MESOGENIC COMPOUNDS

Abstract: Mesogenic compounds with a omega -CF3-alkyl, omega -CF3-alkenyl or omega -CF3-alkinyl terminal group of formula (I), with the meaning of R, Z, Q, (a), (b), m, n and o being indicated in claim 1.

Description: - i - Mesogenic compounds The invention relates to mesogenic compounds with a ω~CF 3 - alkyl, ω-CF 3 -alkenyl or ω-CF 3 -alkinγl terminal group of formula I wherein R is a unsubstituted, a mono cyano or trifluoro- methyl substituted or a mono-, oligo- or polyha- logeno-substituted alkyl or alkenyl residue having 1 to 15 carbon atoms, or such a residue wherein one or more CH 2 groups are each indepen¬ dently replaced by -O-, -CO-, -C0-0-, -0-CO- or -0-CO-O- with the proviso that oxygen atoms are not directly attached to each other. the rings A and B independen ly are (a) a trans-1 . 4-cyclohexγlene group , wherein one or two non-adjacent CH 2 groups may also be replaced by -0- and /or -S- or one or two CH groups may also be replaced by N, SUBSTITUTE SHEET (b) a 1,4-phenylene group, wherein one or two CH groups may also be replaced by N, (c) a group selected from 1,4-bicyclo(2,2,2)oc- tylene, 1,4-cγclohexenylene, naphthalin~2,6- diyl and 1,3-cγclobutγlene, it being possible for groups (a) and (b) to be substituted by one or more of halogen, cyano or methyl, Z is independently from each other -C0-0-, -0-C0-, -CH 2 CH 2 -, -CH 2 0-, -0CH 2 -, -C-C-, -CH=N-, -N=CH- or a single bond, Q is a single bond, -CH=CH- or -C-C-, m is 1, 2 or 3, and n and o are independently from each other zero or integers of 1 to 10, with the proviso that in case Q is a single bond n + o > 1. The invention further relates to liquid crystalline media comprising at least two liquid crystalline components at least one of which being a compound of formula I, further to electro-optical systems containing such media and to the use of the compounds of formula I as components of liquid crystalline media. SUBSTITUTESHEET For simplicity, in the following text Phe is a 1,4-phenylene group, Cyc a trans-1.4-cyclohexγlene group, Che a 1,4-cyclo- hexenylene group, Dio a dioxane-2,5-diγl group, Dit a dithane-2.5-diγl group, Pyr a pyrimidine-l,5-diyl group, Pyd a pγridine-2,5-diγl group, Pyz a pγrazine-2,5-diyl group, Pyn a pyridazine-3,6-diγl group, Pip a piperidine-l,4-diyl group and Thp a tetrahydropyrane-2,5-diγl group. These groups may be substituted by one or more of halogen, cyano or methyl. The substituted groups are denoted by adding the chemical symbol of the substituent to the respective abbre¬ viation of the unsubstituted group. PheF, for example, means a 1,4-phenylene group monosubstituted by a F atom and Phe3F5F is a 3,5-difluoro-l,4-phenγlene group. The denotations for the unsubstituted and substituted groups include all constitutional isomers. The compounds of the formula I can be used as components of liquid crystal media, in particular for electrooptical systems and liquid crystal displays, based on the principle of the twisted nematic cell including cells with twist angles different from 90° (e.g. STN, SBE or OMI) , the guest- host effect, the effect of deformation of aligned phases or the effect of dynamic scattering. Due to their superior stability versus heat and light the compounds of formula I are especially suited for active matrix addressed displays. SUBSTITUTE SHEET The invention was based on the object of discovering new liquid crystal or mesogenic compounds being suited as components of liquid crystal media and especially exhibiting a broad mesophase range, a rather low viscosity, a high stability versus chemicals and thermal and electromagnetical energy, especially versus UV-light and light of the short wavelength range of the visible spectrum, advantageous values for the elastic constants, the optical and dielectric anisotropy, a good electrooptical and thermooptical response and a good miscibility with other, including known liquid crystal compounds. It has been found, that the compounds of formula I are outstandingly suitable as components of liquid crystalline media. In particular, liquid crystalline media having a broad mesophase range, a rather low viscosity and a high stability versus chemicals, heat and light and advantageous values of the optical and dielectric anisotropy can be prepared with the aid of these compounds. 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 liquid crystal media is moreover quite generally considerable extended. The compounds of the formula I have a wide range of appli¬ cation. Depending on the choice of the substitutents, these compounds can be used as base materials of which liquid crystal media are predominantly composed; however, compounds of the formula I can also be added to liquid crystal base materials of other classes of compounds, for example in SUBSTITUTESHEET order to vary the elastic constants, the dielectric and/or optical anisotropy and/or the viscosity and/or the phase range of such dielectric. The compounds of the formula I are furthermore suitable as intermediates for the preparation of other substances which can be used as constituents of liquid crystal dielectrics. The compounds of the formula I are colourless in the pure state and form liquid crystal mesophases in a temperature range which is favourably located for electrooptical use. They are very stable towards chemicals, heat and light and exhibit advantageous values for the optical and dielectric anisotropy, the elastic constants, the phase range and the viscosity and they exhibit a good electrooptical and thermo¬ optical response and a good miscibility with other liquid crystal compounds. The invention thus relates to compounds of the formula I and to the use of the compounds of the formula I as components of liquid crystalline media. The invention furthermore relates to liquid crystalline media containing at least one compound of the formula I and to liquid crystal displays containing such media. Above and below R, the rings A and B, Z, Q, m, n and o have the meaning given, unless expressly indicated otherwise. The compounds of the formula I accordingly include compounds with a ω-CF 3 -alkyl. a ω-CF 3 -alkenyl and a ω-CF 3 -alkinγl group according to formulae la, Ie and Ii SUBSTITUTESHEET these formulae comprise binuclear, trinuclear and tetranuc- lear compounds of the formulae Ia2-Ia4, Ie2-Ie4 and Ii2~Ii4. -<^^-Z-<J^B -(σϊ 2 ) n -(CH 2 ) 0 -CF 3 Ia2 R- A Z- T (CH 2 ) n -CH=CH- (CH 2 ) 0 ~CF 3 Ie2 RVA YZ VAYZ-/B (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 Ie3 R- A z- A Vz- A z B V (CH 2 ) n -CH) =CH-(CH 2 ) 0 -CF 3 Ie4 R- A Vz A Vz B Y (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 113 R-/ A Yz ■ A - A Yz - B V (CH 2 ) n -( C- (CH 2 ) C -CF 3 I i4 SUBSTITUTE SHEET In the compounds of the formulae la the CF 3 -group is not directly linked to ring B (n + o ≥ 1) and the chain length is preferably given via 1 < n + o ≤ 13 and in particular via 1 < n + o < 10. In the compounds of formulae le and li n and o are independently from each other 0-10 and, in particular, 0-7 and the chain length of the ω-CF 3 -alkenγl resp. ω-CF 3 - alkinyl group is preferably given via 0 < n + o < 12. In the compounds of the formulae la, le and li the ring A preferably denotes Cyc, Phe, PheF, PheF 2 , Dio, Che, Pym or Pyr and especially Cyc, Phe, Phe2F, Phe3F, Phe2F3F and Dio and Che; the ring B preferably is Cyc, Phe, PheF, PheF 2 , Dio and Che with PheF resp. PheF 2 preferably denoting Phe2F, Phe3F resp. Phe2F3F and Phe3F5F. The compounds of formulae la, le and li preferably contain not more than one of the radicals Dio, Dit, Pip, Bi, Pyn or Pyr. In the compounds of formulae la, le and li Z preferably denotes independently from each other a single bond, -C00-_ -00C-, -C-C- or -CH 2 CH 2 -, especially a single bond, -C00-, -OOC- or -CH 2 CH 2 - and, in particular, a single bond or -CH 2 CH 2 -. In case = 3 at least one Z preferably denotes a single bond. The compounds of formulae la, le and li preferably contain 2 or 3 rings. 4-ring compounds, however, are especially suited as high clearing point additives for liquid crystalline media. In order to increase their miscibility with other SUBSTITUTE SHEET liquid crystalline compounds and/or to decrease their flow viscosity compounds with 4 rings preferably contain at least one laterally substituted ring A or B and especially at least one group chosen from Phe2F, Phe3F, Phe2F3F and Phe3F5F. In the compounds of the formulae la, le and li, those stereoisomers in which the rings Cyc and Pip are trans-1,4- disubstituted and/or Dio and Dit are trans-2,5-disubstituted are preferred. Those of the formulae mentioned above and below which contain one ore more groups Dio, Dit, Pip, Pyd and/or Pyr include in each case the two 2,5-(Dio, Dit, Pyd or Pyr) or 1,4-position isomers (Pip) . Che comprises in each case 1,4-cγcloheχ-l-enγlene and l,4-cγcloheχ-3-enylene. In the compounds of the formulae la, le and li in which one of the rings represents a Pyd, Pyr or Pyz ring, R is prefer¬ ably alkyl or alkoxy. Compounds of the formulae la, le and li the ω-CF 3 terminal group of which exihibits an odd number of C atoms, that is an even number for n + o, are preferred; n + o in particular is 0, 2, 4 or 6. Secondly preferable n + o is odd and exhibits the values 1, 3, 5 and 7. The elastic constants of the compounds of the formule la, le and li can be influenced and optimized by varying the length of the side chain with the terminal CF 3 group; thus it is possible, for example, to provide compounds, resp. liquid crystalline media containing these compounds exhibiting improved values of the threshold voltage and/or the steepness of the electrooptical characte¬ ristic line. SUBSTITUTE SHEET The terminal substituent R in the compounds of formulae Ia2-Ia4, Ie2 _ Ie4 and Ii2-Ii4 preferably contains 1-13 C atoms and in particular 1-11 C atoms. It is also possible for one or more CH groups in R to be replaced. Preferably, only one CH 2 group is replaced by -0-, -CO-, -0C0-, -COO- or -0C00-, in particular by -0-, -CO-, -OCO- or -C00-. If R is an alkyl radical in which one ("alkoxy" or "oxaal- kyl") or two ("alkoxyalkoxy" or "dioxaalkyl") non-adjacent CH 2 groups can also be replaced by 0 atoms, it can be straight-chain or branched. Preferably, it is straight- chain, has 2, 3, 4, 5, 6 or 7 C atoms and is preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, pro- poxy, butoxy, pentoxy, hexoxy or heptoxy, or furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy, tetradecoxy or pentadecoxy. Oxaalkyl is preferably straight-chain 2-oxapropyl (= me- thoxymethyl) , 2- (= ethoxymethyl) or 3-oxabutγl (= 2-me- thoxymethyl, 2-, 3- or 4-oxapentγl, 2-, 3-, 4- or 5-oxa- hexyl, 2~, 3~, 4-, 5- or 6-oxaheptγl, 2~, 3-, 4-, 5-, 6- or 7-oxaoctγl, 2~, 3-, 4~, 5-, 6-, 7- or 8-oxanonyl, 2-, 3~, 4-, 5-, 6-, 7~, 8- or 9-oxadecyl, 1,3-dioxabutyl (=methoxy- methoxy) , 1,3-, 1,4-, 2,4-dioxapentγl, 1,3-, 1,4-, 1,5-, 2,4-, 2,5- or 3,5-dioxahexγl, 1,3-, 1,4-, 1,5-, 1,6-, 2,4-, 2,5-, 2,6-, 3,5-, 3,6- or 4,6-dioxaheptyl. SUBSTITUTE SHEET If R is an alkyl radical in which a CH 2 group is replaced by -O-CO or -C0-0-, this can be straight-chain or branched. Preferably, it is straight-chain and has 2 to 6 C atoms. It is accordingly in particular acetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetγloxγmethyl, propionyloxymethyl, butγrγloxymethyl, pentanoyloxymethyl, 2-acetyloxγmethγl, 2-propionγloxγethγl, 2-butγrγloxyethγl, 3-acetγloxγpropyl, 3-propionγloxyethγl, 2-butγryloxyethγl, 3-acetγloxγpropγl, 3-propionγloxγpropγl, 4-acetγloxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycar- bonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxycar- bonylmethyl, propoxγcarbonγlmethyl, butoxycarbonylmethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(pro¬ poxycarbonyl)ethyl, 3-(methoxycarbonyl)propy1, 3-(ethoxycar- bonyDpropyl or 4-(methoxycarbonyl)butyl. If R is a mono-, oligo- or polyhalogeno substituted alkyl radical, this can be straight-chain or branched. Preferably it is straight-chain, has 3-12 C atoms and is mono-, di~, tri- or tetrahalogenated, particularly preferably with F and/or Cl. R preferably is 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 2-fluoropropγl, 3,3,3-trifluoropropyl, 2,3-difluoropentγl, 2-chlorobutyl, 4,4,4-trifluorobutγl, 4,5-difluoropentγl, 5-fluorpentyl, 5,5-difluoropentγl, 5,5,5-trifluoropentyl, 5,5,5-trifluoro-3-fluoro-pentyl, 6,6,6-trifluorohexyl, 6-fluorohexyl. 6-chlorohexyl, 6,6-di- fluorohexyl, 6-fluorohexyl, 6-chlorohexγl, 6,6-difluoro¬ hexyl, 7,7,7-trifluoroheptγl, 3,5-difluoroheptyl, 7-chloro- heptyl, 7,7-dichloroheptγl, 8,8-difluorooctyl, 8,8,8-tri- fluorooctyl, 8-chlorooctγl and 9,9,9-trifluorononyl. SUBSTITUTESHEET "Symmetrical" compounds exhibiting identical terminal groups are furthermore preferred. Formulae la, le and li include both the racemates of these compounds and the optical antipodes as well as mixtures thereof. Amongst the compounds of the formulae la, le and li, those in which at least one of the radicals contained therein has one of the preferred meanings given are preferred. Compounds of formula I exhibiting for the unit R ( A /-Z- m -( B V— one of the following structures are preferred: a) Binuclear structures R-Cγc-Phe(F)- 12-1 R-Phe-PheF 2 - 12-2 R-Phe2F-Phe- 12-3 R-Phe-Cγc- 12-4 R-Phe3F-Phe- 12-5 R-Phe-Phe2F- I2~6 R-Phe-Phe3F- 12-7 R-PheF 2 -Phe- 12-8 R-Cγc-Cγc- 12-9 R-Cyc-Dio- 12-10 R-Phe-Dio- I2"ll R-Dio-Phe(F)- 12-12 su B sτrru T- E SH££ T R-Che-Phe (F) - 12-13 R-Phe-Che- 12-14 R-Cγc-Che- 12-15 R-Che-Cyc- 12-16 R-Cγc-COO-Phe (F) - 12-17 R-Cγc-CH 2 CH 2 -Phe (F) - 12-18 R-Phe-C-C-Phe (F) - 12-19 R-Cyc-OOC-Phe (F) - 12-20 R-Pγr-CH 2 CH 2 -Phe (F) - 12-21 R-Phe (F) -COO-Phe (F) - 12-22 R-PheF 2 -C00-Phe- 12-23 R-Pγn-Phe (F) - I 2-24 R-Pyr-Phe (F) - 12-25 R-Phe (F) -OOC-Phe (F) - 12-26 R-Phe-Phe- 12-27 R-Dio-Cyc- 12-28 Trinuclear structures R-Cyc-Cyc-Phe- 13-1 R-Cγc-Cyc-PheF- 13-2 R-Cyc-Cγc-PheF 2 - 13-3 R-Cγc-Cyc-Dio- 13-4 R-Cγc-Phe-Phe- 13-5 R-Cyc-PheF-Phe- 13-6 R-Cyc-Phe-PheF- 13-7 R-Cγc-Phe-PheF 2 - 13-8 R-Cγc-PheF-PheF- 13-9 R-Cγc-Cyc-Che- 13-10 R-Cyc-Che-Phe(F)- 13-11 SUBSTITUTESHEET R-Dio-Phe-Phe (F) - 13-12 R-Phe-Phe-Phe- 13-13 R-Phe-PheF-Phe- 13-14 R-Phe-Phe-PheF- 13-15 R-Phe-COO-Phe (F) -Phe (F) - 13-16 R-Phe-OOC-Phe (F) -Phe (F) - 13-17 R-Cγc-CH 2 CH 2 -Cyc-Cγc- 13-18 R-Cyc-Cyc-OOC-Cyc- 13-19 R-Cyc-Cγc-C00-Cγc- 13-20 R-Cγc-Pyr-Phe (F) - 13-21 R-Cyc-CH 2 CH 2 -Phe (F) -Phe (F) - 13-22 R-Dio-Phe-COO-Phe (F) - 13-23 R-Cyc-COO-Phe-Phe (F) - I 3-24 R-Pγr-PheF-Cγc- 13-25 R-Pγr-Phe-OCH 2 -Cyc- 13-26 R-Phe-COO-Phe (F) -COO-Phe (F) - 13-27 R-Phe-CH 2 CH 2 -Phe (F) -Phe (F) - 13-28 R-Cyc-Phe-C-C-Phe ( F) - I 3-29 R-Cγc-Cyc-CH 2 CH 2 -Phe- 13-30 R-Cyc-Cγc-CH 2 CH 2 -PheF- 13-31 R-Cyc-CH 2 CH 2 -Cyc-Phe ( F) - 13-32 R-Phe-Phe (F) -CH 2 CH 2 -Phe (F) - 13-33 R-Phe-CH 2 CH 2 -Phe (F) -PheF- 13-34 R-Cyc-Phe-Cyc- 13-35 R-Phe-Cγc-Cγc- 13-36 R-Phe-Phe-Cyc- 13-37 R-Phe-Phe-Dio- 13-38 SUBSTITUTE SHEET c) Tetranuclear structures R-Cγc-Phe-Phe-Cyc- 14-1 R-Cyc-PheF-Phe-Cγc- 14-2 R-Cγc-Phe-PheF-Cγc- 14-3 R-Cγc-Cyc-Cyc-Phe- 14-4 R-Cγc-Cyc-Cγc-PheF- 14-5 . R-Cγc-Cyc-Che-Phe (F) - 14-6 R-cγc-Cyc-Phe (F) -Dio- 14-7 R-Cyc-Cyc-Dio-Phe (F) - 14-8 R-Cyc-Cyc-COO-Phe (F) -Phe (F) - 14-9 R-Cγc-Cγc-CH 2 CH 2 -Phe (F) -Phe (F) - 14-10 R-Cγc-Cγc-CH 2 CH 2 -Cyc-Cγc- 14-11 R-Phe-Phe (F) -Phe- 14-12 Compounds of the formula I exhibiting one of the preferred structures 12-1 - 12-27, 13-1 - 13-34 and 14-1 - 14-12 are preferred. These compounds comprise binuclear, trinuclear and tetranuclear compounds with one of the terminal groups being in each case a ω-CF 3 -alkyl group, a ω-CF 3 -alkenγl group or a ω-CF 3 -alkinγl group. The compounds according to formula I with a ω-CF 3 -alkyl, ω-CF 3 -alkenγl or e_-CF 3 -alkinγl group and especially with a ω-CF 3 -alkγl or a ω-CF 3 -alkenγl group are chemically very stable and they exhibit a high temperature and UV stability superior to that of cyano compounds for example. SUBSTITUTESHEET The compounds of formula I with a ω _ CF 3 -alkyl, ω-CF 3 -alkenγl or ω-CF 3 -alkinyl group are further characterized by a rela¬ tively high or even high dielectric anisotropy. These compounds are therefore very well suited as components of liquid crystalline media which are used in displays based on the principle of the twisted ne atic cell. The term twisted nematic cell is used here in a wide sense and comprises cells with twist angles ranging from 0° to 360° such as, for example, TN (twisted nematic) , supertwisted nematic (STN) , supertwisted birefringence (SBE) or low twisted nematic (LTN, β < 90°) cells. Due to their high stability the ω~CF 3 - alkyl, ω-CF 3 -alkenyl and ω-CF 3 -alkinyl compounds are especially preferred for active matrix addressed displays. It is also possible, however, for these compounds to be used in displays based on the guest-host effect, the effect of deformation of aligned phases or the effect of dynamic scattering. ω-CF 3 -alkγl, ω-CF 3 -alkenγl and ω-CF 3 -alkinyl compounds exhibiting the binuclear or trinuclear structures of formu- lae 12-1 - 12-27 and 13-1 - 13-34 are preferred; the tetra¬ nuclear compounds with the structures 14-1 - 14-11 are secondly preferred. The properties of the ω-CF 3 -alkyl, ω-CF 3 -alkenyl and ω~CF 3 - alkinyl compounds according to formula I can be varied to a great extent and readily be optimized with respect to the intended application by properly chosing the rings A and B. SUBSTITUTESHEET ω-CF 3 -alkyl, ω-CF 3 -alkenγl and ω-CF 3 -alkinyl compounds and especially ω _ CF 3 -alkyl compounds with the structures I2~9, 12-10, 12-15, 12-16, 13-1 - 13-4, 13-10, 13-11, 13-18 - 13-20, 13-30 - 13-32, 14-4 - 14-8 and 14-11, for example, are characterized by rather low or even low values of the optical anisotropy. These compounds are well suited, for example, for liquid crystalline media for TN displays being operated under the so-called first-minimum condition and especially for low~Δn- TFT applications. Contrary to these compounds with a ω-CF 3 -alkyl, a ω~CF 3 -al- kenyl and a ω-CF 3 -alkinyl group being composed of aromatic rings mainly or exclusively such as, for example, compounds exhibiting the structures 12-2, 12-3, 12-5 - 12-8, 12-19, 12-21 - 12-26, 13-13 - 13-17, 13-27, 13-28, 13-33, 13-34 and 14-12 are generally characterized by rather high or even high values of Δn. Especially preferred for high-Δn appli¬ cations are compounds with a ω-CF 3 -alkenγl or a ω-CF 3 ~al- kinyl terminal group and one of the preferred high-Δn structures enumerated above. 0--CF 3 -alkyl compound exhibiting a 3-fluoro- or a 3,5-di- fluoro _ l,4-phenylene group for the rings A and/or B are usually characterized by high or even very high values of the dielectric anisotropy and can be used to increase the dielectric anisotropy and hence to lower the threshold voltage of liquid crystalline media. SUBSTITUTE SHEET The threshold voltage is further influenced by the elastic constants of the liquid crystalline compounds. The threshold voltage of a TN structure, for example, is given via k' 1/2 V th = π ( ) ε 0 Δε wherein ε 0 is the dielectric constant of the vacuum. Δε is the dielectric anisotropy of the liquid crystal and k' denotes an elastic constant primarily dependent on the splay elastic constant k n . Since the dioxane-2,5-diyl group, for example, exhibits rather low values for k n the compounds of formulae 12-10, 12-11, 13-4, 14-7 and 14-8 are advanta¬ geously used for low threshold voltage TN displays. The elastic constants of the ω _ CF 3 -alkyl compounds can further be modified to a great extent by varying the chain length of the ω-CF 3 -alkyl group -(CH 2 ) n -(CH 2 ) 0 -CF 3 or the position of the double bond resp. the triple bond in the ω-CF 3 -alkenyl resp. ω-CF 3 ~alkinyl terminal group and/or the chain length of these terminal groups: -(CH 2 ) n -CH=CH-(CH 2 ) 0 -CF 3 -(CH 2 ) n -C*C-(CH 2 ) 0 -CF 3 SUBSTITUTE SHEET Thus it is possible to optimize the elastic properties of the ω-CF 3 -alkyl, the ω-CF 3 -alkenγl and the ω-CF 3 -alkinγl compounds not only for TN applications which were merely considered as an example but also for other applications. Compounds of the formula I wherein one terminal group is a ω-CF 3 -alkyl, ω-CF 3 -alkenyl or a ω-CF 3 -alkinγl group and the other terminal group is a straight-chain or not more than a singly branched alkyl or alkoxy group with 1-12, in particu¬ lar 2-10 C atoms are especially preferred. In the compounds of formula I n preferably denotes 0-8, particularly 0-6 and is preferably even. Compounds exhibiting an odd number for n are secondly preferred. The following smaller group of compounds of formula I with a ω-CF 3 -alkyl terminal group in which Phe-F is 1,4-phenγlene which is substituted in 2- or 3-position, PheF 2 is 1,4- phenyleπe which is substituted in 2- and 3- or 3- and 5-position and in which the other abbreviations have the meaning indicated above are particularly preferred. In these compounds alkyl is preferably unsubstituted straight-chain methyl, ethyl, propyl, butyl, pentyl and hexyl. Alkoxy is preferably unsubstituted straight-chain methoxy, ethoxy, propoxy, butoxy, pentoxy and hexoxy. Alkanoyloxy is prefer¬ ably unsubstituted straight-chain acetoxy, propanoyloxy, butanoyloxy, pentanoyloxy and hexanoyloxy. If the alkyl, alkoxy or alkanoyloxy groups are substituted they are preferably fluorinated. Especially preferred are those SUBSTITUTESHEET groups exhibiting a terminal trifluorinated C atom, n is preferably 1, 2, 3, 4 and 5, particularly preferably 1, 2 and 3 and especially 2. I . alkyl-Phe-Phe-(CH 2 )„-(CH 2 ) 0 -CF 3 alkyl-Phe-PheF-(CH 2 )„-(CH 2 ) 0 -CF 3 alkyl-PheF-Phe-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkyl-Phe-PheF 2 -(CH 2 )„-(CH 2 ) 0 -CF 3 alkoxy-Phe-Phe-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkoxy-Phe-PheF-(CH 2 ) n -(CH 2 ) 0 -CF 3 I. alkyl-Cyc-Phe-(CH 2 ) _-(CH 2 ) 0 -CF 3 alkyl-Cyc-PheF-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkoxy-Cyc-Phe-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkanoyloxy-Cyc-Phe-(CH 2 )„-(CH 2 ) 0 -CF 3 alkyl-Phe-Cyc-(CH 2 ) a -(CH 2 ) 0 -CF 3 alkyl-PheF-Cyc-(CH 2 ) B -(CH 2 ) 0 -CF 3 alkoxy-Phe-Cyc-Phe-Cyc-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkanoyl-Phe-Cyc-Phe-Cyc-(CH 2 ) B -(CH 2 ) 0 -CF 3 II. alkyl-Phe-COO-Phe-(CH 2 ) B -(CH 2 ) 0 -CF 3 alkyl-Phe-COO-PheF-(CH 2 )„-(CH 2 ) 0 ~CF 3 alkyl-Phe-C00-PheF 2 -(CH 2 ) n -(CH 2 ) 0 -CF 3 alkoxy-Phe-COO-Phe-(CH 2 ) n ~(CH 2 ) 0 -CF 3 SUBSTITUTESHEET IV . alkγl-Cyc-CH 2 CH 2 -Phe- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxγ-Cyc-CH 2 CH 2 -Phe- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkyl-Cγc-CH 2 CH 2 -PheF- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxγ-Cγc-CH 2 CH 2 -PheF- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkyl-Cyc-CH 2 CH 2 -Che- ( CH 2 ) n - ( CH 2 ) 0 -CF 3 alkγl-Cyc-CH 2 CH 2 -Dio- (CH 2 ) n - (CH 2 ) 0 -CF 3 V. alkyl-Cyc-Cyc- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxy-Cyc-Cyc- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkanoyloxy-Cyc-Cyc- (CH 2 ) n - (CH 2 ) 0 -CF 3 VI . alkyl-Cyc-Che- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxy-Cyc-Che- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkanoyloxy-Cyc-Che- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkyl-Cyc-Dio- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxy-Cyc-Dio- (CH 2 ) _.- (CH 2 ) 0 -CF 3 alkanoyloxy-Cyc-Dio- (CH 2 ) n - (CH 2 ) 0 -CF 3 VII . alkyl-Cyc-COO-Phe- (CH 2 ) n - (CH 2 ) 0 ~CF 3 alkyl -Cyc-COO-PheF- (CH 2 ) π - (CH 2 ) 0 -CF 3 alkyl-Cyc-C00-PheF 2 - (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxy-Cyc-COO-Phe- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxγ-Cγc-C00-PheF- (CH 2 ) n - ( CH 2 ) 0 -CF 3 alkanoγloxγ-Cγc-C00-Phe- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkanoγloxγ-Cγc-C00-PheF- (CH 2 ) n - (CH 2 ) 0 ~CF 3 SUBSTITUTE SHEET VIII . alkyl-Cγc-CH 2 CH 2 -Phe-Phe-(CH 2 )„-(CH 2 ) 0 -CF 3 alkyl-Cγc-CH 2 CH 2 -Phe-PheF-(CH 2 ) B -(CH 2 ) 0 -CF 3 alkoxy-Cyc-CH 2 CH 2 -Phe-Phe-(CH 2 ) B -(CH 2 ) 0 -CF 3 alkoxγ-Cγc-CH 2 CH 2 -Phe-PheF-(CH 2 ) B -(CH 2 ) 0 -CF 3 IX. alkγl-Cγc-Cyc-Phe-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkoxy-Cγc-Cγc-Phe-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkanoγloxγ-Cγc-Cyc-Phe-(CH 2 )„-(CH 2 ) C -CF 3 alkyl-Cγc-Cγc-PheF-(CH 2 ) B -(CH 2 ) 0 -CF 3 alkoxy-Cγc-Cγc-PheF-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkγl-Cγc-Cγc-PheF 2 -(CH 2 ) n -(CH 2 ) 0 -CF 3 alkoxγ-Cγc-Cγc-PheF 2 -(CH 2 ) n -(CH 2 ) 0 -CF 3 alkyl-Cγc-Cγc-Che-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkγl-Cyc-Cγc-Dio-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkyl-Cyc-Cyc-Cyc-(CH 2 ) B -(CH 2 ) 0 -CF 3 alkoxy-Cyc-Cyc-Cγc-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkyl-Cyc-Phe-Cyc- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxy-Cyc-Phe-Cyc- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkanoγloxγ-Cγc-Phe-Cyc- (CH 2 ) B - (CH 2 ) 0 -CF 3 alkyl-Phe-Phe-Cyc- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxy-Phe-Phe-Cyc- ( CH 2 ) n - ( CH 2 ) 0 -CF 3 alkanoyloxy-Phe-Phe-Cyc- (CH 2 ) B - (CH 2 ) 0 -CF 3 alkyl -Phe-Cyc-Cyc- (CH 2 ) B - (CH 2 ) 0 -CF 3 alkoxy-Phe-Cyc-Cyc- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkanoyloxy-Phe-Cyc-Cyc- (CH 2 ) n - (CH 2 ) 0 ~CF 3 SUBSTITUTE SHEET alkyl-Cyc-Phe-Dio-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkoxy-Cyc-Phe-Dio-(CH 2 ) B -(CH 2 ) 0 -CF 3 alkanoyloxy-Cyc-Phe-Dio-(CH 2 ) B -(CH 2 ) 0 -CF 3 X. alkyl-Cyc-Phe-Phe-(CH 2 ) B -(CH 2 ) 0 -CF 3 alkyl-Cyc-Phe-PheF-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkyl -Cyc-PheF-Phe- (CH 2 ) _- (CH 2 ) 0 -CF 3 alkoxy-Cyc-Phe-Phe- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkanoγloxγ-Cyc-Phe-Phe- (CH 2 ) n - (CH 2 ) 0 "CF 3 XI . alkγl-Phe-Phe-OOC-Phe- (CH 2 ) B - (CH 2 ) 0 -CF 3 alkyl-Phe-Phe-OOC-PheF- (CH 2 ) B - (CH 2 ) 0 -CF 3 alkyl-Phe-PheF-OOC-Phe- (CH 2 ) B - (CH 2 ) 0 -CF 3 alkoxy-Phe-Phe-OOC-Phe- (CH 2 ) B - (CH 2 ) 0 -CF 3 alkoxy-Phe-Phe-OOC-PheF- (CH 2 ) B - (CH 2 ) 0 -CF 3 XI I . alkyl-Cyc-Cyc-COO-Phe- (CH 2 ) B - (CH 2 ) 0 -CF 3 alkγl-Cγc-Cyc-COO-PheF- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxy-Cyc-Cyc-COO-Phe-(CH 2 ) B -(CH 2 ) 0 -CF 3 alkoxγ-Cyc-Cγc-C00-PheF 2 -(CH 2 ) n -(CH 2 ) 0 -CF 3 alkanoyloxy-Cyc-Cyc-COO-Phe-(CH 2 ) B -(CH 2 ) 0 -CF 3 XIII. alkyl-Cyc-Phe-COO-Phe-(CH 2 ) _-(CH 2 ) 0 -CF 3 alky1-Cγc-Phe-COO-PheF-(CH 2 ) n -(CH 2 ) 0 -CF 3 alkyl-Cγc-Phe-C00-PheF 2 -(CH 2 ) B -(CH 2 ) 0 -CF 3 alkoxy-Cyc-Phe-COO-Phe-(CH 2 ) n -(CH 2 ) 0 -CF 3 SUBSTITUTESHEET alkoxy-Cγc-Phe-COO-PheF- (CH 2 ) B - (CH 2 ) 0 -CF 3 alkanoγloxγ-Cyc-Phe-COO-Phe- (CH 2 ) B - (CH 2 ) 0 -CF 3 alkanoγloxy-Cγc-Phe-COO-PheF- (CH 2 ) B - (CH 2 ) „-CF 3 XIV . alkyl-Phe-COO-Phe-COO-Phe- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkyl-Phe-COO-Phe-COO-PheF- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxγ-Phe-COO-Phe-COO-Phe- (CH 2 ) „- (CH 2 ) 0 -CF 3 alkoxy-Phe-COO-PheF-COO-Phe- (CH 2 ) n - (CH 2 ) 0 -CF 3 XV. alkyl -Cγc-Cγc-CH 2 CH 2 -Phe- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkγl-Cyc-Cyc-CH 2 CH 2 -PheF- (CH 2 ) _- (CH 2 ) 0 -CF 3 alkγl-Cyc-Cyc-CH 2 CH 2 -PheF 2 - (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxγ-Cyc-Cyc-CH 2 CH 2 -Phe- (CH 2 ) n - (CH 2 ) 0 -CF 3 alkoxy-Cγc-Cyc-CH 2 CH 2 -PheF- (CH 2 ) B - (CH 2 ) 0 -CF 3 alkanoγloxy-Cyc-Cyc-CH 2 CH 2 -Phe- (CH 2 ) B - (CH 2 ) 0 -CF 3 alkanoγloxγ-Cγc-Cyc-CH 2 CH 2 -PheF- (CH 2 ) n - (CH 2 ) 0 -CF 3 The following compounds with at least one ω-CF 3 -alkyl termi¬ nal group F R-<D 0 >-< 0 WΦ 0 CH, 2 )/ B - ( vO»-" 2 )y R I) " (Σ/ "< G-/ (cHz) n_ (cHz) ° ~cFa R K-v' CC > >--CCHH 22 CCHH 22 --<( 00 ( 00 \_- (CH 2 ) n - (CH 2 ) 0 ~CF 3 SUBSTITUTE SHEET wherein R is alkyl or alkoxy with 1-7 C atoms or (CH 2 ) n - (CH 2 ) 0 -CF 3 , n + o is 1, 2, 3 or 4, especially however 2 and -( C r is -( 0 V or ■ < are especially preferred. Especially preferred are further the following compounds: R /- -C-k- n~ <CH 2 ) 0 -CF 3 (F) "-' >-(__)- -(CH 2 ) -CF (F) (F) R- (H T -) P ^__ - (CH 2 ) n - (CH 2 ) 0 -CF 3 0 SUBSTITUTE SHEET R ^-0 >" (cHz) ° ~ (c " 2) ° ~cF3 R"- (_/ M \_/~ (CH 2 ) -- (CH 2> o-CF 3 R - ~_)~\^) ' ( CH 2 } π~ ( CH 2 ) ° "CF 3 (F) wherein R is alkyl or alkoxy with 1-8 C atoms, n + o is 1-6, especially however 2, 3 or 4, p is 1 or 2, and SUBSTITUTE SHEET is unsubstituted or laterally monofluorinated 1.4-phenylene. In the compounds of formula I with a ω~CF 3 -alkenγl or a ω-CF 3 -alkinγl terminal group the position of the ethenylene or ethinylene group can be varied along the ω-CF 3 -chain. Thus it is possible to modify and optimize physical parame¬ ters like for example the elastic constants and/or the birefringence and/or the phase transition temperatures and/or other parameters with respect to the intended appli¬ cation. The presence of the triple bond in the ω-CF 3 -ethinylene compounds is important, as it can lead to a high birefrin¬ gence of the liquid crystal phase. For such reasons com- pounds are preferred in which n and o are both 0, or n is 0 and m is 1 are preferred, as it is found that when the CF 3 -group is directly linked to the ethine group the latter is stabilized. Liquid crystalline compounds having a high birefringence are particularly suitable for use in a number of types of application, for example those which exploit the electri¬ cally controlled birefringence (ECB) effect (see for example M.F. Schieckel and K. Fahrenshon "App. Phys. Lett. (1971) . 19, 3912") . Such compounds are also of value in other types of known liquid crystal material, such as those intended for use in thin film transistor (TFT) or supertwist twisted SUBSTITUTE SHEET nematic (STN) display devices. Many materials of these types, intended for such applications, and with which compounds of formula I may usefully be mixed, are known. Compounds with a ω-CF 3 -alkenyl group comprise both the (E) and (Z)-homologues (E) -isomer (Z)-isomer Compounds with a ω-CF 3 -alkenyl group are often characterized by especially advantageous values of the elastic constants, the birefringence and/or the phase transition temperatures and these compounds are therefore preferred. Especially preferred are e>-CF 3 -alkenγl terminal groups with the follow- ing values for n, o and n + o: S UBSTITUTESHEET n n + o 0 1 1 2 2 3 3 4 5 6 2 0 2 2 1 3 2 2 4 2 4 6 3 0 3 3 1 4 3 2 5 4 0 4 4 1 5 4 2 6 4 3 7 The following smaller groups of compounds of formula I with a ω-CF 3 -alkenyl resp. a ω-CF 3 -alkinyl group, wherein the meaning of PheF, PheF 2 , Che, Dio and Cyc is indicated above, R is an alkyl-, alkoxy-, alkanoyloxy- or alkoxycarbonyl group with 1-10 and especially 1-7 C atoms and n + o is preferably 1-7, especially however 1, 2, 3, 4 and 5, are preferred. XVII R-Cγc-Cγc-(CH 2 ) n -CH=CH-(CH 2 ) 0 -CF 3 R-Cγc-Che-(CH 2 ) n -CH=CH-(CH 2 ) 0 -CF 3 R-Cyc-Dio-(CH 2 ) -CH=CH-(CH 2 ) -CF 3 XVI11. R-Cyc-Phe-(CH 2 ) n ~CH=CH-(CH 2 ) 0 -CF 3 R-Cγc-PheF-(CH 2 )_.-CH=CH-(CH 2 ) 0 -CF 3 R-Cγc-PheF 2 -(CH 2 ) n -CH=CH~(CH 2 ) 0 -CF 3 R-Phe-Cγc-(CH 2 ) n -CH=CH-(CH 2 ) _-CF 3 SUBSTITUTESHEET IXX. R-Phe-Phe- (CH 2 ) B -CH=CH- (CH 2 ) _-CF 3 R-Phe-PheF- (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 XX . R-Cyc-CH 2 CH 2 -Cγc- ( CH 2 ) _.-CH=CH- ( CH 2 ) 0 -CF 3 R-Cyc-CH 2 CH 2 -Phe- (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 R-Cyc-CH 2 CH 2 -PheF- ( CH 2 ) n -CH=CH- ( CH 2 ) 0 -CF 3 R-Cyc-CH 2 CH 2 -Dio- (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 XXI . R-Cγc-Cγc-Phe- ( CH 2 ) n -CH=CH- ( CH 2 ) 0 -CF 3 R-Cyc-Cyc-PheF- (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 R-Cγc-Cγc-PheF 2 - (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 R-Cyc-Cγc-Che- ( CH 2 ) n -CH=CH- ( CH 2 ) 0 -CF 3 R-Cyc-Cγc-Dio- (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 R-Cyc-Phe-Cyc- (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 R-Phe-Phe-Cyc- (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 R-Phe-Cyc-Cγc- (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 XXI I . R-Cyc-Phe-Phe- ( CH 2 ) n -CH=CH- ( CH 2 ) 0 -CF 3 R-Cyc-PheF-Phe- (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 R-Cγc-Phe-PheF- (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 XXI I I . R-Cyc-CH 2 CH 2 -Phe-Phe- ( CH 2 ) n -CH=CH- ( CH 2 ) 0 -CF 3 R-Cγc-CH 2 CH 2 -Phe-PheF- (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 R-Cγc-CH 2 CH 2 -Che-Phe- (CH 2 ) n -CH=CH- ( CH 2 ) 0 -CF 3 XXIV . R-Phe-Phe- (CH 2 ) n -C=C- (CH 2 ) _-CF 3 R-Phe-Phe2F- (CH 2 ) n "C-C- (CH 2 ) 0 -CF 3 R-Phe-Phe3F- (CH 2 ) n -C (CH 2 ) 0 -CF 3 SUBSTITUTE SHEET R-Phe2F-Phe- (CH 2 ) n ~C-C- (CH 2 ) 0 -CF 3 R-Phe3F-Phe- (CH 2 ) n -0=C- (CH 2 ) 0 -CF 3 R-Phe2F3F-Phe- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 R-Phe-Phe2F3F- (CH 2 ) n -OC- (CH 2 ) 0 -CF 3 XXV. R-Pyr-Phe- (CH 2 ) n -OC- (CH 2 ) 0 -CF 3 R-Pyr-PheF- ( CH 2 ) n ~OC- (CH 2 ) C -CF 3 R-Pyd-Phe- (CH 2 ) n -0-C- (CH 2 ) 0 -CF 3 R-Pyd-PheF- (CH 2 ) a -0-C- (CH 2 ) 0 -CF 3 XXVI . R-Phe (F) -OOC-Phe (F) - (CH 2 ) n -OC- (CH 2 ) 0 -CF 3 R-Phe (F) -COO-Phe (F) - (CH 2 ) n -OC- (CH 2 ) 0 -CF 3 XXVII . R-Cyc-Phe- (CH 2 ) B -C-C- (CH 2 ) 0 -CF 3 R-Phe-Cyc- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 R-Che-Phe- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 R-Phe-Dio- (CH 2 ) n -C=C- (CH 2 ) 0 -CF 3 XXVIII . R-Cyc-Phe-Phe- (CH 2 ) n -C*C- (CH 2 ) 0 -CF 3 R-Cγc-Phe-PheF- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 R-Cyc-PheF-Phe- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 R-Cyc-Phe-Cγc- (CH 2 ) n -C-C- (CH 2 ) 0 ~CF 3 R-Phe-Cyc-Cγc- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 R-Phe-Phe-Cγc- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 SUBSTITUTE SHEET XXIX. R-Phe-Phe2F-Phe- (CH 2 ) n ~C-C- (CH 2 ) 0 -CF 3 R-Phe-Phe3F-Phe- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 R-Phe-Phe-PheF- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 R-Phe-Phe-PheF 2 - (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 R-Phe-Phe-Phe- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 XXX. R-Cyc-Cyc-Phe- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 R-Cyc-Cγc-PheF- (CH 2 ) n ~C-C- (CH 2 ) 0 -CF 3 R-Cyc-Che-Phe- (CH 2 ) B -0-C- (CH 2 ) 0 -CF 3 XXXI . R-Phe-CH 2 CH 2 -Phe- ( CH 2 ) n -C-C- ( CH 2 ) 0 -CF 3 R-Phe-CH 2 CH 2 -PheF- (CH 2 ) n -0-C- (CH 2 ) 0 -CF 3 XXXII . R-Phe-COO-Phe- (CH 2 ) B -C«C- (CH 2 ) 0 -CF 3 R-Phe-COO-PheF- (CH 2 ) B -C-C- (CH 2 ) 0 -CF 3 R-Phe-OOC-Phe- (CH 2 ) n -OC- (CH 2 ) 0 -CF 3 R-Phe-OOC-PheF- (CH 2 ) n -C-C- (CH 2 ) 0 "CF 3 R-Phe-OOC-PheF 2 - (CH 2 ) n -OC- (CH 2 ) 0 ~CF 3 XXXI 11 . R-Cyc-CH 2 CH 2 -Phe2F-Phe- ( CH 2 ) n -OC- ( CH 2 ) 0 -CF 3 R-Cγc-CH 2 CH 2 -Phe3F-Phe- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 R-Cyc-CH 2 CH 2 -Phe-Phe2F- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 R-Cγc-CH 2 CH 2 -Phe-Phe3F- (CH 2 ) n -C-C- (CH 2 ) 0 -CF 3 The following ω _ CF 3 -alkinyl compounds SUBSTITUTE SHEET R-Phe-00C-Phe-C-C-CF 3 R-Phe-C00-Phe-C-C-CF 3 R-Phe-Phe-C-C-CF 3 wherein R is alkyl or alkoxy with 1-7 C atoms and the 1,4-phenylene groups may be unsubstituted or laterally mono- or difluo- rinated, exhibit especially advantageous properties; these compounds are furthermore preferred from the point of view of ease of preparation. The following ω _ CF 3 -alkinyl compounds R-( 0 Y( 0 Y(CH 2 ) 0 -C=C-(CH 2 ) B -CF 3 (CH 2 ) B -CF 3 (F) R-< 0 -C C0000--< 00 -(CH 2 ) 0 -C-C-(CH 2 ) n -CF 3 which have strong nematic tendencies are preferred . SUBSTITUTE SHEET In the ω-CF 3 -alkinγl compounds of classes XXV-XXXII the 1,4-phenylene groups may be laterally substituted and if so mono- or difluoro substitution is preferred as this can increase the birefringence of the compound in the liquid crystal phase. Especially preferred are further the following ω-CF 3 -alkenyl compounds of formula I (F) R- (- V-) (CH 2 ) 0 -CF 3 0 (F) R_< G_)v__/ ~ (cHz) ° _CH=CH" (CH2} ° _cF3 (F) R *-< C->τv 7-. (CH 2 ) n -CH=CH- (CH 2 ) 0 -CF 3 (F) R - _)- < γ " ) " (CH 2 } n " CH=CH- ( CH 2 ) 0 -CF 3 wherein R is alkyl or alkoxy with 1-8 C atoms, SUBSTITUTE SHEET n + o is 1-6, especially, however, 2, 3 or 4, p is 1 or 2, and unsubstituted or laterally monofluorinated ene. 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 Chemi- stry) , Georg-Thieme-Verlag, Stuttgart) , and in particular under reaction conditions which are known and suitable for the reactions mentioned. In these reactions, it is also possible to utilize variants which are known per se and are not mentioned here in more detail. 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 . Compounds of formula I with an e.-CF 3 -alkenγl group can be obtained for example via a Wittig reaction according to the following scheme: SUBSTITUTESHEET Compounds of formula I with a ω-CF 3 -alkinyl group may be prepared by a number of generally applicable routes, for example routes A, B, C shown in figure 1 where R is as defined in formula I. The starting point for both of these routes is the known compound CF 3 -(CH 2 ) 0 -CCl=CCl 2 . The zinc complex is prepared by the reaction 100° CF 3 -(CH 2 ) -C.C1=C.Cl 2 + Zn+ZnCl 2 ► CF 3 (CH 2 ) -C=C.Zn DMF described for example by W.G. Finegan and W.P. Norris, J. Org. Che (1963) , 28, 1139. The conditions for routes A, B, C are as follows: SUBSTITUTE SHEET Route A: Al mix over 20 minutes in DMF solvent (the zinc complex may be used without isolation as prepared above) in the presence of tetrakis (triphenγlphosphine)palladium(o) ("TTPP") at 20 °C, then maintain at 50 °C for 2 hours. A2 hydrolyse using sodium hydroxide in industrial methyla¬ ted spirit (IMS) reflux, then acidify with hydrochloric acid. A3 esterification with the phenol using dicyclohexylcarbo- diimide (DCC) or trifluoroacetic anhydride in dichloro- methane. Route B: coupling reaction as step Al Route C: Cl esterification reaction as A3 C2 coupling reaction as Al and Bl The individual steps of these reactions are known, albeit in some cases using homologous compounds although the overall routes are novel. Suitable stoichiometries and reaction conditions will be apparent to those skilled in the art, the hydrolysis and esterification steps A2, A3, Cl being stan¬ dard. It will be appreciated that reactions Al , Bl , C2 involve coupling of the ethine group to a terminal position of an iodo-substituted phenyl ring, and that therefore this SUBSTITUT ~ SHEET reaction is of general use in the preparation of compounds of formula I with a ω-CF 3 -alkinγl group where n is 0 from phenyls of general formula II Therefore although specific ring systems are illustrated in fig. 1, these routes may be used to prepare analogues containing other ring systems. Standard separation and purification procedures may be used to isolate the products of routes A, B and C. Compounds of formula I with a ω-CF 3 -alkinγl group wherein n #0 can further be obtained, for example, via reacting a ω-CF 3 -alkenγl compound of formula I with bromine with subse¬ quent elimination of HBr. Compounds of formula I with a ω-CF 3 -alkyl group and (n + o) = o + 2 > 2 can be obtained hy hydrogenating the ω~CF 3 -al- kinyl compounds prepared via route A-C or an analogous route at a Pt0 2 catalyst: SUBSTITUTE SHEET The ω-CF 3 -alkyl group can further be introduced as terminal group for example by reacting with bromobenzene via a Friedel-Crafts reaction. The car- bonyl group is reduced and the bromobenzol derivative can be coupled to appropriate boronic acid derivatives thus yiel¬ ding the compounds of formula I or derivatives thereof. Compounds of formula I with a ω~CF 3 -alkyl terminal group can further be prepared by hydrogenating the ω-CF 3 -alkenyl compounds obtained via a Wittig reaction as mentioned above at a Pt0 2 catalyst. Compounds of formula I being obtained via boronic acid coupling of Br - 0LKX_0Ϊ>;-- ( CH ? CH,-CF are furthermore preferred. Compounds of formula I with a ω-CF 3 -alkyl, a ω-CF 3 -alkenyl or ω-CF 3 ~alkinyl group can further preferably be obtained by reacting SUBSTITUTESHEET with sulfur tetrafluoride or diethylamino sulfur trifluoride (DAST) . It is further possible to convert appropriate CF 3 -(CH 2 ) 0 - Q-(CH 2 ) n -terminal substituted precursors to the compounds of formula I via a metal-catalyzed cross-coupling reaction as is described, for example, in E. Poetsch, Kontakte (Darm¬ stadt, 1988 (2), p. 15ff) . Other methods of preparing compounds of formula I are apparent to those ski1led in the art. The liquid crystal media according to the invention prefer¬ ably contain 2 to 40, in particular 4 to 30, components as further constituents in addition to one ore more compounds according to the invention. These media especially prefer¬ ably contain 7 to 25 components in addition to one ore more compounds according to the invention. These other constitu¬ ents are preferably chosen from the nematic or nematogenic (monotropic or isotropic) substances, in particular substan- ces from the classes of azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexylcyclohexanecarboxylates, phenyl or cyclohexyl esters of cyclohexylbenzoid acid, phenyl or cyclohexyl esters of cyclohexylbenzoic acid, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acid, SUBSTITUTESHEET phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexylcy- clohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexenes, cyclohexylcyclohexylcyclohexenes, 1.4-bis-cyclohexylbenze- nes, 4,4'-bis-cyclohexylbiphenγls, phenyl- or cyclohexylpy- ri idines, phenyl- or cyclohexylpyridines, phenyl- or cyclohexyldioxanes, phenyl- or cyclohexyl-1,3-dithianes, 1,2-diphenylethanes, 1,2-dicyclohexγlethanes, l-phenγl-2-cγ- clohexylethanes, l-cyclohexγl-2-(4-phenyl-cyclohexyl)-etha¬ nes, l-cyclohexyl-2-biphenγlγlethanes, 1-phenyl-2-cyclo- hexylphenylethanes, optionally halogenated stilbenes, benzyl phenyl ethers, tolans and substituted cinnamic acids. The 1,4-phenγlene groups in these compounds can also be fluo- rinated. The most important compounds which are possible further constituents of media according to the invention can be characterized by the formulae 1, 2, 3, 4 and 5: R' -L-E-R" 1 R' -L-COO-E-R" 2 R' -L-OOC-E-R" 3 R — L— CH 2 CH 2 — E— R" 4 R' -L-O-C-E-R" 5 In the formulae 1, 2, 3, 4 and 5, L and E, which can be identical or different, in each case independently of one another are a bivalent radical from the group comprising -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe- and -G-Cyc- and mirror images thereof, wherein Phe is 1,4-phenγlene which is unsubstituted or substituted by SUB S T I TUTESHEET fluorine, Cyc is trans-l,4-cγclohexγlene or 1,4-cyclohexenγ- lene, Pyr is pγrimidine-2,5-diyl or pγridine-2,5-diγl, Dio is l,3-dioxane-2,5-diγl and G is 2-(trans-l,4-cγclohexγl)- ethyl, pγrimidine-2,5-diγl, pγridine-2,5~diγl or 1,3-dioχ- ane-2,5-diγl. Preferably, one of the radicals L and E is Cyc, Phe or Pyr. E is preferably Cyc, Phe or Phe-Cyc. The media according to the invention preferably contain one ore more components chosen from the compounds of the formulae 1, 2, 3, 4 and 5, wherein one of the radicals L and E is chosen from the group comprising Cyc, Phe and Pyr and the other radical is chosen from the group comprising -Phe-Phe-, -Phe-Cyc-, -Cγc-Cγc-, -G-Phe- and -G-Cyc-, and if appropriate one ore more compo¬ nents chosen from the compounds of the formulae 1, 2, 3, 4 and 5 wherein the radicals L and E are chosen from the group comprising -Phe-Cyc-, -Cyc-Cyc-, -G-Phe~ and -G~Cγc-. R' and R" in the compounds of the part formulae II, 2a, 3a, 4a and 5a in each case independently of one another are alkyl, alkenyl, alkoxy, alkenyloxy or alkanoyloxy having up to 8 carbon atoms. In most of these compounds, R' and R" differ from one another, one of these radicals usually being alkyl or alkenyl. In the compounds of the part formulae lb, 2b, 3b, 4b and 5b, R" is -CN, -CF 3 , F, Cl or -NCS; R here has the meaning given in the case of the compounds of the part formulae la to 5a, and is preferably alkyl or alkenyl. However, other variants of the envisaged substituents in the compounds of the formulae 1, 2, 3, 4 and 5 can also be used. SUBSTITUTE SHEET Many such substances or mixtures thereof are commercially available. All these substances are obtainable by methods which are known from the literature or by analogous methods The media according to the invention preferably also con- tain, in addition to components from the group of compounds la, 2a, 3a, 4a and 5a (group 1) , components from the group of compounds lb, 2b, 3b, 4b and 5b (group 2) , the proper- tions of which are preferably as follows: Group 1: 20 to 90 %, in particular 30 to 90 %. Group 2: 10 to 80 %, in particular 10 to 50 %, the sum of the proportion of the compounds according to the invention and the compounds from groups 1 and 2 being up to 100 %. Liquid crystalline media containing at least one ω~CF 3 -al- kinyl compound of formula I preferably include one ore more known compounds of general formula IIA or IIB. where R x is C χ -C 10 n-alkyl or alkoxy, R 2 is C^C j -, alkyl and a is 0 or 1. Preferably R x contains 3 to 8 carbon atoms . Each phenyl ring in formula IIB may carry a lateral fluorine SUBSTITUTESHEET substituent provided there is at least one fluorine in the structure. The phenyl rings in structure IIA may also carry one or more substituents, e.g. a fluorine. Other known compounds which may usefully be used in such a remote mixture with at least one ω-CF 3 -alkinγl compound of formula I include those described in GB 11551043, GB 1556994, GB 1592147, GB 1587819, GB 1603076, GB 2011940, GB 2023136, GB 2027708, GB 2027027, GB 2058789, GB 2063250, GB 2071649, GB 2070594, GB 2071131, GB 2081707, GB 2079275. GB 2080820, GB 2089345, GB-A-8203798, EP 0060646, GB 2111974, US 4482472, GB 2118934, US 4506957, GB 2121406, EP-A-83303348.3, GB 2134110, EP-A-8430494.3, EP- A-84303240.0. The media according to the invention preferably contain 1 to 50 %. particularly preferably 5 to 30 %, of compounds according to the invention. Media containing more than 40 %, in particular 45 to 90 %, of compounds according to the invention are furthermore preferred. The media preferably contain three, four or five 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, preferably at elevated tempe¬ rature. The liquid crystal phases according to the invention can be modified by suitable additives so that they can be used in all the types of liquid crystal display elements disclosed to date. Such additives are known to the expert and are described in detail in the literature (H. Kelker/ SUBSTITUTESHEET R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Wein- heim, 1980) . For example, it is possible to add pleochroic dyestuffs to prepare coloured guest-host systems or substan¬ ces to change the dielectric anisotropy, the viscosity and/or the orientation of the nematic phases. The liquid crystalline media according to the invention may be nematic or smectic; preferably, however, they are nematic with the term nematic media embracing also chiral nematic = cholesteric media. The following examples are intended to illustrate the invention without limiting it. p. = melting point, cp. - clearing point. Percentage data above and below are percen¬ tages by weight; all the temperatures are stated in degrees Celsius. "Customary working up" means: 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 abbreviations have the following meanings: C: crystalline-solid state, S: smectic phase (the index identi- fies the phase type) , N: nematic state, Ch: cholesteric state, I: isotropic phase. The number between two symbols indicates the transition temperature in degrees Celsius. SUBSTITUTESHEET Exa ples of substances A) ω-CF 3 -alkyl compounds Example 1 A mixture of 1.4 g 4-(3,3,3-trifluopropyn-l-γl)-phenyl 4-pentγlbenzoate obtained by reacting 1,1,2-trichloro-3,3,3- trifluoroprop-1-ene with 4-iodi-phenyl 4-pentγlbenzoate, 10 ml ethyl acetate and 0.5 g 5 % Pd/C is hydrogenated at 20 ° and atmospheric pressure until the reaction does not longer take up hydrogen. Customary work-up gives 4-(3,3,3-trifluoropropγlphenyl) 4-pentγlbenzoate exhibiting the following physical data: C 54 N (5.5) I The following compounds are prepared analogously: 4-(3,3,3-trifluoropropylphenyl) 4-ethylbenzoate 4-(3,3,3-trifluoropropylphenyl) 4-propγlbenzoate 4-(3,3,3-trifluoropropylphenyl) 4-butylbenzoate 4-(3,3,3-trifluoropropylphenyl) 4-hexylbenzoate 4-(3,3,3-trifluoropropylphenyl) 4-heptγlbenzoate 4-(3,3,3-trifluoropropylphenyl) 4-octylbenzoate 4-(3,3,3-trifluoropropylphenyl) 4-ethoxγbenzoate 4-(3,3,3-trifluoropropylphenyl) 4-propoxγbenzoate 4-(3,3,3-trifluoropropylphenyl) 4-butoxybenzoate 4-(3,3,3-trifluoropropylphenyl) 4-pentoxybenzoate 4-(3,3,3-trifluoropropylphenyl) 4-hexoxybenzoate 4- ( 3,3,3-trifluoropropylphenyl) 4-heptoxγbenzoate SUBSTITUTESHEET 4-(3,3,3-trifluoropropylphenyl) 4-(3,3,3-trifluoropropyl) benzoate 4-(4,4,4-trifluorobutylphenyl) 4-ethγlbenzoate 4-(4,4,4-trifluorobutylphenyl) 4-propγlbenzoate 4-(4,4,4-trifluorobutylphenyl) 4-butγlbenzoate 4-(4,4,4-trifluorobutylphenyl) 4-pentylbenzoate 4-(4,4,4-trifluorobutylphenyl) 4-hexylbenzoate 4-(4,4,4-trifluorobutylphenyl) 4-heptylbenzoate 4-(4,4,4-trifluorobutylphenyl) 4-octγlbenzoate 4-(4,4,4-trifluorobutylphenyl) 4-nonγlbenzoate 4-(4,4,4-trifluorobutylphenyl) 4-ethoxγbenzoate 4-(4,4,4-trifluorobutylphenyl) 4-propoxybenzoate 4-(4,4,4-trifluorobutylphenyl) 4-butoxybenzoate 4-(4,4,4-trifluorobutylphenyl) 4-pentoxybenzoate 4-(4,4,4-trifluorobutylphenyl) 4-hexoxybenzoate 4-(4,4,4-trifluorobutylphenyl) 4-heptoxybenzoate 4-(4,4,4-trifluorobutylphenyl) 4-(4,4,4-trifluorobutyl)- benzoate 4-(5,5,5-trifluoropentylphenyl) 4-ethγlbenzoate 4-(5,5,5-trifluoropentylphenyl) 4-propylbenzoate 4-(5,5,5-trifluoropentylphenyl) 4-butylbenzoate 4-(5,5,5-trifluoropentylphenyl) 4-pentylbenzoate 4-(5,5,5-trifluoropentylphenyl) 4-hexylbenzoate 4-(5,5,5-trifluoropentylphenyl) 4-heptylbenzoate 4-(5,5,5-trifluoropentylphenyl) 4-octylbenzoate 4-(5,5,5-trifluoropentylphenyl) 4-nonylbenzoate 4-(5.5,5-trifluoropentylphenyl) 4-ethoxybenzoate 4~(5,5,5-trifluoropentylphenyl) 4-propoxγbenzoate 4 ~ (5,5,5-trifluoropentylphenyl) 4 _ butoxγbenzoate SUBSTITUTESHEET 4-(5,5,5-trifluoropentylphenyl) 4-pentoxγbenzoate 4-(5,5,5-trifluoropentylphenyl) 4-hexoxybenzoate 4-(5,5,5-trifluoropentylphenyl) 4-heptoxybenzoate 4-(5,5,5-trifluoropentylphenyl) 4-(4,4, ,trifluorobutyl)- benzoate Example 2 0.2 mol of trans-4-(trans-4-pentylcγclohexγl)-cyclohexane methylene carboxylic acid are reacted with 0.7 mol of sulfur tetrafluoride in an autoclave at 130 C C for 15 h to give trans-,trans-4-pentγl-4'-(2,2,2-trifluoroethyl)cyclohexylcy- clohexane. The crude material is purified by crystallization ,- o and/or chromatography: CP. 65 The following compounds are prepared analogously: trans-,trans-4-methγl-4'-(2,2,2-trifluoroethyl)-cyclohexyl- cyclohexane trans-,trans-4-ethγl-4'-(2,2,2-trifluoroethyl)-cyclohexylcy- clohexane trans-,trans-4-propγl-4'-(2,2,2-trifluoroethyl)-cyclohexyl- cyclohexane trans-,trans-4-butγl~4'-(2,2,2-trifluoroethyl)-cyclohexylcy- clohexane trans-,trans-4-hexγl-4'-(2,2,2-trifluoroethyl)-cγclohexγlcγ- clohexane trans-,trans-4-heptγl-4'~(2,2,2-trifluoroethyl)-cyclohexyl- cyclohexane trans-,trans-4-octγl-4'-(2,2,2-trifluoroethyl)-cyclohexylcy- clohexane SUBSTITUTESHEET trans-,trans-4-methoxy-4'-(2,2,2-trifluoroethyl)-cyclohexyl- cyclohexane trans-,trans-4-ethoxy-4'-(2,2,2-trifluoroethyl)-cyclohexγl- cyclohexane trans-,trans-4-propoxy~4'-(2,2,2-trifluoroethyl)-cyclohexyl- cyclohexane trans-,trans-4-butoxy-4'-(2,2,2-trifluoroethyl)-cyclohexyl- cyclohexane trans-,trans-4-pentoxy-4'-(2,2,2-trifluoroethyl)-cyclohexyl- cyclohexane trans-,trans-4-hexoxγ-4'-(2,2,2-trifluoroethyl)-cyclohexyl- cyclohexane trans-,trans-4 _ heptoxy-4'-(2,2,2-trifluoroethyl)-cyclohexyl- cyclohexane trans-, rans-4-octoxy-4'-(2,2,2-trifluoroethyl)-cyclohexyl- cyclohexane Example 3 0.05 mol of [trans-4-(trans-4-pentγlcyclohexγl)-cyclohexyl]- methyl-triphenyl phosphonium iodide are dissolved in 100 ml tetrahydrofuran (THF) and 0.05 mol of 4,4,4-trifluorobutyr- aldehyde are added. To this mixture a solution of potassium tert.-butylate in THF is added dropwise at a temperature of 0-5 °C and the resulting mixture is stirred for one hour at room temperature. Then water and diethylether are added and the w-CF 3 -alkenyl intermediate trans-,trans-4-pentγl-4'- (5,5,5-trifluoropent-1-enγl) -cyclohexylcyclohexane is extracted and purified by chromatography. The purified intermediate is dissolved in THF, 5 g of a Pt0 2 catalyst are added and the intermediate is hydrogenated at atmospheric SUBSTITUTE SHEET pressure. Filtering off the catalyst and distilling off the solvent gives the crude product trans-,trans-4-pentγl-4'- (5,5,5-trifluoropentyl)-cyclohexylcyclohexane which is purified by crystallization. The following compounds are prepared analogously: trans-,trans-4-methyl~4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,trans-4-ethyl-4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,trans-4-propyl~4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,trans-4-butyl-4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,trans-4-hexγl~4'-(5,5,5-trifluoropentyl)-cyclohexyl- cyclohexane trans-,trans-4-heptγl-4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,trans-4-octyl-4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,trans-4-nonyl-4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,trans-4-decγl-4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,traπs-4-methoxγ-4'-(5,5,5-trifluoropentyl)-cyclo- hexylcyclohexane trans-,trans-4-ethoxy-4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,trans-4-propoxγ-4'-(5,5,5-trifluoropentyl)-cyclo¬ hexylcyclohexane SUBSTITUTESHEET trans-, rans-4-butoxy-4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,trans-4-pentoxy-4'-(5,5,5-trifluoropentyl)-cyclo- he y1cyc1ohexane trans-, rans-4-hexoxγ-4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,trans-4~heptoxy-4'-(5,5,5-trifluoropentyl)-cyclo- hexylcyclohexane trans-,trans-4-octoxγ-4'-(5,5,5-trifluoropentyl)-cyclohexyl- cyclohexane trans-,trans-4-nonoxy-4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,trans-4-decoxγ-4'-(5,5,5-trifluoropentyl)-cyclohexyl¬ cyclohexane trans-,trans-4-(2-oxapentyl)-4'-(5,5,5-trifluoropentyl)-cy¬ clohexylcyclohexane trans-,trans-4-(3-oxapenty1)-4'-(5,5,5-trifluoropentyl)-cy- clohexylcyclohexane trans-,trans-4-(4-oxapentγl)-4'-(5,5,5-trifluoropentyl)-cy- clohexylcyclohexane trans-,trans~4-pentanoyloxy-4'-(5,5,5-trifluoropentyl) -cy- clohexylcyclohexane Example 4 According to example 3 (4-(trans-4-propylcyclohexyl)- phenyl) -methyltriphenyl phosphoniu iodide is reacted with 2,2,2-trifluoroacetaldehyde. The ω-CF 3 -alkenyl intermediate thus obtained is hydrogenated to give 4-(trans-4-propylcy- clohexy1)-l-(3,3,3-trifluoropropy1) -benzene. SUBSTITUTE SHEET The following compounds are prepared analogously: 4-(trans-4-methylcyclohexγl)-1-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-ethylcγclohexyl)-1-(3,3,3-trifluoropropyl)-ben- zene 4-(trans-4-butylcyclohexyl)-1-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-pentγlcyclohexyl)-1-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-hexylcγclohexyl)-1-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-heptγlcyclohexyl)-1-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-octylcγclohexyl)-1-(3,3,3-trifluoropropyl)-ben- zene 4-(trans-4-nonγlcyclohexγl)-1-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-decγlcγclohexγl)-1-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-methoxγcγclohexyl)-1-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-ethoxycyclohexyl)-1-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-propoxγcγclohexγl) -1-(3,3,3-trifluoropropyl)-ben- zene 4- (trans-4-butoxγcyclohexyl) -1- (3, 3, 3-trif luoropropyl) -ben¬ zene 4- (trans-4-pentoxycyclohexyl) -1- (3, 3 , 3-trif luoropropyl) -ben¬ zene SUBSTITUTE SHEET 4-(trans-4-hexoxycyclohexyl)-1-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-heptoxγcyclohexyl)-1-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-octoxycγclohexyl)-l-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-nonoxγcyclohexyl)-1-(3,3,3-trifluoropropyl)-ben¬ zene 4-(trans-4-decoxγcγclohexyl)-1-(3,3,3-trifluoropropyl)-ben- zene Example 5 According to example 3 (trans-4-(4-propγlphenyl)-cyclo¬ hexyl)-methyl-triphenyl phosphonium iodide is reacted with 2,2,2-tri luoro-acetaldehγde. The ω-CF 3 -alkenyl intermediate thus obtained is hydrogenated to give trans-4-(4-propyl~ phenyl)-l-(3,3.3-trifluoropropyl)-cyclohexane. The following compounds are prepared analogously: trans-4-(4-methγlphenγl)-l-(3,3,3-trifluoropropyl)-cyclo¬ hexane trans-4-(4-ethγlphenyl)-l-(3,3,3-trifluoropropyl)-cyclo¬ hexane trans-4-(4-butylphenγl)-l-(3,3,3-trifluoropropyl)-cyclo¬ hexane trans-4-(4-pentylphenγl) -1-(3,3,3-trifluoropropyl)-cyclo- hexane trans-4- (4-hexylphenyl) -1- (3, 3, 3-trif luoropropyl) -cyclo¬ hexane SUBSTITUTE SHEET trans-4-(4-heptγlphenyl)-1-(3,3,3-trifluoropropyl)-cyclo¬ hexane trans-4-(4-octylphenγl)-1-(3,3,3-trifluoropropyl)-cyclo- hexane trans-4-(4-nonγlphenγl)-1-(3,3,3-trifluoropropyl)-cyclo¬ hexane trans-4-(4-decylphenγl)-1-(3,3,3-trifluoropropyl)-cyclo¬ hexane trans-4-(4-methoxyphenyl)-l-(3,3,3-trifluoropropyl)-cyclo- hexane hexane trans-4-(4-propoxγphenyl)-1-(3,3,3-trifluoropropyl)-cyclo¬ hexane trans-4-(4-butoxyphenyl)-1-(3,3,3-trifluoropropyl)-cyclo- hexane trans-4-(4-pentoxyphenyl)-1-(3,3,3-trifluoropropyl)-cyclo¬ hexane trans-4-(4-hexoxyphenyl)-1-(3,3,3-trifluoropropyl)-cyclo¬ hexane trans-4-(4-heptoxyphenγl)-1-(3,3,3-trifluoropropyl)-cyclo¬ hexane trans-4-(4-octoxyphenγl)-1-(3,3,3-trifluoropropyl)-cyclo¬ hexane trans-4-(4-nonoxyphenyl)-1-(3,3,3-trifluoropropyl)-cyclo- hexane trans-4- (4-decoxyphenyl) -1- (3.3, 3-trif luoropropyl) -cyclo¬ hexane SUBSTITUTE SHEET Exa ple 6 According to example 24-(trans-4-(trans-4-propylcγclo- hexyl)-cyclohexyl)-1-(2,2,2-trifluoroethyl)-benzene is obtained from 4-(trans-4-(trans-4-propylcyclohexyl)-cγclo- hexyl)-phenyl ethyl carboxylic acid and sulfur tetrafluo¬ ride. The following compounds are prepared analogously: 4-(trans-4-(trans-4-methylcyclohexγl)-cyclohexyl)-1-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-ethylcyclohexyl) -cyclohexyl)-1-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-butylcyclohexyl) -cyclohexyl)-1-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-pentylcyclohexyl)-cyclohexyl)-l-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-hexylcyclohexyl)-cyclohexyl)-1-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-heptylcyclohexyl)-cyclohexyl)-1-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-octylcyclohexyl)-cyclohexyl)-l-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-nonylcyclohexyl) -cyclohexyl)-1-(2,2,2~ trifluoroethyl)-benzene 4-(trans-4-(trans-4-decylcyclohexyl) -cyclohexyl)-1-(2,2,2- trifluoroethyl)-benzene 4-(trans ~ 4-(trans-4-methoxycyclohexyl) -cyclohexyl) -1-(2,2,2- trifluoroethyl)-benzene SUBSTITUTESHEET 4-(trans-4-(trans-4-ethoxycyclohexγl)-cyclohexyl)-1-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-propoxycγclohexyl)-cyclohexyl)-1-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-butoxγcyclohexyl)-cyclohexyl)-1~(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-pentoxycγclohexγl)-cyclohexyl)-1-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-hexoxycγclohexγl)-cyclohexyl)-1-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-heptoxγcγclohexγl)-cyclohexyl)-1-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-octoxγcyclohexyl)-cyclohexyl)-l-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-nonoxycyclohexγl)-cyclohexyl)-l-(2,2,2- trifluoroethyl)-benzene 4-(trans-4-(trans-4-decoxycyclohexγl)-cyclohexyl)-1-(2,2,2- trifluoroethyl)-benzene Example 7 According to example 3 [trans-4-(4-trans-4-propγlcγclo- hexyl)-phenyl)-cyclohexyl]-methyl phosphonium iodide is reacted with 2,2,2-trifluoroacetaldehγde. The ω-CF 3 -alkenγl intermediate thus obtained is hydrogenated to give trans-4-(4-(trans-4-propylcyclohexyl)-phenyl)-l-(3,3.3~tri- fluoropropyl)-cyclohexane. The following compounds are prepared analogously: SUEST_TUTE SHEET trans-4-(4-(trans-4-methylcyclohexyl)-phenyl-1-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-ethylcyclohexyl)-phenγl-l-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-butylcyclohexyl)-phenyl-1-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-pentylcyclohexyl)-phenyl-1-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-hexylcyclohexyl)-phenyl-l-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-heptylcyclohexyl)-phenyl-1-(3,3,3~tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-octylcyclohexyl)-phenyl-1-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-nonylcyclohexyl)-phenγl-1-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-decylcyclohexyl)-phenyl-1-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-methoxγcyclohexyl)-phenyl-1-(3,3,3~tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-ethoxycγclohexyl)-phenyl-l-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-propoxycyclohexγl)-phenyl-1-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4~(trans-4-butoxycγclohexyl)-phenyl-1-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-pentoxycyclohexγl)-phenyl-l-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-hexoxycyclohexyl)-phenyl-1-(3,3,3-tri- fluoropropyl) -cyclohexane SUBSTITUTE SHS=ET trans-4-(4-(trans-4-heptoxγcyclohexγl)-phenyl-1-(3,3,3~tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-octoxycγclohexyl)-phenγl-l-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-nonoxycyclohexyl)-phenyl-l-(3,3,3-tri- fluoropropyl)-cyclohexane trans-4-(4-(trans-4-decoxγcyclohexyl)-phenyl-1-(3,3,3-tri- fluoropropyl)-cyclohexane Example 8 0.1 mol of 3,3,3-trifluoropropyl-triphenγl-phosphonium- bromide, which can be obtained by reacting 1,1,1-tri- fluoro-2-bromo-propane and phosphor-triphenyl (see Hanack, Synthesis (1989) 685) , are dissolved in 300 ml diethylether and a solution of 0.1 mol of n-butγllithium in n-hexane is added dropwise. This mixture is stirred for half an hour and then a solution of 0.1 mol of trans-,trans~4-propyl-4'- methanoyl-cyclohexylcyclohexane in diethylether is added. The resulting mixture is stirred for 15 h at room tempera¬ ture. Working-up and hydrogenation as described in example 3 gives trans-,trans-4~propyl-4'-(4,4,4-trifluorobutyl)-cyclo- hexylcyclohexane. The following compounds are prepared analogously: trans-,trans-4-methyl-4'-(4,4,4-trifluorobutyl)-cyclohexyl¬ cyclohexane trans-,trans-4-ethyl~4'-(4,4,4-trifluorobutyl)-cyclohexylcy clohexane SUBSTITUTESHEET trans-,trans-4-butyl-4'-(4,4,4-trifluorobutyl)-cyclohexylcy- clohexane trans-,trans-4-pentyl-4'-(4,4,4-trifluorobutyl)-cyclohexyl¬ cyclohexane trans-,trans-4-hexyl-4'-(4,4,4-trifluorobutyl)-cyclohexylcy- clohexane trans-,trans-4-heptyl-4'-(4,4,4-trifluorobutyl)-cyclohexyl¬ cyclohexane trans-,trans~4-octyl-4'-(4,4,4-trifluorobutyl)-cyclohexylcy- clohexane trans-,trans-4-nonyl-4'-(4.4,4-trifluorobutyl)-cyclohexylcy- clohexane trans-,trans-4-decyl-4'-(4,4,4-trifluorobutyl)-cyclohexylcy- clohexane trans-,trans-4-methoxy-4'-(4,4,4-trifluorobutyl)-cyclohexyl¬ cyclohexane trans-,trans-4-ethoxγ-4'-(4,4,4-trifluorobutyl)-cyclohexyl¬ cyclohexane trans-,trans-4-propoxy-4'-(4,4,4-trifluorobutyl)-cyclohexyl- cyclohexane trans-,trans~4-butoxy-4'-(4,4,4-trifluorobutyl)-cyclohexyl¬ cyclohexane trans-,trans-4-pentoxγ-4'-(4,4,4-trifluorobutyl)-cyclohexyl¬ cyclohexane trans-,trans-4-hexoxy-4'-(4,4,4-trifluorobutyl)-cyclohexyl¬ cyclohexane trans-,trans-4-heptoxy-4'-(4,4,4-trifluorobutyl)-cyclohexyl¬ cyclohexane trans-, trans-4-octoxy-4 ' -(4,4,4-trifluorobutyl)-cyclohexyl- cyclohexane SUBSTITUTESHEET trans-,trans-4-nonoxy-4'-(4,4,4-trifluorobutyl)-cyclohexyl¬ cyclohexane trans-,trans-4-decoxγ-4'-(4,4,4-trifluorobutyl)-cyclohexyl¬ cyclohexane trans-,trans-4-(2-oxahexyl)-4'-(4,4,4-trifluorobutyl)-cyclo- hexylcyclohexane trans-,trans-4-(3-oxahexγl)-4'-(4,4,4-trifluorobutyl)-cyclo- hexylcyclohexane trans-,trans-4-(4-oxahexyl)-4'-(4,4,4-trifluorobutyl)-cyclo- hexylcyclohexane trans-,trans-4-(5-oxahexγl)-4'-(4,4,4-trifluorobutyl)-cyclo¬ hexylcyclohexane trans-,trans-4-propanoyloxγ-4'-(4,4.4-trifluorobutyl)-cyclo- hexylcyclohexane Example 9 A mixture of 0.02 mol of 2-(trans-4-pentγlcyclohexyl)-pro¬ pane-1,3-diol, 0.02 mol of 4,4,4-trifluorobutγraldehγde, 0.01 g of p-toluenesulfonic acid and 20 ml of toluene is boiled under a water separator and is then cooled, washed with water and evaporated. Purification by chromatography in a customary manner gives trans-2-(trans-4-pentylcγclo- hexγl)-5-(4,4,4-trifluorobutyl)-1,3-dioxane. The following compounds are prepared analogously: trans-2-(trans-4-methγlcyclohexγl)-5-(4,4,4-trifluorobu- tyl)-l,3-dioxane trans-2- ( trans-4-ethylcγclohexγl) -5-(4,4,4-trifluorobu¬ tyl)-1,3-dioxane SUBSTITUTESHEET trans-2-(trans-4-propylcyclohexyl)-5-(4,4,4-trifluorobu¬ tyl)-1,3-dioxane trans-2-(trans-4-butylcyclohexyl)-5-(4,4,4-trifluorobu¬ tyl)-1,3-dioxane trans-2-(trans-4-hexylcyclohexyl) -5-(4,4,4-trifluorobu¬ tyl)-1,3-dioxane trans-2-(trans-4-heptylcyclohexyl)-5-(4,4,4-trifluorobu¬ tyl)-1,3-dioxane trans-2-(trans-4-octylcyclohexyl)-5-(4,4,4-trifluorobu- tγl)-l,3-dioxane trans-2-(trans-4-methoxycγclohexγl)-5-(4,4,4-trifluorobu¬ tyl)-1,3-dioxane trans-2-(trans-4-ethoxycyclohexyl)-5-(4,4,4-trifluorobu¬ tyl)-1,3-dioxane trans-2-(trans-4-propoxycyclohexyl)-5-(4,4,4-trifluorobu¬ tyl)-1,3-dioxane trans-2-(trans-4-butoxycyclohexyl)-5-(4,4,4-trifluorobu¬ tyl)-1,3-dioxane trans-2-(trans-4-pentoxycyclohexyl)-5-(4, ,4-trifluorobu- tγl)-l,3-dioxane trans-2-(trans-4-hexoxγcyclohexγl)-5-(4,4,4-trifluorobu¬ tyl)-1,3-dioxane trans-2-(trans-4-heptoxycγclohexyl)-5-(4,4,4-trifluorobu¬ tyl)-l,3-dioxane trans-2-(trans-4-octoxγcyclohexyl) -5-(4,4,4-trifluorobu¬ tyl)-1,3-dioxane trans-2-(trans-4-(trans-4-methγlcγclohexyl)-cyclo¬ hexyl)-5-(4,4,4-trifluorobutyl) -1.3-dioxane trans-2-(trans-4-(trans-4-ethylcyclohexγl)-cyclo- hexyl) -5-(4.4.4-trifluorobutyl) -1 ,3-dioxane SUBSTITUTE SHEET trans-2-(trans-4-(trans-4-propylcyclohexγl)-cyclo¬ hexyl)-5-(4,4,4-trifluorobutyl)-1,3-dioxane trans-2-(trans-4-(trans-4-butylcyclohexyl)-cyclo¬ hexyl)-5-(4.4,4-trifluorobutyl)-1,3-dioxane trans-2-(trans-4-(trans-4-pentylcyclohexγl)-cyclo¬ hexyl)-5-(4,4,4-trifluorobutyl)-1,3-dioxane ' trans-2-(trans-4-(trans-4-hexγlcyclohexγl)-cyclo¬ hexyl)-5-(4.4.4-trifluorobutyl)-l,3-dioxane trans-2-(trans-4-(trans-4-heptγlcyclohexyl)-cyclo- hexyl)-5-(4.4,4-trifluorobutyl)-1,3-dioxane trans-2-(trans-4-(trans-4-octylcγclohexyl)-cyclo¬ hexyl)-5-(4,4,4-trifluorobutyl)-1,3-dioxane trans-2-(trans-4-(trans-4-methoxγcyclohexyl)-cyclo¬ hexyl)-5-(4,4,4-trifluorobutyl)-1,3-dioxane trans-2-(trans-4-(trans-4-ethoxγcyclohexγl)-cyclo¬ hexyl)-5-(4,4, -trifluorobutyl)-1,3-dioxane trans-2-(trans-4-(trans-4-propoxγcyclohexγl)-cyclo¬ hexyl)-5-(4,4,4-trifluorobutyl)-1,3-dioxane trans-2-(trans-4-(trans-4-butoxγcyclohexγl)-cyclo- hexyl)-5-(4,4,4-trifluorobutyl)-1,3-dioxane trans-2-(trans-4-(trans-4-pentoxγcγclohexγl)-cyclo¬ hexyl)-5-(4.4, -trifluorobutyl)-1,3-dioxane trans-2-(trans-4-(trans-4-hexoxγcγclohexγl)-cyclo¬ hexyl)-5-(4,4,4-trifluorobutyl)-1,3-dioxane trans-2-(trans-4-(trans-4-heptoxycγclohexyl)-cyclo¬ hexyl)-5-(4,4,4-trifluorobutyl)-1,3-dioxane trans-2-(trans-4-(trans-4-octoxγcγclohexγl)-cyclo¬ hexyl) -5-(4,4,4-trifluorobutyl) -1,3-dioxane SUBSTITUTE SHEET Example 10 trans-2-(4-propylphenyl)-5-(3,3,3-trifluoropropyl)-1,3-diox- ane is obtained by reacting 4-propylbenzaldehγde with 2-(3,3,3- rifluoropropyl)-propane-1,3-diol according to example 5. The following compounds are prepared analogously: traπs-2-(4-methylphenyl)-5-(3,3,3-trifluoropropyl)-1,3- dioxane trans-2-(4~'ethγlphenyl)-5-(3,3,3-trifluoropropyl)-1,3- dioxane trans-2-(4-butylphenyl)-5-(3,3,3-trifluoropropyl)-1,3- dioxane trans-2-(4-pentγlphenyl)-5-(3,3,3-trifluoropropyl)-1,3- dioxane trans-2-(4-hexylphenyl)-5-(3,3,3-trifluoropropyl)-1,3- dioxane trans-2-(4-heptγlphenyl)-5-(3,3,3-trifluoropropyl)-1,3- dioxane trans _ 2-(4-octylphenyl)-5-(3,3,3-trifluoropropyl)-1,3- dioxane trans-2-(4-methoxyphenyl)-5-(3,3,3-trifluoropropyl) -1,3- dioxane trans-2-(4-ethoxyphenyl)-5-(3,3,3-trifluoropropyl)-1,3- dioxane trans-2-(4-propoxyphenyl) -5-(3,3,3-trifluoropropyl) -1,3- dioxane trans~2-(4-butoxyphenyl) -5-(3,3,3-trifluoropropyl)-l ,3- dioxane SUBSTITUTE SHEET trans-2-(4-pentoxyphenγl)-5-(3,3,3-trifluoropropyl)-1,3- dioxane trans-2-(4-hexoxyphenyl)-5-(3,3,3-trifluoropropyl)-1,3- dioxane trans-2-(4-heptoxyphenγl)-5-(3,3,3-trifluoropropyl)-1,3- dioxane trans-2-(4-octoxyphenγl)-5-(3,3,3-trifluoropropyl)-1,3- dioxane B) ω-CFg-alkenyl compounds Example 11 trans-,trans-4-pentγl-4'-(5,5,5-trifluoropent-1-enγl)-cyclo- hexylcyclohexane is prepared analogously to example 3 with the hydrogenation step being omitted. This and the following compounds comprise both the (E)- and (Z)-isomers which can be separated by chromatography and/or crystallization. The following compounds are prepared analogously: trans-,trans-4-methyl~4'-(5,5,5-trifluoropent-1-enγl)-cyclo- hexylcyclohexane trans-,trans-4~ethyl-4'-(5,5,5-trifluoropent-1-enyl)-cyclo- hexylcyclohexane trans-,trans-4-propyl-4 ' -(5,5,5-trifluoropent-l-enγl)-cyclo- hexylcyclohexane trans-,trans-4 ~ butyl-4'-(5,5,5-trifluoropent-1-enyl)-cyclo- hexylcyclohexane trans-,trans-4-hexyl-4 ' - ( 5,5,5-trifluoropent-1-enyl) -cyclo- hexylcyclohexane SUBSTITUTE SHEET trans- , trans-4-heptyl-4 ' - (5 ,5 ,5-trifluoropent-l-enγl) -cyclo- hexylcyclohexane trans-,trans-4-octyl~4'-(5,5,5-trifluoropent-1-enγl) -cyclo- hexylcyclohexane trans-,trans-4-methoxγ-4'-(5,5,5-trifluoropent-1-enyl)-cy- clohexylcyclohexane trans-.trans-4-ethoxy-4'-(5,5,5-trifluoropent-l-enyl)-cyclo- hexylcyclohexane trans-,trans-4-propoxγ-4'-(5,5,5-trifluoropent-1-enγl)-cy- clohexylcyclohexane trans-,trans-4-butoxy-4'-(5,5,5-trifluoropent-1-enyl)-cyclo- hexylcyclohexane trans-,trans-4-pentoxγ-4'-(5,5,5-trifluoropent-1-enyl)-cy- clohexylcyclohexane trans-,trans-4-hexoxy-4'-(5,5,5-trifluoropent-1-enyl)-cyclo¬ hexylcyclohexane trans-,trans-4-heptoxy-4'-(5,5,5-trifluoropent-1-enγl)-cy- clohexylcyclohexane trans-,trans-4-octoxy-4'-(5,5,5-trifluoropent-1-enyl)-cyclo- hexylcyclohexane trans-,trans-4-(2-oxabutyl)-4'-(5,5,5-trifluoropent-1-enyl)- cyclohexylcyclohexane trans-,trans-4-(3-oxabutyl)-4 ' -(5,5,5-trifluoropent-1-enyl)- cyclohexylcyclohexane trans-,trans-4-propanoyloxy-4'-(5,5,5-trifluoropent-1-enyl)- cyclohexylcyclohexane trans-,trans-4-propoxycarbonyl-4'-(5,5,5-trifluoropent-1- enyl)-cyclohexylcyclohexane trans-,trans-4-acetyloxymethyl-4'-(5,5,5-trifluoropent-1- enyl)-cyclohexylcyclohexane SUBST.TUTE SHEET Example 12 According to example 3 trans-4-(4-(trans-4-propylcyclo- hexyl)-phenyl)-1-(3,3,3-trifluoropropen-1-yl)-cyclohexane is obtained [trans-4-(4-(trans-4-propylcyclohexyl)-phenyl)-cy- clohexyl]-methyl phosphonium iodide and 2,2,2-trifluoroace- taldehyde with the hydrogenation step being omitted. This and the following compounds comprise both the (E)- and (Z)-isomers which can be separated by chromatography and/or crystallization. The following compounds are prepared analogously: trans-4-(4-(trans-4-methylcγclohexyl)-phenyl)-1-(3,3,3-tri- fluoropropen-1-γl)-cyclohexane trans-4-(4-(trans-4-ethγlcγclohexγl)-phenyl)-1-(3,3,3-tri- fluoropropen-:l-γl)-cyclohexane trans-4-(4-(trans-4-butγlcyclohexyl)-phenyl)-l-(3,3,3-tri- fluoropropen-1-γl)-cyclohexane trans-4-(4-(trans-4-pentγlcγclohexγl) -phenyl)-l-(3,3,3-tri- fluoropropen-1-γl)-cyclohexane trans-4-(4-(trans-4-hexγlcyclohexγl)-phenyl)-l-(3,3,3-tri- fluoropropen-1-yl)-cyclohexane trans-4-(4-(trans-4-heptylcyclohexγl)-phenyl)-1-(3,3,3~tri- fluoropropen-1-γl)-cyclohexane trans-4-(4-(trans-4-octγlcyclohexγl)-phenyl)-l-(3,3,3-tri- fluoropropen-1-γl)-cyclohexane trans-4-(4-(trans-4-nonγlcyclohexγl)-phenyl)-1-(3,3,3-tri~ fluoropropen-1-yl) -cyclohexane trans-4-(4-(trans-4-decylcyclohexyl)-phenyl)-l-(3,3,3-tri- f luoropropen-1-yl) -cyclohexane SUBSTITUTE SHEET trans-4-(4-(trans-4-methoxycyclohexyl)-phenyl)-1-(3,3,3-tri- fluoropropen-1-yl)-cyclohexane trans-4-(4-(trans-4-ethoxycyclohexyl)-phenyl)-1-(3,3,3-tri- fluoropropen-1-yl)-cyclohexane trans-4-(4-(trans-4-propoxycyclohexyl)-phenyl)-l-(3,3,3 _ tri- fluoropropen-1-yl)-cyclohexane trans-4-(4-(trans-4-butoxycyclohexyl)-phenyl)-l-(3,3,3-tri- fluoropropen-1-γl)-cyclohexane trans-4-(4-(trans-4-pentoxycγclohexyl)-phenyl)-1-(3,3,3-tri- fluoropropen-1-yl)-cyclohexane trans-4-(4-(trans-4-hexoxycyclohexyl)-phenyl)-l-(3,3,3-tri- fluoropropen-1-yl)-cyclohexane trans-4-(4-(trans-4-heptoxycyclohexyl)-phenyl)-1-(3,3,3~tri- fluoropropen-1-γl)-cyclohexane trans-4-(4-(trans-4-octoxγcyclohexyl)-phenyl)-1-(3,3,3-tri- fluoropropen-1-yl)-cyclohexane trans-4-(4-(trans-4-nonoxycyclohexyl)-phenyl)-1-(3,3,3-tri- fluoropropen-1-yl)-cyclohexane trans-4-(4-(trans-4-decoxycyclohexyl)-phenyl)-1-(3,3,3-tri- fluoropropen-1-yl)-cyclohexane C) ω-CF 3 -alkinyl compounds Example 13 Using route A shown in Fig. 1 the compound: is prepared, using 4-n-pentylphenol in step A3. This com¬ pound had the properties: SUBSTITUTE SHEET K-I 62.5°, SA-I 54°, n = 0.17 (extrapolated value obtained from a solution of the compound in a eutectic mixture of compounds of formula IIB) By comparison the analogous phenylbenzoate: n-C 3 H 7 - 0 YcOO- 0 Yc 5 H n -n has the properties: K-I 17° (N-I 7°) , Δn = ca 0.13 Therefore, the compound of formula I has a higher Δn and an improved clearing point (liquid crystal to isotropic liquid transition) compared to that of its analogue lacking an ethine group. Using route A a fluorinated analogue: was prepared, using 2-fluoro-4-n-pentyl phenol in step A3. This compound showed liquid crystal transitions: K-I 62.5 °C (S A - I 54 °C) SUBSTITUTESHEET Using route B the biphenyl: was prepared, having a melting point of 108 °C and a bire¬ fringence, measured as above, of 0.169. Using route C, a compound n-C 5 H u - 0 YcOO- 0 Yc-C-CF 3 was prepared, having a liquid crystal transition K-I = 77 °C and a birefringence of 0.206 measured as above. Synthesis details The intermediate zinc compound CF 3 C.CZn was prepared as follows: Zinc powder was cleaned by stirring with 10 % hydrochloric acid for 5 min, filtering, washing successively with water and IMS and then drying under vacuum. Zinc chloride was dried by fusion under vacuum. Zinc powder (90 % purity, 5.8 g = 0.08 mol) and zinc chloride (0.54 g = 0.004 mol) were stirred in 20 ml dry DMF under a nitrogen atmosphere, and the whole mixture heated to 100° on an oil bath. 1,l,2-trichloro-3,3,3-trifluoro-propene (8.8 g, 0.044 mol) was added dropwise until the exothermic reaction began. The flask was then removed from the oil bath, and the rate of addition adjusted so as to keep the temperature between 100° and 110°. After the addition was complete, the reaction mixture was maintained at 100° for 1 hour, and then cooled to room temperature. SUBSTITUTE SHEET Route B The zinc reagent was prepared by the above method, using the same quantities, and cooled to room temperature. 4-pentγl-4- iodobiphenyl (11.7 g, 0.033 mol) was dissolved in 20 ml THF with tetrakis (triphenylphosphine) palladium (0) (0.5 g, 0.0043 mol) , to which the solution of the zinc reagent was then added. The reaction mixture was heated to 50° for 4 1/2 hours, cooled and poured into 100 ml 10 % hydrochloric acid. The product was extracted into dichloromethane, washed with water, dried over Na 2 S0 4 and distilled to dryness. The crude product was columned on 20 g silica, eluting with 40-60° petrol, and then recrystallised from 2 volumes 60-80° petrol. Yield 2.45 g Route C 4-pentγlbenzoic acid (9.6 g, 0.05 mol) and 4-iodophenol (11.0 g, 0.05 mol) were mixed in 50 ml dichloromethane with trifluoroacetic anhydride (8.5 ml, 0.06 mol) and left 18 hours at room temperature. The reaction mixture was poured into water and the organic layer separated, washed with water to neutral pH, dried over Na 2 S0 4 and distilled to dryness. The crude product was columned on 20 g silica over 20 g alumina, eluting with 1:1 dichloromethane/40-60° - petrol, and then recrystallised from 50 ml IMS. Yield 13.0 g SUBSTITUTESHEET 4-iodophenyl 4-pentylbenzoate (12.9 g, 0.032 mol) was added dissolved in 20 ml dry THF, followed by tetrakis (triphenyl- phosphine) palladium (0) (0.5 g, 0.00043 mol) . The reaction mixture was heated to 50° for 5 hours then cooled and poured into 100 ml hydrochloric acid. The product was extracted into dichloromethane, washed twice with water, dried over Na 2 S0 4 and the solvent distilled off. The crude material was columned on 120 g silica, eluting with 4:1 40-60° petrol/dichloromethane, and then recrystallised from 5 volumes IMS. Yield 3.9 g HPLC 99.0 X SUB S TITUTESHEET Example 4 0.05 mol of [trans-4-(trans-4-pentylcyclohexyl)-cyclohexyl]- methyl-triphenyl phosphonium iodide are dissolved in 100 ml tetrahydrofuran (THF) and 0.05 mol of 4,4.4-trifluoroacet aldehyde are added. To this mixture a solution of potassium tert.-butylate in THF is added dropwise at a temperature of 0-5 °C and the resulting mixture is stirred for one hour at room temperature. Then water and diethylether are added and the w-CF 3 -alkenγl intermediate trans-,trans-4-pentyl-4'- (3,3,3 -trifluoroprop-l-enγl)-cγclohexylcγclohexane is extracted and purified by chromatography. The purified intermediate is dissolved in THF, 5 g of a Pt0 2 catalyst are added and the intermediate is hydrogenated at atmospheric pressure. Filtering off the catalyst and distilling off the solvent gives the crude product trans-.trans-4-pentyl-4'- (3,3,3-trifluoropropyl)-cyclohexylcyclohexane which is purified by crystallization: mp.50°, cp. 75° The following compounds are prepared analogously: trans- , trans-4-methyl-4'-(3.3, 3-trifluoropropyl.)-cyclohexyl- cyclohexane trans-.trans-4-ethyl-4 ' - ( 3.3 ,3-trifluoropropyl )-cyclohexyl¬ cyclohexane -cyclohexyl- trans- , trans-4-butyl-4 ' - ( 3,3,3 -trifluoropropyl )-cyclohexyl ¬ cyclohexane SUB S TITUTESHEET trans-, trans-4-hexyl-4' - (3, 3, 3 -trif luoropropyl ) -cyclohexyl- cyclohexane trans- , trans-4-heptyl-4 ' - ( 3, 3 ,3 -trif luoropropyl ) -cyclohexyl¬ cyclohexane 5 trans-, trans-4-octyl~4' - ( 3 # 3, .3-trif luorop ropyl ) -cyclohexyl¬ cyclohexane trans- , trans-4-nonyl-4 ' - (3 . 3.3-trif luorop ropyl ) -cyclohexyl¬ cyclohexane trans-, trans-4-decyl~4 ' - (3 , 3, 3-trif luorop ropyl j -cyclohexyl- \ o cyc 1 ohexane trans-,trans-4-methoxy-4'-(3.3, 3-trifluoropropyl. -cyclo¬ hexylcyclohexane traπs-.trans-4-ethoxy-4'-(3,3, 3-trifluoropropyl )-cyclohexyl¬ cyclohexane 15 trans-,trans~4-propoxy-4'-(3,3, 3-trifluoropropyl.)-cyclo¬ hexylcyclohexane trans-,trans-4-butoxy-4'-(3.3,3 -trifluoropropyl )-cyclohexyl¬ cyclohexane trans-.trans-4-ρentoxy-4'-(3.3,3-trifluoropropyl ■ -cyclo- 20 hexylcyclohexane trans-,trans-4-hexoxy-4'~( 3, 3.3-trifluoropropyl.)-cyclohexyl¬ cyclohexane trans-,trans-4-heptoxy-4'-( 3.3, _t r ifluoroprop l)-cyclo¬ hexylcyclohexane 25 trans-.trans-4-octoxy-4'-(3,3.3 -trifluoropropyl.)-cyclohexyl¬ cyclohexane trans-.trans-4-nonoxy-4'- ( 3.3.3~trifluoropropyl )-cyclohexyl¬ cyclohexane trans-,trans-4-decoxy-4'-(3.3.3 -trifluoropropyl )-cyclohexyl¬ cyclohexane SUBSTITUTESHEET trans-,trans-4-(2-oxapentyl)-4'-(3.3,3 -trifluoropropyl )-cy-r clohexylcyclohexane trans-,trans-4-(3-oxapentγl)-4 ' -(3.3,3 -trifluoropropyl.)-cy¬ clohexylcyclohexane trans-,trans-4-(4-oxapentyl)-4'-(3.3.3 -trifluoropropyl.,-cy¬ clohexylcyclohexane trans-.trans-4-pentanoγloxγ-4'-(3,3,3 -trifluoropropyl )-cy¬ clohexylcyclohexane Example of mixtures Example A A liquid crystalline mixture consisting of 17 % of trans-1-(p-ethylphenyl)-4-propylcyclohexane 15.4 % of trans-l-(p-methoxγphenγol)-4-propγlcγclohexane 11.6 °ό of trans-1-(p-ethoxyphenγl)-4-propγlcyclohexane 14.6 % of 4-(trans-4-propylcγclohexyl)-4'-ethγlbiphenγl 10.8 °o of 4-(trans-4-ρentγlcyclohexyl)-4'-ethγlbiphenγl 3.8 % of 4-(trans-4-propylcγclohexyl)-4'-(traπs-4-propyl- cyclohexyl)-biphenyl 3.8 % of 4-(trans-4-pentylcyclohexyl) -4'-(trans-4-propyl- ' " cyclohexyl)-biphenyl 23 % of 4-(3,3.3-trifluoropropylphenyl) 4-pentylbenzoate exhibits a clearing point of N 56.5 I and an optical anisot¬ ropy of Δn = 0.11. SUBSTITUTESHEET Fiσ. 1 Route A Route B Route C

Claims: 7- Claims Mesogenic compounds with a ω-CF 3 -alkγl, a ω-CF 3 -alkenγl or a ω-CF 3 -alkinγl terminal group of formula I R- -ζ -Z m -< "(CH 2 ) B -Q-(CH 2 ) e -CF 3 I wherein R is a unsubstituted, a mono cyano or trifluoromethyl substituted or a mono-, oligo- or polyhalogeno-substituted alkyl or alkenyl residue having 1 to 15 carbon atoms, or such a residue wherein one or more CH 2 groups are each independently replaced by -0-. -CO-, -C0-0-, -0-CO- or -0-C0-0- with the proviso that oxygen atoms are not directly attached to each other. the rings A and B independently are (a) a trans-1,4-cγclohexγlene group, wherein one or two non-adjacent CH 2 groups may also be replaced by -0- and/or -S- or one or two CH groups may also be replaced by N, SUBSTITUTESHEET • ϊr- (b) a 1,4-phenylene group, wherein one or two CH groups may also be replaced by N, (c) a group selected from 1,4-bicγclo- (2,2,2)octylene, 1,4-cyclohexenylene, naphthalin-2,6-diγl and 1,3-cγclo- butylene, it being possible for groups (a) and (b) to be substituted by one or more of halogen, cyano or methyl, Z is independently from each other -C0-0-, -0-C0-, -CH 2 CH 2 -, -CH 2 0-, -0CH 2 -, -CC-, -CH=N-, -N=CH- or a single bond, Q is -C≡C-,-CH=CH- or a single bond, m is 1, 2 or 3, and n and o are in dependently from each other zero or integers from 1 to 10 with the proviso that in case Q is a single bond n + o > 1. 2. Liquid crystalline medium with at least two liquid crystalline components one component being a compound of formula I . 3. Electro-optical system containing a liquid crystalline medium according to claim 6. 4. Use of the compounds of the formula I according to claim 1 as components of liquid crystalline media. SUBSTITUTE SHfciΞT

Inventors: COATES DAVID, GREENFIELD SIMON, REIFFENRATH VOLKER, RIEGER BERNHARD, SAGE IAN CHARLES, COATES, DAVID, GREENFIELD, SIMON, REIFFENRATH, VOLKER, RIEGER, BERNHARD, SAGE, IAN, CHARLES
Applicants: MERCK PATENT GMBH, MERCK PATENT GESELLSCHAFT MIT BESCHRAENKTER HAFTUNG
Application year: 1990
Main classification: C07C69
IPC codes: C07C22, C07C43, C07C49, C07C69, C07D319, C09K19