| 摘要 |
Optically active compounds of the formula <IMAGE> I wherein m stands for the number 1 and R2 is an unsubstituted or halogen-substituted alkyl or alkenyl group in which optionally one methylene group is replaced by oxygen and/or optionally one methylene group is replaced by an ester group -COO- or -OOC-; or m stands for the number 0 or 1 and R2 denotes a group of the formula <IMAGE> II R1 and R3 each independently represent an alkyl or alkenyl group in which optionally one methylene group is replaced by oxygen; Z1, Z2 and Z3 each independently are a single covalent bond, -CH2O-, -OCH2-, -CH2CH2-, -COO- or -OOC-; n stands for the number 0 or 1; rings A1 an A2 each independently are unsubstituted or halogen, cyano and/or methyl-substituted 1,4-phenylene in which optionally 1 CH group or 2 CH groups is/are replaced by nitrogen; and C* denotes a chiral carbon atom; with the proviso that simultaneously R1 does not are an alkyl group, m and n do not are the number 1, Z1 does not are the group -CH2CH2- or -CH2O- and ring A1, Z2, ring A2 and R2 together do not are 4-(5-alkyl-2-pyrimidinyl)-phenyl, their preparation, liquid crystalline mixtures which contain these compounds and their use for electro-optical purposes.
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