-propyl carbonate in a molar ratio of 2 to 1 are very particularly preferred (melting point (-20 ⁰ C; clearing point 76, I ⁰ C) as well as from

p - [(pn-hexylbenzylidene) amino] benzonitrile and of p- [N- (p-cyanophenyl) formimidoyl] phenyl-n-hexyl carbonate in a molar ratio of 2 to 1 (melting point (-20 ⁰ Cj clearing point 73 * 1 ° C).

The preparation of the compounds I according to the invention and the compounds of the formula VI in which R is straight-chain Means alkyl carbonate is illustrated by the following examples. All temperatures are in degrees Celsius specified. , - ■

509815 / 13U.

example 1

A mixture of 6.1 g (53.9 mmol) of methyl p-formylphenyl carbonate and 4.0 g (33.9 mmol) of p-amlnobenzonitrile is gassed with argon in 100 ml of benzene and refluxed for 1 hour (bath temperature 135 °) . The resulting water is separated off with a water separator. For a further hour, the benzene condensing in the reflux condenser is then returned to the reaction vessel through a layer of 100 g of aluminum oxide (act. I). After cooling, the reaction mixture is freed from the solvent in vacuo at a bath temperature of 50 °. 9 * 3 S practically colorless crystals remain, which are recrystallized several times from isopropanol up to a constant melting point and until the by-products in the gas chromatogram have disappeared. The pure colorless p- / N- (p-cyanophenyl) formimidoyl phenyl methyl carbonate obtained has a melting point of 139 * 0-139.2 ° and a clearing point of 156.0 °. UV (EtOH): E ₂₇ ^ = 24100 (shoulders at 315 and 234 nm; minimum at 242 nm).

Example 2

A mixture of 6.6 g (33 * 9 mmol) of ethyl p-formylphenyl carbonate (bp _{Q Q2} = 92-94 °) and 4.0 g (33.9 mmol) of p-amino-benzonitrile in 100 ml of benzene is obtained as in Example 1 implemented. After evaporation, 10.0 g of practically colorless crystals remain which, as in Example 1, are recrystallized several times from isopropanol for purification. The pure colorless p- / N- (p-cyanophenyl) formimidoyl / phenyl-ethyl carbonate obtained has a melting point of 133 * 0-133 * 1 ° and a clearing point of 139 * 7 °

UV (EtOH): £ _{? 6} = 26,000 (shoulders at 317 and 232 nm; minimum at 240 nm).

B 0 9 8 1 5/1 3 U

Example 3

A mixture of 7 * 05 g (35 * 9 mmol) of p-formylphenyl carbonic acid n-propyl ester (bp _{n Ί} = 115-120 °) and 4.0 g (33 * 9 mmol) of p-aminobenzonitrile in 100 ml of benzene is implemented as in Example 1. After evaporation, 10.1 g of practically colorless crystals remain which, as in Example 1, are recrystallized several times from isopropanol for purification. The pure colorless p- / N- (p-cyanophenyl) -formimidoy] y phenyl-n-propyl carbonate obtained has a melting point of 144.2-144.5 ° and is liquid crystal on cooling at 113 * 2 °. UV (EtOH): £ _{? I |} = 24100 (shoulders at 313 and 234 nm; minimum at 243 nm).

Example 4

A mixture of 6.2 g (27.9 mmol) of p-formylphenyl-

carbonic acid n-butyl ester (Kp_ = II5-II7 ⁰ ) and 3.3 g '

u, d

(27 * 9 mmol) p-aminobenzonitrile in 100 ml benzene is reacted as in Example 1. After evaporation, 8.9 g of practically colorless crystals remain which, as in Example 1, are recrystallized several times from isopropanol for purification. The pure colorless p- / N- (p-cyanophenyl) formimidoyl / phenyl-η-butyl carbonate obtained has a melting point of 68.3-68.4 ° and a clearing point of 105.7 °. UV (EtOH): ε ^ = 24300 (shoulders at 313 and 233 nm; minimum at 242 nm).

Example 5

A mixture of 8.0 g (33.9 mmol) of p-formylphenyl carbonic acid n-pentyl ester (bp _n , = 124-125 °) and 4.0 g (33.9 mmol) of p-aminobenzonitrile in 100 ml of benzene is like implemented in example 1. After evaporation, 11.1 g remain

5 0 9 8 15/1 3 U

practically colorless crystals which, as in Example 1, are recrystallized several times from isopropanol for purification. The pure colorless p- / N- (p-cyanophyl) formimidoyiy phenyl-n-pentyl carbonate obtained has a melting point of 70.5-70.7 ° and a clearing point of 99.4 °. UV (EtOH): ^ ₆ = 24600 (shoulders at 313 and 233 nmj minimum at 242 nm).

Example 6

A mixture of 6.6 g (26.4 mmol) of p-formylphenyl carbonic acid n-hexyl ester (bp _n , = 14O-14l °) and 3.12 g (26.4 mmol) of p-aminobenzonitrile in 100 ml of benzene is like implemented in example 1. After evaporation, 8.9 g of practically colorless crystals remain which, as in Example 1, are recrystallized several times from isopropanol for purification. The pure colorless p- / N- (p-cyanophenyl) formimidoyl7 phenyl-n-hexyl carbonate obtained has a melting point of 62.5-62.7 ° and a clearing point of 96.4 °. UV (EtOH) S ^ ₂₇₃ = 24200 (shoulders at 312 and 232 nmj minimum at 242 nm).

Example 7

A mixture of 8.95 g (33 * 9 mmol) of p-formylphenyl carbonic acid n-heptyl ester (bp _{n Λ} = 137-138 °) and 4.0 g (33.9 mmol) of p-aminobenzonitrile in 100 ml of benzene is like implemented in example 1. After evaporation, 11.9 g of practically colorless crystals remain which, as in Example 1, are recrystallized several times from isopropanol for purification. The pure colorless p - / * N- (p-cyanophenyl) formimidoylphenyl-nheptyl carbonate obtained has a melting point of 63.6-63 * 9 ° and a clearing point of 95 * 1 °.
UV (EtOH): ^ ₂₇ , = 238ΟΟ (shoulders at 313 and 234 nm;

5 0 9 8 1 5/1 3 U

Minimum at 243 nm).

Example 8

A mixture of 9.42 g (33 * 9 mmol) of p-formylphenyl carbonic acid n-octyl ester (bp _QQ g = 147-148 °) and 4.0 g (33.9 mmol) of p-aminobenzonitrile in 100 ml of benzene is as implemented in example 1. After evaporation, 12.1 g of practically colorless crystals remain which, as in Example 1, are recrystallized several times from isopropanol for purification. The pure colorless p- / "N- (p-cyanophenyl) -formimidoyl / phenyl-n-octy1-carbonate obtained has a melting point of 64.8-65.0 ° and a clearing point of 95.0 °. UV (EtOH) : ε ^ = 23700 (shoulders at 312 and 233 nm; minimum at 242 nm).

Example 9

A mixture of 10.0 g (33.9 mmol) of p-formylphenyl-

carbonic acid n-nonyl ester (bp _n = 152-153 °) and 4.0 g

υ, ι

(33.9 mmol) p-aminobenzonitrile in 100 ml of benzene is reacted as in Example 1. After evaporation, 13 * 0 g remain practically colorless crystals which, as in Example 1, are recrystallized several times from isopropanol for purification. The pure colorless p - / * N- (p-cyanophenyl) formimidoylJ obtained phenyl-n-nony 1-carbonate has a melting point of 62.9-63.0 ° and a clearing point of 94.4 °. The connection is up to 83.7 ° smectic.

UV (EtOH): ε = 24,000 (shoulders at 314 and 233 nm; Minimum at 243 nm).

Example 10 A mixture of 10.4 g (33.9 mmol) of p-formylphenyl-

5 0 9 8 1 B / 1 3 U

Carbonic acid n-decyl ester (bp _n , = 164-165 °) and 4.0 g (33 * 9 mmol) of p-aminobenzonitrile in 100 ml of benzene are reacted as in Example 1. After evaporation, 13.2 g of practically colorless crystals remain which, as in Example 1, are recrystallized several times from isopropanol for purification.

The pure colorless p- / N- (p-cyanophenyl) -formimidoyl7 obtained phenyl-n-decyl carbonate has a melting point of 60.9-61.0 ° and a clearing point of 95.0 °. This is up to 93.0 ° Connection smectic.

UV (EtOH): € _ ", _K - 24600 (shoulders at 310 and 232 nm; minimum at 242 nm).

Example 11

A mixture of 0.835 g (5 * 0 mmol) p-methoxycarbonyloxyaniline and 0.655 g (5 * 0 mmol) p-cyanobenzaldehyde is gassed with argon in 50 ml benzene and refluxed for 1 hour (bath temperature I30 ⁰ ). The resulting water is separated off with a water separator. For a further hour, the benzene condensing in the reflux condenser is then returned to the reaction vessel through a layer of 20 g of aluminum oxide (Act. I). After cooling, the reaction mixture is freed from the solvent in vacuo at a bath temperature of 50 °. 1.395 g of yellowish crystals remain, which are recrystallized several times from isopropanol up to a constant melting point and clearing point and until the by-products in the gas chromatogram have disappeared. The pure, slightly yellowish p - / "(p-cyanobenzylidene) amino / phenylmethyl carbonate obtained has a melting point of 145 * 1-146.2 ° and a clearing point of 163.4 °. UV (EtOH): S _37n = 20250, € ^ = 1080 (shoulders at 243 and 221 nm; minima at 312 and 233 nm.

509815 / 13U

Example 12

A mixture of 0.905 g (5 * 0 mmol) of p-EthyIoxycarbonyl oxy-aniline and 0.655 g (5 * 0 mmol) p-cyanobenzaldehyde in 50 ml Benzene is reacted as in Example 11. After evaporation, 1.435 g of yellowish crystals remain, which are necessary for purification recrystallized several times from isopropanol as in Example 11. The pure, slightly yellowish p- / ~ (p-cyanobenzylidene) amine phenyl-ethyl carbonate obtained has a melting point of 143.2-143.9 ° and is at 140.9 ° on cooling liquid crystalline. UV (EtOH): ε = 19300, «^ = 10400 (Shoulders at 243 and 223 nmj minima at 322 and 230 nm).

Example 13

A mixture of 0.975 g (5 * 0 mmol) of pn-propyloxycarbonyloxy-aniline and 0.655 g (5 * 0 mmol) of p-cyanobenzaldehyde in 50 ml of benzene is reacted as in Example 11. After evaporation, 1.505 S yellowish crystals remain, which are recrystallized several times from isopropanol for purification as in Example 11. The pure, slightly yellowish P - / "(p-cyanobenzylidene) amino / phenyl-n-propyl carbonate obtained has a melting point of 75 * 7-76.3 ° and a clearing point of 117 * 8 °. UV (EtOH): ^ ₂₇₁ = 20800, ^ ₃₃₅ = 11500 (shoulders at 243 and 220 nmi minima at 313 and 234 nm).

Example 14

A mixture of 1.045 g (5.0 mmol) of p-n-butyloxycarbonyloxy aniline and 0.655 g (5 * 0 mmol) p-cyanobenzaldehyde in 50 ml benzene is reacted as in Example 11. After this Evaporation left 1.680 g of yellowish crystals, which for Purification as in Example 11 can be recrystallized several times from isopropanol. The pure, slightly yellowish obtained

5 0 9 8 1 5/1 3 U

P - / "(p-Cyanot» enzyliden) amino7phenyl-n-butyl-carbonate possesses a melting point of 91.2-91.8 ° and a clearing point of 110.5 °.

UV (EtOH): € β 21100, ε = II550 (shoulders at 245 and 220 nm; minima at 312 and 234 nm).

Example 15

A mixture of 1.35 S (6.05 mmol) of pn-perityloxyoarbonyloxy-aniline and 0.792 g (6.05 mmol) of p-cyanobenzaldehyde in 50 ml of benzene is reacted as in Example 11. After evaporation, 1.995 g of yellowish crystals remain, which are recrystallized several times from isopropanol for purification as in Example 11. The pure, slightly yellowish p - / "(p-cyanobenzylidene) amino / phenyl-n-pen ty 1-carbonate obtained has a melting point of 93.4-94.3 ° and a clearing point of 104.8 °. UV (EtOH ): ^ ₂₇₂ = 19900, ^ ₃₃₆ = 10750 (shoulders at 245 and 225 nm; minima at 314 and 230 nm).

Example l6

A mixture of 1.185 g (5.0 mmol) of p-n-hexyloxycarbonyloxy aniline and 0.655 g (5.0 mmol) of p-cyanobenzaldehyde in 50 ml of benzene is reacted as in Example 11. After this After evaporation, 1.680 g of yellow crystals remain which, as in Example 11, recrystallize several times from isopropanol for purification will. The pure, yellowish p - / * (p-cyanobenzylidene) obtained amino / phenyl-n-hexyl carbonate has a melting point of 82.4-83.2 ° and a clearing point of 102.1 °.

UV (EtOH): ^ ₂₇₁ = 18800, ^ ₃₂₆ = IO300 (shoulders at 244 and 220 nm; minima at 312 and 233 nm).

B0981B / 13U

Example 17

A mixture of 1.255 g (5 * 0 mmol) of pn-heptyloxycarbonyloxy-aniline and 0.655 g (5 * 0 mmol) of p-cyanobenzaldehyde in 50 ml of benzene is reacted as in Example 11. After evaporation, 1.60 g of yellow crystals remain, which are recrystallized several times from isopropanol for purification as in Example 11. The pure, yellowish p - / "(p-cyanobenzylidene) aminojphenyl-n-heptyl carbonate obtained has a melting point of 75 * 0-75.6 ° and a clearing point of 99 * 4 °, UV (EtOH): ^ ₂₇₁ = .19400, <r, ₂₅ = 10450 (shoulders at 244 and 226 nm; minimum at ^>1J> nm).

Example 18

A mixture of 1.525 g (5 * 0 mmol) of pn-octyloxycarbonyloxy-aniline and 0.655 g (5.0 mmol) of p-cyanobenzaldehyde in 50 ml of benzene is reacted as in Example 11. After evaporation, 1.845 g of yellow crystals remain, which are recrystallized several times from isopropanol for purification as in Example 11. The pure, yellowish p - / (p-cyanobenzylidene) amino / phenyl-n-octyl carbonate obtained has a melting point of 75 * 4-75 * 9 ° and a clearing point of 99.2 °. UV (EtOH): c "= 20800, ζ ^ = ll400 (shoulders at 245 and 221 nmj minima at jjll and 223

Example 19

A mixture of 1.445 g (5.0 mmol) of p-n-nonyloxycarbonyloxy aniline and 0.655 g (5.0 mmol) of p-cyanobenzaldehyde in 50 ml of benzene is reacted as in Example 11. After this After evaporation, 1.955 g of yellow crystals remain which, as in Example 11, recrystallize several times from isopropanol for purification will. The pure, yellowish p - / "(p-cyanobenzylidene) obtained

509815/13 1.4

aminojphenyl-n-nonyl carbonate has a melting point of 81.7-82.3 ° and a clearing point of 98.7 °. The connection is smectic up to 91.9 °.
UV (EtOH): € »20900, £ ^ = 11130 (shoulders at 244 and

222 nm; Minima at 313 and 233 nm).

Example 20

A mixture of 1.47 g (5.0 mmol) of pn-decyloxycarbonyloxy-aniline and 0.655 g (5.0 mmol) of p-cyanobenzaldehyde in 50 ml of benzene is reacted as in Example 11. After evaporation, 2.00 g of yellow crystals remain, which are recrystallized several times from isopropanol for purification as in Example 11. The pure, yellowish p - / (p-cyanobenzylidene) amino / phenyl-n-decyl carbonate obtained has a melting point of 75.6-76.3 ° and a clearing point of 100.0 °. The connection is smectic up to 99.5 °.
UV (EtOH): e = 2O600, € ^ = II25O (shoulders at 244 and

223 nm; Minima at 313 and 231 nm).

Example 21

5.66 g of p-cyanophenol (47.6 mmol) are dissolved in 66 ml of abs. Pyridine dissolved and cooled to -10 ° with stirring. In the course of 10 minutes, a total of 8.6 g (37j7 mmol) of crude p-carbethoxy-oxybenzoyl chloride are added in portions. The temperature rises to 0 ° and pyridine hydrochloride precipitates. The mixture is then stirred overnight at room temperature and the suspension is poured onto a mixture of 200 ml of ice and 200 ml of 20 percent strength. Poured hydrochloric acid. It is extracted three times with ethyl acetate, washed with water, dried over sodium sulfate and evaporated in vacuo. The 12.4 g of reddish crystals obtained as residue are dissolved in benzene and chromatographed on 400 g of silica gel. Elute benzene- 1 % acetone (v / v)

50 98 1 5/1 3U

8.1 g of yellowish crystals, which are recrystallized from acetone / hexane to a constant melting point and clearing point. The pure p - / (p-cyanophenoxy) carbonyl] phenyl ethyl carbonate obtained melts at 144.7-144.8 ° and is liquid crystalline (monotropic) on cooling at 115.8 °. UV (EtOH): £ _{2i | a} - 29700.

The raw material is produced as follows:

The method of E. Fischer , Ber. 4l _t 2877 (1908) ethyl chloroformate act on p-hydroxybenzoic acid in the presence of N-sodium hydroxide solution. Crystalline p-carbethoxy-oxybenzoic acid is obtained, which is treated with thionyl chloride according to the information provided by H.Sohb * nenberp; er et al ., Arzneimittelforschung 14 , 324 (1964). After removing the excess thionyl chloride in vacuo, crude p-carbethoxy-oxybenzoyl chloride is obtained, which is reacted directly as described above.

0 9 8 15/1314

Claims (1)

Claims ! .Method for establishing connections of the general formula ROCOO wherein X -CH = N- or -N = CH- and R straight-chain alkyl having 1 to 10 carbon atoms means, characterized in that one a) for the preparation of a compound in which X is -QH = N-, a compound of formula II ROCOO CHO where R has the meaning mentioned above, reacts with p-aminobenzonitrile, for the preparation of a compound in which X is -N = CH-, a compound of the formula ROCOO wherein R has the meaning mentioned above, with 5 0 9 8 15 / Ί 2 14 p-cyanobenzaldehyde converts. 2. The method according to claim 1, for the preparation of P- [N- (p-cyanophenyl) formimidoy1] phenyl-methy1-carbonate, characterized in that one p-formylphenyl carbonate reacts with p-aminobenzonitrile. 3. The method according to claim 1 for the production of p- [N- (p-Cyanophenyl) formimidoyl] phenyl ethyl carbonate, characterized in that one p-formylphenyl carbonate is ethyl reacts with p-aminobenzonitrile. 4. The method according to claim 1 for the production of p- [N-Cp-CyanopftenylJformimidoylJphenyl-n-propyl-carbonate, characterized in that one p-formylphenyl carbonic acid propyl ester reacts with p-aminobenzonitrile. 5. The method according to claim 1 for the preparation of p-t N- (p-cyanophenyl) formimidoyl] phenyl-n-butyl carbonate, characterized in that p-formylpheny! carbonic acid butyl ester reacts with "p-aminobenzonitrile. 6. The method according to claim 1 for the preparation of p- [N- (p-cyanophenyl) formimidoyl] phenyl-n-pentyl carbonate, characterized in that p-formylphenyl carbonic acid pentyl ^ ester reacts with p-aminobenzonitrile. 7. The method according to claim 1 for the preparation of p- [N- (p-cyanophenyl) formimidoyl] phenyl-n-hexyl carbonate, characterized in that one p-formylphenyl carbonic acid hexyl ester reacts with p-aminobenzonitrile. 5 0 9 8 1 b / Ί 3 8. The method according to claim 1 for the preparation of p- [N- (p-cyanophenyl) formimidoyl] phenyl ~ n-heptyl carbonate, characterized in that one p-formylphenyl carbonic acid heptyl ester reacts with p-aminobenzonitrile. 9. The method according to claim 1 for the preparation of p- [N- (p-cyanophenyl) formimidoyl] phenyl-n-octyl carbonate, characterized in that p-formylphenyl carbonic acid octyl ester reacts with p-aminobenzonitrile. 10. The method according to claim 1 for the preparation of p- [N- (p-cyanopheny1) formimidoy1] phenyl-n-nonyl-carbonate, characterized in that p-formylphenyl carbonic acid nonyl ester reacts with p-aminobenzonitrile. 11. The method according to claim 1 for the preparation of p- [N- (p-cyanophenyl) formimidoyl] phenyl-n-decyl carbonate, characterized in that p-formylphenyl carbonic acid decyl ester reacts with p-aminobenzonitrile. 12. The method according to claim 1 for the preparation of p - [(p-cyanobenzylidene) amino] phenyl methyl carbonate, characterized characterized in that one p-methoxycarbonyloxy-aniline with p-cyanobenzaldehyde converts. 13. The method according to claim 1 for the production of p - [(p-Cyanobenzyliden) amino] phenyl ethyl carbonate, characterized in that p-ethoxycarbonyloxy aniline with p-cyanobenzaldehyde converts. 14. The method according to claim 1 for the production of p- [(p-Cyanobenzylidene) amino] phenyl-n-propyl carbonate, thereby characterized in that one p-n-propyloxycarbonyloxy-aniline with p-cyanobenzaldehyde converts. 5 0 9 8 15/1314 15. Process according to Claim 1 for the preparation of P- [(p-Cyanobenzylidene) amino] phenyl-n-butyl carbonate, thereby characterized in that one p-n-butyloxycarbonyloxy-aniline with p-cyanobenzaldehyde converts. 16. The method according to claim 1 for the production of P-! (p-Cy.anobenzylidene) amino] phenyl-n-pentyl carbonate, thereby characterized in that one p-n-pentyloxycarbonyloxy-aniline with p-cyanobenzaldehyde converts. 17. The method according to claim 1 for the preparation of p - [(p-cyanobenzylidene) amino] phenyl-n-hexyl carbonate, characterized characterized in that one p-n-hexyloxyearbonyloxy-aniline with p-cyanobenzaldehyde converts. 18. The method according to claim 1 for the production of p- [(p-Cyanobenzylidene) amino] phenyl-n-heptyl-carbonate, thereby characterized in that one p-n-heptyloxycarbonyloxy-aniline with p-cyanobenzaldehyde converts. 19. The method according to claim 1 for the production of P - [(p-Cyanobenzylidene) amino] phenyl-η-octyI-carbcnate, thereby characterized in that one p-n-octyloxycarbonyloxy-aniline with p-cyanobenzaldehyde converts. 20. The method according to claim 1 for the production of p- [(p-Cyanobenzylidene) amino] phenyl-n-nonyl carbonate, thereby characterized in that one p-n-nonyloxycarbonyloxy-aniline with p-cyanobenzaldehyde converts. 21. The method according to claim 1 for the production of p - [(p-Cyanobenzylidene) amino] phenyl-n-decyl-carbcnate, thereby characterized in that one p-n-decyloxycarbonyloxy-aniline with p-cyanobenzaldehyde converts. 509815/1314 22. Nematic mixture for electro-optical purposes, characterized in that it contains one or more compounds of the formula I in claim 1 and, if necessary, others nematic substances and / or non-nematic substances contains. 23. Nematic mixture according to claim 22 »characterized in that it consists exclusively of compounds of the Formula I in claim 1 contains. 24. Nematic mixture according to claim 22 > characterized in that it contains compounds of the formula I in
Claim 1 and compounds of the formula IV CH = N wherein R, straight-chain alkyl with 2 to 8
Carbon atoms, straight-chain alkoxy with
K to 7 carbon atoms or straight chain
Alkanoyloxy of 2 to 8 carbon atoms
means,
contains. 25th Nematic mixture according to claim 22 > characterized in that there are compounds of the formula I in claim 1 and compounds of the formula V N = CH wherein Rp is straight-chain alkyl of 4 to 7
Carbon atoms means
contains. 5098 15/131 U 26th Nematic mixture according to claim 22, characterized in that that there are compounds of the formula I in claim and compounds of the formula VI COO wherein R, straight-chain alkyl with 4 to 8 carbon atoms, straight-chain alkoxy with 5 to 8 carbon atoms or straight-chain alkyl carbonate with 3 to 11 carbon atoms,
contains, 27 Nematic mixture according to claim 22, characterized characterized in that there are compounds of the formula I in claim and compounds of the formula VII VII where R ^ is straight-chain alkyl or straight-chain alkoxy, contains, 28. Nematic mixture according to claim 24, characterized in that it consists of ρ [(p-n-hexylbenzylidene) amino] benzonitrile and ρ [(p-cyanobenzylidene) amino] phenyl n-propyl carbonate consists. 29 Nematic mixture according to claim 24, characterized in that it consists of ρ [(p-n-hexylbenzylidene) amino] 50981 5/131 k benzonitrile with ρ- [N- (p-cyanophenyl) formimidoyl) phenyl n-hexyl carbonate. 30. Use of a according to any one of claims 1-21 produced connection as a dielectric for electro-optical purposes. 31. Use of a according to any one of claims 1-21 connection established in a rotating cell. 32. Use of a mixture according to one of the Claims 22 to 29 as a dielectric for electro-optical purposes. . Use of a mixture according to any one of claims 22 to 29 in a rotating cell. 34. Compounds of the general formula ROCOO wherein X -CH = N- or -N = CH- and R straight-chain alkyl with 1 to 10 Means carbon atoms. 509815/1 3U 35. Vertings of the formula I in which X is -CH = Ii- and R is straight-chain alkyl having 4 "to 8 carbon atoms". ³⁶ . Compounds of the formula I in which X is -M ^- = CH- and E. is n-propyl, n-hexyl or n-heptyl ". 37. p- [N- (p-Cyanophenyl) formimidoyl] phenyl methyl carbonate. ³⁸ .. p- [N- (p-Cyanophenyl) formimidoyl] phenyl ethycarbonate. 39. p- {N- (p-Cyanophenyl) formimidoyl] phenyl-n-propyl · carbonate. 40. p- [N- (p-Cyanophenyl) formimidoyl] phenyl-n-butyl carbonate. 41. p- [N- (p-Cyanophenyl) formimidoyl] phenyl-n-pentyl carbonate. ⁴² . p- [N- (p-Cyanophenyl) formimidoyl] phenyl-n-hexyΙο carbonate. 43. p- [N- (p-Cyanophenyl) formimidoyl] phenyl-n-heptyl carbonate. ⁴⁴ . p- [N- (p-Cyanophenyl) formimidoyl] phenyl n-octyl carbonate. 45. ρ- [N- (p-cyanophenyl) formimidoyl] phenyl-n-nonyl carbonate. 46, p- [N- (p-Cyanophenyl) formomidoyl] phenyl-n-decyl carbonate 5 0 9- 8 1 B / Ί: .i 1 A 47. ρ - ((p-Cyanobenzylidene) amino] phenyl methyl carbonate. 48. p- [(p-Cyanobenzylidene) amino] phenyl.ethyl carbonate. 49. p - [(p-Cyanobenzylidene) amino] phenyl-n-propyl carbonate, 50. p - [(p-Cyanobenzylidene) amino] phenyl n-butyl carbonate. 51. p - [(p-Cyanobenzylidene) amino] phenyl-n-pentyl carbonate, 52. p - [(p-Cyanobenzylidene) amino] phenyl-n-hexyl carbonate. 53. ρ - [(p-cyanobenzylidene) amino] phenyl-n-heptyl carbonate, 54. p - [(p-Cyanobenzylidene) amino] phenyl n-octyl carbonate. ⁵⁵ . p- [(p-Cyanobenzylidene) amino] phenyl n-nonyl carbonate. 56. p - [(p-Cyanobenzylidene) amino] phenyl n-decyl carbonate. 509815/1314