Super-fluorinated liquid crystals: Towards the limits of polarity

Article abstract of DOI:10.1002/ejoc.200800149

Highly fluorinated liquid crystals with unprecedented polarity were obtained by introducing a tetrahydropyran moiety into their mesogenic core structure. The new materials exhibit an unusually favourable combination of mesophase properties, excellent solubility and low rotational viscosity, which renders them highly attractive for application in fast-switching active matrix LCDs. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejoc.200800149

FULL PAPER
DOI: 10.1002/ejoc.200800149
Super-Fluorinated Liquid Crystals: Towards the Limits of Polarity
Peer Kirsch,*[a] Werner Binder,[b] Alexander Hahn,[b] Kai Jährling,[b] Marc Lenges,[b]
Lars Lietzau,[b] David Maillard,[b] Volker Meyer,[b] Eike Poetsch,[b] Andreas Ruhl,[b]
Gerald Unger,[b] and Roland Fröhlich[c]
Keywords: Liquid crystals / Oxygen heterocycles / Density functional calculations / Mesogens / Iminoenolates / Chirality
Highly fluorinated liquid crystals with unprecedented po-
larity were obtained by introducing a tetrahydropyran moi-
ety into their mesogenic core structure. The new materials
exhibit an unusually favourable combination of mesophase
properties, excellent solubility and low rotational viscosity,
which renders them highly attractive for application in fast-
switching active matrix LCDs.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
so-called super-fluorinated materials (SFM), whose dipole
moment is mainly derived from polar carbon–fluorine, and
in a few cases from carbon–oxygen, bonds (Scheme 1).
Introduction
In the recent few years, liquid crystal display (LCD) tech-
nology has been firmly established, and it has permeated
nearly every aspect of our daily lives. However, the devel-
opers of liquid crystalline materials for active matrix (AM)
LCD are still facing many technical challenges.[1,2]
The most important issue in need of improvement are
materials for application in LCD TVs. Here, extreme endur-
ance of the liquid crystal towards long-term thermal or
photochemical stress is asked for.[2] Another problem area
is the design of liquid crystals for displays with very low
power consumption, as they are used for mobile devices,
such as notebook PCs, mobile phones or PDAs.
On the level of materials design, a major problem is how
to combine high dielectric anisotropy (∆ε)[3,4] with good
mesogenic properties, sufficient solubility and – in particu-
lar – high reliability. There are also some limitations in the
toolbox of the designer of liquid crystals for AM LCDs:
nitrogen heterocycles or nitrile groups that would enhance
the molecular dipole moment should not be used, because
they either promote photochemical degradation of the LC
mixture or cause image sticking in the LCD panel as a re-
sult of their strong affinity towards ionic trace impurities.[5]
Accordingly, all materials currently in use for AM LCD are
Scheme 1. Examples of highly fluorinated (SFM) liquid crystals
currently in use for LCD applications. Compounds 3 and 4 repre-
sent the current limits of polarity for commercial materials of AM
LCDs.
This leaves three possible strategies for the design of very
polar materials, and these methods involve the use of: (1)
extremely polar fluorinated terminal groups, such as CF3
or SF5,[6] enhanced by laterally fluorinated aromatic ring
structures;[7] (2) intrinsically polar bridge structures, such
as CF2O bridges[8] and (3) polar aliphatic oxygen heterocy-
cles.[9] Strategies (1) and (2) alone are usually not sufficient,
and the use of 1,3-dioxane building blocks (strategy 3) often
causes reliability problems under oxidative or hydrolytic
stress. Another problem of polar liquid crystals with exten-
sive aromatic fluorination is their generally quite high melt-
ing points, which are limiting the solubility in nematic mix-
tures.
[a] Merck Ltd. Japan, New Technology Office,
4084 Nakatsu, Aikawa-machi, Aiko-gun, Kanagawa 243-0303,
Japan
Fax: +81-46-286-2592
E-mail: peer.kirsch@merck.co.jp
[b] Merck KGaA, Liquid Crystals Division,
Frankfurter Str. 250, 64271 Darmstadt, Germany
[c] University of Münster, Institute for Organic Chemistry,
48149 Münster, Germany
Results and Discussion
A structural building block combining the polarity of di-
oxanes with high chemical stability and a tendency to pro-
mote the solubility of its derivatives is the tetrahydropyran
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Eur. J. Org. Chem. 2008, 3479–3487
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P. Kirsch et al.
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(THP) structure. Singular examples of THP-based liquid ation and fractionated crystallization of the trans,trans iso-
crystals have been mentioned in the literature for years,[10] mer gives liquid crystal 13, which is a structural analogue
but several practical obstacles have impeded the systematic of 1.
exploration of this highly interesting compound class. As
Bromide 10 is a versatile intermediate for the synthesis
the major problem, there is a lack of a generally applicable of THP derivatives. Suzuki coupling with suitable boronic
synthetic procedure. There are several examples for chiral, acids[17] furnishes liquid crystals 14 and 15 (Scheme 3).
THP-based liquid crystals where the synthesis starts from
natural, chiral pool carbohydrate precursors. The methods
reported so far for the preparation of liquid crystals based
on racemic THP[11–14] often have only a rather limited
structural scope.
In order to fully explore the potential of liquid crystals
with a THP substructure, we developed two new synthetic
approaches: one based on the ring opening of alkyl
oxetanes,[15] and the other one starting from alkyl δ-valero-
lactones.[16]
The δ-valerolactone synthesis (Scheme 2) gives the best
yields for the ethyl, n-propyl and n-butyl analogues. For
longer side chains, an increased tendency towards polymeri-
zation decreased the reaction yield as well as the purity of
the lactone. Lactone 8 was treated with 4-bromo-1-lithio-
benzene, and intermediate 9 was then reduced and iso-
merized into trans-10. Bromide 10 can serve as a key inter-
mediate for a variety of liquid crystals that are structurally
analogous to commonly used, highly fluorinated materials
for AM LCDs. Another central intermediate is ketone 12,
which is readily available in two steps via phenol 11. For
example, addition of Grignard compounds, followed by
acid-catalyzed elimination of the tertiary alcohol, hydrogen-
Scheme 3. Use of bromide 10 as a versatile intermediate for the
synthesis of liquid crystals 14 and 15. Reagents and conditions:
(a) 3,4,5-trifluorobenzene boronic acid, N2H4·H2O, Na3BO3·8H2O,
cat. PdCl2(PPh3)2, H2O, THF, reflux, 90 min (71%); (b) 16,
N2H4·H2O, Na3BO3·8H2O, cat. PdCl2(PPh3)2, H2O, THF, reflux,
18 h (61%), (c) 1. iPrMgCl, THF, –5 °C, 1 h; 2. B(OMe)3, THF,
–5 °C, 1 h; 3. 16% HCl, –5 °C, 30 min (95%).
The synthesis of another THP analogue of 1 (Scheme 4)
started with oxetane 18,[15] which was treated with an ester
enolate[13] to give lactone 20. Addition of 3,4,5-trifluoro-
1-lithiobenzene and subsequent reduction of the resulting
hemiketal furnished liquid crystal 21.
Scheme 4. Synthesis of lactone 20 as a precursor of tetrahydropy-
ran-based liquid crystal 21. Reagents and conditions: (a) tBuOAc,
LDA, THF, –78 °C, 25 min, then 18, BF3·OEt2, –78 °C (1 h), then
room temp. (27%); (b) CF3COOH, CH2Cl2, room temp., 18 h
(81%); (c) 1. LiPhF3, Et2O, –70 °C (2 h), then room temp. (85%
crude); 2. BF3·OEt2, Me3SiH, CH2Cl2, –70 (2 h) to –10 °C (54%).
Scheme 2. Synthesis of tetrahydropyran derivatives by the δ-valero-
lactone route. Reagents and conditions: (a) 1. methyl acrylate,
Et2NSiMe3, CH3CN, reflux, 18 h; 2. HOAc, H2O, reflux, 18 h
(68%, crude product used for subsequent step); (b) NaBH4, 2-pro-
Peterson olefination of versatile intermediate 12 with 2-
panol, room temp., 18 h (87%); (c) 1. cat. p-TsOH, toluene, reflux trimethylsilyl-1,3-dithiane[18] furnished ketene dithioketal
with azeotropic water removal; 2. distillation (61%); (d) 1,4-dibro-
22, which was subsequently converted into difluoroether
mobenzene, nBuLi, Et2O, –50 (2 h) to –10 °C (crude product used
24 by a one-step protonation–equilibration–fluorodesul-
for subsequent reaction); (e) 1. BF3·OEt2, Me3SiH, CH2Cl2, –70
furation procedure (Scheme 5).[8]
(2 h) to –10 °C (44%); 2. AlCl3 (0.2 equiv.), CH2Cl2, –20 °C, 30 min
The preparation of difluoroether liquid crystal 29 with
the THP unit as the middle ring was basically done in anal-
ogy to the synthesis of 24, but required some small but es-
sential modifications (Scheme 6). Enolketene dithioketal 25
was prepared by a Horner–Emmons reaction of lactone 21
with activated phosphonic ester 26.[19] Differently from the
(95%); (f) 1. nBuLi, THF, –70 °C (2 h), then B(OMe)3, –70 (2 h) to
–10 °C, 2  HCl (75%, crystallized from n-hexane); 2. 30% H2O2,
H2O, HOAc, THF, room temp., 6 h (89%);·(g) H2, 5% Pd–C, xy-
lene, 5 bar, 120 °C (75%); (h) 1. 1-bromo-3,4,5-trifluorobenzene, 2-
PrMgCl, THF, room temp., 1 h, then 12, room temp., 1 h; 2. Me-
SO2Cl, NEt3, CH2Cl2, 0 °C to room temp., 18 h (45%); 3. H2, 5%
Pd–C, THF, 1 bar, room temp. (60%).
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Eur. J. Org. Chem. 2008, 3479–3487

Super-Fluorinated Liquid Crystals: Towards the Limits of Polarity
Scheme 5. Synthesis of difluorooxymethylene-linked liquid crystal
24 by the one-pot conversion of ketene dithioketal 22. Reagents
and conditions: (a) 2-Me3Si-1,3-dithiane, nBuLi, THF, –70 °C to
room temp., 18 h (82%); (b) CF3SO3H, CH2Cl2, –20 °C to room
temp. (30 min) to –70 °C; (c) 1. F3PhOH, NEt3, CH2Cl2, –70 °C,
30 min; 2. NEt3·3HF, –70 °C; 3. DBH, CH2Cl2, –70 °C (1 h) to
room temp. (19%).
usual procedure,[8] the protonation–alkoxydifluorodesulfur-
ation had to be carried out at very low temperatures (be-
tween –90 and –100 °C) and the reagents had to be added
as fast as temperature control allowed. Otherwise, not even
trace amounts of any defined product or byproduct were
isolated. Only by applying these modifications could di-
fluoroether 27 be obtained in a very modest yield of 0.9%.
At first, our prime suspect for these complications was
that the protonation of the double bond in intermediate 26
might occur at the wrong position. However, computational
analysis [MP2/6-311+G(2d,p)//B3LYP/6-31G(d)+ZPE level
of theory][20] of the relative energies of the different possible
protonation products ruled out this scenario. It might be
speculated that during the fluorodesulfuration sequence a
competing rearrangement of the THP oxygen atom to one
of the transient electrophilic centres occurs.
Scheme 6. Conversion of lactone 20 into ketene dithioketal 25 and
subsequent one-pot fluorodesulfuration into 27. Box: The forma-
tion of the “right” intermediate protonation product 29a is energet-
ically preferred by 9.8 kcalmol–1 [MP2/6-311+G(2d,p)//B3LYP/6-
31G(d)+ZPE level of theory] relative to the alternative double-
bond protonation product 29b.[20] The relative energies of the other
possible O- and S-protonation products 29c–e are even higher. Rea-
gents and conditions: (a) 1. 26, tBuOK, THF, –10 °C, 1 h; 2. 20,
THF, –10 °C to room temp., 18 h (60%); (b) 1. CF3SO3H, CH2Cl2,
–25 °C to room temp. (10 min) to –90 °C; 2. F3PhOH, NEt3,
CH2Cl2, –90 °C, 30 min; 3. NEt3·3HF, –70 °C; 4. Br2, CH2Cl2,
–90 °C (1 h) to room temp. (0.9%).
Compounds 32 and 34 were selected as candidates for
polar liquid crystals with very low birefringence (∆n) – a
target that is not easily achievable with purely carbocyclic
ring structures. Ketone 12 was treated with the Ruppert–
[21]
Prakash reagent, Me3SiCF3
under fluoride catalysis
(Scheme 7). Resulting trifluoromethyl carbinol 30 was first
eliminated to olefin 31, which was subsequently hydroge-
nated to a mixture of the cis and trans isomers of 32. De-
sired isomer trans,trans-32 was isolated by repeated
crystallization from n-heptane. Isomeric compound 34 was
prepared according to our recently developed method.[15]
Finally, we wanted to explore the limits of polarity (i.e.,
∆ε) that can be achieved by using the tetrahydropyran
structure. As already mentioned, liquid crystals whose
strong polarity is derived from extensive aromatic fluorina-
tion tend to have very high melting points.[1] The corre-
sponding poor solubility in liquid-crystal mixtures limits
the size of the mesogenic core structure of practically useful
Scheme 7. Synthesis of the polar, low birefringent liquid trifluoro-
methyl derivatives 32 and 34. Reagents and conditions: (a) 1. Me3-
SiCF3, Bu4NF, THF, 0 °C to room temp.; 2. KF, MeOH, reflux,
3 h (100%, crude product); (b) SOCl2, pyridine, room temp., 3 d
(73%); (c) H2, 5% Pd–C, THF, 1 bar, r.t. (6%); (d) 2,2,6,6-tet-
ramethylpiperidine, nBuLi, THF, –78 °C, 20 min, then 35, –78 °C,
15 min, then 18 (15 min), BF3·OEt2, –78 °C (2.5 h), then room
temp., 13 h (24%); (e) BF3·OEt2, Me3SiH, CH2Cl2, –50 to 40 °C,
4 h (55%).
liquid crystals to a maximum of four ring elements. The lateral fluorination in combination with a polar terminal
introduction of the polar and at the same time solubility- group and polar bridge structures, such as the difluoroether
enhancing THP ring is supposed to increase this limit to at link. The synthesis of some extremely polar but well-soluble
least five rings, which can infer strong polarity by “heavy” four- and five-ring liquid crystals is depicted in Scheme 8.
Eur. J. Org. Chem. 2008, 3479–3487
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P. Kirsch et al.
FULL PAPER
Scheme 9. Synthesis of extremely polar material 45 containing a
sequence of oxygen heterocyclic ring structures. Reagents and con-
ditions: (a) 2,2,6,6-tetramethylpiperidine, nBuLi, THF, –78 °C,
30 min, then 46, –78 °C, 20 min, then 42 (15 min), BF3·OEt2,
–78 °C (1 h), then room temp., 13 h (20%); (b) BF3·OEt2, Me3SiH,
CH2Cl2, –50 to –10 °C, 3 h (69%); (c) 16, N2H4·H2O,
Na3BO3·8H2O, cat. PdCl2(PPh3)2, H2O, THF, reflux, 18 h (60%).
Scheme 8. Synthesis of extremely polar THP-based liquid crystal
38. Reagents and conditions: (a) 1. 1-bromo-3,5-difluorobenzene,
nBuLi, Et2O, –70 (2 h) to –10 °C; 2. BF3·OEt2, Me3SiH, CH2Cl2,
–70 (2 h) to –10 °C (69%); (b) 1. nBuLi, THF, –70 °C, 1 h; 2.
B(OMe)3, –65 (30 min) to –10 °C; 3. 2  HCl, room temp. (67%);
(c) 17, N2H4·H2O, Na3BO3·8H2O, cat. PdCl2(PPh3)2, H2O, THF,
reflux, 18 h (55%). Compounds 39–41 were prepared by a similar
method by using suitable building blocks analogous to 17.[17]
Table 1. The physical properties of the new pyran-based liquid crys-
tals in comparison to some conventional carbocyclic or 1,3-diox-
ane-based materials (1–4).[22]
No. Phase sequence[a]
∆εvirt
∆nvirt
TNI,virt γ1,virt
Apart from lateral fluorination, another strategy to in-
duce strong polarity in liquid crystals is the use of 1,3-diox-
ane building blocks as a part of the mesogenic core struc-
ture. The use of multiple dioxane units has been explored
previously,[9] but this was found to cause poor solubility
and a very strong tendency to induce smectic phases. Be-
cause the effect of a solubility-enhancing THP unit on the
electrooptical properties of liquid crystals is rather similar
to that of dioxane, the usefulness of this structural element
as a part of extremely polar five-ring liquid crystals was
explored. Compound 45 was available through the Lewis
acid catalyzed ring opening of oxetane 42 with the lithium
iminoenolate of 46.[15] The subsequent reaction steps were
analogous to previously described syntheses (Scheme 9).
All THP-based liquid crystals (Table 1) share several
common characteristics,[22] which renders them highly at-
tractive for practical application in fast switching AM
LCDs: they combine strong dielectric anisotropy (∆ε)[3,4]
with extremely good solubility and a small rotational vis-
cosity (γ1), particularly when seen in relation to the high
1
C 66 N 94.1 I
C 44 N 105.3 I
C 74 N (51.2) I
C 48 I
C 74 I
C 41 I
C 75 N 118.0 I
C 57 N (52.2) I
C 35 N 66.3 I
C 58 N (39.8) I
C? 7 SB 15 I
9.7
0.0750
0.0668
0.0680
0.1579
0.0744
0.1363
0.1401
0.0778
0.0654
0.0751
0.0483
0.0606
0.1316
0.1568
0.1544
0.1827
0.1353
74.3
91.5
63.2
–20.6
32.4
44.4
160
145
201
96
136
178
300
–
2
10.5
17.0
25.2
15.0
15.6
26.0
12.7
14.0
12.4
10.5
8.8
3
4
13
14
15
21
24
27
32
34
38
39
40
41
45
111.3
63.6
58.1
41.5
158
–
–77.8
–57.6
56.4
76
–
457
1016
1225
–
C 59 I
C 83 N (83.0) I
C 74 SC (67) N 144.8 I
C 98 N 193.0 I
Tg –14 C 96 N 240.6 I
35.6
66.6
37.1
70.3
87.7
134.7
167.3
212.4
C 127 SA 212 N 251.1 I 35.6
–
[a] The phase transition temperatures are cited in °C, the rotational
viscosities γ1 in mPas; C = crystalline, S = smectic, N = nematic,
I = isotropic.
clearing temperatures. Therefore, they can be used as com- sulting in highly fluorinated liquid crystals with unprece-
ponents of liquid-crystal mixtures, even in very high con- dented polarity: for SFM material 40, a ∆ε value of 37.1 is
centrations without the risk of crystallization or formation achieved. By using a terminal cyano group, the value of
of smectic phases on long-term storage at low temperatures. ∆ε is further increased to 70.3 for compound 41. Also, the
Relative to a cyclohexane moiety, the THP ring increases combination of THP with polar dioxane rings (45) gives
the ∆ε of the liquid crystal by 2–5 units (1Ǟ13, 21; 2Ǟ24, satisfactory solubility and a very high clearing point and
27), depending on the location of the THP unit within the dielectric anisotropy as well. For conventional, commer-
mesogenic core structure. The effect is less pronounced than cially used liquid crystals without a THP moiety, insuf-
that for the 1,3-dioxane structure, but as a result of the ex- ficient solubility limits the number of rings within the me-
cellent solubility-enhancing effect of the THP moiety, even sogenic core structure to a maximum of four.
five-ring materials such as 40, 41 and 48 show sufficient
Amongst the various strategies for increasing the molecu-
solubility to be of practical use. Additional aromatic rings lar dipole moment, the use of THP building blocks offers a
can serve as a scaffold for extensive lateral fluorination re- particular advantage for liquid crystals with very low bire-
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Eur. J. Org. Chem. 2008, 3479–3487

Super-Fluorinated Liquid Crystals: Towards the Limits of Polarity
fringence (∆n). Because lateral fluorination intrinsically re- with the absolute configuration (Figure 1). The absolute
lies on the presence of a polarizable aromatic ring, it always HTP of the THP enantiomers of 49 is 0.8 µm–1 (Table 2),[22]
produces a concomitant increase in ∆n. The THP unit, in which is very low relative to commonly used chiral dopants
contrast, allows the design of polar materials without (32, for liquid-crystal mixtures with an HTP of 10 µm–1 or
33) or with a minimum (13, 21, 26, 27) of polarizable more.[24]
double bonds.
Comparison of the isomer pairs 13/21, 24/27 and 32/34
shows that the position of the THP ring within the mesog-
enic core structure has a significant influence on the elec-
trooptic, as well as the mesogenic, properties of the liquid
crystal. In all three cases, the isomer with the THP moiety
closest to the polar terminal group has the lowest dielectric
anisotropy.
Figure 1. The absolute configuration of -49 as determined by X-
ray crystallography.[25]
For the pairs 24/27 and 32/34, the tendency to form ther-
modynamically stable mesophases is also diminished for
these isomers. One possible reason for the pronounced dif-
ferences in the physical properties of the isomers may be a
stereoelectronic effect, analogous to the anomeric effect,[23]
which is well known in carbohydrate chemistry. In com-
Table 2. Comparison of the physical properties of racemic and
enantiopure liquid crystal 49.[22]
No.
Phase sequence[a]
∆HCN ∆HNI [α]2D0
HTP
rac-49
C 39 N 75.3 I
C 41 N* 73.3 I
C 42 N* 74.3 I
5900
7400
7400
100
100 +4.5
100 –4.9
–
–
+0.8
–0.8
pounds 27 and 34, a strongly electron-withdrawing group is -49
directly connected to the 2-position of the THP ring. Ener-
-49
getically favourable interaction of the axial oxygen lone
electron pair with the axial σ* orbital of the C–C bond
connecting the electronegative CF3 or CF2OR group to the
THP ring stabilizes the bis(axial) conformation of the 2,5-
substituents relative to the situation in the corresponding
cyclohexane system. In contrast, the bis(equatorial) confor-
mation is a prerequisite for the elongated, rod-like shape of
nematic liquid crystals. This means, an increased equilib-
rium population of the bis(axial) conformer will result in a
reduced clearing point, as well as a general decrease in
the anisotropic properties, of the nematic mesophase
(Scheme 10).
[a] The phase-transition temperatures are cited in °C, the melting
enthalpies (∆HCN) and the enthalpy of nematic-isotropic transition
(∆HNI) in calmol–1, the optical rotations in ° and the helical twist-
ing power (HTP) in µm–1; C = crystalline, N = nematic, N* =
chiral nematic (cholesteric), I = isotropic.
Comparison of the melting enthalpies of the pure
enantiomers of 49 and racemate rac-49 (Table 2) points out
the possible reason for the generally excellent solubility of
THP-derived liquid crystals in nematic host mixtures: the
racemate has a significantly lower melting enthalpy al-
though the phase-transition temperatures are very similar.
Summary and Outlook
The incorporation of a tetrahydropyran (THP) moiety
into the mesogenic core structure of liquid crystals allows
the design of new materials with an unprecedented combi-
nation of extremely high dielectric anisotropy (∆ε), high
clearing point, low rotational viscosity (γ1) and excellent
solubility in nematic liquid crystal mixtures. This unique
property profile is of particular interest for so-called super-
fluorinated materials (SFM) for use in AM LCDs, but it
may also open the way to totally new display applications
requiring materials with extreme electrooptical or mesog-
enic properties.
Scheme 10. The influence of the anomeric effect on the conforma-
tional equilibrium of liquid crystalline tetrahydropyran derivatives:
In cyclohexane-based system 47, the bis(equatorial) conformer is
energetically preferred by 4.5 kcalmol–1 and for THP system
48 only by 2.7 kcalmol–1 [MP2/6-311+G(2d,p)//B3LYP/6-
31G(d)+ZPE level of theory].[20]
The THP-based liquid crystals discussed so far are all
racemic mixtures. Because there are various applications for
chiral liquid crystals,[24] we also wanted to explore the prop-
erties of a pure enantiomer of at least one of the new liquid
crystals. In order to measure the helical twisting power
(HTP) of the enantiomers, a sample of rac-49 (the pentyl
homologue of 24) was separated by preparative HPLC on
a chiral phase. The crystal structure of one of the enantio-
mers was determined by anomalous X-ray diffraction,[25]
Experimental Section
General: All reactions were performed in carefully dried solvents
and under a dry nitrogen atmosphere. Intermediates 6–8, 19 and
20 tend to polymerize even on short-term storage and should be
used immediately.
6: A solution of pentanal (117 mL, 1.10 mol), methyl acrylate
(100 mL, 1.10 mol; stabilized with hydroquinone monomethyl
ether) and Et2NSiMe3 (214 mL, 1.10 mol) in acetonitrile (1.3 L)
which allowed the correlation of the chiroptical properties was heated at reflux under a nitrogen atmosphere for 3 d. The mix-
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P. Kirsch et al.
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ture was concentrated at 10 mbar. The residue (227 g) was treated
with 96% acetic acid (250 mL) and water (500 mL), and the solu-
tion was heated at reflux for 18 h. After cooling down to room
temperature, water (2.5 L) was added, and the mixture was ex-
tracted with methyl tert-butyl ether (MTBE; 4ϫ). The combined
organic phase was washed with water, saturated aqueous NaHCO3
and water, dried with Na2SO4, filtered and concentrated in vacuo
to yield crude 6 (133 g) as a yellowish oil, which was used for the
next step without further purification.
with CH2Cl2 (2ϫ). The combined organic layer was washed with
brine and dried with Na2SO4, and the solvent was evaporated to
dryness. The crude product was dissolved in n-heptane/toluene
(1:1) and filtered through a short silica-gel column. Recrystalli-
zation from n-pentane at –20 °C afforded 10 (30.6 g, 61%) as
colourless crystals (96% purity by HPLC). 1H NMR (500 MHz,
CDCl3, 303 K): δ = 7.44 (d, J = 8.5 Hz, 2 H, ar-H), 7.21 (d, J =
8.5 Hz, 2 H, ar-H), 4.21 (dd, J = 11.3 Hz, J = 2.3 Hz, 1 H), 4.06
(dquart., J = 11.1 Hz, J = 2.0 Hz, 1 H), 3.18 (t, J = 7.4 Hz, 1 H),
2.00–1.87 (m, 1 H), 1.83–1.79 (m, 1 H), 1.75–1.08 (m, 7 H), 0.91 (t,
J = 7.3 Hz, 3 H, CH3) ppm. 13C NMR (75 MHz, CDCl3, 303 K): δ
= 142.7, 131.7, 128.0, 121.4, 79.7, 74.5, 35.7, 35.1, 34.5, 31.2, 20.2,
14.7 ppm.
7: NaBH4 (90 g, 2.37 mol) was dissolved in 2-propanol (3.6 L) and
water (360 mL). Then, crude 6 (1000 g, 5.8 mol) was added drop-
wise under cooling at 15 °C, and the mixture was stirred for 18 h
at room temperature. After the addition of MTBE (1500 mL), the
solution was acidified with 15% HCl (1000 mL) under ice cooling.
The major part of the volatiles was removed in vacuo, the residue
was diluted with MTBE (1000 mL), and the aqueous phase was
separated. The organic phase was washed with brine (2ϫ500 mL)
and dried with Na2SO4. The volatiles were removed in vacuo to
yield crude 7 (878 g) as a yellowish oil, which was used for the next
step without further purification.
10a: A solution of 10 (90.5 g, 320 mmol) in THF (600 mL) was
cooled to –70 °C and treated dropwise with n-butyllithium (15%
solution in hexane; 210 mL, 334 mmol). After stirring for 2 h at the
same temperature, trimethyl borate (38.0 mL, 341 mmol) was
added slowly. After stirring for another 2 h, the solution was
warmed up to –10 °C. HCl (2 ) was added in order to adjust the
pH to ca. 2, and the mixture was extracted with MTBE. The com-
bined organic phase was washed with water, dried with Na2SO4
and filtered, and the solvent was evaporated to dryness to furnish
crude boronic acid intermediate 10a (85 g), which was used for the
next step without further purification.
8: A solution of crude 7 (68 g, 390 mmol) and p-toluenesulfonic
acid (10 g, 53 mmol) in toluene (150 mL) was heated at reflux un-
der azeotropic water removal for 2 h. When the boiling point of
toluene (109 °C) was reached, another 100 mL of toluene was
added, and the solution was heated at reflux for an additional 1 h.
After cooling, the mixture was washed with water, saturated aque-
ous NaHCO3 and water, dried with Na2SO4 and filtered, and the
solvent was removed in vacuo. The residue (53.1 g) was distilled
(b.p. 89–92 °C/0.05 mbar) to furnish 8 (29.8 g, 44%) as a colourless
11: A mixture of crude 10a (79.4 g, 320 mmol), THF (1.2 L), water
(150 mL) and acetic acid (150 mL) was treated at room temperature
(temperature control by water cooling) with 30% H2O2 (65 mL,
630 mmol) and stirred for 6 h. After addition of water (500 mL)
and toluene (500 mL), the organic phase was separated and washed
with water and brine. The aqueous phase was extracted with tolu-
ene (300 mL). The combined organic phase was stirred with aque-
ous FeCl2 (5%w/v) until the mixture was peroxide free. The organic
phase was separated, washed with water (2ϫ) and brine (1ϫ).
Then, the combined aqueous phase was extracted with toluene
(3ϫ100 mL). The combined organic phase was dried with Na2SO4
and filtered, and the solvent was evaporated in vacuo. The crude
product (80 g) was purified first by chromatography (silica gel; tolu-
ene/ethyl acetate, 4:1), then by crystallization from n-heptane at
room temperature to yield 11 (52.9 g, 74%) as colourless crystals
(99.1% purity by GC). 1H NMR (500 MHz, CDCl3, 303 K): δ =
7.20 (d, J = 8.8 Hz, 2 H, ar-H), 6.73 (d, J = 8.5 Hz, 2 H, ar-H),
5.06 (br. s, 1 H, OH), 4.20 (dd, J = 11.1 Hz, J = 2.3 Hz, 1 H), 4.06
(dquart., J = 11.2 Hz, J = 2.1 Hz, 1 H), 3.20 (t, J = 11.1 Hz, 1 H),
2.03–1.92 (m, 1 H), 1.87–1.79 (m, 1 H), 1.75–1.54 (m, 2 H), 1.37–
1.07 (m, 5 H), 0.91 (t, J = 7.3 Hz, 3 H, CH3) ppm. MS (EI, 70 eV):
m/z (%) = 220 (96) [M]+, 203 (18), 159 (25), 133 (16), 121 (100),
107 (48), 94 (42), 77 (15), 69 (21), 65 (17), 55 (33).
1
oil (purity 82% by GC). H NMR (500 MHz, CDCl3, 303 K): δ =
4.36–4.30 (m, 1 H), 3.99–3.92 (m, 1 H), 2.61–2.43 (m, 1 H), 2.37–
2.26 (m, 1 H), 2.06–1.86 (m, 2 H), 1.69–1.22 (m, 5 H), 0.93 (t, J =
7.0 Hz, 3 H) ppm. 13C NMR (75 MHz, CDCl3, 303 K): δ = 204.1,
73.4, 33.5, 32.3, 28.8, 25.3, 19.7, 13.8 ppm. MS (EI, 70 eV): m/z
(%) = 142 (36) [M]+, 110 (23), 84 (100), 74 (16), 70 (40), 60 (20),
55 (81).
9: A solution of 1,4-dibromobenzene (48.3 g, 205 mmol) in diethyl
ether (350 mL) was cooled to –50 °C and then treated dropwise
under temperature control with n-butyllithium (15% solution in
hexane; 130 mL, 207 mmol). After stirring at –50 °C for 1 h, a solu-
tion of 8 (29.5 g, 170 mmol) in diethyl ether (50 mL) was added
dropwise. The mixture was stirred for 30 min at the same tempera-
ture and then warmed up to 0 °C. After careful addition of water
(100 mL), the aqueous phase was separated and extracted with
MTBE (2ϫ). The combined organic phase was dried with Na2SO4,
and the solvent was evaporated to dryness. Crude product 9
(51.1 g) was used for the next step without further purification. 1H
NMR (500 MHz, CDCl3, 303 K): δ = 7.41 (m, 4 H, ar-H), 5.33 (m,
1 H), 4.32 (m, 1 H), 3.72 (t, J = 10.2 Hz, 1 H), 2.24–2.16 (m, 1 H),
2.02–1.92 (m, 1 H), 1.86–0.85 (m, 10 H) ppm. 13C NMR (75 MHz,
CDCl3, 303 K): δ = 150.7, 131.2, 126.0, 121.5, 97.7, 69.5, 39.7, 39.6,
37.4, 33.3, 30.5, 30.0, 25.4, 20.0, 14.4 ppm. MS (EI, 70 eV): m/z
(%) = 213 (11), 198/200 (57), 183/185 (95), 164 (100), 157 (18), 155
(18), 152 (18), 132 (13), 121/123 (20), 109 (23), 107 (13), 104 (11),
95 (22), 93 (10), 83 (17), 79 (16), 69 (30), 67 (35), 55 (46).
12: A solution of 11 (70.0 g, 318 mmol) in xylene (isomer mixture;
460 mL) was hydrogenated in the presence of wet 5% Pd–C (water
content 54%; 4.55 g) and Na2CO3 (340 mg, 3.2 mmol) under H2
(5 bar) at 120 °C for 8 h. The mixture was filtered through Celite,
and the solvent was evaporated to dryness. The residue was dis-
solved in n-heptane (500 mL) and stirred together with pyridine–
SO3 complex (10 g) for 2 h at 40 °C in order to remove phenol and
alcohol byproducts. After filtration through Celite, the solution was
washed with water, dried with Na2SO4 and filtered, and the solvent
was evaporated to dryness to furnish 12 (47 g, 84%) as a colourless
oil (95% purity by GC).1H NMR (500 MHz, CDCl3, 303 K): δ =
3.97–3.90 (m, 1 H), 3.10–2.95 (m, 2 H), 2.45–2.19 (m, 5 H), 2.08–
0.99 (m, 13 H), 0.89 (t, J = 7.2 Hz, 3 H) ppm. MS (EI, 70 eV): m/z
(%) = 224 (35) [M]+, 220 (14), 127 (100), 121 (16), 109 (77), 97 (11),
83 (34), 69 (25), 67 (38), 55 (55).
10: A solution of adduct 9 (51.1 g, 171 mmol) in CH2Cl2 (400 mL)
was treated dropwise at –75 °C first with triethylsilane (47.0 g,
404 mmol) in CH2Cl2 (10 mL) and then with BF3·OEt2 (51 mL,
406 mmol). The mixture was stirred for 3 h at the same temperature
and then warmed up to –10 °C. The reaction was quenched and
neutralized by careful addition of saturated aqueous NaHCO3. The
organic phase was separated, and the aqueous phase was extracted
3484
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 3479–3487

Super-Fluorinated Liquid Crystals: Towards the Limits of Polarity
22: A solution of 2-trimethylsilyl-1,3-dithiane (43.0 g, 223 mmol) in
THF (800 mL) was treated dropwise at –70 °C with n-butyllithium
(15% solution in hexane; 142 mL, 226 mmol) and warmed up to
0 °C over 4 h. Then, the mixture was cooled again to –70 °C, and
a solution of 12 (47.3 g, 200 mmol) in THF (200 mL) was added
slowly. After removing the cooling bath, the viscous, yellow mixture
was stirred for 18 h at room temperature. Saturated aqueous
NaHCO3 (1 L) and MTBE (500 mL) were added, and the organic
phase was separated. The aqueous phase was extracted with MTBE
(2ϫ250 mL). The combined organic phase was washed with water
(2ϫ350 mL) and dried with Na2SO4, and the solvent was evapo-
rated to dryness. The crude residue (74.4 g) was recrystallized from
n-heptane (350 mL) to furnish 22 (53.4 g, 82%) as colourless crys-
4.49–4.44 (m, 1 H), 3.60–3.56 (m, 1 H), 2.28 (t, J = 7.0 Hz, 2 H),
1.78–1.58 (m, 7 H), 1.45 (s, 9 H), 1.35–0.84 (m, 13 H) ppm. MS
(EI, 70 eV): m/z (%) = 152 (100), 123 (71), 109 (81), 95 (31), 81
(77), 67 (81), 55 (45).
20: A solution of 19 (24.1 g, 80.7 mmol) in CH2Cl2 (300 mL) was
treated dropwise at 0 °C with trifluoroacetic acid (30 mL,
389 mmol). The mixture was subsequently stirred at room tempera-
ture for 18 h and then poured into water (500 mL). The phases
were separated, and the aqueous phase was extracted with CH2Cl2.
The combined organic phase was washed with saturated aqueous
NaHCO3, dried with Na2SO4 and filtered, and the solvent was
evaporated to dryness. The residue was purified by chromatography
(silica gel; n-heptane/ethyl acetate, 4:1) to furnish lactone 20
1
tals (99.9% purity by GC). H NMR (500 MHz, CDCl3, 303 K): δ
1
(14.8 g, 81%) as a colourless oil (98.7% purity by GC). H NMR
= 3.95–3.88 (m, 1 H), 3.20–3.08 (m, 2 H), 3.01–2.82 (m, 6 H), 2.17–
2.07 (m, 2 H), 2.04–1.97 (m, 1 H), 1.90–1.70 (m, 4 H), 1.67–1.00
(m, 11 H), 0.88 (t, J = 7.2 Hz, 3 H) ppm. MS (EI, 70 eV): m/z (%)
= 326 (92) [M]+, 218 (17), 197 (20), 179 (67), 171 (100), 119 (23),
91 (14), 81 (11), 67 (12), 55 (27).
(500 MHz, CDCl3, 303 K): δ = 4.40–4.33 (m, 1 H), 4.08 (dd, J =
10.1 Hz, J = 9.9 Hz, 1 H), 2.67–2.39 (m, 2 H), 2.01–1.90 (m, 1 H),
1.80–1.55 (m, 6 H), 1.35–0.93 (m, 10 H), 0.87 (t, J = 7.1 Hz, 3 H)
ppm. 13C NMR (75 MHz, CDCl3, 303 K): δ = 172.2, 72.5, 39.9,
39.7, 38.7, 37.6, 33.4, 30.6, 30.4, 29.7, 23.3, 20.3, 14.7 ppm. MS
(EI, 70 eV): m/z (%) = 224 (33) [M]+, 193 (17), 176 (20), 151 (19),
140 (100), 127 (12), 122 (43), 109 (32), 100 (49), 95 (31), 81 (70),
69 (80), 55 (85).
24: To a solution of 22 (26.7 g, 82 mmol) in CH2Cl2 (600 mL) was
dropwise added trifluoromethanesulfonic acid (7.5 mL, 85 mmol)
at –20 °C. The cooling bath was removed, and the mixture was
stirred for 30 min at room temperature. Then, the mixture was co-
oled down to –70 °C, and a solution of 3,4,5-trifluorophenol
(18.0 g, 122 mmol) and triethylamine (20 mL, 144 mmol) in
CH2Cl2 (100 mL) was added. After stirring for 1 h at –70 °C,
NEt3·3HF (66 mL, 409 mmol) was added. After 5 min, a suspen-
sion of DBH (1,3-dibromo-5,5-dimethylhydanthoin; 117 g,
409 mmol) in CH2Cl2 (300 mL) was added portionwise over a time
period of 30 min. After stirring for an additional 60 min, the mix-
ture was warmed up to 0 °C and then poured into ice-cold 2 
aqueous NaOH (2 L); the pH of the resulting mixture was ca. 9.
The organic layer was separated, washed with water, dried with
Na2SO4 and concentrated in vacuo. The residue was dissolved in
n-heptane/toluene (3:2) and filtered through a short silica-gel col-
umn. The crude product was then further purified by chromatog-
raphy (silica gel; n-heptane/toluene, 7:3) and two crystallizations (n-
heptane; –20 °C) to furnish 24 (6.2 g, 19%; 99.9% purity by GC).
25: A solution of 26[2] (16.4 g, 45.0 mmol) in THF (100 mL) was
cooled to –10 °C, and then a solution of potassium tert-butoxide
(5.0 g, 44.6 mmol) in THF (50 mL) was added dropwise. After stir-
ring for 1 h, a solution of 20 (9.9 g, 44.1 mmol) in THF (50 mL)
was added dropwise at –10 °C. The mixture was stirred for 18 h at
room temperature, and it was then diluted with MTBE (300 mL)
and water (500 mL). The aqueous phase was separated and ex-
tracted with MTBE (2ϫ). The combined organic phase was washed
with brine, dried with Na2SO4 and filtered, and the solvent was
evaporated to dryness. The crude product was purified by
chromatography (silica gel; 1-chlorobutane) and subsequent
crystallization (n-heptane) to furnish 25 (8.7 g, 60%) as colourless
crystals (96.8% purity by GC). 1H NMR (500 MHz, CDCl3,
303 K): δ = 4.69–4.93 (m, 0.5 H), 4.54 (s, 0.5 H), 4.24–4.16 (m, 1
H), 3.74–3.54 (m, 1.5 H), 3.26–3.16 (m, 0.5 H), 2.96–2.75 (m, 3 H),
2.62–2.53 (m, 0.5 H), 2.30–0.84 (m, 22.5 H) ppm. MS (EI, 70 eV):
m/z (%) = 326 (100) [M]+, 161 (80), 119 (25), 69 (8), 55 (19).
1
For mesophases see Table 1. H NMR (500 MHz, CDCl3, 303 K):
δ = 6.86–6.81 (m, 2 H), 3.96–3.90 (m, 1 H), 3.02–2.92 (m, 2 H),
2.09–1.85 (m, 6 H), 1.65–1.47 (m, 2 H), 1.43–1.25 (m, 6 H), 1.15–
0.99 (m, 5 H), 0.88 (t, J = 7.3 Hz, 3 H) ppm. 13C NMR (75 MHz,
CDCl3, 303 K): δ = 107.0, 106.7, 81.8, 74.0, 43.5 (t, J = 25.8 Hz),
42.4, 35.8, 34.8, 30.6, 28.7, 27.6, 27.4, 25.2, 19.8, 14.3 ppm. 19F
NMR (235 Hz, CDCl3, 300 K): δ = –165.2 (mc, 1 F, ar-4-F), –133.7
(mc, 2 F, ar-3,5-F), –79.3 (d, J = 8.0 Hz, 2 F, CF2O) ppm. MS (EI,
70 eV): m/z (%) = 148 (9), 127 (100), 109 (56), 83 (19), 67 (22), 55
(29).
27: To a solution of 25 (7.9 g, 24.2 mmol) in CH2Cl2 (150 mL) was
dropwise added trifluoromethanesulfonic acid (2.2 mL, 25 mmol)
in CH2Cl2 (15 mL) at –30 °C. The cooling bath was removed, and
the mixture was stirred for 10 min at room temperature. Then, the
mixture was cooled down to –90 °C, and a solution of 3,4,5-trifluo-
rophenol (6.5 g, 43.9 mmol) and triethylamine (6.5 mL, 46.9 mmol)
in CH2Cl2 (50 mL) was added. After stirring for 30 min at –90 °C,
NEt3·3HF (19.5 mL, 121 mmol) was added. Then, a solution of
19: To a cooled (–78 °C) solution of tert-butyl acetate (18.1 mL, Br2 (6.2 mL, 121 mmol) in CH2Cl2 (35 mL) was added dropwise
134 mmol) in THF (130 mL) was slowly added lithium diisopro-
pylamide (2  solution in heptane/THF/ethyl benzene; 66.5 mL,
133 mmol). After stirring for 25 min, a solution of 18[1] (8.0 g,
44 mmol) in THF (130 mL) was added dropwise, followed by
BF3·OEt2 (16.6 mL, 132 mmol). The mixture was stirred for 1 h at
–78 °C and then warmed up to room temperature. After stirring
for 15 h, the reaction was finally quenched by addition of aqueous
NH4Cl (100 mL). The phases were separated, and the aqueous
layer was extracted with MTBE. The combined organic extract was
washed with brine, dried with Na2SO4 and concentrated in vacuo.
The crude product was chromatographed (silica gel; n-heptane/
ethyl acetate, 6:1) to afford 19 (3.5 g, 27%) as a colourless oil,
which was used for the subsequent step without further purifica-
under strict temperature control (never exceeding –85 °C!). After
stirring for 60 min at –80 °C, the mixture was warmed up to room
temperature and then poured into ice-cold aqueous NaOH (0.1 ,
400 mL); the pH of the resulting mixture was ca. 9. The aqueous
layer was separated and extracted with CH2Cl2 (2ϫ). The com-
bined organic phase was washed with water (2ϫ), dried with
Na2SO4 and concentrated in vacuo. The residue was dissolved in
n-heptane/MTBE (4:1) and filtered through a short silica-gel col-
umn. The crude product (0.5 g) was then further purified by
crystallization from n-heptane and subsequent preparative HPLC
(RP-18 Super 250–4; acetonitrile) to furnish 27 (85 mg, 0.9%) as
colourless crystals (99.8% purity by GC). For mesophases, see
1
Table 1. H NMR (500 MHz, CDCl3, 303 K): δ = 6.93–6.83 (m, 2
H), 4.20–4.15 (m, 1 H), 3.68–3.64 (m, 1 H), 3.26–3.19 (m, 1 H),
1
tion. H NMR (500 MHz, CDCl3, 303 K): δ = 4.75–4.69 (m, 1 H),
Eur. J. Org. Chem. 2008, 3479–3487
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3485

P. Kirsch et al.
FULL PAPER
[8]
P. Kirsch, M. Bremer, A. Taugerbeck, T. Wallmichrath, Angew.
Chem. 2001, 113, 1528–1532; Angew. Chem. Int. Ed. 2001, 40,
1480–1484.
2.04–2.00 (m, 1 H), 1.93–1.86 (m, 1 H), 1.77–1.10 (m, 12 H), 1.05–
0.82 (m, 8 H) ppm. 13C NMR (75 MHz, CDCl3, 303 K): δ = 107.3,
107.0, 72.4, 40.6, 39.9, 39.7, 37.4, 33.2, 30.2, 29.9, 26.2, 24.8, 20.0,
14.4 ppm. 19F NMR (235 Hz, CDCl3, 300 K): δ = –164.3 (mc, 1 F,
ar-4-F), –133.3 (mc, 2 F, ar-3,5-F), –83.5 (mc, 2 F, CF2O) ppm. MS
(EI, 70 eV): m/z (%) = 406 (13) [M]+, 258 (17), 208 (100), 191 (42),
135 (13), 123 (15), 109 (31), 95 (24), 86 (13), 83 (46), 69 (72), 55
(76).
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rac-49 was prepared in analogy to 24.
Enantiomer Separation of
D-49 and L-49: rac-49 (1.35 g) was dis-
solved in a mixture of acetonitrile (13.5 mL) and methanol
(81.0 mL) and separated in nine portions over two columns in
series (Hibar 25ϫ5 cm Chiralpak AD 20 µm) with methanol as the
eluent. Fraction 1 (600 mg) had an ee of 98.6% and fraction 2
(580 mg) of 97.1%. Both fractions were crystallized from ethanol
to afford ee values of 100% (Fraction 1, -49) and 99% (Fraction
2, -49).
[11]
[12]
Supporting Information (see footnote on the first page of this arti-
cle): Selected crystal data of -49; computational analysis of 28 and
its protonation products; calculated proton affinities and relative
energies of possible protonation products 29a–e.
[13]
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Acknowledgments
We thank K. Altenburg, Dr. G. Bernatz, A. Goetz, J. Haas, Dr. M.
Heckmeier and H. Heldmann for the physical characterization of
the new compounds. We also gratefully acknowledge helpful dis-
cussions with Prof. G. Haufe (University of Münster). D. M.
thanks the European Commission for a Marie Curie Fellowship
(G5TR-CT-2002–00093).
[15]
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P. Kirsch, D. Pauluth, A. Ruhl, J. Krause, K. Tarumi, M. Heck-
meier, DE 10151300, 2001 [Chem. Abstr. 2003, 138, 329109].
Preparation analogous to the methods described in: D. J. Ager,
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M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian 03, revision
D.01, Gaussian, Inc., Wallingford, CT, 2004. The minimum
geometries were optimized at the B3LYP/6-31G(d) level of
theory and were verified to have only positive eigenfrequencies.
The energies were calculated at the MP2/6-311+G(2d,p) level
of theory by using the B3LYP/6-31G(d) geometries and zero-
point energies.
[2] a) D. Pauluth, K. Tarumi, J. Mater. Chem. 2004, 14, 1219–
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gence as ∆n = nʈ – nЌ, where ʈ stands for parallel and Ќ for
perpendicular to the nematic phase director, which is approxi-
mated by the molecular orientation axis or the long molecular
axis, respectively. The correlation between ∆ε, the molecular
dipole moment µ and the angle β between the dipole and the
orientation axis is the following: ∆ε ϰ [∆α – F(µ2/2kBT) (1–
3cos2β)]S; ∆α is the anisotropy of the polarizability, F the reac-
tion field factor, S the order parameter: a) W. Maier, G. Meier,
Z. Naturforschg. 1961, 16a, 262–267; b) D. Demus, G. Pelzl, Z.
Chem. 1982, 21, 1; c) J. Michl, E. W. Thulstrup, “Spectroscopy
with Polarized Light: Solute Alignment by Photoselection” in
Liquid Crystals, Polymers, and Membranes, VCH, Weinheim
1995, pp. 171–221.
[4] For recent examples: P. Kirsch, A. Hahn, R. Fröhlich, G.
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[22]
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The “virtual” parameters TNI,virt, ∆εvirt, ∆nvirt and γ1,virt were
determined by linear extrapolation from a 10%w/w solution
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Eur. J. Org. Chem. 2008, 3479–3487

Super-Fluorinated Liquid Crystals: Towards the Limits of Polarity
in the commercially available Merck mixture ZLI-4792 (TNI
=
4.888(2) Å, b = 46.787(5) Å, c = 9.591(1) Å, β = 96.89(1)°, V =
2177.6(9) Å3, ρcalcd. = 1.325 gcm–3, µ = 0.953 mm–1, empirical
absorption correction (0.555ՅTՅ0.797), Z = 4, monoclinic,
space group P21 (No. 4), λ = 1.54178 Å, T = 223 K, ω scans,
4975 reflections collected (+h, +k, Ϯl), [(sinθ)/λ] = 0.62Å–1,
4455 independent (Rint = 0.026) and 3273 observed reflections
[IՆ2σ(I)], 544 refined parameters, R = 0.050, wR2 = 0.167,
Flack parameter 0.0(2), max. residual electron density 0.29
(–0.29) eÅ–3, hydrogen atoms calculated and refined as riding
atoms. A second crystal structure as well as more detailed in-
formation on the measurement technique is provided in the
Supporting Information of this paper. CCDC-667613 contains
the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
92.8 °C, ∆ε = 5.3, ∆n = 0.0964). The extrapolated values are
corrected empirically for differences in the order parameter,
which are induced by the analyte. For the pure substances, the
phase-transition temperatures were measured by differential
scanning calorimetry (DSC), and the phase type was assigned
by optical polarization microscopy. The helical twisting powers
(HTP) were measured at 20 °C in the Merck liquid crystal mix-
ture MLC-6260 (TNI = 103.5 °C, ∆ε = 4.0, ∆n = 0.088) and are
given in µm–1. The optical rotations [α]2D0 were determined from
a 0.01 g mL–1 solution in CH2Cl2.
[23] a) A. J. Kirby, The Anomeric Effect and Related Stereoelec-
tronic Effects at Oxygen, Springer, Berlin, 1983; b) D.
O’Hagan, H. S. Rzepa, Chem. Commun. 1997, 645–652.
[24] D. Pauluth, A. E. F. Wächtler, “Synthesis an Application of
Chiral Liquid Crystals” in Chirality in Industry II (Eds.: A. N.
Collins, G. N. Sheldrake, J. Crosby), John Wiley & Sons Ltd.,
New York, 1997, pp. 263–286.
Received: February 7, 2008
Published Online: May 27, 2008
[25] X-ray crystal structure analysis for -49 (C23H31F5O2): M =
434.48, colourless crystal 0.70ϫ0.30ϫ0.25 mm,
a
=
Eur. J. Org. Chem. 2008, 3479–3487
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3487