| 摘要 |
Chiral dopants of the formula <IMAGE> I in which n represents the number 0 or 1; R3 denotes a group of the general formula <IMAGE> II or <IMAGE> III A1, A2 and A3, independently of one another, represent 1,4-phenylene which is unsubstituted or substituted by halogen, cyano and/or methyl and in which 1 or 2 CH groups may be replaced by nitrogen, or represent trans-1,4-cyclohexylene, trans-1,3-dioxane-2,5-diyl or naphthalene-2,6-diyl, and ring A2 additionally represents 1,4-biphenylene; Z1 and Z4, independently of one another, denote a single covalent bond or -CH2CH2-; Z2 and Z3, independently of one another, denote a single covalent bond, -CH2CH2-, -COO-, -OOC-, -CH2O-, -OCH2-, -C 3BOND C-, -(CH2)4-, -(CH2)3O-, -O(CH2)3- or the trans-form of -CH=CH-CH2CH2-, -CH2CH2-CH=CH-, -CH=CH-CH2-O- or -O-CH2-CH=CH-; with the proviso that, if R3 denotes a group of the formula II, at least one of the groups Z2 and Z3 denotes -(CH2)4-, -(CH2)3-O-, -O-(CH2)3- or the trans-form of -CH=CH-CH2-CH2-, -CH2-CH2-CH=CH-, -CH=CH-CH2-O- or -O-CH2-CH=CH-; R1, R5 and R6 denote hydrogen, alkyl, phenyl or alkoxycarbonyl; R2 denotes alkyl, phenyl or alkoxycarbonyl; R4 denotes halogen, cyano, trifluoromethyl, trifluoromethoxy or alkyl in which one -CH2-CH2- may be replaced by -CH=CH- and/or one or two non-adjacent methylene groups may be replaced by -O-, -COO- and/or -OOC- and/or one methylene group methylene group may be replaced by -CHX-; X denotes halogen, cyano or methyl; and the dioxolane ring shown in the formula I is in optically active form, liquid-crystalline mixtures which contain such dopants, and their use for optical and electrooptical purposes.
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