Optically active compounds of the general formula ##STR1## wherein n stands for the number 0 or 1; R.sup.3 denotes a group R.sup.4 or a group of the general formula ##STR2## A.sup.1, A.sup.2 and A.sup.3 each independently represent 1,4-phenylene, which is unsubstituted or mono- or multiply-substituted with halogen, cyano and/or methyl and in which, where it is unsubstituted, 1 or 2 CH groups is/are optionally replaced by nitrogen, trans-1,4-cyclohexylene, trans-1,3-dioxane-2,5-diyl, bycyclo[2.2.2]octane-1,4-diyl, naphthalene-2,6-diyl, tetralin-2,6-diyl or trans-decalin-2,6-diyl; Z.sup.1 and Z.sup.4 each independently signify a single covalent bond or --CH.sub.2 CH.sub.2 --; Z.sup.2 and Z.sup.3 each independently denote a single covalent bond, --CH.sub.2 CH.sub.2 --, --COO--, --OOC--, --CH.sub.2 O--, --OCH.sub.2 --, --C.tbd.C--, --(CH.sub.2).sub.4 --, --(CH.sub.2).sub.3 O--, --O(CH.sub.2).sub.3 -- or the trans form of --CH.dbd.CH--CH.sub.2 CH.sub.2 --, --CH.sub.2 CH.sub.2 --CH.dbd.CH--, --CH.dbd.CH--CH.sub.2 O-- or --OCH.sub.2 --CH.dbd.CH--; R.sup.1 and R.sup.5 each independently signify alkyl with 1 to 12 carbon atoms, alkoxymethyl with 2 to 12 carbon atoms, p-alkoxyphenyl or p-alkoxybenzyl; R.sup.2 and R.sup.6 each independently signify hydrogen, alkyl with 1 to 12 carbon atoms or phenyl; R.sup.4 denotes hydrogen, halogen, cyano, trifluoromethyl, trifluoromethoxy or alkyl or alkenyl with 1 to 12 and, respectively, 2 to 12 carbon atoms, which are unsubstituted or mono- or multiply-substituted with halogen, cyano and/or methyl and in which one methylene group or two non-adjacent methylene groups can be replaced by --O--, --COO-- and/or --OOC--; and the oxazoline ring in formula I is present in optically active form, liquid crystalline mixtures which contain such dopants and their use for optical and electro-optical purposes.

FIELD OF THE INVENTION 
The invention is concerned with optically active dopants for liquid 
crystals and with liquid crystalline mixtures which contain such dopants 
and their use for optical and electro-optical purposes. 
BACKGROUND OF THE INVENTION 
Liquid crystal materials for electro-optical indicaters frequently contain 
one or more optically active additives for the induction of a chiral 
structure. For example, a nematic liquid crystal doped with an optically 
active additive is preferably used in indicators having a twisted nematic 
structure, e.g. to avoid a reversal of the direction of twisting (reverse 
twist) in TN cells (twisted-nematic) or in order to produce a sufficient 
twisting in cells having a highly twisted nematic structure such as STN 
cells (super twisted-nematic), SBE cells (super birefringence effect) or 
OMI cells (optical mode interference). Further, cholesteric liquid 
crystals for phase-change cells can preferably consist of a nematic basic 
material and one or more optically active dopants and ferroelectric liquid 
crystals for indicators based on chiral tilted smectic phases can 
preferably consist of a material having a tilted smectic phase and one or 
more optically active dopants. 
The electro-optical characteristics of liquid crystal indicators are 
temperature-dependent, which is especially troublesome in the case of 
multiplex operation. It is, however, known that this temperature 
dependence can be compensated for at least partially by the addition of 
chiral dopants, which induce a pitch which decreases with increasing 
temperature. Such an inverse temperature dependence has hitherto been 
found only for a few compounds. It can, however, also be achieved by the 
use of at least two chiral dopants, which have a different relative 
temperature dependence and which induce a different twisting direction 
(U.S. Pat. No. 4,264,148). Of course, this requires for the most part a 
relatively high amount of chiral dopants. 
Cholesteric liquid crystals reflect light in a wavelength range for which 
the wavelength is approximately equal to the helical pitch. The spectral 
width of this reflected light can be varied by a suitable choice of the 
liquid crystal. The reflected light is completely circularly polarized. 
The direction of rotation of the reflected light depends on the direction 
of rotation of the cholesteric helical structure. The light circularly 
polarized in the opposite direction is transmitted unimpaired. These 
properties can be utilized for the production of optical filters, 
polarizers, analyzers etc. Further, cholesteric liquid crystals have also 
variously been used for thermochromic applications and in cosmetic 
preparations. 
Cholesteric liquid crystals for the above applications can preferably 
consist of a nematic or cholesteric basic material and one or more chiral 
dopants, which permits a simple adjustment of the desired helical pitch. 
In order to produce cholesteric mixtures having a pitch in the range of the 
wavelength of visible light, the chiral dopants should have a twisting 
capacity which is as high as possible and should have a good solubility in 
usual liquid crystal materials. Furthermore, the chiral dopants should 
have an adequate stability, should have a good compatibility with the 
mesophase type of the liquid crystal material and should not restrict the 
mesophase range too severely. Such properties would also be desirable for 
chiral dopants for the production of the twisted nematic structures 
referred to earlier, since their amount can be held low in order that the 
properties of the liquid crystal material are influenced only 
immaterially. 
SUMMARY OF THE INVENTION 
The invention is directed to optically active compounds of the formula 
##STR3## 
wherein n stands for the number 0 or 1; R.sup.3 denotes a group R.sup.4 or 
a group of the formula 
##STR4## 
wherein A.sup.1, A.sup.2 and A3 each independently represent 
1,4-phenylene, which is unsubstituted or mono- or multiply-substituted 
with halogen, cyano and/or methyl, and where the 1,4-phenylene is 
unsubstituted, 1 or 2 CH groups can be optionally replaced by nitrogen; 
trans-1,4-cyclohexylene; trans-1,3-dioxane-2,5-diyl; 
bycyclo[2.2.2]octane-1,4-diyl; naphthalene-2,6-diyl; tetralin-2,6-diyl or 
trans-decalin-2,6-diyl; Z.sup.1 and Z.sup.4 each independently are a 
single covalent bond or --CH.sub.2 CH.sub.2 --; Z.sup.2 and Z.sup.3 each 
independently denote a single covalent bond, --CH.sub.2 CH.sub.2 --, 
--COO--, --OOC--, --CH.sub.2 O--, --OCH.sub.2 --, --C.tbd.C--, 
--(CH.sub.2).sub.4 --, --(CH.sub.2).sub.3 O--, --O(CH.sub.2).sub.3 -- or 
the trans form of --CH.dbd.CH--CH.sub.2 CH.sub.2 --, --CH.sub.2 CH.sub.2 
--CH.dbd.CH--, --CH.dbd.CH--CH.sub.2 O-- or --OCH.sub.2 --CH.dbd.CH--; 
R.sup.1 and R.sup.5 each independently are alkyl with 1 to 12 carbon 
atoms, alkoxymethyl with 2 to 12 carbon atoms, p-alkoxyphenyl or 
p-alkoxybenzyl; R.sup.2 and R.sup.6 each independently is hydrogen, alkyl 
with 1 to 12 carbon atoms or phenyl; R.sup.7 and R.sup.8 each 
independently is hydrogen, alkyl with 1 to 12 carbon atoms, phenyl or 
alkoxycarbonyl with 2 to 12 carbon atoms, with the proviso that R.sup.7 
and R.sup.8 do not simultaneously represent hydrogen; R.sup.9 is alkyl 
with 1 to 9 carbon atoms or alkenyl with 2 to 9 carbon atoms, which alkyl 
or alkenyl are unsubstituted or mono- or multiply-substituted with 
fluorine and in which one --CH.sub.2 -- group can be replaced by --O--; 
R.sup.4 denotes hydrogen, halogen, cyano, trifluoromethyl, 
trifluoromethoxy or alkyl with 1 to 12 carbon atoms or alkenyl with 2 to 
12 carbon atoms, which alkyl or alkenyl are unsubstituted or mono- or 
multiply-substituted with halogen, cyano and/or methyl and in which one 
methylene group or two non-adjacent methylene groups can be replaced by 
--O--, --COO-- and/or --OOC--; and the oxazoline ring in formula I is 
present in optically active form. 
DETAILED DESCRIPTION OF THE INVENTION 
The invention relates to optically active compounds of the formula 
##STR5## 
wherein n stands for the number 0 or 1; R.sup.3 denotes a group R.sup.4 or 
a group of the formula 
##STR6## 
wherein A.sup.1, A.sup.2 and A.sup.3 each independently represent 
1,4-phenylene, which is unsubstituted or mono- or multiply-substituted 
with halogen, cyano and/or methyl, and where the 1,4-phenylene is 
unsubstituted, 1 or 2 CH groups can be optionally replaced by nitrogen; 
trans-1,4-cyclohexylene; trans-1,3-dioxane-2,5-diyl; 
bycyclo[2.2.2]octane-1,4-diyl; naphthalene-2,6-diyl; tetralin-2,6-diyl or 
trans-decalin-2,6-diyl; Z.sup.1 and Z.sup.4 each independently are a 
single covalent bond or --CH.sub.2 CH.sub.2 --; Z.sup.2 and Z.sup.3 each 
independently denote a single covalent bond, --CH.sub.2 CH.sub.2 --, 
--COO--, --OOC--, --CH.sub.2 O--, --OCH.sub.2 --, --C.tbd.C--, 
--(CH.sub.2).sub.4--, --(CH.sub.2).sub.3 O--, --O(CH.sub.2).sub.3 -- or 
the trans form of --CH.dbd.CH--CH.sub.2 CH.sub.2 --, --CH.sub.2 CH.sub.2 
--CH .dbd.CH--, --CH.dbd.CH--CH.sub.2 O-- or --OCH.sub.2 --CH.dbd.CH-- ; 
R.sup.1 and R.sup.5 each independently are alkyl with 1 to 12 carbon 
atoms, alkoxymethyl with 2 to 12 carbon atoms, p-alkoxyphenyl or 
p-alkoxybenzyl; R.sup.2 and R.sup.6 each independently is hydrogen, alkyl 
with 1 to 12 carbon atoms or phenyl; R.sup.7 and R.sup.8 each 
independently is hydrogen, alkyl with 1 to 12 carbon atoms, phenyl or 
alkoxycarbonyl with 2 to 12 carbon atoms, with the proviso that R.sup.7 
and R.sup.8 do not simultaneously represent hydrogen; R.sup.9 is alkyl 
with 1 to 9 carbon atoms or alkenyl with 2 to 9 carbon atoms respectively, 
which alkyl or alkenyl are unsubstituted or mono- or multiply-substituted 
with fluorine and in which one --CH.sub.2 -- group can be replaced by 
--O--; R.sup.4 denotes hydrogen, halogen, cyano, trifluoromethyl, 
trifluoromethoxy or alkyl with 1 to 12 carbon atoms or alkenyl with 2 to 
12 carbon atoms respectively, which alkyl or alkenyl are unsubstituted or 
mono- or multiply-substituted with halogen, cyano and/or methyl and in 
which one methylene group or two non-adjacent methylene groups can be 
replaced by --O--, --COO-- and/or --OOC--; and the oxazoline ring in 
formula I is present in optically active form. 
The compounds of formula I have very good solubility in usual liquid 
crystal materials and permit very high twisting of the liquid crystal 
structure. In contrast to known materials having high twisting capacities, 
the clearing points of liquid crystals with the addition of compounds of 
formula I are as a rule not lowered or are lowered only immaterially. Many 
of the compounds in accordance with the invention themselves even have 
liquid crystalline properties. The compounds of formula I can be produced 
readily, have a relatively low viscosity and are sufficiently stable to 
electric and magnetic fields. They therefore fulfil in an optimum manner 
the requirements referred to above. 
The properties of the compounds of formula I can be varied in a wide range 
depending on the number and significance of the rings and of the 
substituents. For example, aromatic rings lead to high values of the 
optical anisotropy and saturated rings lead to low values of the optical 
anisotropy. A clearing point increase can be achieved, for example, by the 
introduction of an additional ring. Accordingly, compounds of formula I in 
which n signifies the number 1 and/or R.sup.3 signifies a group of formula 
II often have liquid crystalline properties themselves. Polar end groups 
such as cyano, halogen, trifluoromethyl or trifluoromethoxy and rings such 
as pyrimidine-2,5-diyl or trans-1,3-dioxane-2,5-diyl increase the 
dielectric anisotropy; rings such as pyridazine-3,6-diyl or 
2,3-dicyano-1,4-phenylene reduce the dielectric anisotropy. Lateral 
halogen or cyano substitutents contribute to the dielectric constant not 
only parallel to, but also perpendicular to the longitudinal axis of the 
molecule, which, depending on the substitution pattern, can be utilized to 
increase or reduce the dielectric anisotropy. Further, a possible tendency 
to form highly ordered smectic phases can often largely be suppressed and 
the solubility can also often be improved by lateral substituents on one 
or more rings. Furthermore, the elastic properties, the threshold 
potentials, the response times, the mesophases etc. can be modified 
further by a C.dbd.C double bond in the side-chain. 
The compounds in accordance with the invention therefore also permit, in 
addition to the induction of high twisting, the ability to optimize liquid 
crystalline and electro-optical properties in a wide range according to 
application and desired properties. 
As used herein, the term "halogen" denotes fluorine, chlorine, bromine or 
iodine. Preferred are fluorine or chlorine. 
What is meant by the term "1,4-phenylene, which is unsubstituted or mono- 
or multiply-substituted with halogen, cyano and/or methyl and when the 
1,4-phenylene is unsubstituted, 1 or 2 CH groups is/are optionally 
replaced by nitrogen" are groups such as 1,4-phenylene, 
2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 
2-chloro-1,4-phenylene, 2-bromo-1,4-phenylene, 2-cyano-1,4-phenylene, 
2,3-dicyano-1,4-phenylene, 2-methyl-1,4-phenylene, pyridine-2,5-diyl, 
pyrazine-2,5-diyl, pyrimidine-2,5-diyl, pyridazine-3,6-diyl, and the like. 
1,4-Phenylene, 2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 
pyridine-2,5-diyl, pyrazine-2,5-diyl and pyrimidine-2,5-diyl are preferred 
groups. 
The term "tetralin-2,6-diyl" denotes 
1,2,3,4-tetrahydronaphthalene-2,6-diyl. The term "trans-decalin-2,6-diyl" 
embraces 2,6-disubstituted groups derived from trans-decahydronaphthalene, 
especially 
(4a.alpha.H,7a.beta.H)-decahydronaphthalene-2.alpha.,6.beta.-diyl. 
The term "alkyl" embraces straight-chain and branched, optionally chiral 
groups, with 1-12 carbon atoms such as methyl, ethyl, propyl, isopropyl, 
butyl, isobutyl, tert.butyl, 2-butyl (same as methylpropyl), 
2-methylbutyl, pentyl, hexyl, heptyl, octyl, 2-octyl (same as 
1-methylheptyl), nonyl, decyl, undecyl, dodecyl and the like. Alkyl 
residues with 1 to 7 carbon atoms, especially alkyl residues with 1 to 5 
carbon atoms such as, for example, methyl, isopropyl and tert.butyl, are 
preferred. 
The term "alkoxymethyl" embraces straight-chain and branched, optionally 
chiral groups with 2 to 12, preferably 2 to 7, carbon atoms such as, for 
example, methoxymethyl, ethoxymethyl, propyloxymethyl, butyloxymethyl, 
isopropyloxymethyl, tert.-butyloxymethyl and the like; those residues with 
2 to 5 carbon atoms are especially preferred. 
The term "alkoxycarbonyl" embraces straight-chain and branched, optionally 
chiral groups with 2-12 carbon atoms such as methoxycarbonyl, 
ethoxycarbonyl, propyloxycarbonyl, isopropyloxycarbonyl, butyloxycarbonyl, 
isobutyloxycarbonyl, (2-butyl)oxycarbonyl, (2-methylbutyl)oxycarbonyl, 
pentyloxycarbonyl, hexyloxycarbonyl and the like. Groups with 2 to 7 
carbon atoms are preferred. 
In the terms "p-alkoxyphenyl" and "p-alkoxybenzyl", alkoxy signifies a 
straight-chain or a branched, optionally chiral, residue with 1 to 7 
carbon atoms. Examples of preferred p-alkoxyphenyl- and 
p-alkoxybenzyl-groups are 4-methoxyphenyl, 4-ethoxyphenyl, 
4-propyloxyphenyl, 4-butyloxyphenyl, 4-pentyloxyphenyl, 4-hexyloxyphenyl, 
4-heptyloxyphenyl, 4-methoxybenzyl, 4-ethoxybenzyl, 4-propyloxybenzyl, 
4-butyloxybenzyl, 4-pentyloxybenzyl, 4-hexyloxybenzyl, 4-heptyloxybenzyl 
and the like. 
As used herein the term "alkyl with 1 to 9 carbon atoms or alkenyl with 2 
to 9 carbon atoms respectively, which is unsubstituted or mono- or 
multiply-substituted with fluorine and in which one --CH.sub.2 -- group 
can be replaced by --O--", signifies straight-chain and branched 
(optionally chiral) residues with 1 to 9 and, respectively, 2 to 9 carbon 
atoms such as alkyl, 3E-alkenyl, 4-alkenyl, alkenyl having a terminal 
double bond, alkoxy, 2E-alkenyloxy, 3-alkenyloxy, alkenyloxy having a 
terminal double bond, alkoxyalkyl, alkenyloxyalkyl, alkoxyalkenyl, 
fluoroalkyl and the like. Residues with 1 to 7 carbon atoms and, 
respectively, 2 to 7 carbon atoms are preferred. Methyl, ethyl, propyl, 
butyl, pentyl, hexyl, heptyl, 1-methylpropyl, 2-methylbutyl, 
3-methylpentyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 
4-pentenyl, 4Z-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl, methoxy, 
ethoxy, propyloxy, butyloxy, pentyloxy, hexyloxy, heptyloxy, 
1-methyl-propyloxy, 2-methylbutyloxy, 3-methylpentyloxy, allyloxy, 
2E-butenyloxy, 2E-pentenyloxy, 2E-hexenyloxy, 2E-heptenyloxy, 3butenyloxy, 
3Z-pentenyloxy, 3Z-hexenyloxy, 3Z-heptenyloxy, 4-pentenyloxy, 
5-hexenyloxy, 6-heptenyloxy, methoxymethyl, ethoxymethyl, propyloxymethyl, 
allyloxymethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 
5-fluoropentyl, 6-fluorohexyl, 1-fluoropropyl, 1-fluoropentyl, 
2fluoropropyloxy, 2-fluoro-butyloxy, 2-fluoropentyloxy, 2-fluorohexyloxy, 
2-fluorobutyloxy and the like are examples of preferred residues. It is 
especially preferred that the aforementioned residues have 1 to 5 carbon 
atoms and, respectively, 2 to 5 carbon atoms. 
The term "alkyl or alkenyl, which alkyl or alkenyl is unsubstituted or 
mono- or multiply-substituted with halogen, cyano and/or methyl and in 
which one methylene group or two non-adjacent methylene groups can be 
replaced by --O--, --COO-- and/or --OOC--" embraces straight-chain and 
branched (optionally chiral) alkyl residues with 1 to 12 carbon atoms and, 
alkenyl residues with 2 to 12 carbon atoms such as alkyl, 1E-alkenyl, 
3E-alkenyl, 4-alkenyl, alkenyl having a terminal double bond, alkoxy, 
2E-alkenyloxy, 3-alkenyloxy, alkenyloxy having a terminal double bond, 
alkoxyalkyl, alkenyloxyalkyl, alkoxycarbonyl, alkoxycarbonylalkoxy (e.g. 
(1-alkoxycarbonyl)-1-ethoxy), alkoxycarbonylalkoxycarbonyl (e.g. 
(1-alkoxycarbonyl)-1-ethoxy-carbonyl), alkanoyloxy, 1-haloalkyl, 
2-haloalkyl, 2-haloalkoxy, 2-haloalkoxycarbonyl, 1-cyanoalkyl, 
2-cyanoalkyl, 2cyanoalkoxy, 2-cyanoalkoxycarbonyl, 1-methylalkyl, 
2-methylalkyl, 1-methyl-alkoxy, 2-methylalkoxy, 2-methylalkoxycarbonyl and 
the like. Methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, 
nonyl, decyl, undecyl, dodecyl, 1-methylpropyl, 1-methylheptyl, 
2-methylbutyl, 3-methylpentyl, vinyl, 1E-propenyl, 1 E-butenyl, 
1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 
3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl, 
7-octenyl, 8-nonenyl, 9-decenyl, 10-undecenyl, 11-dodecenyl, methoxy, 
ethoxy, propyloxy, butyloxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, 
nonyloxy, decyloxy, undecyloxy, dodecyloxy, 1-methylpropyloxy, 
1-methylheptyloxy, 2-methylbutyloxy, 3-methylpentyloxy, allyloxy, 
2E-butenyloxy, 2E-pentenyloxy, 2E-hexenyloxy, 2E-heptenyloxy, 
3-butenyloxy, 3Z-pentenyloxy, 3Z-hexenyloxy, 3Z-heptenyloxy, 
4-pentenyloxy, 5-hexenyloxy, 6-heptenyloxy, 7-octenyloxy, 8-nonenyloxy, 
9-decenyloxy, 10-undecenyloxy, 11-dodecenyloxy, methoxymethyl, 
ethoxymethyl, propyloxymethyl, allyloxymethyl, methoxycarbonyl, 
ethoxycarbonyl, propyloxycarbonyl, 1-methylpropyloxycarbonyl, 
1-(methoxycarbonyl)ethoxy, 1-(ethoxycarbonyl)ethoxy, 
1-(methoxycarbonyl)ethoxycarbonyl, 1-(ethoxy-carbonyl)ethoxy-carbonyl, 
1-(isopropyloxycarbonyl)ethoxycarbonyl, 
1-(butyloxycarbonyl)ethoxycarbonyl, acetoxy, propionyloxy, butyryloxy, 
1-fluoropropyl, 1-fluoropentyl, 1-chloropropyl, 2-fluoropropyl, 
2-fluoropentyl, 2-chloropropyl, 2-fluoropropyloxy, 2-fluorobutyloxy, 
2-fluoropentyloxy, 2fluorohexyloxy, 2-chloropropyloxy, 2-fluorobutyloxy, 
2-fluoropropyloxycarbonyl, 2-fluorobutyloxycarbonyl, 
2-fluoropentyloxycarbonyl, 2-fluoro-3methylbutyloxycarbonyl, 
2-fluoro-4-methylpentyloxycarbonyl, 2-chloropropyloxycarbonyl, 
1-cyanopropyl, 1-cyanopentyl, 2-cyanopropyl, 2-cyanopentyl, 
2-cyanopropyloxy, 2-cyanobutyloxy, 2-cyanopentyloxy, 2-cyanohexyloxy, 
2-cyanopropyloxycarbonyl, 2-cyanobutyloxycarbonyl, 
2-cyano-3methylbutyloxycarbonyl, 2-cyano-4-methylpentyloxycarbonyl and the 
like are examples of preferred residues. Preferably, the aforementioned 
alkyl residues have 1 to 12 carbon atoms and, the alkenyl residues have 2 
to 12 carbon atoms. Alkyl residues of R.sup.4 with 1 to 7 carbon atoms 
and, alkenyl residues of 2 to 7 carbon atoms are especially preferred. 
Formula I embraces optically active compounds of the following formulas 
##STR7## 
wherein R.sup.1, R.sup.2, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, 
R.sup.9, A.sup.1, A.sup.2, Z.sup.1, Z.sup.2 and Z.sup.4 have the above 
definitions. 
The compounds of formula I have at least one optically active oxazoline 
ring. The oxazoline ring in formula I has a chiral carbon atom in position 
4 and, where R.sup.2 is different from hydrogen, a further chiral carbon 
atom in position 5. It will be evident to a person skilled in the art that 
in order to achieve optical activity the carbon atom in position 4 of the 
oxazoline ring must be present completely or predominantly in the R- or 
S-form and, where R.sup.1 and R.sup.2 are identical, the carbon atom in 
position 5 of the oxazoline ring should have completely or predominantly 
the same configuration as the carbon atom in position 4 or basically can 
also have a R/S ratio of 50:50. In order to achieve a twisting capacity 
which is as high as possible, the carbon atom in position 4 of the 
oxazoline ring should preferably be present in the R- or S-configuration 
in the optically purest form possible and, where R.sup.2 is different from 
hydrogen, the carbon atom in position 5 of the oxazoline ring should 
preferably be present in either configuration and in the optically purest 
form as possible, which increases the twisting capacity. Preferred optical 
isomers having a high twisting capacity are the (4R)-isomers and the 
(4S)-isomers of the compounds of formula I in which R.sup.2 signifies 
hydrogen and the (4R,5R)-isomers and the (4S,5S)-isomers of the compounds 
of formula I in which R.sup.2 signifies alkyl or phenyl. 
Especially preferred are those compounds of formula I and, respectively, 
I-1 to I-10 in which A.sup.1, A.sup.2 and A.sup.3 each independently 
represent 1,4-phenylene, which is unsubstituted or mono- or 
multiply-substituted with halogen, cyano and/or methyl (especially 
1,4-phenylene, 2-fluoro-1,4-phenylene or 2,3-difluoro- 1,4-phenylene), or 
trans-1,4-cyclohexylene. Alternatively, one of groups A.sup.1, A.sup.2 and 
A.sup.3 also represents pyrimidine-2,5-diyl or pyridine-2,5-diyl and, 
further, one of the optionally present groups Z.sup.2 and Z.sup.3 denotes 
a single covalent bond, --CH.sub.2 CH.sub.2 --, --COO-- or --OOC-- 
(especially a single covalent bond) and, where present, the other of 
groups Z.sup.2 and Z.sup.3 denotes a single covalent bond. These compounds 
are very stable and as a rule are especially readily synthesized from 
known liquid crystal intermediates. 
The twisting capacity of the compounds in accordance with the invention is 
determined mainly by the optically active oxazoline residue; it will thus 
be evident that the preferred rings and bridging groups named just above 
have an influence on the liquid crystalline properties of the compounds 
only and thus can be replaced by other rings specified for A.sup.1, 
A.sup.2 and A.sup.3 in formula I and bridging groups specified for Z.sup.2 
and Z.sup.4 in formula I in order to achieve a similar effect and likewise 
good compatibility with usual liquid crystals. 
Z.sup.1 and Z.sup.2 in formulae I and, respectively, I-1 to I-10 above can 
have the same significance or different significances. Preferably, Z.sup.1 
and/or Z.sup.2 stands for a single covalent bond. 
The optically active compounds of the following formulas are examples of 
especially preferred compounds of formula I 
##STR8## 
wherein R.sup.1, R.sup.2, R.sup.4, R.sup.5 and R.sup.6 have the above 
significances and ring B represents 1,4-phenylene, which is unsubstituted 
or mono- or multiply-substituted with halogen (preferably 1,4-phenylene, 
2-fluoro-1,4-phenylene or 2,3-difluoro-1,4-phenylene), or 
trans-1,4-cyclohexylene. 
In formulas I, I-1 to I-4 and I-11 to I-19 above, R.sup.4 preferably 
denotes halogen (especially fluorine or chlorine), cyano, trifluoromethyl, 
trifluoromethoxy, alkyl, alkenyl, alkoxy or alkenyloxy. However, if 
desired, in an alkyl residue R.sup.4 one methylene group or two 
non-adjacent methylene groups can be replaced by --O--, --COO-- and/or 
--OOC-- and/or one methylene group can be replaced by --CHX-- (wherein X 
signifies halogen, cyano or methyl). This possibility can be utilized e.g. 
to increase the twisting capacity by the introduction of chiral groups 
staring from simple, optically active compounds. Preferred examples of 
such groups are the residues derived from optically active lactic acid 
such as 1-(alkoxycarbonyl)ethoxy and 1-(alkoxycarbonyl)ethoxycarbonyl. 
R.sup.4 in the above formula can therefore preferably also signify one of 
these residues. 
R.sup.4 stands for alkyl- and alkenyl-groups with 1 to 12 carbon atoms and, 
respectively 2 to 12 carbon atoms. Preferred residues R.sup.4 are those 
with 1 to 7 carbon atoms and, respectively, 2 to 7 carbon atoms, 
especially those with 1 to 5 carbon atoms and, respectively, 2 to 5 carbon 
atoms. 
The compounds of formula I can, also contain an end group of formula III, 
i.e. an additional oxazoline residue. This group can be optically 
inactive. However, there are preferred groups of formula III which are 
present in an optically active form, which increases the twisting 
capacity. Such compounds having an increased twisting capacity, which can 
also be produced especially readily, are those in which both oxazoline 
rings have the same configuration and the same substituents. Preferably, 
therefore, in formula III R.sup.5 has the same significance and at the 
adjacent C atom the same configuration as R.sup.1 and R.sup.6 has the same 
significance and at the adjacent C atom the same configuration as R.sup.2. 
This also accordingly applies to the two oxazoline residues in formulae 
I-5, I-6, I-19, I-20, I-21 and I-22. 
Of the compounds of formula I in which R.sup.3 signifies a group of formula 
IV or of formula V (i.e. I-7, I-8, I-9 and I-10) there are preferred those 
in which the dioxane ring (formula IV) and, respectively, the dioxane ring 
(formula V) is present in optically active form. 
R.sup.7 and R.sup.8 have, when different from hydrogen and phenyl, 1 to 12 
carbon atoms. In general, there are preferred residue R.sup.7 and R.sup.8 
with 1 to 7 carbon atoms, but especially those with 1 to 5 carbon atoms. 
The residue R.sup.9 has 1 to 9 carbon atoms. Especially preferred residues 
of R.sup.9 have 1 to 5 carbon atoms. 
Preferred optical isomers are therefore the compounds having the relative 
configuration given in the following formula 
##STR9## 
wherein R.sup.3 denotes a group R.sup.4 or a group of the formula 
##STR10## 
n, A.sup.1, A.sup.2, A.sup.3, Z.sup.1, Z.sup.2, Z.sup.3, Z.sup.4, R.sup.1, 
R.sup.2 and R.sup.4, R.sup.5, R.sup.6, R.sup.7 R.sup.8 and R.sup.9 have 
the above significances; the chiral center (R*) is absent when R.sup.2 
signifies hydrogen and stands for R* when R.sup.2 is different from 
hydrogen; and the asymmetric carbon atoms denoted by R* are all present in 
the R-configuration or are all present in the S-configuration. 
Formula IA embraces the optical isomers indicated by R* as well as their 
optical antipodes (S-form) which have the same twisting capacity, but with 
opposite direction of twisting. 
Preferred optically active compounds of formula IA are those in which 
R.sup.1 and R.sup.2 have different significances or preferably the same 
significance. Especially preferred are compounds wherein R.sup.1 denotes 
C.sub.1 -C.sub.5 -alkyl, p-alkoxy-phenyl or p-alkoxybenzyl, especially 
isopropyl and tert.butyl. These compounds are readily accessible from the 
corresponding, optically active 2-amino-1-ethyl alcohols. Those compounds 
of formulae I-1 to I-21 in which R.sup.1 denotes isopropyl or tert.butyl 
and R.sup.2 denotes hydrogen are especially preferred with regard to their 
preparation. 
In formula IA above and in the sub-groups of compounds of formula I 
referred to above as being preferred rings A.sup.1, A.sup.2, A.sup.3, ring 
B, the bridging groups Z.sup.1, Z.sup.2, Z.sup.3, Z.sup.4 especially have 
the preferred significances given in connection with formulas I and I-1 to 
I-21. 
The compounds in accordance with the invention can be readily produced in a 
manner known per se. They can be produced, for example, by reaching an 
acid chloride of the formula Cl.OC--Z.sup.1 --A.sup.1 --(Z.sup.2 
--A.sup.2).sub.n --R.sup.3 with an optically active aminoalcohol of the 
formula R.sup.1 --CH(NH.sub.2)--CH(OH)--R.sup.2. The reaction of the acid 
chloride with the aminoalcohol can be effected in a manner known per se. 
Conveniently, the reaction is effected in an inert organic solvent (for 
example dichloromethane). Temperature and pressure are not critical, but 
the reaction is preferably carried out at 0.degree. C. and atmospheric 
pressure. The formation of the oxazoline ring can be effected in a manner 
known per se. Conveniently, the reaction is effected in an inert solvent 
(for example dichloromethane) in the presence of thionyl chloride. 
An optionally present second oxazoline ring (when R.sup.3 signifies a group 
of formula III) can be formed in analogous manner, likewise from an acid 
chloride and aminoalcohol. If both aminoalcohols [R.sup.1 
--CH(NH.sub.2)--CH(OH)--R.sup.2 and R.sup.5 
--CH(NH.sub.2)--CH(OH)--R.sup.6 ] are identical, both oxazoline rings can, 
if desired, be formed in one step. 
If the compound of formula I contains one or more ester groups in Z.sup.2, 
Z.sup.3 and/or R.sup.4, then the esterification can preferably be effected 
after the oxazoline ring has been formed. If desired, ether groups and 
other functional groups can also be introduced after the oxazoline ring 
has been formed. 
Such methods will basically be known to a person skilled in the art, e.g. 
from the production of liquid crystalline dioxanes. The aminoalcohols 
required as starting materials are known compounds or are analognes of 
known compounds. The acid chlorides required as starting materials are 
also known compounds or can be prepared according to methods known per se. 
Such compounds and methods are e.g. known from U.S. Pat. Nos. 4,676,604, 
4,621,901 and EP-A-0168683. 
The invention is also concerned with liquid crystalline mixtures containing 
a liquid crystalline carrier material and one or more optically active 
compounds of formula I. Suitable carrier materials are all liquid crystal 
materials which have a twistable liquid crystal phase with an adequate 
mesophase range. The compounds of formula I are especially suitable as 
chiral dopants for nematic or cholesteric carrier materials. The liquid 
crystalline carrier material can be a single compound or a mixture and 
preferably has a clearing point of at least about 60.degree. C. 
The content of chiral dopant of formula I is determined essentially by its 
twisting capacity and the desired pitch. The content of chiral dopant can 
therefore vary in a wide range according to application and can be, for 
example, about 0.1-30 wt. %. Depending on the type and thickness of cell, 
a pitch of about 3-40 mm is mainly required for indicators based on liquid 
crystal having a twisted nematic structure and therefore a correspondingly 
smaller content is sufficient. On the other hand, for applications which 
are based on the reflection of visible light by cholesteric layers, 
pitches of less than 2 mm, for example about 0.4-0.6 mm, are necessary and 
this requires a correspondingly higher content of chiral dopant. 
Suitable liquid crystalline carrier materials are known in large numbers 
and are commercially available. As a rule, liquid crystalline mixtures 
containing two or more components are preferred carrier materials. 
Basically, however, a liquid crystalline compound can be used as the 
carrier material when it has a sufficiently broad mesophase. 
Compounds of the following formulas are especially suitable as components 
for liquid crystalline carrier materials 
##STR11## 
wherein R.sup.10 and R.sup.13 signify alkyl, alkoxyalkyl, 3E-alkenyl, 
4-alkenyl or on saturated rings also 1E-alkenyl; p signifies 0 or 1; ring 
C denotes 1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 
trans-1,4-cyclohexylene or trans-1,3-dioxane-2,5-diyl; R.sup.11 represents 
cyano, isothiocyanato, fluorine, alkyl, 3E-alkenyl, 4-alkenyl, alkoxy, 
2E-alkenyloxy, 3-alkenyloxy or 1-alkynyl; ring D signifies 1,4-phenylene 
or trans-1,4-cyclohexylene; R.sup.12 denotes alkyl, 3E-alkenyl, 4-alkenyl 
or on trans-1,4-cyclohexylene also 1E-alkenyl or on 1,4-phenylene also 
cyano, isothiocyanato, alkoxy, 2E-alkenyloxy or 3-alkenyloxy; R.sup.14 
signifies alkyl, 1E-alkenyl, 3E-alkenyl or 4-alkenyl; R.sup.15 represents 
cyano, alkyl, 1E-alkenyl, 3E-alkenyl, 4-alkenyl, alkoxy, 2E-alkenyloxy, 
3-alkenyloxy, alkoxymethyl or (2E-alkenyl)oxymethyl; Z.sup.5 and Z.sup.6 
denote a single covalent bond or --CH.sub.2 CH.sub.2 --, whereby two 
aromatic rings are always linked by a single covalent bond; R.sup.16 
signifies hydrogen, fluorine or chlorine; R.sup.17 represents cyano, 
fluorine or chlorine; R.sup.18 denotes hydrogen or fluorine; R.sup.19 
represents fluorine or chlorine. 
R.sup.10, R.sup.11, R.sup.12, R.sup.13, R.sup.14 and R.sup.15 each have a 
maximum of 12 carbon atoms, preferably a maximum of 7 carbon atoms. 
1E-Alkenyl, 3E-alkenyl and 4Z-alkenyl are preferred alkenyl groups. 
2E-Alkenyloxy and 3Z-alkenyloxy are preferred alkenyloxy groups.

The invention is illustrated in more detail by the following Examples. 
In connection with liquid crystal phases and phase transitions, C signifies 
a crystalline phase, S.sub.B signifies a smectic B phase, N signifies a 
nematic phase, N.sup.* signifies a cholesteric phase and I signifies the 
isotropic phase. The helical pitch is denoted by p and the wavelength of 
the selectively reflected, circularly polarized light is denoted by 
l.sub.max. Optical antipodes have in each case "mirror image properties", 
i.e. the same melting points etc, but lead to the opposite helical 
rotation and opposite circular polarization of the reflected light. Unless 
indicated otherwise, the Examples were carried out as written. 
EXAMPLE 1 
A suspension of 1.05 g of 
4-(trans-4-heptylcyclohexyl)-N-[(S)-2-hydroxy-1-isopropylethyl)benzamide 
in 40 ml of acetenitrile was treated dropwise with 0.7 ml of thionyl 
chloride at 0.degree. C. and while gassing with nitrogen. The reaction 
mixture was stirred at 0.degree. C. overnight, poured into 100 ml of 
saturated potassium carbonate solution and then extracted three times with 
50 ml of diethyl ether each time. The combined organic phases were washed 
twice with 50 ml of saturated sodium chloride solution each time, dried 
over magnesium sulphate, filtered and subsequently concentrated. 
Chromatography of the residue on silica gel with hexane/ethyl acetate 
(vol. 2:1) and recrystallization from acetone at -25.degree. C. gave pure 
(S)-2-[4-(trans-4-heptylcyclohexyl)phenyl]-4-isopropyl-2-oxazoline with 
m.p. (C-I) 51.degree. C. and cl.p. (S-I) 46.degree. C. 
The 
4-(trans-4-heptylcyclohexyl)-N-[(S)-2-hydroxy-1-isopropylethyl)benzamide u 
sed as the starting material was prepared as follows: 
2.1 g of 4-(trans-4-heptylcyclohexyl)benzoic acid were heated at 80.degree. 
C. for 1 hour with 10 ml of thionyl chloride in toluene. The solution 
obtained was evaporated under reduced pressure, the residue was treated 
with 20 ml of absolute toluene and the solution was again evaporated under 
reduced pressure. The acid chloride obtained was taken up in 50 ml of 
dichloromethane and added dropwise to a solution of 1.45 g of 
S(+)-2-amino-3-methyl-1-butanol in 20 ml of dichloromethane at 0.degree. 
C. and while gassing with nitrogen. The reaction mixture was stirred at 
room temperature overnight, then poured into 100 ml of potassium 
carbonate, stirred intensively for 5 minutes, then extracted three times 
with 50 ml of diethyl ether each time. The combined organic phases were 
washed twice with 100 ml of saturated sodium chloride solution each time, 
dried over magnesium sulphate, filtered and subsequently concentrated. 
This gave 1.05 g of 
4-(trans-4-heptylcyclohexyl)-N-[(S)-2-hydroxy-1-isopropylethyl)benzamide. 
The following compounds can be produced in an analogous manner: 
(S)-2-[4-(trans-4-Propylcyclohexyl)phenyl]-4-isopropyl-2-oxaxoline; 
(S)-2-[4-(trans-4-pentylcyclohexyl)phenyl]-4-isopropyl-2-oxaxoline; 
(S)-2-[4-(trans-4-propylcyclohexyl)phenyl]-4-tert.butyl-2-oxaxoline; 
(S)-2-[4-(trans-4-pentylcyclohexyl)phenyl]-4-tert.butyl-2-oxaxoline; 
(S)-2-[4-(trans-4-heptylcyclohexyl)phenyl]-4-tert.butyl-2-oxaxoline; 
(S)-2-[4-(trans-4-vinylcyclohexyl)phenyl]-4-isopropyl-2-oxaxoline; 
(S)-2-[4-(trans-4-allylcyclohexyl)phenyl]-4-isopropyl-2-oxaxoline; 
(S)-2-[4-(trans-4-(3-butenyl)cyclohexyl)phenyl]-4-isopropyl-2-oxaxoline; 
(S)-2-[4-(trans-4-(1-pentenyl)cyclohexyl)phenyl]-4-isopropyl-2-oxaxoline; 
(S)-2-[4-(trans-4-(3-pentenyl)cyclohexyl)phenyl]-4-isopropyl-2-oxaxoline; 
(S)-2-[4-(trans-4-(4-pentenyl)cyclohexyl)phenyl]-4-isopropyl-2-oxaxoline; 
(S)-2-[4-(5-pentyl-2-pyrimidinyl)phenyl]-4-isopropyl-2-oxazoline, m.p. 
113.degree. C.; 
(S)-2-[4-(trans-4-propylcyclohexyl)-4'-biphenyl]-4-isopropyl-2-oxaxoline; 
(S)-2-[4-(trans-4-pentylcyclohexyl)-4'-biphenyl]-4-isopropyl-2-oxaxoline, 
m.p. C-S.sub.B 132.degree. C., S.sub.B -S.sub.A 175.degree. C., cl.p. 
(S.sub.A -I) 210.degree. C.; 
(S)-2-[4-(trans-4-heptylcyclohexyl)-4'-biphenyl]-4-isopropyl-2-oxaxoline; 
(S)-2-[4-(trans-4-propylcyclohexyl)-4'-biphenyl]-4-tert.butyl-2-oxaxoline; 
(S)-2-[4-(trans-4-pentylcyclohexyl)-4'-biphenyl]-4-tert.butyl-2-oxaxoline; 
(S)-2-[4-(trans-4-hepylcyclohexyl)-4'-biphenyl]-4-tert.butyl-2-oxaxoline; 
(S)-2-(4-[1-(trans-4-pentylcyclohexyl(-2-ethyl]phenyl)-2-isopropyl-2-oxaxol 
ine; 
(S)-2-(4-[(trans-4-pentylcyclohexyl)methoxy]phenyl)-2-isopropyl-2-oxaxoline 
; 
(S)-2-(4-[3-(trans-4-pentylcyclohexyl)-1-propyloxy]-phenyl)-2-isopropyl-2-o 
xaxoline; 
(S)-2-(4-[(E)-3-(trans-4-pentylcyclohexyl)allyloxy]-phenyl)-2-isopropyl-2-o 
xaxoline, m.p. 62.degree. C.; 
(S)-2-(4-[4-(trans-4-pentylcyclohexyl)-1-butyl]phenyl)-2-isopropyl-2-oxaxol 
ine; 
(S)-2-(4-[4(E)-(trans-4-pentylcyclohexyl)-3-butenyl]-phenyl)-2-isopropyl-2- 
oxaxoline; 
2,2'-(2,6-naphthyl)-bis-(S)-isopropyl-2-oxaxoline, m.p. 182.degree. C.; 
2,2'-(2,6-naphthyl)-bis-(S)-tert.butyl-2-oxaxoline; 
2,2'-(1,4-phenyl)-bis-(S)-isopropyl-2-oxaxoline; 
2,2'-(1,4-phenyl)-bis-(S)-tert.butyl-2-oxaxoline; 
2,2'-(4,4'-biphenyl)-bis-(S)-isopropyl-2-oxaxoline; 
2,2'-(4,4'-biphenyl)-bis-(S)-tert.butyl-2-oxaxoline; 
(S)-2-(4-fluorophenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-chlorophenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-bromophenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-cyanophenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-methylphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-ethylphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-propylphenyl)-4-isopropyl-2-oxaxoline, colourless liquid; 
(S)-2-(4-butylphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-pentylphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-hexylphenyl)-4-isopropyl- 2-oxaxoline; 
(S)-2-(4-heptylphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-octylphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-methoxyphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4- ethoxyphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-propyloxyphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-butyloxyphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-pentyloxyphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-hexyloxyphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-heptyloxyphenyl)-4-isopropyl-2-oxaxoline, m.p. 31.degree. C.; 
(S)-2-(4-fluoro-4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-chloro-4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-bromo-4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-cyano-4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-methyl-4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-ethyl-4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-propyl-4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-butyl -4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-pentyl-4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-methoxy-4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-ethoxy-4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-propyloxy-4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-butyloxy-4'-biphenyl)-4-isopropyl-2-oxaxoline; 
(S)-2-(4-pentyloxy-4'-biphenyl)-4-isopropyl-2-oxaxoline, m.p. 125.degree. 
C.; 
(S)-2-(4-heptyloxy-4'-biphenyl)- 4-isopropyl-2-oxaxoline; 
(S)-2-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]-4-isopropyl-2-oxazolin 
e, m.p. (C-S.sub.B) 38.degree. C., cl.p. (S.sub.B -N) 126.degree. C. 
EXAMPLE 2 
(S)-2-(4-Carboxyphenyl)-4-isopropyl-2-oxazoline (2.0 g), 0.5 g of methyl 
(S)-lactate and 0.1 g of 4-(dimethylamino)pyridine are dissolved in 50 ml 
of dichloromethane and the solution is treated portionwise with 1.4 g of 
N,N'-dicyclohexylcarbodiimide within 10 minutes while stirring. The 
mixture is stirred at room temperature overnight and then filtered. The 
filtrate is diluted with dichloromethane, washed twice with 50 ml of 
saturated sodium carbonate solution each time and then with water, dried 
over magnesium sulphate and concentrated. The crude product obtained is 
purified by chromatography on silica gel with toluene. The 
(S)-2-[4-([(S)-1-(methoxycarbonyl)-1-ethoxy]carbonyl)phenyl]-4-isopropyl-2 
-oxazoline obtained is recrystallized from ethanol; 
The (S)-2-(4-carboxyphenyl)-4-isopropyl-2-oxazoline used as the starting 
material is prepared as follows: 
A mixture of 3 g of 
(S)-2-(4-[methoxycarbonyl]phenyl)-4-isopropyl-2-oxazoline, 3 g of 
potassium hydroxide, 5 ml of water and 50 ml of methanol is heated at 
75.degree. C. on an oil bath for 4 hours. The cooled mixture is treated 
with 10 ml of ice-cold 3N hydrochloric acid and the liberated acid is 
taken up in 150 ml of diethyl ether. The separated aqueous phase is 
back-extracted twice with 100 ml of diethyl ether each time. The combined 
organic phases are washed with 50 ml of 2N sodium carbonate solution and 
several times with water, dried over magnesium sulphate and concentrated. 
Recrystallization of the resulting crude product from ethanol yields 
(S)-2-(4-carboxyphenyl)-4-isopropyl-2-oxazoline. 
The following compounds can be produced in an analogous manner: 
(S)-2-[4-([(S)-1-(ethoxycarbonyl)-1-ethoxy]carbonyl)-phenyl]-4-isopropyl-2- 
oxazoline; 
(S)-2-[4-([(S)-1-(propyloxycarbonyl)-1-ethoxy]carbonyl)-phenyl]-4-isopropyl 
-2-oxazoline; 
(S)-2-[4-([(S)-1-(butyloxycarbonyl)-1-ethoxy]carbonyl)-phenyl]-4-isopropyl- 
2-oxazoline; 
(S)-2-[4-([(S)-2-octyl]carbonyl)phenyl]-4-isopropyl-2-oxazoline and the 
optical antipodes of the said compounds. 
EXAMPLE 3 
The following liquid crystal basic mixture BM-1 was used to measure the 
induced pitch and its temperature dependence in liquid crystal materials: 
______________________________________ 
5.36 wt. % of 
4'-ethyl-4-cyanobiphenyl, 
3.18 wt. % of 
4'-propyl-4-cyanobiphenyl, 
6.08 wt. % of 
4'-butyl-4-cyanobiphenyl, 
6.53 wt. % of 
4-(trans-4-propylcyclohexyl)benzonitrile, 
14.67 wt. % of 
4-(trans-4-pentylcyclohexyl)benzonitrile, 
5.21 wt. % of 
4-ethyl-1-(trans-4-propylcyclohexyl)benzene, 
16.54 wt. % of 
4-ethoxy-1-[2-(trans-4-propylcyclohexyl)- 
ethyl]benzene, 
5.0 wt. % of 
4"-pentyl-4-cyano-p-terphenyl, 
5.71 wt. % of 
4'-(trans-4-pentylcyclohexyl)-4-cyano- 
biphenyl, 
15.95 wt. % of 
1-[2-(trans-4-butylcyclohexyl)ethyl]-4- 
(trans-4-pentylcyclohexyl)benzene, 
4.74 wt. % of 
4-[2-(trans-4-butylcyclohexyl)ethyl]-4'- 
(trans-4-pentylcyclohexyl)biphenyl, 
7.59 wt. % of 
4-[2-(trans-4-butylcyclohexyl)ethyl]-4'- 
(trans-4-pentylcyclohexyl)-1,1'-ethylene- 
dibenzene, 
2.84 wt. % of 
trans-4-[2-(trans-4-propylcyclohexyl)ethyl]- 
cyclohexanecarboxylic acid 4-cyanophenyl 
ester; 
______________________________________ 
m.p. &lt;-30.degree. C., cl.p. (N-I) 90.degree. C.; .DELTA..epsilon.=8.5, 
.DELTA.n=0.139 and .eta.=22 mPa.s measured at 22.degree. C. 
Liquid crystal basic mixture BM-1 was treated with each of the following 
optically active dopants: 
D-1=(S)-2-[4-(trans-4-heptylcyclohexyl)phenyl]-4-isopropyl-2-oxazoline, 
D-2=2,2'-(2,6-naphthyl)-bis-(S)-isopropyl-2-oxazoline. 
The results compiled in Table 1 were obtained for the chiral doped 
mixtures, whereby A, B and C denote the parameters of the equation 
EQU F(1,pc)=A+BT.sub.1 CT S(2,1) 
and p, c and T.sub.1 have the following significances 
T.sub.1 =T-22.degree. C. 
T=temperature in .degree.C. 
p=pitch in mm (a positive value signifies a clockwise helical structure and 
a negative value signifies an anticlockwise helical structure) 
c=concentration of the optically active dopant in wt. %. 
TABLE 1 
__________________________________________________________________________ 
A B C p .multidot. c 
(from 22.degree. 
C.) 
Mixture 
Dopant 
[10.sup.-2 .multidot. .mu.m.sup.-1 .multidot. wt. %.sup.-1 
[10.sup.-4 .multidot. .mu.m.sup.-1 .multidot. wt. 
%.sup.-1 .multidot. .degree.C..sup.-1 ] 
[10.sup.-6 .multidot. .mu.m.sup.-1 
.multidot. wt. %.sup.-1 .multidot. 
.degree.C..sup.-2 ] 
[.mu.m .multidot. 
wt. 
__________________________________________________________________________ 
%] 
M-1 1.0 wt. % 
-5.36 0.805 0.800 -18.65 
D-1 
M-2 1.0 wt. % 
+5.75 1.234 0.656 +17.39 
D-2 
__________________________________________________________________________ 
A solution of 0.8 g of (S)-2-(4-formylphenyl)-4-isopropyl-2-oxazoline and 1 
g of dimethyl L(+)-tartrate in 50 ml of toluene is treated with 0.1 g of 
toluene-4-sulphonic acid. The mixture is heated to boiling for 2.5 hours 
and the water formed is distilled off simultaneously. Then, 4 drops of 
triethylamine are added to the reaction mixture. After cooling the mixture 
is washed with 20 ml of 1N sodium hydrogen carbonate solution and twice 
with 20 ml of water each time, dried over sodium sulphate and 
concentrated. Chromatography of the residue on silica gel with 
toluene/ethyl acetate (vol. 1:1) and recrystallization from ethanol gives 
pure dimethyl 
(4R,5R)-2-(4-[(S)-4-isopropyl-2-oxazolinyl]phenyl)-1,3-dioxolane-4,5-dicar 
boxylate 
The (S)-2-(4-formylphenyl)-4-isopropyl-2-oxazoline used as the starting 
material is prepared as follows: 
A solution of 2 g of (S)-2-(4-bromophenyl)-4-isopropyl-2-oxazoline in 20 ml 
of absolute tetrahydrofuran is treated drop-wise with 5 ml of 1.6M 
butyllithium in hexane at -78.degree. C. and while gassing with nitrogen, 
stirred at this temperature for 2 hours, then treated dropwise with 2 ml 
of absolute N,N-dimethyl-formamide and then warmed slowly to room 
temperature. The reaction mixture is poured into 100 ml of water and 
extracted three times with 50 ml of diethyl ether each time. The combined 
organic phases are washed twice with 100 ml of saturated sodium chloride 
solution each time, dried over magnesium sulphate, filtered and then 
concentrated. Chromatography of the residue on silica gel with 
hexane/ethyl acetate (vol. 9:1) yields 0.8 g of pure 
(S)-2-(4-formylphenyl)-4-isopropyl-2-oxazoline. 
The following compounds can be produced in an analogous manner: 
diethyl 
(4R,5R)-2-(4-[(S)-4-isopropyl-2-oxazolinyl]-phenyl)-1,3-dioxolane-4,5-dica 
rboxylate; 
diisopropyl 
(4R,5R)-2-(4-[(S)-4-isopropyl-2-oxazolinyl]phenyl)-1,3-dioxolane-4,5-dicar 
boxylate; 
dibutyl 
(4R,5R)-2-(4-[(S)-4-isopropyl-2-oxazolinyl]-phenyl)-1,3-dioxolane-4,5-dica 
rboxylate; 
dimethyl 
(4R,5R)-2-(4-[(S)-4-tert.butyl-2-oxazolinyl]-phenyl)-1,3-dioxolane-4,5-dic 
arboxylate; 
diethyl 
(4R,5R)-2-(4-[(S)-4-tert.butyl-2-oxazolinyl]-phenyl)-1,3-dioxolane-4,5-dic 
arboxylate; 
diisopropyl 
(4R,5R)-2-(4-[(S)-4-tert.butyl-2-oxazolinyl]phenyl)-1,3-dioxolane-4,5-dica 
rboxylate 
dibutyl 
(4R,5R)-2-(4-[(S)-4-tert.butyl-2-oxazolinyl]-phenyl)-1,3-dioxolane-4,5-dic 
arboxylate. 
EXAMPLE 5 
(R)-2-(4-Formylphenyl)-4-isopropyl-2-oxazoline (1.0 g), 1.0 g of 
(2S,3R)-2-octyl-1,3-butanediol and 0.1 g of p-toluenesulphonic acid in 50 
ml of absolute toluene are reacted in an analogous manner to Example 4 to 
give 
2-(4-[2S,4R,5S]-4-methyl-5-octyl-m-dioxan-2-yl]phenyl)-(R)-4-isopropyl-2-o 
xazoline. 
The following compounds can be produced in an analogous manner: 
2-(4-[2S,4R,5S]-4-methyl-5-methyl-m-dioxan-2-yl]phenyl)-(R)-4-isopropyl-2-o 
xaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-ethyl-m-dioxan-2-yl]phenyl)-(R)-4-isopropyl-2-ox 
axoline; 
2-(4-[2S,4R,5S]-4-methyl-5-propyl-m-dioxan-2-yl]phenyl)-(R)-4-isopropyl-2-o 
xaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-butyl-m-dioxan-2-yl]phenyl)-(R)-4-isopropyl-2-ox 
axoline; 
2-(4-[2S,4R,5S]-4-methyl-5-pentyl-m-dioxan-2-yl]phenyl)-(R)-4-isopropyl-2-o 
xaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-hexyl-m-dioxan-2-yl]phenyl)-(R)-4-isopropyl-2-ox 
axoline; 
2-(4-[2S,4R,5S]-4-methyl-5-heptyl-m-dioxan-2-yl]phenyl)-(R)-4-isopropyl-2-o 
xaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-vinyl-m-dioxan-2-yl]phenyl)-(R)-4-isopropyl-2-ox 
axoline; 
2-(4-[2S,4R,5S]-4-methyl-5-allyl-m-dioxan-2-yl]phenyl)-(R)-4-isopropyl-2-ox 
axoline; 
2-(4-[2S,4R,5S]-4-methyl-5-(3-butenyl)-m-dioxan-2-yl]phenyl)-(R)-4-isopropy 
l-2-oxaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-(4-pentenyl)-m-dioxan-2-yl]phenyl)-(R)-4-isoprop 
yl-2-oxaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-methyl-m-dioxan-2-yl]phenyl)-(R)-4-tert.butyl-2- 
oxaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-ethyl-m-dioxan-2-yl]phenyl)-(R)-4-tert.butyl-2-o 
xaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-propyl-m-dioxan-2-yl]phenyl)-(R)-4-tert.butyl-2- 
oxaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-butyl-m-dioxan-2-yl]phenyl)-(R)-4-tert.butyl-2-o 
xaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-pentyl-m-dioxan-2-yl]phenyl)-(R)-4-tert.butyl-2- 
oxaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-hexyl-m-dioxan-2-yl]phenyl)-(R)-4-tert.butyl-2-o 
xaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-heptyl-m-dioxan-2-yl]phenyl)-(R)-4-tret.butyl-2- 
oxaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-octyl-m-dioxan-2-yl]phenyl)-(R)-4-tert.butyl-2-o 
xaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-vinyl-m-dioxan-2-yl]phenyl)-(R)-4-tert.butyl-2-o 
xaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-allyl-m-dioxan-2-yl]phenyl)-(R)-4-tert.butyl-2-o 
xaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-(3-butenyl)-m-dioxan-2-yl]phenyl)-(R)-4-tert.but 
yl-2-oxaxoline; 
2-(4-[2S,4R,5S]-4-methyl-5-(4-pentenyl)-m-dioxan-2-yl]phenyl)-(R)-4-tert.bu 
tyl-2-oxaxoline.