New 2,2′-substituted 4,4′-dimethoxy-6,6′-dimethyl[1, 1′-biphenyls], inducing a strong helical twisting power in liquid crystals

Article abstract of DOI:10.1002/chem.200400035

Based on the stabilisation of the molecular motion by the chiral residue, novel optically active biphenylic chiral dopants for nematic liquid crystals were developed. This molecular congestion was obtained by introducing mesogenic residues on the 2,2′-positions of the chiral biphenyl; this led to a novel molecular architecture that was found to be efficient. The synthesised optically active biphenyls were characterised with very short cholesteric pitches when used as chiral dopants in nematic liquid crystals. The synthesis of the enatiomerically pure biphenyl dopants and their preliminary physicochemical characterisations are described.

Full text of DOI:10.1002/chem.200400035

FULL PAPER
New 2,2’-Substituted 4,4’-Dimethoxy-6,6’-dimethyl[1,1’-biphenyls],
Inducing a Strong Helical Twisting Power in Liquid Crystals
[
a]
[a]
[b]
[a]
Richard Holzwarth, Richard Bartsch, ZoubairChe rk aoui,
and Guy Solladiÿ*
Abstract: Based on the stabilisation of
the molecular motion by the chiral resi-
due,novel optically active biphenylic
chiral dopants for nematic liquid crys-
tals were developed. This molecular
congestion was obtained by introducing
mesogenic residues on the 2,2’-posi-
tions of the chiral biphenyl; this led to
a novel molecular architecture that was
found to be efficient. The synthesised
optically active biphenyls were charac-
terised with very short cholesteric
pitches when used as chiral dopants in
nematic liquid crystals. The synthesis of
the enatiomerically pure biphenyl dop-
ants and their preliminary physico-
chemical characterisations are descri-
bed.
Keywords: asymmetric synthesis ¥
biaryls
¥
helical structures
¥
liquid crystals
Introduction
trations; p [mm] is the pitch of induced helix, + for P, ꢀ for
M helicies; x is the mole fraction of conformer I.
i
The most striking consequence of the macroscopic helical
structure of cholesteric mesophases is the selective circularly
polarised light reflection and the angular dependence of the
reflected wavelength. The reflected light can range from few
nm to the entire UV-visible-IR spectral range. Based on this
property unique to cholesteric liquid crystals,applications
mainly in reflective displays,reflective polarisers,diffusive
reflectors,optical filters and so forth still arouse great inter-
est. The rapid growth of these applications and their
mother technologies is mainly driven by material develop-
ment,as the width and the wavelength of reflected light are
directly related to molecular parameters. In addition,the
understanding and the control of the interactions between
the chiral dopant and the nematic host are important in
order to design and develop materials with definite proper-
ties. Here the helical twisting power (HTP),which is the
quantitative measure of the cholesteric guest±host interac-
tions,is the most important parameter of cholesteric chiral
induction.
ꢀ dpꢀ1
ꢁ
pꢀ1
X
HTP ¼
ffi
¼
xiðHTPÞi
ð1Þ
dx x¼0
x
i
Since the chiral guest and the achiral host compounds are
not necessarily compatible at the molecular scale,their
binary solution is frequently characterised by undesirable
changes of the thermotropic properties with respect to the
pure liquid-crystalline host material,like,for example,a de-
pression of the clearing point. Those changes could in turn
have negative effects on the physicochemical properties of
the host,such as a decrease of the birefringence. Therefore,
a chiral dopant is sought so that only very small concentra-
tions are necessary to obtain large HTP values.
[
1]
Binaphthol derivatives are examples of such efficient
[3]
chiral dopants. However,applications of chiral binaphthols
are strongly limited by their relatively poor photostability
when they are exposed to strong light sources such as those
used in projection systems.
The HTP,given in Equation (1),is directly dependent on
[2]
[4]
the chiral dopant molecular structure. In Equation (1)
Chiral biphenyls could represent a stable alternative to
ꢀ
1
HTP [mm ] is the helical twisting power for small concen-
binaphthols,taking into account their weaker molecular po-
larisability. Besides biphenyls are from the chemical access
point of view obtainable by a wide variety of synthetic
methods,such as symmetrical or unsymmetrical coupling re-
actions performed on benzene functional derivatives,which
are commercially available in a broad assortment. This
offers the possibility to access various biphenyl-based chemi-
cal structures. Nevertheless chiral biphenyl derivatives syn-
thesised so far,bearing mesogenic residues at 44 , ’-posi-
[
a] Dr. R. Holzwarth,Dr. R. Bartsch,Prof. G. Solladiÿ
Laboratoire de stÿrÿochimie associÿ au CNRS
URA 7008,Universitÿ Louis Pasteur,ECPM
2
5 rue Becquerel,67087 Strasbourg Cedex 2 (France)
Fax : (+33)390-242-742
E-mail: solladie@chimie.u-strasbg.fr
[
b] Prof. Dr. Z. Cherkaoui
ROLIC,Research and Technology,Gewerbestrasse 18
[5]
4
123 Allschwil (Switzerland)
tions, are compatible with liquid crystal (LC) molecular ar-
Chem. Eur. J. 2004, 10,3931 ± 3935
DOI: 10.1002/chem.200400035
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
3931

FULL PAPER
chitecture and have provided mixtures with a relatively
small HTP when they are used as doping agents in nematic
liquid crystals.
When analysing the molecular structures of the chiral
dopants reported in literature it appears that the ones bear-
ing overcrowded molecular structure around the chiral cen-
tres generally induce strong HTP in nematic hosts. As such
[6]
[7]
[8a]
chiral dopants are binaphthol, Taddols, butanetetraol
[8b]
and pyrrolidine derivatives. Based on this,we anticipated
that moving mesogenic residues from 4,4’- to 2, 2’ -positions
on the chiral biphenyl could lead to novel chiral dopants
with high HTP. In fact in this novel molecular design of
chiral biphenyl the sought overcrowding around the chiral
group is increased and therefore better stabilisation of bi-
phenyl dihedral angle could be induced due to the increase
of intramolecular steric interactions at the 2,2’-positions.
We present here the synthesis of first examples of such
enantiomerically pure biphenyl dopants and preliminary re-
sults of their pitch measurements in a nematic host. The mo-
lecular overcrowding of the optically active group and its in-
fluence on the cholesteric pitch is briefly discussed by com-
parison of the length of the mesogenic residues and their
linking nature to the optically active biphenyl core.
Scheme 2. Reaction conditions: a) BH
oxy[1,1’-bipheyl]-4-carboxylic acid,(CoCl)
c) PCC,DCM (88%); d) mCPBA,DCM,NaHCO
3
/THF,0 8C (96%); b) 4’octyl-
Results and Discussion
2
,Et
,Et
3
N,DMAP (27%);
(20%); e) 4’-octyl-
N,CH SO Cl,THF,
3
Synthesis: The synthesetic routes to the chiral dopants 10,
2 and 15 are shown in Schemes 1 and 2. The common
oxy(1,1’-biphenyl)-4-carboxylic acid,(COCl)
ꢀ258C (73%).
2
3
3
2
1
parent step of these syntheses involves the preparation of
enantiomerically pure 4,4’-dimethoxy-6,6’-dimethyl(1,1’-bi-
phenyl)-2,2’-dicarboxylic acid 9,which was prepared from
3
,5-dimethylphenol (Scheme 1). Phenol protection with di-
methyl sulphate (84% yield),followed by aromatic bromi-
nation para to the methoxy group with bromine in carbon
tetrachloride (85% yield) and benzylic bromination with
NBS (92% yield) led to the benzylbromide 4. Compound 4
was then hydrolysed to the corresponding benzyl alcohol 5
using aqueous calcium carbonate (95% yield) followed by
benzylic oxidation using KMnO to give the benzoic acid 6
4
(
85% yield). After esterification via the acid chloride (93%
yield),the resulting methyl ester 7 was submitted to Ull-
mann coupling reaction. The obtained racemic biphenyl di-
carboxylic ester 8 (92% yield) was saponified to the racemic
acid rac-9 (97% yield).
For the optical resolution of racemic dicarboxylic acid
[9]
rac-9 we followed the procedure developed by Suda et al.
Hence upon treatment of rac-9 with one mole equivalent of
brucine in an acetone/methanol mixture under reflux fol-
lowed by cooling,the ( +)-M isomer was exclusively ob-
tained in 38% yield. Evaporation of the solvent of the
mother liquor to dryness and recrystallisation from acetone,
gave exclusively the (ꢀ)-P isomer in 31% yield.
Scheme 1. Reaction conditions: a) KOH,MeOH,Me
b) CCl ,Br
, ꢀ58C (85%); c) CCl4, NBS;AIBN; reflux (92%); d) diox-
ane water,CaCO ,reflux (95%); e) acetone,KMnO 4, reflux (85%);
f) SOCl ,MeOH (93%); g) Cu,DMF,reflux (92%); h) NaOH,water,
reflux (97%); i) brucine,MeOH,acetone,HCl (38%); j) THF,CH
Cl,Et
N, ꢀ258C; 10a: p-ethoxyphenol (63%), 10b: 4’-octyloxy(1,1’-bi-
phenyl)-4-ol (59%).
2
SO
4
(84%);
4
2
3
The acid (ꢀ)-(M)-9 was then esterified with p-ethoxyphe-
nol (63% yield) or 4’-octyloxy(1,1’-biphenyl)-4-ol (59%
yield) to givethe optically active dopants (ꢀ)-(M)-10a and
(ꢀ)-(M)-10b,respectively.
2
3
SO2-
3
3932
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
www.chemeurj.org
Chem. Eur. J. 2004, 10,3931 ± 3935

Helical Twisting in Liquid Crystals
3931 ± 3935
Despite the variation of the molecular structure of the
mesogenic residues,the molecular nature of their linking
groups to the biphenyl core could also have a strong effect
on the molecular overcrowding of the optically active bi-
phenyl. In order to study the effect of this structural change,
the dicarboxylic acid (ꢀ)-(M)-9 was reduced to the diol (+)-
with the LC host may differ from the other chiral dopants
for which better defined segregation with LC host molecules
is allowed through the long mesogenic residue axis.
Conclusion
(
M)-11 with BH /THF followed by esterification with 4’-oc-
3
tyloxy(1,1’-biphenyl)-4-carboxylic acid,to give the diester
In this paper we demonstrated that chiral biphenyls with ap-
propriate molecular architecture are able to induce a large
HTP into nematic liquid crystals. The efficiency of these
novel chiral dopants is attributed to the intramolecular con-
gestion in the chiral biphenyl residue induced by rigid graft-
ing of the 2,2’-positions with long mesogenic residues. From
the chemical point of view,if the chemistry of biphenyls is
varied,the optical resolution has to be further improved in
order to foresee their commercial and practical use in
modern cholesteric devices.
(
+)-(M)-12 (Scheme 2).
Along this line the dibenzylalcohol (+)-(M)-11 was con-
verted into the dialdehyde (+)-(M)-13 by using PCC
PCC=pyridinium chlorochromate,followed by Baeyer±
Villiger rearrangement and hydrolysis to obtain the known
(
[10]
optically active biphenol (+)-(M)-14 . Esterification with
’-octyloxy(1,1’-biphenyl)-4-carboxylic acid afforded the
4
chiral dopant (ꢀ)-(M)-15.
Helical twisting powermeasu er ments : The HTP=1/px of
the optically active biphenyls,given in Table 1,were meas-
ured in ROTN 3010 nematic mixture (from Rolic Technolo-
gy,Allschwil Switzerland),where p is the pitch in mm and x
is the mole fraction.
Experimental Section
1
13
General remarks: H and C NMR spectra were recorded at 200 and
0 MHz on a Bruker AC-200 instrument. Chemical shifts are reported
relative to CHCl . Infrared spectra were recorded on a Perkin±Elmer
5
3
Table 1. Helical twisting powers of chiral biphenyls in ROTN3010.
Spectrum One. Optical rotations were measured on a Perkin±Elmer 241
MC Polarimeter. Melting points are uncorrected. Tetrahydrofuran and di-
ethyl ether were distilled from sodium benzophenone ketyl. Dichlorome-
[
a]
ꢀ1
ꢀ1
Pitch [mm]
HTP [gmm mmol
]
Screw sense
(
(
(
(
ꢀ)-(M)-10a
ꢀ)-(M)-10b
+)-(M)-12
ꢀ)-(M)-15
7.4
2.3
7.3
1.8
8
39
13
50
right
left
left
2 5
thane was distilled from P O . Hexane and dimethylformamide were
dried over 4 ä molecular sieves. Flash chromatography was performed
over Merck silica gel Si 60 (40±63 mm). Elemental analyses were per-
formed by the Service Central de Microanalyse at the CNRS,Institut de
Chimie,Strasbourg (France). Pitches were determined following the
method of Grandjean-Cano using an Olympus BH-2 Microscope.
left
[
a] The pitch was measured in a solution of 1% of dope in nematic
ROTN3010.
1
-Methoxy-3,5-dimethylbenzene (2): Dimethyl sulphate (48 mL,0.50
mol) was added slowly to solution of 3,5-dimethylphenol (61 g,
0.50 mol) and potassium hydroxide (29 g,0.52 mol) in methanol
250 mL). The exothermic reaction was kept at reflux for 1 h. Then the
solvent was evaporated and the residue dissolved in diethyl ether
200 mL). The organic layer was washed with aqueous sodium hydroxide
solution (10%,3î50 mL) and with brine (3î50 mL). The organic phase
was dried over (MgSO ) and concentrated in vacuum. The crude material
was distilled to give 57.8 g of 2 as colourless oil (0.42 mol,84%).
NMR (CDCl ): d=2.31 (s,1H),3.79 (s,3H),6.55 (s,2H),6.62 ppm (s,
H); C NMR (CDCl ): d=21.6,55.2,111.8,122.6,139.3,159.8 ppm.
-Bromo-5-methoxy-1,3-dimethylbenzene (3): solution of bromine
(200 mL) was added dropwise to a solution
a
A global analysis of the obtained results shows that rela-
tively high HTPs are obtained by using the new 2,2’-substi-
tuted optically active biphenyls as chiral dopants. By in-
creasing the length of the mesogenic residues and varying
the nature of their linking groups to the chiral residue it was
(
(
4
ꢀ
1
ꢀ1
1
H
possible to achieve HTP up to 50 gmm mmol into the
nematic host ROTN 3010. This confirms our assumption rel-
ative the chiral dopant intramolecular congestion as an effi-
cient molecular architecture concept for achieving high
HTPs. In addition,only a slight molecular decoupling of the
chiral residue from the mesogenic groups led to a drastic de-
crease of the HTP. By comparison with (ꢀ)-(M)-15,the
strong decrease of HTP observed for (+)-(M)-12 (from 50
to 13 gmm mmol ) could be attributed to the insertion of
the two methylene groups,which reduces the molecular
overcrowding and dihedral angle stability of the chiral bi-
phenyl dopant.
3
1
3
1
3
2
A
(
20.6 mL,0.40 mol) in CCl
4
of 2 (55 g,0.40 mol) in CCl 4 (800 mL) at ꢀ58C. A solution of aqueous
sodium hydroxide (10%,400 mL) was added slowly and the two layers
were separated. The organic phase was washed with brine (2î200 mL)
and dried over MgSO
pound 3 was obtained as colourless oil (73 g,0.34 mol,85%).
4
,and the solvent was evaporated in vacuum. Com-
1
H NMR
C NMR
ꢀ
1
ꢀ1
13
(
CDCl
3
): d=2.39 (s,6H),3.76 (s,3H),6.65 ppm (s,2H);
): d=24.1,55.3,113.9,118.3,139.1,158.2 ppm.
(CDCl
3
2-Bromo-1-(bromomethyl)-5-methoxy-3-methylbenzene (4): A mixture of
(86 g,0.40 mol),NBS (71 g,0.40 mol) and AIBN (0.2 g) in CCl
500 mL) was heated for 4 h at reflux. The reaction mixture was cooled
3
4
(
Among the synthesised chiral dopants that all have the
same absolute biphenyl configuration,it is interesting to
point out that only compound (ꢀ)-(M)-10a induces chole-
steric helix with an opposite helix sign. Here,even if an ap-
proach to the explanation of this behaviour needs more sys-
tematic variation of the molecular structure of the chiral
dopant,it is reasonable to attribute it to a different intermo-
lecular chiral induction mechanism. Taking into account the
short mesogenic residue axis in (ꢀ)-(M)-10a,interactions
to 08C and filtered,and the organic phase was washed successively with
saturated sodium bicarbonate (200 mL),water (2î100 mL) and brine
(2î100 mL). The combined organic phases were dried (MgSO ) and con-
4
centrated in vacuum to give 108 g of 4 as a white solid (0.37 mol,92%).
1
M.p. 75±768C; H NMR (CDCl
2
3
): d=2.41 (s,3H),3.80 (s,3H),4.61 (s,
1
3
H),6.77 (d, J=3 Hz,1H),6.85 ppm (d,
CDCl ): d=24.0,34.8,55.6,114.0,117.0,117.6,138.0,140.4,158.4 ppm.
2-Bromo-5-methoxy-3-methylphenyl)methanol (5): A mixture of 4 (50 g,
.20 mol),1 4, -dioxane (150 mL),water (150 mL) and calcium carbonate
(50 g,0.50 mol) was heated for 10 h at reflux. The mixture was filtered
J=3 Hz,1H);
C NMR
(
3
(
0
Chem. Eur. J. 2004, 10,3931 ± 3935
www.chemeurj.org
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
3933

G. Solladiÿ et al.
FULL PAPER
and concentrated in vacuum,then diluted with methylene chloride
CH
2
Cl
2
). The mother liquor was concentrated in vacuum and the residue
(
150 mL). The organic layer was washed with HCl (2m,50 mL) and a so-
lution of saturated sodium bicarbonate (50 mL),dried (MgSO ) and con-
centrated in vacuum to give 43.9 g of compound 5 as white crystals (0.19
crystallised in acetone in order to obtain (P)-9-brucine salt (2.6 g,33%),
2
0
4
[a] =ꢀ41 (c=1 in CH
D
2 2
Cl ). The nonracemic salts were hydrolysed sepa-
rately by shaking them at room temperature in a separation funnel con-
taining a mixture of ethyl acetate/hydrochloric acid (1m) 1:1. The aque-
ous phases were extracted with ethyl acetate the obtained organic layers
were washed with saturated sodium bicarbonate (50 mL) and brine (2î
50 mL),dried over MgSO 4 and concentrated in vacuum to obtain 1.4 g of
1
3
mol,95%). M.p. 48±49 8C; H NMR (CDCl ): d=2.39 (s,3H),3.80 (s,
3
NMR (CDCl ): d=23.5,55.5,65.4,111.4,115.6,139.3,141.1,140.4,
3
1
1
3
H),4.72 (s,2H),6.75 (d, J=3 Hz,1H),6.91 ppm (d, J=3 Hz,1H);
C
58.6 ppm.
2
0
(
(
ꢀ)-(M)-9 (4.3 mmol,38%),[ a] =ꢀ20 (c=1 in EtOH) and 1.1 g of (+)-
2
(
-Bromo-5-methoxy-3-methylbenzoic acid (6): A solution of KMnO
4
D
2
0
P)-9 (3.5 mmol,31%),[ a] =+19 (c=1 in EtOH); m.p. 202±2048C; IR
16.6 g,105 mmol) in water (350 mL) was added slowly to a solution of
D
and NMR spectra were identical to those of rac-9.
alcohol 5 (12.2 g,52.5 mmol) in acetone (250 mL),which was kept at
reflux for further 30 minutes. The mixture was cooled down and acidified
with HCl (2m,50 mL). The brown precipitate was dissolved by adding a
solution of saturated sodium bicarbonate (100 mL) and acetone was
evaporated in vacuum. Ammonia (150 mL) was added. The mixture was
filtered over celite and acidified with concentrated HCl. The product was
extracted with diethyl ether (3î50 mL),the combined organic phases
4,4’-Dimethoxy-6,6’-dimethyl(1,1’-biphenyl)-2,2’-dimethanol ((+)-(M)-11
and (ꢀ)-(P)-11): A solution of BH /THF 1m (20 mL,20 mmol) was
3
added slowly at 08C to diacid (ꢀ)-(M)-9 or (+)-(P)-9 (1.56 g,4.73 mmol)
dissolved in THF (60 mL). The mixture was stirred at room temperature
for 12 h before being hydrolysed at 08C with saturated aqueous NH Cl
4
(5 mL). The mixture was filtered,extracted with ethyl acetate and the or-
were dried (MgSO
4
) and concentrated in vacuum to obtain 13.5 g of the
ganic layer washed with brine (2î20 ml),dried (MgSO ) and concentrat-
4
acid 6 as white crystals (0.55 mol,85%). M.p. 129 8C; IR (KBr): n˜ =926,
ed in vacuum to obtain 1.37 g (4.53 mmol,96%) as white crystals of re-
ꢀ
1
1
20
20
D
1
159,1277,1411,1682,2631,2563±3125 cm
; H NMR (CDCl
3
): d=2.45
spectively (+)-(M)-11: [a]D =+15 (c=1 in EtOH) or (ꢀ)-(P)-11: [a]
=
(
1
1
s,3H),3.82 (s,3H),6.98 (d, J=2.6 Hz,1H),7.26 (d, J=2.6 Hz,1H),
ꢀ13 (c=1 in EtOH); m.p. 79±828C; IR (KBr): n˜ =867,999,1173,1305,
1
3
ꢀ1 1
0.3 ppm (brs,1H); C NMR (CDCl
36.3,139.9,157.8,168.0 ppm.
3
): d=23.1,55.6,111.7,112.2,118.2,
1439,1604,2840,2944,3257 cm
3
(br); H NMR (CDCl ): d=1.84 (s,
6H),3.84 (s,6H),4.16 (AB,
2.4 Hz,2H),6.89 ppm (d, J=2.4 Hz,2H);
J=11.5 Hz, Dn=24 Hz,4H),6.79 (d, J=
1
3
Methyl 2-bromo-5-methoxy-3-methylbenzoate (7): A mixture of acid 6
9.5 g,37 mmol) and thionyl chloride (20 mL) was heated at reflux for
h. The mixture was concentrated in vacuum; methanol (50 mL) and
C NMR (CDCl
3
): d=20.3,
(
3
55.1,63.2,111.9,115.4,130.1,138.0,140.2,158.8 ppm.
4,4’-Dimethoxy-6,6’-dimethyl(1,1’-biphenyl)-2,2’-dicarbaldehyde
((+)-
pyridine (10 mL) were added and altogether stirred for 2 h at room tem-
perature. The mixture was concentrated in vacuum,dissolved in methyl-
ene chloride (50 mL),washed successively with HCl (2 m,20 mL) and
(M)-13 and (ꢀ)-(P)-13): A mixture of alcohol (+)-(M)-11 or (ꢀ)-(P)-11
(0.80 g,2.9 mmol) and PCC (2.6 g,12 mmol) in methylene chloride
(20 mL) was stirred at room temperature for 45 minutes and afterwards
filtered over silica gel and washed with ethyl acetate/hexane 50:50 in
4
brine (2î30 mL),dried (MgSO ) and filtered,and the solvents were
2
0
evaporated in vacuum. The crude product was purified by flash chroma-
tography (hexane/ethyl acetate,40:60) to give 8.8 g of ester 7 as a white
solid (34 mmol,93%). M.p. 49±51 8C; IR (KBr): n˜ =856,1146,1245,
order to obtain 0.77 g (2.6 mmol,88%) of ( +)-(M)-13: [a] =+32 (c=1
D
2
D
0
in EtOH) or (ꢀ)-(P)-13: [a] =ꢀ30 (c=1 in EtOH); m.p. 95±988C; IR
ꢀ
1
1
(KBr): n˜ =867,947,1147,1305,1391,1600,2854,2925,2958 cm
; H
ꢀ
1
1
1
3
3
1
438,1593,1727,2845,2955,3006 cm
;
H NMR (CDCl
3
): d=2.39 (s,
NMR (CDCl ): d=1.95 (s,6H),3.90 (s,6H),7.13 (dd,
J=2.7,0.6 Hz,
3
1
3
H),3.76 (s,3H),3.90 (s,3H),6.89 (d,
J=3.1 Hz,1H),6.97 ppm (d, J=
2H),7.39 (d, J=2.7 Hz,2H),9.55 ppm (s,2H);
C NMR (CDCl ): d=
3
1
3
.1 Hz,1H); C NMR (CDCl
34.5,140.8,158.1,167.6 ppm.
3
): d=24.0,52.6,55.6,113.0,113.6,119.4,
19.8,55.5,108.4,123.1,132.7,136.1,139.7,159.5,191.3 ppm.
,4’-Dimethoxy-6,6’-dimethyl(1,1’-biphenyl)-2,2’-diol ((+)-(M)-14 or( ꢀ)-
P-14):
4
Dimethyl 4,4’-dimethoxy-6,6’-dimethyl(1,1’-biphenyl)-2,2’-dicarboxylate
A
mixture of aldehyde (+)-(M)-13 or (ꢀ)-(P)-13 (224 mg,
(
rac-8): A mixture of ester 7 (11 g,43 mmol) and freshly activated
0.75 mmol) and mCPBA (1.3 g,7.5 mmol) in methylene chloride (10 mL)
was stirred at room temperature for 20 h. The excess mCPBA was re-
duced by adding Na S O 1m (10 mL). The mixture was washed with a sa-
[
11]
copper powder
(10 g) in DMF (50 mL) was heated to reflux for 3 h
under argon atmosphere. The mixture was cooled down to room temper-
ature,filtered over celite by washing the residue with ethyl acetate (5î
2
2
3
turated solution of NaHCO (3î10 mL). The organic layer was stirred in
3
1
0 mL). DMF was extracted with water (10î30 mL). Then the organic
Na CO 1m (5 mL) for 30 minutes at room temperature and then extract-
2
3
phase was washed with brine (50 mL),dried over MgSO ,filtered and
4
ed with methylene chloride (3î5 mL) and concentrated in vacuum; the
residue was purified by preparative chromatography (ethyl acetate/
hexane 40:60) to obtain 30 mg (0.11 mmol,20%) of respectively ( +)-
concentrated in vacuum. The crude product was purified by flash chro-
matography (hexane/ethyl acetate,80/20) to give 7.2 g of diester rac-8 as
a white solid (20 mmol,92%). M.p. 73±74 8C; IR (KBr): n˜ =860,1014,
2
0
20
(M)-14: [a] =+15 (c=1 in EtOH) or (ꢀ)-(P)-14: [a] =ꢀ13 (c=1 in
D
D
ꢀ
1 1
1
173,1234,1435,1605,1723,2838,2951 cm
; H NMR (CDCl
3
): d=1.88
EtOH); m.p. 155±1608C; IR (KBr): n˜ =837,977,1156,1343,1305,1579,
ꢀ1
1
(
s,6H),3.59 (s,6H),3.86 (s,6H),6.98 (d,
J=2.7 Hz,2H),7.34 ppm (d,
2842,2957,3338 cm
(br); H NMR (CDCl ): d=1.97 (s,6H),3.81 (s,
3
1
3
J=2.7 Hz,2H);
C NMR (CDCl
3
): d=20.4,51.8,55.2,111.8,119.7,
6
2
H),4.80 (s,2H),6.47 (AB,
J=2.4 Hz,2H),6.50 ppm (AB, J=2.4 Hz,
1
3
1
30.7,133.2,138.7,157.9,167.5 ppm.
H); C NMR (CDCl
3
): d=11.6,55.8,99.2,109.2,112.7,141.0,156.2,
4
,4’-Dimethoxy-6,6’-dimethyl(1,1’-biphenyl)-2,2’-dicarboxylic acid (rac-9):
161.5 ppm.
A mixture of diester 8 (5.0 g,14 mmol) and sodium hydroxide (5.6 g,
40 mmol) in water (50 mL) was heated at reflux for 3 h. The solution
was cooled down to room temperature and acidified with HClconc until
pH 1 was attained. The white precipitate was extracted with ethyl ace-
tate,and the organic layer washed with saturated sodium bicarbonate
Bis(4-ethoxyphenyl) 4,4’-Dimethoxy-6,6’-dimethyl(1,1’-biphenyl)-2,2’-di-
carboxylate ((ꢀ)-(M)-10a): Oxalyl chloride (0.5 mL,6 mmol) was added
1
slowly to a solution of (ꢀ)-(M)-9 (0.3 g,0.9 mmol) in CH
2 2
Cl (2 mL) at
0
8C and stirred for 3 h at room temperature. The solvent was evaporated
in vacuum and the residue dissolved in benzene (5 mL). p-Ethoxyphenol
190 mg,1.38 mmol),freshly distilled pyridine (1 mL) and DMAP (8 mg)
(
50 mL) and brine (2î50 mL),dried over MgSO
4
and concentrated in
(
vacuum to obtain 4.5 g of rac-9 as white crystals (13.6 mmol,97%): m.p.
were added. The mixture was stirred at room temperature for 5 minutes,
and then heated to 658C for 3 h. The cold mixture was dissolved in
2
1
6
2
1
02±2048C; IR (KBr): n˜ =795,852,942,1147,1240,1313,1459,1602,
ꢀ
1
667,1689,2524±2984 cm
; 1H NMR (CDCl3): d=1.85 (s,6H),3.86 (s,
EtOAc (5 mL),washed successively with HCl 2 m (5 mL),Na
2 3
CO 1m
H),7.04 (d, J=2.1 Hz,2H),7.29 (d, J=2.1 Hz,2H),10.56 ppm (brs,
(
5 mL) and brine (2î5 mL),dried over MgSO and evaporated in
4
1
3
H); C NMR (CDCl
58.0,172.8 ppm.
3
): d=20.4,55.4,112.7,121.6,129.1,134.5,138.6,
vacuum. The residue purified by flash chromatography (ethyl acetate/
hexane 20:80) to obtain 110 mg (0.19 mmol,63%) of ( ꢀ)-(M)-10a:
2
D
0
4
,4’-Dimethoxy-6,6’-dimethyl(1,1’-biphenyl)-2,2’-dicarboxylic acid ((ꢀ)-
[a] =ꢀ77 (c=1 in CH
2 2
Cl ); pitch=+7.4 mm (1% in ROTN 3010); IR
ꢀ
1
(
M)-9 and (+)-(P)-9): A mixture of diacid rac-9 (3.7 g,11 mmol) and bru-
(KBr): n˜ =854,1009,1171,1314,1465,1505,1603,1741,2927,2979 cm
H NMR (CDCl
;
1
cine (4.2 g,11 mmol) was dissolved at reflux in methanol (5 mL) and ace-
tone (10 mL). The solution was allowed to cool down slowly and the pre-
cipitated crystals were filtered off by washing with cold methanol (2 mL)
3
): d=1.39 (t, J=3.5 Hz,6H),2.02 (s,6H),3.88 (s,6H),
3.98 (q, J=3.5 Hz,4H),6.80 (d, J=1.8 Hz,8H),7.06 (d, J=1.3 Hz,2H),
1
3
7.50 ppm (d, J=1.5 Hz,2H); C NMR (CDCl
3
): d=15.2,20.8,55.8,64.2,
2
0
in order to obtain (M)-9-brucine salt (3.1 g,39%),[ a] =+59 (c=1 in
112.8,120.6,115.4,122.9,131.2,133.6,139.5,144.5,156.9,158.7,
D
3934
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
www.chemeurj.org
Chem. Eur. J. 2004, 10,3931 ± 3935

Helical Twisting in Liquid Crystals
3931 ± 3935
1
66.6 ppm; elemental analysis calcd (%) for C34
H
34
O
8
: C 71.5,H 6.0;
113.4,114.9,121.1,126.4,127.6,128.3,130.5,132.1,139.9,145.5,149.9,
159.2,159.5,164.7 ppm; elemental analysis calcd (%) for C 58
8.2,H 7.5; found C 77.5,H 7.6.
found C 71.5,H 6.2.
66 8
H O : C
7
Bis[4’-(octyloxy)(1,1’-biphenyl)-4-yl]-4,4’-dimethoxy-6,6’-dimethyl(1,1’-bi-
phenyl)-2,2’-dicarboxylate ((ꢀ)-(M)-10b): Compound (ꢀ)-(M)-10b was
prepared according the procedure described above ((ꢀ)-(M)-10a). 4’-Oc-
tyloxy(1,1’-biphenyl)-4-ol was used instead of p-ethoxyphenol. After flash
chromatography (ethyl acetate/hexane 20:80) 157 mg (0.18 mmol,59%)
2
D
0
of (ꢀ)-(M)-10b [a] =ꢀ147 (c=1 in CH
2 2
Cl ) were obtained; pitch=
Acknowledgement
ꢀ
2.3 mm (1% in ROTN 3010); m.p. 80±828C; IR (KBr): n˜ =857,997,
166,1318,1466,1603,1728,1746,2852,2922 cm
ꢀ1
1
1
3
; H NMR (CDCl ):
This work was enabled and financed by ROLIC Research Ltd.,All-
schwil,Switzerland. Dr. Richard Buchecker,Dr. M. Schadt and Prof.
Zoubair M. Cherkaoui are acknowledged for both fruitful discussions
and material support. We thank Dr. Klaus Schmitt for his kind technical
cooperation.
d=0.96 (t, J=6.9 Hz,6H),1.2±1.9 (m,24H),2.07 (s,6H),3.88 (s,6H),
3
7
7
2
1
7
.98 (t, J=6.4 Hz,4H),6.90 (d, J=3.2 Hz,4H),6.94 (d, J=3.2 Hz,4H),
.06 (d, J=2.4 Hz,2H),7.42 (d, J=5.1 Hz,4H),7.46 (d, J=5.1 Hz,4H),
.52 ppm (d, J=2.7 Hz,2H); C NMR (CDCl
1
3
3
): d=14.1,20.3,22.8,26.0,
9.3,31.7,55.3,68.0,112.4,120.3,114 7, ,121.7,127.5,128.0,130.4,131.7,
33.2,138.5,139.1,149.5,158.2,158.6,165.9 ppm; C
8.1,H 7.5; found C 77.9,H 7.5.
58 66 8
H O : calcd. C
[
1] a) D. J. Broer,J. A. M. van Haaren,J. Lub, Proc. SPIE-Int. Soc. Opt.
Eng. 2000, 4107,59±68; b) K. Schmitt,J. F¸nfschilling,M. Z. Cher-
kaoui,M. Schadt, Eurodisplay 99, 1999,437; c) X. Y. Huang,A.
Khan,N. Miller,J. W. Doane, Proc. SPIE-Int. Soc. Opt. Eng. 2002,
Bis[4’-(octyloxy)(1,1’-biphenyl)-4-carbonyloxymethyl]-4,4’-dimethoxy-
,6’-dimethyl(1,1’-biphenyl)-ꢀ2,2’-diyl ((+)-(M)-12): Oxalyl chloride
0.5 mL,6 mmol) was added slowly to a solution of 4 ’-octyloxy(1,1’-bi-
phenyl)-4-carboxylic acid (0.3 g,0.9 mmol) in CH Cl (5 mL) at 08C and
stirred for 3 h at room temperature. The solvent was evaporated in
vacuum and the residue dissolved in CH Cl (5 mL). Benzylic alcohol
+)-(M)-11 (100 mg,0.33 mmol),triethylamine (0.3 mL,2 mmol) and
6
(
2
2
4
658,1±6; d) A. W. Hall,J. Hollingshurst,J. W. Goodby, Handbook
of Liquid CrystalResearch 1997,17±70.
2
2
[
2] a) G. Gottarelli,M. Hilbert,B. Samori,G. Solladiÿ,G. P. Spada,R.
Zimmermann, J. Am. Chem. Soc. 1983, 105,7318; b) A. Ferranini,
G. J. Moro,P. L. Nordico, Phys. Rev. E 1996, 53,681; c) H.-G.
(
DMAP (8 mg) were added at 08C. The mixture was stirred at room tem-
perature for 12 h. The cold mixture was washed successively with HCl
1
Kuball,Th. M¸ller,H. Br¸ning A. Schˆnhofer,
Mol. Cryst. Liq.
m (5 mL),NaHCO
3 4
1m (5 mL) and brine (2î5 mL),dried over MgSO
Cryst. 1995, 261,205.
and evaporated in vacuum. After flash chromatography (ethyl acetate/
[
[
3] a) H.-J. Deu˚en,P. V. Shibaev,R. Vinokur,T. Bj˘rnholm,K.
Schaumburg,K. Bechgaard,V. P. Shibaev, Liq. Cryst. 1996, 21,327±
2
0
hexane 20:80) 225 mg (0.25 mmol,27%) of ( +)-(M)-12 [a]D =+29 (c=1
in CH Cl
0±848C; IR (KBr): n˜ =827,1096,1157,1248,1372,1467,1604,1713,
2
2
) were obtained. Pitch=ꢀ7.3 mm (1% in ROTN 3010); m.p.
3
40; b) K. H. Etzbach,P. Delavier,K. Siemensmeyer,G. Wagen-
blast,L. Laupichler,V. Vill,BASF AG,patent 1998,US 5-780-629.
4] a) A. di Matteo,S. M. Todd,G. Gottarelli,G. Solladiÿ,V. E. Wil-
liams,R. P. Lemieux,A. Ferrarini,G. P. Spada, J. Am. Chem. Soc.
001, 123,7842±7851; b) D. Vizitiu,C. Lazar,J. P. Radke,C. S. Hart-
8
2
ꢀ1
1
854,2925 cm
;
H NMR (CDCl
3
): d=0.91 (t, J=6.3 Hz,6H),1.2±1.9
J=6.2 Hz,4H),4.98 (AB,
J=12.9 Hz, Dn=19 Hz,4H),6.86 (d, J=2.0 Hz,2H),6.93 (d, J=8.3 Hz,
(
m,24H),1.95 (s,6H),3.85 (s,6H),3.96 (t,
2
4
4
2
1
H),7.00 (d, J=2.0 Hz,2H),7.46 (d, J=8.9 Hz,4H),7.52 (d, J=8.3 Hz,
ley,M. A. Glaser,R. P. Lemieux, Chem. Mater. 2001, 13,1692±1699
and references therein.
1
3
3
H),8.00 ppm (d, J=8.1 Hz,4H); C NMR (CDCl ): d=14.1,20.1,22.5,
6.0,29.2,29.4,31.8,55.1,64.9,68.1,111.9,115.2,114.9,126.3,128.2,
30.1,128.0,129.8,131.9,135.5,138.4,145.1,158.9,159.4,166.1 ppm; ele-
[
5] a) G. Solladiÿ,P. Hugelÿ,R. Bartsch,A. Skoulios,
Angew. Chem.
1
1
3
996, 108,1640±1642; Angew. Chem. Int. Ed. Engl. 1996, 35,1533±
535; b) G. Solladiÿ,P. Hugelÿ,R. Bartsch, J. Org. Chem. 1998, 63,
895±3898.
mental analysis calcd (%) for C58
.7.
Bis[4’-(octyloxy)(1,1’-biphenyl)-4-carbonyloxy]-4,4’-dimethoxy-6,6’-di-
methyl(1,1’-biphenyl)-2,2’-diyl ((ꢀ)-(M)-15): solution of 4’-octyl-
oxy(1,1’-biphenyl)-4-carboxylic acid (175 mg,0.5 mmol),triethylamine
0.14 mL,0.98 mmol) and methylsulfonyl chloride (37 mL,0.48 mmol) in
66 8
H O : C 78.4,H 7.7; found C 78.2,H
7
[6] S. Kelly,F. Leenhouts,Patent, 1992,US 5-093-027.
[7] D. Seebach,A. K. Beck,A. Heckel, Angew. Chem. 2001, 113,96;
Angew. Chem. Int. Ed. 2001, 40,92.
[8] a) K. Schmitt,M. Z. Cherkaoui,R. Bucheker, WO 99/64383, 1999;
b) K. Schmitt,M. Z. Cherkaoui, WO 2000/002856, 2000.
A
(
THF (2 mL) was stirred between ꢀ258C and ꢀ358C for 1 h. Biphenol
(
(
+)-(M)-14 (40 mg,0.15 mmol) and DMAP (4 mg) dissolved in THF
2 mL) were added. The mixture was stirred at room temperature for
[9] S. Kanoh,H. Muramoto,N. Kobayashi,M. Motoi,H. Suda,
Chem. Soc. Jpn. 1987, 60,3659±3662.
Bull.
2
4 h,filtered over celite and purified by preparative TLC (ethyl acetate/
[10] H. Musso,W. Steckelberg, Chem. Ber. 1968, 101,1510.
2
0
hexane 20:80) to obtain 96 mg (0.11 mmol,73%) of ( ꢀ)-(M)-15 [a]
=
[11] Activation of copper powder: Prior to use the copper powder (10 g)
was stirred in a solution of iodine (2 g) in acetone (50 mL). As soon
as the mixture became colourless the liquid was decanted and the
copper powder was washed once with a mixture of acetone/HClconc
1/1 (50 mL),then with acetone (5î50 mL). The copper powder was
dried in vacuum at 1708C for 2 h.
D
ꢀ
238 (c=1 in CH
2
Cl
2
); pitch=ꢀ1.8 mm (1% in ROTN 3010); m.p. 63±
6
1
1
68C; IR (KBr): n˜ =823,998,1078,1139,1182,1251,1314,1463,1603,
ꢀ1
1
733,2853,2921 cm
.2±1.9 (m,24H),2.09 (s,6H),3.76 (s,6H),4.00 (t,
J=8.9 Hz,4H),7.54 (d,
.9 Hz,4H),7.56 (d, J=8.6 Hz,4H),7.92 ppm (d, J=8.6 Hz,4H);
;
H NMR (CDCl
3
): d=0.89 (t, J=6.2 Hz,6H),
J=6.5 Hz,4H),6.71
J=
(
8
AB, J=2.3 Hz, Dn=5 Hz,4H),7.97 (d,
1
3
C
Received: January 13,2004
NMR (CDCl
3
): d=14.1,19.9,22.7,26.1,29.3,29.4,31.8,55.4,68.2,105.5,
Published online: June 21,2004
Chem. Eur. J. 2004, 10,3931 ± 3935
www.chemeurj.org
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
3935