Phenyldioxanes
The invention relates to Phenyldioxanes of the formula I ##STR3## wherein R 1  is an alkyl or alkenyl residue each with up to 16 C atoms, wherein one or two non-adjacent CH 2  groups of these residues may be replaced by --O--, --S--, --CO--O-- or --O--CO--, 
     Q 1  and Q 2  are each independently ##STR4## 
     L 1  and L 2  are each independently F or H, and 
     Y is Cl, F, CN, CF 3 , OCF 3  or OCF 2  H, 
     m and n are 0 or 1 
     with the provisos that 
     a) in the case m and n are O, L 1  is F and Y is Cl, F, --CF 3 , --OCF 3  or OCF 2  H or L 1  and L 2  are H and Y is Cl or F. 
     b) in the case that n is O, m is 1 and Q 1  is ##STR5## one of L 1  and L 2  is F and Y is Cl, F, CF 3 , OCF 3  or OCF 2  H, and 
     c) in the case that n is 1 and m is O and Q 2  is ##STR6## one of L 1  and L 2  is F or L 1  and L 2  are H and Y is Cl, --CF 3 , --OCF 3  or --OCF 2  H. 
     The compounds of the formula I can be used as components of liquid crystal media, in particular for displays which are based on the principle of the twisted nematic cell, including TN cells with a higher twist angle like STN, SBE, OMI etc., on the guest-host effect on the effect of deformation of orientated phases or on the effect of dynamic scattering. 
     Compounds similar to those of formula I are known from DE 29 44 905. These compounds comprising 2 rings but no terminal chlorine tend to reduce the mesophase range. 
     JP-57 064 689 describes ##STR7## 
     Compounds of the formula I with three rings and L=H or F are claimed in EP 0 087 679 and EP 0 154 840 via a very broad formula. There are, however, no specific examples for these compounds so that it may be stated that the surprisingly advantageous properties of these compounds have neither been realized nor used. 
     Similar phenyldioxanes with terminal OCF 3  -group but without ethyllinhage are known from WO 89 02 884. 
     WO 87/06602 describes ##STR8## and 
     WO 90/01056 describes ##STR9## 
     Furthermore ethyl-linked phenyldioxanes with a negative or neutral value of the dielectricity are known: ##STR10## 
     EP-0 154 840. 
     The invention was based on the object of discovering new stable liquid crystalline or mesogenic compounds which are especially suitable for active matrix displays without exhibiting the shortcomings of the prior art compounds. 
     Surprisingly, it has been found that the compounds according to formula I meet these criteria to an outstanding degree and allow the realization of a very high resistivity and simultaneously favorable electro-optic characteristics. These compounds also show a surprisingly good solubility at -20° C. in many LC base materials from other compound classes. 
     By providing the compounds of the formula I, the range of liquid crystal substances which are suitable, under various technological aspects for the preparation of nematic mixtures is also quite generally widened considerably. 
     The compounds of the formula I have a wide field of application and they are preferably added to liquid crystal base materials from other classes of compounds, for example in order to increase the clearing point while having little effect on other physical properties. 
     The compounds of the formula I are colourless in the pure state and form liquid crystal mesophases in a temperature range which is favorably placed for electrooptical use. They are sufficiently stable towards chemicals, heat and light. 
     The invention thus relates to the compounds of the formula I in particular to the compounds of the formula I1, ##STR11## wherein R 1 , Q 2 , L 1  and Y have the meaning given and Y is Cl or in the case that one of L 1  and L 2  is F also F, in particular, wherein Q 2  is 1,4-phenylene and n is 1 and Y is Cl, and furthermore to the compounds of the formula I2 ##STR12## wherein R 1 , L 2  and Y have the meaning given o is 0 or 1, and ##STR13## with the proviso that in the case that o is O Y is different form CN and one of L 1  and L 2  is F. 
     Furthermore the invention relates to the use of these compounds as components of liquid crystal media. The invention furthermore relates to liquid crystal media containing at least one compound of the formula I and to liquid crystal display elements, in particular electrooptical display elements, which contain media of this type. 
     The compounds of the formula I are in particular suitable as compounds of liquid crystal media for displays which are based on the principle of polymer dispersed (pdlc) or polymer network (pn) liquid crystals due to their favorable optical anisotropy and their dielectric anisotropy. 
     Above and below R 1  has the mentioned meaning, unless expressly stated otherwise. 
     The compounds of the formula I1 accordingly include compounds of the part formulae I1a to I1h: ##STR14## The compounds of the formulae I1c and I1d are particularly preferred. 
     The compounds of the formula I2 include ethyl-linked phenyldioxanes of the formula I2a to I2f: ##STR15## 
     Y is Cl, F, CN, CF 3  or OCF 3  ; in the laterally fluorinated compounds of the formulae I2c, I2d and I2f Y denotes preferably F, Cl or CN. 
     In the compounds of the formulae I2a, I2b and I2c Y denotes preferably Cl, CF 3  or OCF 3 . 
     The compounds of the formulae I2 include phenyldioxanes without ethyl-linkage of the formulae I2g to I2n: ##STR16## The compounds of the formulae I2g to I2j wherein ##STR17## are particularly preferred. 
     R 1  is preferably alkyl, alkoxy, oxaalkyl or alkenyl and can exhibit a straight-chain or branched structure. 
     Alkyl or alkoxy preferably are straight-chain and have 2, 3, 4, 5, 6 or 7 C atoms. Accordingly they are preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, also methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy. Oxaalkyl is preferably straight-chain 2-oxapropyl (=methoxymethyl), 2-(=ethoxymethyl) or 3-oxybutyl (=2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-, 7-, 8-, or 9-oxadecyl. 
     In the compounds of these formulae R 1  is preferably alkyl, furthermore also groups in which one CH 2  group is replaced by oxygen. 
     If R 1  is alkyl and/or alkoxy group, these can be straight-chain or branched. Preferably, they are straight-chain and have 2, 3, 4, 5, 6 or 7 C atoms and are accordingly preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, also methyl, octyl, nonyl, methoxy, octoxy or nonoxy. 
     The compounds of the formula I1a, wherein R 1  is Ethyl, n-Butyl, n-Pentyl or n-Hexyl, are particularly preferred. As a rule they are suitable to lower the threshold voltage of liquid crystal mixtures. 
     Oxaalkyl is preferably straight-chain 2-oxapropyl (=methoxymethyl), 2-(=ethoxymethyl) or 3-oxybutyl (=2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl or 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl. 
     Compounds of the formula I with branched terminal group R 1  can be of importance because of a better solubility in the customary liquid crystal base materials, but in particular as chiral doping substances if they are optically active. 
     Branched groups of this type as a rule contain not more-than one chain branching. Preferred branched groups are isopropyl, 2-butyl (=1-methylpropyl), isobutyl (=2-methylpropyl), 2-methylbutyl, isopentyl, (=3-methyl- butyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, 2-octyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 1-methylheptoxy (=2-octyloxy), 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl and 6-methyloctoxy. 
     In the case of compounds with branched terminal groups, formula I includes both the optical antipodes and racemates as well as mixtures thereof. 
     Of the compounds of the formula I and subformulae thereof, those in which at least one of the radicals contained therein has one of the preferred meanings given are preferred. 
     The compounds of the formula I are prepared by methods which are known per se, such as are described in the literature (for example in the standard works, such as Houben-Weyl, Methoden der Organischen Chemie Methods of Organic Chemistry, Gerog-Thieme-Verlag, Stuttgart), and in particular under reaction conditions which are known and suitable for the reactions mentioned. Variants which are known per se and are not mentioned in more detail here can also be used in this connection. 
     If desired, the starting substances can also be formed in situ, such that they are not isolated from the reaction mixture but are immediately reacted further to give the compounds of the formula I. 
     The preferred synthetic routes are shown in the following schemes I to III: ##STR18## 
     A preferred route for preparation of the ethyl-linked phenyldioxanes of the formula I2 is shown in the following scheme IV: ##STR19## 
     A preferred route for preparation of phenyldioxanes of the formula I2 without ethyl-linkage is shown in the following scheme V: ##STR20## 
     All starting materials are known or prepared in analogy to known starting materials. 
     All steps are fully conventional and the reaction conditions are known to the skilled worker. The starting materials are known or easily prepared in analogy to known materials. 
     Other methods of making compounds of formula I are apparent to those skilled in the art. 
     In addition to one or more compounds of formula I the liquid crystal media according to the invention preferably contain 2-40 components and in particular 4-30 components. Liquid crystal media being composed of one or more compounds of formula I and 7-25 other components are especially preferred. 
     These additional components are preferably chosen from the nematic or nematogenic (monotropic or isotropic) substances; in particular from the classes of azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl cyclohexanecarboxylates, phenyl or cyclohexyl cyclohexylbenzoates, phenyl or cyclohexyl cyclohexylcyclohexanecarboxylates, cyclohexylphenylbenzoates, cyclohexylphenyl cyclohexanecarboxylates, cyclohexylphenyl cyclohexylcyclohexanecarboxylates, phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexyleyclohexanes, cyclohexylcyclohexanes, cyclohexyleyclohexenes, cyclohexylcyclohexylcyclohexene, 1,4-bis-cyclohexylbenzenes, 4,4&#39;-bis-cyclohexylbiphenyls, phenyl- or cyclohexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- or cyclohexyldioxanes, phenyl- or cyclohexyl-1,3-dithianes, 1,2-diphenylethanes, 1,2-dicyclohexylethanes, 1-phenyl-2-cyclohexylethanes, 1-cyclohexyl-2-(4-phenyl-cyclohexyl)-ethanes, 1-cyclohexyl-2-biphenylethanes, 1-phenyl-2-cyclo- hexyl-phenylethanes, optionally halogenated stilbenes, benzyl phenyl ethers, tolanes and substituted cinnamic acids. 
     The 1,4-phenylene groups of these compounds may be fluorinated. 
     The most important compounds which are possible constituents of liquid crystal media according to the invention can be characterized by the formulae 1, 2, 3, 4 and 5: 
     
         R&#39;--L--E--R&#34;                                               1 
    
     
         R&#39;--L--COO--E--R&#34;                                          2 
    
     
         R&#39;--L--OOC--E--R&#34;                                          3 
    
     
         R&#39;--L--CH.sub.2 CH.sub.2 --E--R&#34;                           4 
    
     
         R&#39;--L--C--C--E--R&#34;                                         5 
    
     In the formulae 1, 2, 3, 4 and 5 L and E may be equal or different from each other. L and E independently from each other denote a bivalent residue selected from the group consisting of --Phe--, --Cyc--, --Phe--Phe--, --Phe--Cyc--, --Cyc--Cyc--, --Pyr--, --Dio--, --G--Phe--, --G--Cyc-- and their mirror images; in this compilation of residues Phe denotes unsubstituted or fluorinated 1,4-phenylen, Cyc trans- 1,4-cyclohexylene or 1,4-cyclohexenylen, Pyr pyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio 1,3-dioxane-2,5-diyl and G 2-(trans-1,4-cyclohexyl)-ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl. 
     One of the residues L and E is preferably Cyc, Phe or Pyr. E preferably denotes Cyc, Phe or Phe--Cyc. The liquid crystal media according to the invention preferably contain one or more components selected from the compounds of formulae 1, 2, 3, 4 and 5 with L and E meaning Cyc, Phe and Pyr, said liquid crystal media further containing at the same time one ore more components selected from the compounds of formulae 1, 2, 3, 4 and 5 with one of the residues L and E denoting Cyc, Phe and Pyr and the other residue being selected from the group consisting of --Phe--Phe--, --Phe--Cyc--, --Cyc--Cyc--, --G--Cyc--, said liquid crystal media containing in addition to this optionally one or more components selected from the compounds of formulae 1, 2, 3, 4 and 5 with L and E being selected from the group consisting of --Phe-Cyc--, --Cyc--Cyc--, --G--Phe-- and --G--Cyc. In a preferred subgroup of the compounds of formulae 1, 2, 3, 4 and 5 (subgroup 1) R&#39; and R&#34; are independently from each other alkyl, alkenyl, alkoxy, alkenoxy with up to 8 carbon atoms. R&#39; and R&#34; differ from one another in most of these compounds, one of the residues usually being alkyl or alkenyl. In another preferred subgroup of the compounds of formulae 1, 2, 3, 4 and 5 (subgroup 2) R&#34; denotes --CN, --CF 3 , --OCF 3 , --OCHF 2 , --F, --Cl or --NCS while R&#39; has the meaning indicated in subgroup 1 and is preferably alkyl or alkenyl. Other variants of the envisaged substituents in the compounds of formulae 1, 2, 3, 4 and 5 are also customary. Many such substances are commercially available. All these substances are obtainable by methods which are known from the literature or by analogous methods. 
     The liquid crystal media according to the invention preferably contain in addition to components selected from subgroup 1 also components of subgroup 2, the percentage of these components being as follows: 
     subgroup 1: 20 to 90%, in particular 30 to 90% 
     subgroup 2: 10 to 50%, in particular 10 to 50% 
     In these liquid crystal media the percentages of the compounds according to the invention and the compounds of subgroup 1 and 2 may add up to give 100%. 
     The media according to the invention preferably contain 1 to 40%, in particular 5 to 30% of the compounds according to the invention. Media containing more than 40%, in particular 45 to 90% of the compounds according to the invention are further preferred. The media contain preferably 3, 4 or 5 compounds according to the invention. 
     The media according to the invention are prepared in a manner which is customary per se. As a rule, the components are dissolved in one another, advantageously at elevated temperature. The liquid crystal media according to the invention can be modified by suitable additives so that they can be used in all the types of liquid crystal display devices. Such additives are known to the expert and are described in detail in the literature (H. Kelker/R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, it is possible to add pleochroic dyestuffs to prepare colored guest-host systems or substances for modifying the dielectric anisotropy, the viscosity and/or the orientation of the nematic phases. 
     The following examples are to be construed as merely illustrative and not limitative. m.p.=melting point, c.p.=clearing point. In the foregoing and in the following all parts and percentages are by weight and the temperatures are set forth in degrees Celsius. &#34;Customary work-up&#34; means that water is added, the mixture is extracted with methylene chloride, the organic phase is separated off, dried and evaporated, and the product is purified by crystallization and/or chromatography. 
     Further are: 
     C: crystalline-solid state, S: smectic phase (the index denoting the typ of smetic phase), N: nematic phase, Ch: cholesteric phase, I: isotropic phase. The number being embraced by 2 of these symbols denotes the temperature of phase change. 
    
    
     EXAMPLE 1 
     According to Scheme I given above 4-(5-propyldioxan-2-yl)-chlorobenzene is obtained from p-bromochlorobenzene and 2-(hydroxymethyl)-pentan-1-ol, C 72 I, Δε=8.6. 
     EXAMPLES 2 TO 20 
     The following compounds are prepared analogously 
     
         __________________________________________________________________________
R.sup.1      n Q.sup.2 L Y                                                
__________________________________________________________________________
(2)                                                                       
   C.sub.5 H.sub.11                                                       
             0 --      H Cl, K 66 I, Δε = 7.0               
(3)                                                                       
   C.sub.7 H.sub.15                                                       
             0 --      H Cl                                               
(4)                                                                       
   C.sub.3 H.sub.7                                                        
             0 --      F Cl, C 33 I, Δε = +11.8             
(5)                                                                       
   C.sub.5 H.sub.11                                                       
             0 --      F Cl, C 30 I, Δε = 9.5               
(6)                                                                       
   C.sub.7 H.sub.15                                                       
             0 --      F Cl                                               
(7)                                                                       
   C.sub.3 H.sub.7                                                        
             0 --      F F                                                
(8)                                                                       
   C.sub.5 H.sub.11                                                       
             0 --      H F, C 25 I, Δε = +7.7               
(9)                                                                       
   C.sub.7 H.sub.15                                                       
             0 --      H F, C 15 I, Δε = +6.9               
(10)                                                                      
   C.sub.3 H.sub.7                                                        
             1                                                            
                ##STR21##                                                 
                       H Cl                                               
(11)                                                                      
   C.sub.5 H.sub.11                                                       
             1                                                            
                ##STR22##                                                 
                       H Cl                                               
(12)                                                                      
   C.sub.7 H.sub.15                                                       
             1                                                            
                ##STR23##                                                 
                       H Cl                                               
(13)                                                                      
   C.sub.3 H.sub.7                                                        
             1                                                            
                ##STR24##                                                 
                       F Cl                                               
(14)                                                                      
   C.sub.3 H.sub.7                                                        
             1                                                            
                ##STR25##                                                 
                       H F                                                
(15)                                                                      
   C.sub.2 H.sub.5                                                        
             0 --      H Cl                                               
(16)                                                                      
   C.sub.4 H.sub.9                                                        
             0 --      H Cl                                               
(17)                                                                      
   C.sub.6 H.sub.13                                                       
             0 --      H Cl                                               
(18)                                                                      
    ##STR26##                                                             
             0 --      F Cl C 96 N 142 I, Δε = 10.3         
(19)                                                                      
   C.sub.3 H.sub.7                                                        
             1                                                            
                ##STR27##                                                 
                       H Cl                                               
(20)                                                                      
   C.sub.5 H.sub.11                                                       
             1                                                            
                ##STR28##                                                 
                       H Cl                                               
__________________________________________________________________________
 
    
     EXAMPLE 21 
     According to Scheme II given above 1-(4-chloro-3-fluorophenyl)-2-(4-(5-propyldioxane-2-yl)-phenyl)-ethane is obtained from 1-(4-chloro-3-fluorophenyl)-2-(4-bromophenyl)-ethane and 2-(hydroxymethyl)-pentan-1-ol. 
     EXAMPLES 22 TO 24 
     The following compounds are obtained analogously 
     
         ______________________________________                                    
R.sup.1    n      Q.sup.2          L    Y                                 
______________________________________                                    
(22)  C.sub.5 H.sub.11                                                    
               1                                                          
                       ##STR29##     F    Cl                              
(23)  C.sub.5 H.sub.11                                                    
               1                                                          
                       ##STR30##     H    Cl                              
(24)  C.sub.5 H.sub.11                                                    
               1                                                          
                       ##STR31##     F    F                               
______________________________________                                    
 
    
     EXAMPLE 25 
     According to Scheme III given above 1-(4&#39;-chloro-3&#39;-fluorobiphenyl-4-yl)-2-(5-propyldioxane-2-yl)-ethane is obtained from 3-(4&#39;chloro-3&#39;-fluorobiphenyl-4-yl)-proponaldehyde and 2-(hydroxymethyl)-pentan-2-ol. 
     EXAMPLES 26 TO 28 
     The following compounds obtained analogously: 
     
         ______________________________________                                    
R.sup.1    n      Q.sup.2          L    Y                                 
______________________________________                                    
(26)  C.sub.5 H.sub.11                                                    
               1                                                          
                       ##STR32##     F    Cl                              
(27)  C.sub.5 H.sub.11                                                    
               1                                                          
                       ##STR33##     H    Cl                              
(28)  C.sub.5 H.sub.11                                                    
               1                                                          
                       ##STR34##     F    F                               
______________________________________                                    
 
    
     EXAMPLE 29 
     Mixture (A) contains: ##STR35## and exhibits N 72 I, Δε+0.06, n=0.1139 
     Mixture (B) contains 90% of mixture (A) and 10% of ##STR36## and exhibits N 65.2 I, Δε=+1.04, Δn=0.1097. 
     EXAMPLE 30 
     Mixture (C) contains 90% of mixture (A) and 10% of ##STR37## and exhibity N 60.1 I, Δε=+1.24, Δn=0.1076. 
     EXAMPLE 31 
     Preparation of 1(trans-4-Propylcyclohexyl)-2-[-(4-chlorophenyl)-dioxane-5-yl]-ethane ##STR38## The trans-4-propylcyclohexylmethyleyanide (0.1 mole), NAOH (0.39 moles) and water (20 ml) are refluxed in digol (100 ml) for 30 hours. The reaction mixture is added, at 50° C., to water acidified and the product extracted into dichloromethane. The combined organic layers are washed with water, dried and the solvent removed. The crude acid is recrystallised from 7 vols of petrol ether (60-80˜). ##STR39## 
     A solution of the 2-(trans-4-propyleyclohexyl)- acetic acid (0.1 moles) of STEP 1 in ether (8.0 moles) is slowly added to a mixture of LiAlH 4  (0.211 moles) in dry ether (200 ml) at such a rate to give a gentle reflux. The mixture is then stirred for a further 3 hours. Excess LiAlH 4  is destroyed with ethyl acetate: ether (1:1) at 10° C. Dilute HCl is added and the product extracted into ether, washed with water and dried. After removal of the solvent the product was distilled under high vacuum. ##STR40## The (2-trans-4-propylcyclohexyl)-ethyl alcohol (0.1 moles) is refluxed in a mixture of HBr (50 ml) and H 2  SO 4  (10 ml). Water is added and the product extracted into dichloromethane. The crude bromide is distilled under high vacuum. ##STR41## To a solution of sodium ethoxide (made from Na in 70 ml IMS) is added diethyl malonate (0.105 moles), followed by the 2-(trans-4-propylcyclohexyl)-ethyl bromide (0.1 moles) of Step Three at 50° C. The mixture is refluxed for 4 hours and then the solvent removed. Water is added and the product extracted into ether and purified by distillation. ##STR42## The 2-(trans-4-propylcyclohexyl)-ethyl (0.1 moles) of STEP 3 in THF (50 ml) is slowly added to LiAlH 4  (0.114 moles) in THF (75 ml) at 40° C. under nitrogen. The mixture is refluxed for a further 4 hours and the excess LiAlH 4  is destroyed with dilute solution of water in THF. Sodium carbonate (12 g) in water (35 ml) is added at 80° C. After cooling to room temperature the solids are removed by filtration and the solvent removed. The product is then distilled under high vacuum. ##STR43## The 4-(trans-4-propylcyclohexyl)-2-(hydroxymethyl)-butane-2-ol (0.1 moles of STEP 5 is refluxed in toluene (220 ml) with the p-chloro-benzaldehyde (0.1 moles) and toluene sulphonic acid (0.8 g). Water being removed using a Dean Stark apparatus. After 3 hours at reflux the mixture is cooled and washed wit aq. NaHCO 3  then water, dried and the solvent evaporated. The crude product is chromatographed over silica gel and recrystallised from methanol. 
     EXAMPLES 32 TO 48 
     In place of the used trans-4-propylcyclohexylmethylcyanide and the p-chloro-benaldehyde other homologues cyclohexylmethyleyanides and benzaldehydes can be used for preparation of the following compounds in analogy to example 25: 
     
         ______________________________________                                    
 ##STR44##                                                                
       n           L.sup.1   Y                                            
______________________________________                                    
(32)     5             H         Cl                                       
(33)     7             H         Cl                                       
(34)     3             F         Cl                                       
(35)     5             F         Cl                                       
(36)     7             F         Cl                                       
(37)     3             F         F                                        
(38)     5             F         F                                        
(39)     7             F         F                                        
(40)     5             H         OCF.sub.3                                
(41)     5             H         CF.sub.3                                 
(42)     5             H         CN                                       
(43)     5             H         F                                        
(44)     5             F         OCF.sub.3                                
(45)     5             F         CF.sub.3                                 
(46)     3             F         CN                                       
(47)     5             F         CN                                       
(48)     7             F         CN                                       
______________________________________                                    
 
    
     EXAMPLE 49 
     Preparation of 1-(4-Pentyloxyphenyl)-2-[2-(4-cyanophenyl)]-ethane ##STR45## The 2-(4-Pentyloxyphenyl)-ethanol (0.1 moles/obtained from benzylcyanide in an analogous way to Example 1 STEP 1/2) is stirred in pyridine (35 ml) and toluene sulphonyl chloride (0.125 moles). Dilute HCl is added and the product is filtered under vacuum, washed with water and recrystallised from 2 volumes of methanol at 3° C. ##STR46## To a solution of sodium methoxide (made from Na in 7o ml (MS) is added diethyl malenate (0.105 moles), followed by the tosylate of STEP 1 (0.1 moles). The product is obtained analogously to Example 1 STEP 4. ##STR47## The diester (0.1 moles) of STEP 2 is reduced with LiAlH 4 , analogously to Example 1 STEP 5 and condensed with p-formylbenzonitrile (0.1 moles) with toluene sulphonic acid in a Dean and Stark trap in analogy to Example 1 STEP 6. 
     EXAMPLES 50 TO 70 
     In place of the used 2-(4-pentyloxyphenyl)-ethanol and p-formylbenzonitrile other homologue 2-phenylethanoles and benzaldehydes can be used for preparation of the following compounds in analogy to example 43: 
     
         ______________________________________                                    
 ##STR48##                                                                
Example     R.sup.1   L.sup.1 L.sup.2                                     
                                    Y                                     
______________________________________                                    
(50)        H.sub.7 C.sub.3                                               
                      H       H     CN                                    
(51)        H.sub.11 C.sub.5                                              
                      H       H     CN                                    
(52)        H.sub.7 C.sub.3 O                                             
                      F       H     CN                                    
(53)        H.sub.11 C.sub.5                                              
                      F       H     CN                                    
(54)        H.sub.11 C.sub.5                                              
                      H       F     CN                                    
(55)        H.sub.11 C.sub.5 O                                            
                      H       H     F                                     
(56)        H.sub.7 C.sub.3                                               
                      H       H     F                                     
(57)        H.sub.7 C.sub.3 O                                             
                      H       H     F                                     
(58)        H.sub.11 C.sub.5                                              
                      F       H     F                                     
(59)        H.sub.11 C.sub.5                                              
                      H       F     F                                     
(60)        H.sub.9 C.sub.4 O                                             
                      H       H     Cl                                    
(61)        H.sub.7 C.sub.3                                               
                      H       H     Cl                                    
(62)        H.sub.11 C.sub.5                                              
                      H       H     Cl                                    
(63)        H.sub.7 C.sub.3 O                                             
                      H       H     Cl                                    
(64)        H.sub.11 C.sub.5                                              
                      F       H     Cl                                    
(65)        H.sub.11 C.sub.5                                              
                      H       F     Cl                                    
(66)        H.sub.11 C.sub.5                                              
                      H       H     OCF.sub.3                             
(67)        H.sub.11 C.sub.5                                              
                      H       H     CF.sub.3                              
(68)        H.sub.11 C.sub.5                                              
                      H       F     OCF.sub.3                             
(69)        H.sub.11 C.sub.5                                              
                      F       H     CF.sub.3                              
(70)        H.sub.11 C.sub.5                                              
                      F       H     OCF.sub.3                             
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     EXAMPLE 71 
     Mixture (D) contains ##STR49## and exhibits N 69.1 I, V 90  2.24 Volt (measured in a 90° TN cell). 
     EXAMPLE 72 
     Mixture (E) contains ##STR50## and exhibits N 71 I, V 90  2.37 Volt (measured in a 90° TN cell). 
     EXAMPLE 73 
     Mixture (F) contains ##STR51## and exhibits 
     N 94 I, η 19.6 cSt, Δn 0.139 and V 90  of 2.809 Volts in a 240° STN cell.