Fluorine-substituted alkenyl liquid crystalline compounds

Technical Field

The present invention relates to novel liquid crystalline compounds showing preferable physical properties and liquid crystalline compositions having preferable physical properties obtained by using the above-mentioned novel liquid crystalline compounds.

Background Art

Liquid crystalline display elements utilize optical anistropy and dielectric anistropy, both of which are possessed by liquid crystalline compounds, and there are known a twist nematic type (TN type) , a supertwist nematic type (STN type) , a dynamic scattering type (DS type) and a guest/host type (G/H type) etc. as display methods therefor. Also, there are known a static driving method, a time-separating driving method, an active matrix driving method and a 2-frequency driving method etc. as driving methods threrfor.

Properties of liquid crystalline compounds used in these various liquid crystalline display elements are different according to their applications, but any of the liquid crystalline compounds is required to be stable against external environmental factors such as water content, air, heat and light etc., and also to show a liquid crystalline phase within a high

range as possible, preferably with centering around the room temperature.

Furthermore, in order that the liquid crystalline compounds show optimal properties required for individual display elements, the liquid crystalline compositions are consistuted from several or more than 20 liquid crystalline compounds. Thus, they are required to be compatible with other liquid crystalline compounds, and in particular recently required to have good compatibility at low temperatures because of requests resulted from uses under various environments.

Compositions used in a STN driving method which are most practiced recently are particularly required to have sharp threshold value characteristics in order to realize high image qualities. It is known that the said sharpness is a function of an elastic constant ratio K33/K11, wherein the more the liquid crystalline compound has the constant ratio, the sharper the liquid crystalline compsition which uses the said compound has the threshold value (F. Leenhouts and et al., Proceedings of the Japan Display 388 (1986)) . Furthermore, it is necessary to use compositions with rapid response speed in order to realize enhighment of display element planes. The response speed is known to be a function of viscosity (E. Jakeman and et al., Phys. Lett., 39A, 69 (1972)). That is, it is important to use liquid crystalline compounds with low viscosity, which is required to realize compositions with low viscosity.

The following compounds having alkenyl sites are known as

compounds with high elastic constant ratio K33/K11. That is, there may be mentioned

described in Mol. Cryst. Liq. Cryst. , 122 (1985) and Toku-Kai- Sho 61-83136, or

having an introduced fluorine atom described in Toku-Gan-Hei 6-92740.

Any of these alkenyl compounds has high elastic constant ratio K33/K11, and any of liquid crystalline compositions obtained by using them has comparatively preferable sharpness. However, liquid crystalline compositions showing more rapid response speed, in other words, the compositions showing lower viscosity, are required owing to increase in requests for display ability of display elements.

Furthermore, compounds

having 1, 3-butadienyl groups described in Toku-Gan-Hei 6-151445 are known as compounds with high elastic constant ratio K33/K11.

However, the substituent, a 1 , 3-butadienyl group, is very unstable chemically, so that it is impossible to use them for practical liquid crystalline compositions.

Furthermore, dienyl compounds having multiple double bonds in one same chain are disclosed in Toku-Gan-Hei 7-26029. Although

the compounds with high elastic constant ratio K33/K11 and high stability are disclosed in the said invention, it is impossible to prepare liquid crystalline compositions having low viscosity and sufficiently rapid response property. Thus, liquid crystalline compounds which have high elastic constant ratio K33/K11, lower viscosity than the conventional liquid crystalline compounds, high chemical stability, and good compatibility with other liquid crystalline compounds are expected.

Diclosure of Invention

We inventors have studied zealously in order to solve the above-mentioned problems, and thus found compounds which have novel structures and improved properties compared to known liquid crystalline compounds, to complete the present invention. As clear from the above-mentioned description, an object of the invention is to propose novel liquid crystalline compounds having high elastic constant ratio, lower viscosity compared to known liquid crystalline compounds, superior compatibility with other liquid crystalline compounds, particularly compatibility at low temperatures, and chemical stability, as well as liquid crystalline compositions containing the said compounds.

Best Mode for Carrying Out the Invention The present invention consisted of the following first to ninth inventions.

The first of the invention is a liquid crystalline compound

expressed by the following general formula (1)

,-{ ( )-X,) _m -( -T)-X ₂ )n- (C -X ( ^" ) - ^R 2 ( ¹ )

(wherein, Ri and R ₂ are each independently a cyano group, a halogen atom, an alkyl group with from 1 to 20 carbon atoms, a halogenated alkyl group with from 1 to 20 carbon atoms or a dienyl group shown by the general formula (1-1) , in which one or non-adjacent two CH ₂ group (s) may be substituted by (an) oxygen atom(s) , -CH=CH- group (s) or -C≡C- group (s) and furthermore (a) hydrogen atom(s) may be substituted by (a) fluorine atom(s) , Xi, X ₂ and X ₃ are independently each other -CH ₂ CH ₂ -, -C0-0-, -0-C0-, -CH=CH-, -C≡C-, -(CH ₂ ) ₄ -, -CF.0-, -OCF2-, -CH ₈ 0-, -0CH ₂ - or a covalent bond, rings A, B, C and D denote each independently a 1, 4-phenylene ring or a 1 , 4-cyclohexylene ring, a bicyclo [1.1.0] butane ring, a bicyclo [1.1.1] pentane ring, a bicyclo [2.2.2] octane ring, a cyclobutane ring, a spiro [3.3] heptane ring, in which (a) halogen atom(s) in the said rings may be substituted, and (a) carbon atom(s) in the said rings may be substituted by (a) nitrogen atom(s) , (an) oxygen atom (s) or (a) silicon atom(s) , X ₄ , Xs, Xe, X? and X ₈ denote each independently a hydrogen atom, a halogen atom or an alkyl group with from one to five carbon atoms, in which at least one of them denotes a halogen atom, m and n are

independently each other 0 or 1, and p and q are each independently form 0 to 5.)

The second of the invention is a liquid crystalline compound according to the above-mentioned first item, wherein X ₄ is a fluorine atom.

The third of the invention is a liquid crystalline compound according to the above-mentioned first item, wherein X ₅ is a fluorine atom.

The fourth of the invention is a liquid crystalline compound according to the above-mentioned first item, wherein X ₆ is a fluorine atom.

The fifth of the invention is a liquid crystalline composition according to the above-mentioned first item, characterized in that a liquid crystalline compound expressed by the general formula (1) is contained as at least one component.

The sixth of the invention is a liquid crystalline composition, characterized in that at least one compound according to the above-mentioned items 1 to 4 is contained as the first component, and one or more than one compound (s) selected from a group consisting of the general formulae (2) , (3) and (4) :

^Q ,

(wherein, R ₃ denotes an alkyl group with from 1 to 10 carbon atoms, Y denotes a fluorine atom or a chlorine atom, Qi and Q ₂ denote each independently a hydrogen atom or a fluorine atom, r denotes 1 or 2, and Zi and Z ₂ denote each independently -CH ₂ CH ₂ - or a covalent bond) is (are) contained as the second component.

The seventh of the invention is a liquid crystalline compositior. characterized in that at least one compound according to the above-mentioned items 1 to 4 is contained as the first component, and one or more than one compound (s) selected from a group consisting of the general formulae (5) , (6), (7) , (8) and (9) :

(wherein, R ₄ denotes an alkyl group with from 1 to 10 carbon atoms or an alkenyl group with from 2 to 10 carbon atoms, in which (an) optional methylene group (s) of them may be substituted by (an) oxygen atom (s) in each cases, but two or more than two methylene atoms may not be substituted continuously, Z ₃ denotes -CH ₂ CH ₂ -, -C00- or a covalent bond, Q ₃ and Q ₄ denote a hydrogen atom or a fluorine atom, E denotes a cyclohexane ring, a benzene ring or a 1,3-dioxane ring, and s denotes 0 or 1) ,

(wherein, R _s denotes an alkyl group with from 1 to 10 carbon atoms, Q _s denotes a hydrogen atom or a fluorine atom, and k denotes 0 or 1) ,

R ₆ - " ^"2i -( ^G )n-COO- -F (7) '-

(wherein, R _ε denotes an alkyl group with from 1 to 10 carbon atoms, G denotes a cyclohexane ring or a benzene ring, Q ₆ and 0τ denote each independently a hydrogen atom or a fluorine atom, Z ₄ denotes -COO- or a covalent bond, and h denotes 0 or 1) , (wherein, R ₇ and R. denote each independently an alkyl group, an alkoxy group or an alkoxy ethyl group with from 1 to 10 carbon atoms, H denotes a cyclohexane ring, a pyπmidine ring or a benzene ring, J denotes a cyclohexane ring or a benzene ring, Z ₅ denotes -C≡≡C-, -C00-, -CH ₂ CH ₂ - or a covalent bond) , Q ₈

/ R9-(K)-Z _β -(L)-Z ₇ -( ) -R,o (9)

(wherein, R ₉ denotes an alkyl group or an alkoxy group with from 1 to 10 carbon atoms, Rio denotes an alkyl group, an alkoxyl group or an alkoxymethyl group with from 1 to 10 carobn atoms, K denotes a cyclohexane ring or a pyπinidine r ng, L and M denote each independently a cyclohexane ring or a benzene ring, Z ₆

denotes -COO- , -CH ₂ CH ₂ - or a covalent bond, l i denotes -C≡C-,

-COO- or a covalent bond, and Q ₈ denotes a hydrogen atom or a fluorine atom) is (are) contained as the second component. The eighth of the invention is a liquid crystalline display element with use of a liquid crystalline composition consisting of at least two components, characterized in that a liquid crystalline compound expressed by the general formula (1) is contained as at least one component. The ninth of the invention is a liquid crystalline display element with use of a liquid crystalline composition according to the above-mentioned items 5 to 8.

Preferable compounds amongst the compounds (1) according to the invention are compound groups expressed by the general formula groups (1-a) ~ (1-f). In the following τmulae, W and

W are substituents given in the general formula (l- , and Ri,

Xi. X ₂ , Xs, as well as rings A, B, C and D have the same meanings as the above-mentioned ones.

Furthermore, particularly preferable compounds amongst the general formula groups (1-a) ~ (1-f) are the following compounds.

R R ,- ^~CH2CH2 - ^" W R (CH ₂ ) ₄ - w

R,-< XCH=CH- XW

~^)-CH ₂ CH ₂ - )-W

xocox X-W

^■ OCF 2 \\ // w

R ^ι -X ^~ __ ^{~{ "w}

R ₁ ^_ ^-CH ₂ CH ₂ ^XCH ₂ CH ₂ w

\ _{\ //} -c≡cx _{x /} w w- coo -w w oco ^■ w

w CH, 20 ^U λ\ / -w

w- w // ^■ OCF _? ^■ w

R \\ //— //- A w

w (CH ₂ ),-:

\\ // w w :-(CH ₂ ),- ^/ ^ V w

R, w

W w w

W ^ — <^ C H 2 C H ₂ y w w „y- ^~ \ ^• CH,CH- V \ w w- •(Ch ₂ ) ₄ V \ w

=\ N=N

R ¹ W // ^■ W

N-

-N ^l ι^\ W

N =

R CO: ^• W

N

N=\

R, _{\ /} /-co ₂ x Vw

N- ⁷

^R ι N\ X ^■ C0 ₂ X _/ Vw

R,- xcoV V w

W \\ // // w

N

w λ\ N W // w

W O , N=

// w

^w' ΦχO w

N = w W // VCO,X ^■ w

N-

N w ^■ CO 2Λ\ // W

N

= N ^w -Cx =-\ w

N ^co

N =

R-, w // ^■ ∞z -w

R,-< /XC0 ₂ w

^=N

W'X //-\\ // ^• w

N=N

W \\ // w

w- / ^ x w // -w

w ^C0 2Λ\ ^■ W

w \\ // ^: -co ₂ ^ _/ Vw

w-( _{\ /} VC0 ₂ w

=\ N-.N

N:N

/=\ N = N

N-.N

W C0 ₂ X /> ^• W

N:N w CO,X -W

N = N

Rf -W

W // N-

N:N v

W

-N

_=\ N:N w \\ // w

N J ^■

N: /=\

W W

-N w //

N = N

W // ^" W

N-

N N w

^■ ι\

=\ N: w ^■ -o: ^■ w -

= _\ N:|N

W \\ // / W

N /

w C0 ₂ X V /XW

N:N

W _X <XC0- W

=\ o ^ll ^v // -W

O-

^■ O =

R o W // -w

^« .-OV> w

R.

\\ // ^■ w

^• o

R W // ^■ CO xw

^■ o rO

R. _{X /} -co ₂ - xw ^o rt, λ X co ₂ ^: x xw o

CD

(In the above formulae, Ri and W denote the same meanings as the above-mentioned ones, wherein a 1, 4-phenylene ring, a trans-1, 4- cyclohexylene ring, a bicyclo [1.1.0] butane ring, a bicyclo- [1.1.1] pentane ring, a bicyclo [2.2.2] octane ring, a cyclobutane ring and a spiro [3, 3] heptane ring may be substituted with (a) halogen atom(s) , and (a) carbon atom(s) in the said rings may be substituted with (a) nitrogen atom(s) or (an) oxygen atom(s) .)

Any of W and W shows preferable characteristics if satisfying the conditions shown in the general formula (1-1) , but the following WI - W24 are particularly preferable.

In the case of considering stability in particular, W and W in which q is 2 or more than 2 are preferable.

Furthermore, Ri and R_ show the above-mentioned W, W\ a cyano group, a halogen atom, an alkyl group with from 1 to 20 carbon atoms or a halogenated alkyl group with from 1 to 20 carbon atoms, wherein (a) methylene group (s) in the said groups may be substituted with (an) oxygen atom(s) or -OC- (s) . A fluorine atom and a chlorine atom are preferable as halogen atoms, and alkyl groups with from 1 to 10. particularly from 1 to 6, carbon atoms are preferable as alkyl groups.

Furthermore, as halogenated alkyl groups, trifluoromethyl, trifluoromethoxy, difluoromethoxy, 2-fluoroethyl, 2, 2-difluoroethyl, 2, 2, 2-trifluoroethyl, 3-fluoropropyl, 2-fluoropropyl, 2, 2-difluoropropyl, 4-fluorobutyl, 3-fluorobutyl, 2-fluorobutyl, 3, 3-difluorobutyl, 2, 2-difluorobutyl, 5-fluoropentyl, 4-fluoropentyl, 3-fluoropentyl, 3, 3-difluoropentyl and 10-fluorodecyl are preferable. As those in which a methylene group being substituted with an oxygen atom, methoxy ethyl, ethoxymethyl, propoxymethyl, butoxy ethyl, pentoxymethyl, ethoxyethoxy, methoxypropyl, ethoxyethoxy and ethoxypropoxyl groups are preferable. As those in which a methylene group being substituted with -CH=CH-, vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl and 3-pentenyl are preferable.

Any compound of the formula (1) according to the invention has high elastic constant ratio K33/K11 and low viscosity.

Furthermore, any compound is quite stable chemically.

Although any of the compounds according to the invention shows preferable physical properties, liquid crystalline compositions having properties according to their objects can be prepared by using compounds in which R., R ₂ , Xi, X ₂ , X ₃ , Xt, X _ε , Xβ, Xv, Xβ, A, B, C, D, m, n, p and q are appropriately selected. That is, in the case of using the compounds for compositions in which the liquid crystalline temperature range being particularly within higher temperature sides, 3-ring type or 4-ring type compounds can be used, and if not, 2-rings type or 3-ring type compounds can be used.

In the case to be required particularly high dielectric anisotropy values, compounds with positive dielectric anisotropy value (P type compounds) are used, and P type compounds may be obtained by selecting a halogen atom, a cyano group or a halogenated alkyl group as Ri in the formula (1) . In the case to be required higher dielectric anisotropy value, the object may be attained by introducing a halogen atom on a ring bonded to R i . In order to obtain compounds with negative dielectric anisotropy value (N type compounds) , groups without high dipole moment such as an alkyl group may be introduced.

Optical index anisotropy values can be also controlled by selecting Ri, R2, Xi, X2, Xs, X , Xs, Xβ, X?, Xβ, A, B, C, D, m, n, p and q in the general formula (1) optionally. That is, in the case to be required high refractive index anisotropy values, compounds containing much 1, 4-phenylene rings may be used, and in the case to be required low optical index anisotropy

values, compounds containing much 1.4-cyclohexylene rings may be used.

A liquid crystalline composition according to the invention preferably contains one or more than one compound (s) shown by (1) at a proportion of 0.1 - 99% by weight, in order to realize superior properties.

In more detail, a liquid crystalline composition proposed by the invention is accomplished by adding the first component containing at least one compound (1) and if required then mixing a compound optionally selected from the compound groups expressed by the general formulae (2) ~ (9) according to the object of the liquid crystalline composition.

As compounds expressed by the general formulae (2) ~ (4) used in the invention, the following compounds may be preferably mentioned. (Wherein, R ₃ denotes the same meaning as the above one. )

R, C!

\\ // (2-4)

^■ Cl

W // (2-5)

^■ CF, (2-7)

\\ //

\\ // ^■ OCF,,H (2-9)

R- (3-4)

\\ ^■ Cl

Compounds expressed by the general formulae (2) - (4) are compounds with positive dielectric anisotropy value, which are very superior in thermal stability and chemical stability and which are necessary compounds in the case to prepare liquid crystalline compositions particularly for TFT (AM-LCD) , which in turn is required high reliability such as high voltage holding ratio or high specific resistant value.

Amounts of compounds expressed by the general formulae (2) ~ (4) used may be optionally within a range of from 1 to 99% by weight ralative to the total weight of the liquid crystalline compositions in the case to prepare liquid crystalline compositons for TFT, but from 10 to 97% by weight is preferable. More preferably, from 40 to 95% by weight is preferable. Furthermore, in such cases, some compounds expressed by the general formulae (5) ~ (9) may be contained. Compounds expressed by the general formulae (2) ~ (4) may be used in the case to prepare liquid crystalline compositions for STN display methods or conventional TN display methods.

As compounds expressed by the general formulae (5) ~ (7) according to the invention, the following compounds may be preferably mentioned. (R+, 5 and Re have the same meanings as above ones.)

R. CN (5-1)

\\ //

R ₄ CN (5-7)

O = ^■

R ₄ C

\\ // (5-8)

O

R ₄ -;

W // ^• CN (5-17)

Compounds expressed by the general formulae (5) - (7) have positive and high dielectric anisotropy values, and they are used particularly for an object to lower threshold voltages. Furtheremore, they are used for objects to enlarge nematic ranges such as control of viscosity, control of optical index anisotropy value and raise of clearing point etc. Furthermore, they are used for an object to improve sharpness of threshold voltage.

As compounds expressed by the general formulae (8) and (9) according to the invention, the following compounds may be preferably mentioned.

(R7, Re, 9 and Rio have the same meanings as above ones.)

R, R _f (8-1)

Compounds expressed by the general formulae (8) and (9) are compounds having negative or low dielectric anisotropy values. Compounds of the general formula (8) are used for an object to lower viscosity and/or to control refractive index anisotropy value. Furtheremore, compounds of the general formula (8) are used for an object to enlarge nematic ranges such as raise of clearing point etc. and for an object to control refractive index anisotropy value.

Compounds expressed by the general formulae (5) ~ (9) are necessary compounds in the case to prepare liquid crystalline compositions particularly for STN display methods or conventional TN display methods.

Amounts of compounds expressed by the general formulae (5) ~ (9) used may be optionally within a range of from 1 to 99% by weight ralative to the total weight of the liquid crystalline compositions in the case to prepare liquid crystalline compositons for conventinal TN display methods and STN display methods, but from 10 to 97% by weight is preferable. More preferably, from 40 to 95% by weight is preferable. Furthermore, in such cases, some compounds expressed by the general formulae (2) - (4) may be contained.

Sharpness and angle range of vision can be improved by using liquid crystalline compositions according to the invention for TFT liquid crystalline display elements. Furthermore, since compounds of the formula (1) are low viscous compounds, response speeds of liquid crystalline display elements in which the said comopunds being used may be improved.

Liquid crystalline compositions used according to the invention are prepared by conventional methods per se. In general, methods for dissolving various components each other at high temperatures are taken. Furthermore, liquid crystalline materials of the invention may be improved according to intended applications by means of suitable additives and optimized. Those additives are known by the skilled men in the art and described in detail in literatures etc. Generally, chiral doping agents etc. are added in order to induce spiral structures of liquid crystals and to control necessary twist angles as well as to prevent opposite twists.

Furthermore, liquid crystalline compositions may be used as liquid crystalline compositions for guest-host (GH) modes by adding dichromatic dyestuffs such as erocyanine type, styryl type, azo type, azomethine type, azoxy type, quinophthalone type, anthraquinone type and tetrazine type ones etc. Alternatively, they may be used as liquid crystalline compositions for polymer dispersion type liquid crystalline display elements (PDLCD) represented by NCAP which is prepared by microcapsulating nematic liquid crystals or a polymer network liquid crystalline display element (PNLCD) in which three- dimentional network polymer is made in liquid crystals. Additionally, they may be used as liquid crystalline compositions for effective control birefringence (ECB) modes or dynamic scattering (DS) modes.

As nematic liquid crystalline compositions containing compounds according to the invention prepared as described

above, the following examples of compositions may be shown. Wherein, the compounds described in the composition examples are shown according to the rules of the following tables.

Composition Example 1

Composition Example 2

Composition Example 3

Composition Example 4

V 1 VF-HHB- 2 VF 2 V V2VF-HB-C

C

Composition Example 5

3 -HB (F) B H-VF2V 0%

Composition Example 6

V 2 V F-HBTB-3 V 2 V F-HVHB- 3

Composition Example 7

V2 V F-HHB-C 6. 0%

F) -C

Composition Example 8

Composition Example 9

FFV2 V F-HB B (F) -0 C F 3 8. 0%

F

Composition Example 10

F FVF 2 V-HH-3 V2 VF-HVHB- 3

Composition Example 11

FV 2 FV-HB-3 V2 VF-HB- 1

Composition Example 12

V 2 V F-HB TB - 3 6. 0%

Composition Example 13

FFV2VF-HBB (F) -0 C F 3

V2VF-HB0CF2B-3

FV 2 FV-HB - 3

Composition Example 14

FFV 2VF-HBB C F) - 0 C F 3 V 2 V F-HVHB - 3

Composition Example 15

) -c

Compounds (1) according to the invention can be prepared by utilizing general organic synthetic chemical methods. That is. known reactions described in books and magazines such as Novel Experimental Chemical Courses. Organic S.ynthesis and Organic Reactions etc. may be combined to carry out synthesis.

l) Ka!-(CH ₂ ) _q -Ha! ( ₁₃ ) et .) Pd(0)

DAST

, ^X -

MG-(CH ₂

(CH ₂ ) _c -CF ₂ CF ₂ h

(X) χ ₅ base

base

co Co

__ o CJ -

Cj

(In the above formulae, MG denotes a methogen, i.e. a central backbone constituted by a ring, Hal denotes a bromine atom or an iodine atom, Met denotes Li or MgBr, and X ₄ , X ₅ . p and q denote the same meanings as above ones. ) That is, alkyl lithium or magnesium is reacted with a halogenated alkenyl derivative (10) or an alkenyl derivative (11), to obtain an organometallic compound (12). Then, α , ω -dihalogenoalkane (13) is reacted with it for carrying out a cross-coupling reaction, to obatin (14) . By reacting (14) with a zinc compound (15) prepared from zinc and halogenataed trifluoroethene, there can be prepared a compound (1-a), that is a compound of formula (1) in which all of X ₆ , X ₇ and X ₈ being fluorine atoms.

After treating (14) with alkyl lithium, difluoroacetic chloride is reacted with it to make a ketone derivative (16) , and thereafter a fluorinating agent such as DAST etc. is reacted with it for fluorination of a carbonyl group, to prepare (17). By treating (17) with a base, there can be prepared a compound (1-b) , that is, a compound of formula (1) in which X ₆ and X ₈ being fluorine atoms and X ₇ being a hydrogen atom.

By reacting a dioxane derivative such as (18) or a dioxolane derivative with (12) for carrying out a cross-coupling reaction and thereafter carrying out an open-ring reaction of the treated dioxane ring or dioxolane ring under an acidic condition, there can be prepared an aldehyde derivative (19) . By reacting triphenyl phosphine and sodium chlorodifluoroacetate with (19), there can be prepared a compound (1-c) , that is a compound of

formula (1) in which Xs being a hydrogen atom and X? and X ₈ being fluorine atoms.

By reacting alkyl lithium with (1-b) , the preparing method of which is already shown above, then substituting a terminal fluorine atom by metal such as lithium etc. and thereafter treating with a protic solvent, there can be prepared a compound (1-d) , that is a compound of formula (1) in which X ₆ being a fluorine atom and X? and X ₈ being hydrogen atoms.

By reacting alkyl lithium with (21) which may be prepared by the reaction of (19) and a phosphonium salt of fluorotribromo- methane and then treating it under the above-mentioned condition, there can be prepared a compound (1-e) , that is a compound of formula (1) in which X _s and X ₇ being hydrogen atoms and Xβ being a fluorine atom. By treating (23) which is obtained by fluorination of a carbonyl co opund (22) , which is in turn prepared in a cross- coupling reaction of (14) and acetic chloride, under a basic condition to carry out dehydro luorination, there can be prepared a compound (1-f) , that is a compound of formula (1) in which Xβ being a fluorine atom and X ₇ and X ₈ being hydrogen atoms.

Furthermore, by reacting a phosphonium salt of methylbro ide with aldehyde (19) , there can be easily prepared a compound in which all of X ₆ . X and X ₈ being hydrogen atoms. The above-mentioned halogenated alkenyl comopund (10) can be preferably prepared by the following methods.

That is. by reacting a phosphonium salt of methylbromide with

(24) which may be synthesized by any known method from literatures, there can be prepared (10-1) in which X« and X ₅ being hydrogen atoms.

By reacting a phosphonium salt of fluorotribromomethane with (24), there can be prepared (10-2) in which X« being a hydrogen atom and Xs being a fluorine atom.

By carrying out lithiation of one terminal fluorine atom of (26) , which is obtained by the reaction of halide (25) prepared by any known method from literatures and (15), under the same condition as the above one and treating it with a halogen, there can be prepared (10-3) in which both of X ₄ and Xs being fluorine atoms.

By carrying out lithiation, treatment with a protic solvent, again lithiation with (26) , and then treatment with halogen, (10-4) can be prepared.

By carrying out lithiation of halogen sites in the above- mentioned (10-1) ~ (10-4) and treatment with a protic solvent, (11) can be prepared.

Furthermore, chlorides can be prepared similar to the above- mentioned methods. For example, by reacting chloroacetic chloride with (14) according to the above-mentioned method, chlorides such as (1-g) can be prepared.

Examples The invention will be illustrated in more detail by the following examples.

Example 1

Preparation of 4- (4- (4- (1, 2-difluoro-1.5-hexadιenyl) cyclohexyl) - cyclohexyl) -1-pentylbenzene

(Compound h o 1, a compound according to the formula (1) wherein Ri is a pentyl group. X. and X ₃ are covalent bonds. C and D are 1, 4-cyclohexane rings, B is a 1, 4-phenylene ring, m=0, n=l. p is 0, q is 2, are hydrogen atoms)

A corresponding zinc compound (correspoding to 0 10 mol) prepared from lodotrifluoroethene and zinc powders in a solution of THF was added to a mixture of 4- (4- - cyclohexyl) -1-pentylbenzene (0 05 mol) , tetrakis (tπpheny1) - phosphine) palladium (0) (0.005 mol) and 70ml of THF at -30°C, stirred for 30 minutes, thereafter returned to the room temperature gradually, and heated under reflux for 1 hour They were cooled again to below 0°C , to which 20ml of an aqueous saturated ammonium chloride solution was added and then returned to the room temperature with stirring Extraction ith 150ml of heptane was carried out, and an organic layer was ashed with water for three times and dried with anhydrous magnesium sulfate The solvent was distilled off under a decreased pressure and the residue was recrystallized from 75ml of ethanol, to obtain 4- (4- (4- (tπfluoroethenyl) cyclohexyl) - cyclohexyl) -1-pentylbenzene (0 042 mol)

45ml of a solution of 4- (4- (4- (trifluoroethenyl) cyclohexyl) - yclohexyl) -1-pentylbenzene (0.04 mol) in THF was cooled to -78 °C, to which butyl lithium (corresponding to 0.04 mol) was added dropwise and stirred for 1 hour at the same temperature. Bis (triphenylphosphine) palladium (II) dichloride (0.004 mol) was added, then 50ml of a solution of 2- (2-bromoethyl) -1, 3-dioxane (0.044 mol) in THF was added with maintaining the same temperature, and stirred for 1 hour. 20ml of an aqueous saturated ammonium chloride solution was added, returned to the room temparature gradually, and thereafter extracted with 100ml of toluene. After washing an organic layer with water twice, toluene was distilled off under a decreased pressure, to obtain crude 4- (4- (4- (1.2-difluoro-4- (1, 3-dioxy-2-yl) -1-butene) - cyclohexyl) cyclohexyl) -1-pentylbenzene. A mixture of the prepared compound (unpurified) , 10ml of 955. formic acid and 100ml of toluene was heated under reflux for 1 hour and allowed to cool to the room temperature. The reactant was transferred to a separatory funnel and an organic layer was washed with water twice, washed with a saturated sodium hydrogen carbonate solution twice, and dried with anhydrous magnesium sulfate. The solvent was distilled off under a decreased pressure and the residue was treated with a column chromatography (eluate: toluene), to obtain 4- (4- (4- (1, 2- difluoro-5-oxo-l-pentenyl) -cyclohexyl) cyclohexyl) -1- pentylbenzene (0.021 mol).

Potasium-t-butoxide (0.031 mol) was added to a mixture of triphenyl phosphonium methane iodide (0.03 mol) and 50ml of THF

and stirred for 20 minutes, to obtain a red solution. To the said solution, 20ml of a solution of 4- (4- (4- (1.2-difluoro-5- oxo-1-pentenyl) -cyclohexyl) cyclohexyl) -1-pentylbenzene (0.02 mol) in THF was added dropwise at below 10°C and stirred for 1 hour. To the reactant, 50ml of water and 100ml of heptane were added to carry out extraction.

An organic layer was washed with water for three times and dried with anhydrous magnesium sulfate. After distilling off the solvent under a decreased pressure, the residue was purified by a column chromatography (eluate: a mixture of toluene and heptane = 1:9) and recrystallization (for three times from 20ml of ethanol) , to obtain the title compound as a white solid (0.011 mol) . Various spectra data thereof support the structure well. Example 2

Preparation of 4-4 ^' -bis (6, 6-difluoro-1 , 5-hexadienyl) - bicyclohexane

(Compound No. 2, a compound according to the formula (1) wherein Ri and R ₂ are 6.6-difluoro-1.5-hexadienyl groups, X ₃ is a covalent bond, C and D are 1 , -cyclohexane rings, and m=n=0) . A mixture of methoxy methyl triphenyl phosphonium chloride (0.1 mol) , potassium-t-butoxide (0.11 mol) and 300ml of THF was stirred for 2 hours, to obtain a red solution. To it, bicycloexane-1.4-dione (0.05 mol) in 300ml of THF was added and

stirred for 2 hours. To the reactant, 500ml of toluene and 500ml of water were added to carry out extraction, then an organic layer was extracted twice with 500ml of water and the solvent was distilled off under a decreased pressure from the organic layer. IL of heptane was added to the residue and stirred well to filter off the undissolved materials. Heptane was distilled off under a decreased presure, to obtain the residue as a white solid.

300ml of THF and 150ml of 6N-HC1 were added and stirred for 12 hours. The reactant was extracted with 300ml of toluene, washed for three times with 500ml of water, and thereafter dried on anhydrous magnesium sulfate. The solvent was distilled off under a decreased pressure, to obtain bicyclohexane-4, 4 ^' - dicarboaldehyde (0.03 mol) as a white solid. The said material was used for the subsequent reaction after dried sufficiently. Potassium-t-butoxide (0.02 mol) was added to a mixture of 2- 1, 3-difluoro-2-yl) ethyl triphenyl phosphonium bromide (0.02 mol) and 200ml of THF and stirred for 1 hour, to which 100ml of a solution of bicyclohexane-4, 4 ^' -dicarboaldehyde (0.01 mol) in THF was added dropwise for 2 hours at below -20 °C and stirred for 2 hours. 100ml of toluene and 100ml of water were added to the reactant to carry out extraction, then an organic layer was extracted for three times with 100ml of water, and the solvent was distillled off under a decreased pressure from the organic layer.

500ml of heptane was added to the residue and stirred, and the insolubles were filtered off. To it, 10ml of formic acid and

100ml of toluene were added and refluxed for 2 hours. The reactant was extracted with 200ml of toluene, washed with water for three times, and thereafter dried with anhydrous magnesium sulfate. The solvent was distilled off under a decreased pressure, to obtain 4,4 ^' -bis (5-oxo-l-pentenyl) bicyclohexane (0.007 mol) as a white solid.

A mixture of 4,4 ^' -bis (5-oxo-l-pentenyl) bicyclohexane (0.007 mol) , sodium chlorodifluoroacetate (0.01 mol) and 80ml of DMF was stirred for 2 hours within a range of 100 ~ 120 °C , to obtain a black solution. 200ml of heptane was added to carry out extraction, and an organic layer was washed twice with 100ml of water. The solvent was distilled off under a decreased pressure, and the residue was purified by a column chromatography (eluate: heptane) and recrystallization (benzene:ethanol = 1:1, twice) , to obtain the title compound (0.005 mol). Various spectra data thereof support the structure well. Example 3

The following compounds according to the formula (1) are prepared similar to Examples 1 and 2.

G = ( (A) -X,)n- ⁽ (jϊ - ₂ ⁾ π- ( } -X3- ζθ)

R, MG

F ⁿ 7 \\ // \ / \\

: ₂ H ₇ w // \_ _t

F

NC W //

F

^CH ₃ ^OCH ₂ →C^- -^I}- ^ / w

F C \\ X ^{^} \\ //

F

C ₃ H ₇ // \ ^\ CH ₂ CH ₂ ^ ^~ ^— \ / w

F

C ₃ H ₇ // \ CH = CH w

CF ₃ O // W

^" W /^CH ₂ CH ₂ - c

F

^C * ^H * - ^{~ "CH2C'} ^ \

F

/=

C ₃ nHπ TO- \

C ₃ H ₇ -Q- O-

F

F

CJ CJ CJ CJ CJ ro ro ro ro ro ro C) ro σ <o m Ul r-

Effect of the Invention

A compound according to the present invention shows very high elastic constant ratio K33/K11 and also shows extremely low viscosity. It has approximately same degree of high elastic constant ratio K33/K11 and lower viscosity compared to those of alkenyl compounds (17) described in Toku-Kai-Sho 61-83136 and Toku-Kai-Sho 61-56137 etc., which are used now mostly and have high elastic constant ratio K33/K11 and low viscosity.

Furthermore, the compound according to the present invention shows high stability and has sufficient chemical stability for use in a practical liquid crystalline composition.

By using the compound (1) according to the present invention with such superior characteristics, a liquid crystalline composition also with superior physical properties, namely sharp threshold value characteristics and rapid response speed, can be obtained.