Chiral oxiranylmethyl ethers, and their use as dopants in liquid-crystal mixtures

A liquid-crystal mixture which contains from 0.01 to 60% by weight of at least one oxiranylmethyl ether of the formula (I) ##STR46## in which the symbols and indices have the following meanings:

• * is a center of chirality,
• R.sup.1 is a straight-chain or branched alkyl radical having 1 to 16 carbon atoms (with or without an asymmetric carbon atom), it also being possible for one or more non-adjacent --CH.sub.2 -- groups to be replaced by --O--, --CO--, --CO--O--, --O--CO--, --O--CO--O--, --CH.dbd.CH--, --C.tbd.C-- or .DELTA., and/or for one or more H atoms of the alkyl radical to be substituted by F or is one of the following chiral groups:
• ##STR47## R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.8, independently of one another, are H or a straight-chain or branched alkyl radical having 1 to 16 carbon atoms, or R.sup.5 and R.sup.6 together may alternatively be --(CH.sub.2).sub.4 -- or --(CH.sub.2).sub.5 -- if they are bonded as substituents to a dioxolane system,
• A.sup.1, A.sup.2 and A.sup.3 are identical or different and are 1,4-phenylene, in which one or two H atoms may be replaced by F and/or CN, pyrazine-2,5-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, trans-1,4-cyclohexylene, in which one H atom may be replaced by CN, 1,3,4-thiadiazole-2,5-diyl, 1,3-dioxane-2,5-diyl, 1,3-thiazole-2,4-diyl, 1,3-thiazole-2,5-diyl, thiophene-2,4-diyl, thiophene-2,5-diyl or naphthalene-2,6-diyl, where A.sup.1 and A.sup.2 and A.sup.3 cannot simultaneously be unsubstituted 1,4-phenylene if M.sup.1 or M.sup.2 is --COO--,
• M.sup.1 and M.sup.2 are identical or different and are --CO--O--, --O--CO--, --O--CO--O--, --CH.sub.2 --O--, --O--CH.sub.2 --, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH-- or --C.tbd.C--,
• M.sup.3 is --CH.sub.2 --O--, --O--CH.sub.2 --, --CO--O--, --O--CO-- or a single bond,
• a, b, c, d and e are zero or one, with the proviso that the sum a+c+e is 1, 2 or 3,
• with the exception of the compounds in which the (--A.sup.1).sub.a (--M.sup.1).sub.b (--A.sup.2).sub.c (--M.sup.2).sub.d (--A.sup.3).sub.e -group has the following meanings:
• ##STR48## and with the exception of the compounds in which the R.sup.1 (--A.sup.1).sub.a (M.sup.1).sub.b (--A.sup.2).sub.c (--M.sup.2).sub.d (--A.sup.3).sub.e -- group has the following meanings:
• ##STR49## where R.sup.9 is straight-chain or branched (C.sub.3 -C.sub.12)-alkenyl containing a terminal double bond, in which one or two non-adjacent CH.sub.2 groups may be replaced by O and/or S atoms,
• R.sup.10 is straight-chain or branched alkyl having 1-12 carbon atoms, in which one or two non-adjacent CH.sub.2 groups may be replaced by O and/or S atoms, and
• R.sup.11 is an alkoxy group having 5-12 carbon atoms, ##STR50## where X is straight-chain or branched alkylene having 1 to 16 carbon atoms, in which one or two non-adjacent --CH.sub.2 -- groups may also be replaced by --O--, --S--, --O--CO--, --CO--O--, --CO-- or --O--CO--O--.