New 2,2′-substituted 6,6′-dimethylbiphenyl derivatives inducing strong helical twisting power in liquid crystals

Article abstract of DOI:10.1002/ejoc.200500100

New optically active tetra-ortho-substituted biphenyl chiral dopants for nematic liquid crystals are described. It was shown, with respect to our previous results, that biphenyl chiral dopants bearing only mesogenic residues on their 2,2′-positions and wi

Full text of DOI:10.1002/ejoc.200500100

FULL PAPER
New 2,2Ј-Substituted 6,6Ј-Dimethylbiphenyl Derivatives Inducing Strong
Helical Twisting Power in Liquid Crystals
Richard Holzwarth,[a] Richard Bartsch,[a] Zoubair Cherkaoui,[b] and Guy Solladié*[a]
Keywords: Biphenyl / Asymmetric synthesis / Induced cholesteric / Pitch / Screw sense
New optically active tetra-ortho-substituted biphenyl chiral
dopants for nematic liquid crystals are described. It was
shown, with respect to our previous results, that biphenyl
chiral dopants bearing only mesogenic residues on their 2,2Ј-
positions and without any substituents on their 4,4Ј-positions
gave rise to very high twisting powers in nematic liquid crys-
tals. This powerful and unconventional chiral dopant mol-
ecular architecture allowed the design of new tetra-ortho-
substituted biphenyl derivatives, easier to prepare in op-
tically active form. This simplification of the molecular archi-
tecture still affords chiral dopants for nematic liquid crystals
with large helical twisting powers and allows more economi-
cal large-scale preparation.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
stead of the 4,4Ј-ones. Indeed, acceptable compatibility with
nematic liquid crystalline materials such as AN5, developed
by Rolic for applications purposes, was obtained.
In view of the remarkable properties of these biphenyl
chiral dopants and their potential use in cholesteric devices,
we were interested in designing other derivatives with easier
chemical access.
The use of methoxy groups at the 4,4Ј-positions in our
former biphenyl derivatives had only been to allow for pos-
sible substitution (e.g., with mesogenic residues for increas-
ing compatibility with liquid crystalline hosts). As accept-
able compatibility was observed, the presence of the meth-
oxy groups was no longer needed from a structural point
of view. Other easily accessible biphenyl chiral dopants then
become interesting to explore.
Introduction
We have recently reported[1] the synthesis and the helical
twisting powers (HTPs) of new chiral biphenyls in nematic
liquid crystals. We have demonstrated that the introduction
of mesogenic residues at the 2,2Ј-positions of the chiral bi-
phenyl produced very efficient dopants of nematic liquid
crystal. The compound shown in Figure 1 is a typical exam-
ple among the newly developed dopants[1] and induced a
very short cholesteric pitch (1.8 μm) when dissolved in very
low concentrations in nematic liquid crystals.
Figure 1. A biphenyl chiral dopant with a strong helical twisting
power in nematic liquid crystals.
The performance of the newly discovered chiral dopants
was mainly attributed to conformational stabilisation of the
optically active form as a result of strong congestion of the
molecular architecture. No significant drawbacks on ther-
motropic behaviour were observed with biphenyls bearing
mesogenic residues at the unconventional 2,2Ј-positions in-
[a] Laboratoire de stéréochimie associé au CNRS, UMR 7008,
Université Louis Pasteur, ECPM,
25 rue Becquerel, 67087 Strasbourg Cedex 2, France
Fax: +33-3-90242742
E-mail: solladie@chimie.u-strasbg.fr
[b] ROLIC, Technologies Ltd.,
Gewerbestrasse 18, 4123 Allschwil, Switzerland
Figure 2.
3536
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejoc.200500100
Eur. J. Org. Chem. 2005, 3536–3541

New Biphenyls Inducing Strong Helical Twisting Power in Liquid Crystals
Here we present the synthesis of optically active biphenyl
FULL PAPER
The optical resolution of biphenol rac-5 was carried out
chiral dopants (–)-(M)-7 and (–)-(M)-9 (Figure 2). We dem- by the method described by Suda et al.[4] Compound rac-5
onstrate that the presence of mesogenic residues on the 2,2Ј- was treated with phosphoryl chloride to afford the hydro-
positions maintained very high helical twisting powers even genphosphate rac-6. Compound rac-6, when added to one
in the absence of substituents in the 4,4Ј-positions. The syn- equivalent of cinchonidine in aqueous methanol, afforded
thetic route to these new molecules without substituents in the crystallisation of the diastereomerically enriched salt of
the 4,4Ј-positions is much shorter (four steps only instead (+)-(M)-5/cinchonidine (41% yield).
of nine previously) and should allow economical large-scale
preparation.
Treatment of the mother liquors with quinine after hy-
drolysis of the salts allowed the crystallisation of (–)-(P)-5/
quinine salt (38% yield). Hydrolysis of the optically active
salts followed by the cleavage of the hydrogenphosphate
group in (–)-(M)-6 and (+)-(P)-6 with LiAlH4 yielded the
corresponding chiral biphenols (+)-(M)-5 and (–)-(P)-5
(95%). Finally (+)-(M)-5 was esterified[5] in the presence of
methanesulfonyl chloride and 4Ј-(octyloxy)biphenyl-4-car-
boxylic acid or 4Ј-(8-acryloyloxyoctyloxy)biphenyl-4-car-
boxylic acid to give the optically active dopants (–)-(M)-7a
and (–)-(M)-7b, respectively.
Results and Discussion
Synthesis
The synthetic routes to the chiral dopants (–)-(M)-7a,
(–)-(M)-7b, (–)-(M)-9a and (–)-(M)-9b are shown in
Schemes 1 and 2.
For (–)-(M)-7a and (–)-(M)-7b, Sandmeyer-type bromi-
nation[2] of 2-methyl-6-nitroaniline (93% yield) was used as
the first reaction step. This was followed by Ullmann coup-
ling (86% yield) and reduction of the nitro group to the
corresponding diamine rac-4 under hydrogen (99% yield),
The absolute configurations of these new products, as
well as their high optical purities, were deduced by compari-
son with the known compounds (+)-(M)-5 and (–)-(M)-6.[4]
Compounds (–)-(M)-9a and (–)-(M)-9b were prepared by
(Scheme 1). After diazotization, the resulting diazonium homocoupling of the freshly prepared diazonium salt of
[3]
salt was hydrolysed
yield).
to afford the biphenol rac-5 (50% commercially available 3-methylanthranilic acid[6] (72%
yield, Scheme 2). Optical resolution of the resulting biphen-
Scheme 1. Reagents and conditions: a) HBr, NaNO2, 0 °C, CuBr, 0 °C to 60 °C. b) Cu, 200 °C, 2 h. c) MeOH, Pd, H2. d) H2SO4, NaNO2,
0 °C, H2SO4, 110 °C. e) POCl3, H2O, THF. f) Cinchonidine, MeOH, H2O, HCl. g) LiAlH4, THF. h) 7a: 4Ј-(octyloxy)biphenyl-4-carboxylic
acid, THF, CH3SO2Cl, Et3N, –25 °C; 7b: 4Ј-(8-acryloyloxyoctyloxy)biphenyl-4-carboxylic acid, THF, CH3SO2Cl, Et3N, –25 °C.
Eur. J. Org. Chem. 2005, 3536–3541
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R. Holzwarth, R. Bartsch, Z. Cherkaoui, G. Solladié
FULL PAPER
yldicarboxylic acid rac-8 was achieved by diastereoselective Table 1. Helical twisting powers of chiral biphenyls in ROTN3010.
crystallisation of the corresponding brucine salt,[7] and the
acid (–)-(M)-8 was obtained in 32% yield. Finally, esterifi-
cation with p-ethoxyphenol or 4Ј-(octyloxy)biphenyl-4-ol in
the presence of methanesulfonyl chloride gave (–)-(M)-9a
(45% yield) or (–)-(M)-9b (52% yield), respectively. The ab- (–)-(M)-7b
solute configurations of these new products as well as their
Compound
Pitch[a]
[μm]
HTP
Screw sense
[g·μm–1·mmol–1]
(–)-(M)-7a
(+)-(P)-7a
2.1
2.0
2.4
2.1
10.2
3.9
42
42
41
46
5.1
21
right
left
right
left
right
right
(+)-(P)-7b
(–)-(M)-9a
high optical purities were deduced by comparison with the
(–)-(M)-9b
[7]
known compound carboxylic acid (–)-(M)-8.
[a] The pitch was measured in a solution of 1% of dopant in ne-
matic ROTN3010.
intramolecular congestion[1,8] as an efficient molecular
architecture concept for achieving high HTPs.
This efficiency of biphenyl chiral dopants allows con-
sideration of their application in modern cholesteric de-
vices: namely, reflective and transflective cholesteric films.
For this purpose optically active biphenyl derivatives bear-
ing polymerisable acrylic groups at the ends of the mesog-
enic residues were prepared. The presence of acrylic groups
allows the chiral dopant to be crosslinked with polymeris-
able nematic. The specific cholesteric properties induced at
the monomeric scale are then frozen into the sample by
photochemical radical polymerisation.
The introduction of the polymerisable group had no sig-
nificant influence on the measured HTPs, which varied be-
tween 41 and 46 g·μm–1·mmol–1 for the polymerizable op-
tically active dopant 7b and around 42 g·μm–1·mmol–1 for
the nonpolymerizable dopant 7a.
Furthermore, consistently with our expectations we con-
firmed that compound (–)-(M)-9b, with a longer side chain
containing a rigid biphenyl core, induces a higher HTP than
compound (–)-(M)-9a with an ethoxyphenyl group.
We observed that the crosslinkable compound (–)-(M)-
7b with an acrylic group at the end of the side chain has
about the same helical twisting power as compound (–)-
(M)-7a.
Scheme 2. Reagents and conditions: a) NaNO2, NaOH, 0 °C, HCl,
NH4OH, CuSO4, (NH2OH)2·H2SO4, 0 °C. b) Brucine, acetone,
MeOH, HCl. c) 9a: p-ethoxyphenol, THF, CH3SO2Cl, Et3N,
–25 °C; 9b: 4Ј-(octyloxy)biphenyl-4-ol; THF, CH3SO2Cl, Et3N,
–25 °C.
Conclusions
We have demonstrated that chiral biphenyls with appro-
priate molecular architecture are able to induce large HTPs
in nematic liquid crystals. We thus confirmed the validity
of molecular congestion around the chiral group as an ef-
ficient molecular architecture concept for chiral dopant de-
velopment. Chiral biphenyls based on this concept and
characterised by very easy chemical access were developed
and offer potential application in various modern and clas-
sic cholesteric devices regarding the high efficiency of both
polymerisable and nonpolymerisable forms.
Helical Twisting Power Measurements
The HTPs (= 1/px, where p is the pitch in μm and x
is the mol fraction) of the newly prepared optically active
biphenyls are listed in Table 1. Measurement were per-
formed in the nematic mixture ROTN 3010 (from Rolic
Technology, Allschwil, Switzerland).
A global analysis of the results shows relatively high
HTPs for these new 2,2Ј-substituted optically active biphen-
yls as chiral dopants. By increasing the length of the meso-
genic residues and varying the nature of their linking
groups to the chiral residue it was possible to achieve HTPs
of up to 42 g·μm–1·mmol–1 in the nematic host ROTN 3010.
Experimental Section
1
General Remarks: H and 13C NMR spectra were recorded at 200
and 50 MHz on a Bruker AC 200 instrument. Chemical shifts are
reported relative to CHCl3. Infrared spectra were recorded on a
Perkin–Elmer Spectrum One instrument. Optical rotations were
This confirms our assumption relating to chiral dopant measured on a Perkin–Elmer 241 MC Polarimeter. Melting points
3538 © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjoc.org
Eur. J. Org. Chem. 2005, 3536–3541

New Biphenyls Inducing Strong Helical Twisting Power in Liquid Crystals
FULL PAPER
are uncorrected. Tetrahydrofuran and diethyl ether were distilled
from benzophenone. Dichloromethane was distilled from P2O5.
Hexane and dimethylformamide were dried over 4-Å molecular
sieves. Flash chromatography was performed on Merck silica gel
Si 60 (40–63 μm). Elemental analyses were performed at the Service
Central de Microanalyse at the CNRS, Institut de Chimie, Stras-
bourg, France. Pitches were determined by Grandjean–Cano
method with use of an Olympus BH-2 microscope.
was dissolved in diethyl ether, washed with brine (2×50 mL), dried
over MgSO4, and evaporated in vacuo to afford biphenol 5 (2.64 g,
50%, 12 mmol). – m.p. 159–160 °C. 1H NMR (CDCl3): δ = 2.00
(s, 6 H), 4.73 (s, 2 H), 6.8–6.9 (m, 4 H), 7.25 (dd, J = 7.9 and
7.6 Hz, 2 H) ppm. 13C NMR (CDCl3): δ = 19.5, 113.2, 119.5, 122.6,
130.1, 138.9, 153.8 ppm. IR (KBr): ν = 739, 782, 1162, 1176, 1259,
˜
1281, 1461, 1574, 3409, 3463 cm–1.
6-Hydroxy-1,11-dimethyl-6λ5-dibenzo[d,f][1,3,2]dioxaphosphepin-6-
one (rac-6): Phosphoryl chloride (0.63 mL, 6.8 mmol) was added to
a solution of biphenol 5 (1.22 g, 5.69 mmol) in CH2Cl2 (20 mL).
Et3N (1.93 mL, 13.7 mmol) was added slowly and the mixture was
kept at reflux for 30 minutes. The obtained chlorophosphate was
extracted with CH2Cl2 (2×25 mL) and hydrolysed by heating in a
mixture of water/THF (1:1) at 50 °C for 1 h. The THF was evapo-
rated and the obtained hydrogen phosphate rac-6 was recrystallised
from aqueous methanol. Yield: 1.4 g (87%, 4.9 mmol). 1H NMR
((CD3)2CO): δ = 2.20 (s, 6 H), 4.90 (broad s, 1 H), 7.1-7.4 (m, 6
H) ppm. 31P NMR ((CD3)2CO): δ = 0.30 (s, 1 P) ppm.
6-Hydroxy-1,11-dimethyl-6λ5-dibenzo[d,f][1,3,2]dioxaphosphepin-6-
one [(–)-(M)-6 and (+)-(P)-6]: Hydrogenphosphate rac-6 (1.16 g,
4.20 mmol) and cinchonidine (1.28 g, 4.30 mmol) were dissolved in
methanol (9.5 mL) at reflux. Water (1.9 mL) was added to the hot
solution and the mixture was then allowed to cool down slowly.
The cinchonidine salt crystals, [α]2D0 = –153 (c = 0.5, MeOH), reco-
vered after filtration were hydrolysed by shaking with HCl (20%,
15 mL). The mixture was extracted with EtOAc (2×20 mL) and
the combined organic phases were dried over MgSO4, filtered and
evaporated in vacuo to afford (–)-(M)-6 (0.45 g, 39%, 1.6 mmol),
[α]2D0 = –168 (c = 0.5, MeOH), (ref.[4] –179 (c = 0.5, MeOH).
2-Bromo-3-nitrotoluene (2): Na2S2O5 (12 g), dissolved in water
(120 mL), was added over 5 minutes to a warm (60 °C) solution of
CuSO4 (45 g, 0.18 mol) and NaBr (19 g, 0.19 mol) in water
(150 mL). The mixture was allowed to cool down to room temp.
and the solid was decanted. The solid was washed with water
(3×100 mL) and dissolved in aqueous HBr (48%, 30 mL).
Aqueous HBr (48%, 85 mL) was added over 20 minutes to a solu-
tion of 2-methyl-6-nitroaniline (1, 25 g, 0.16 mol) at reflux in water
(150 mL) and dioxane (75 mL). After a further 15 minutes at reflux
the mixture was cooled down to 0 °C and a solution of NaNO2
(11.3 g, 0.16 mol) in water (100 mL) was added dropwise. The tem-
perature was still maintained at 0 °C and the mixture was poured
over freshly prepared CuBr and stirred for further 15 minutes, and
was then heated to 60 °C for 15 minutes and finally stirred at room
temp. overnight. The product was extracted with diethyl ether, the
organic layer was dried (MgSO4) and filtered, and the solvent was
evaporated to afford compound 2 (32.9 g, 93%, 0.15 mmol). 1H
NMR (CDCl3): δ = 2.50 (s, 3 H), 7.32 (dd, J = 7.8 and 7.5 Hz, 1
H), 7.43 (ddd, J = 7.5, 1.9 and 0.8 Hz, 1 H), 7.50 (ddd, J = 7.8,
1.9 and 0.5 Hz, 1 H) ppm. 13C NMR (CDCl3): δ = 23.6, 115.8,
122.2, 126.7, 127.5, 133.5, 141.2 ppm. IR (KBr): ν = 696, 790, 804,
˜
1038, 1326–1381, 1454, 1529 cm–1.
The mother liquor was hydrolysed in HCl (20%) and the recovered
hydrogenphosphate was added to 1 equivalent of quinine dissolved
in aqueous methanol in order to precipitate the corresponding qui-
nine salt [α]2D0 = –42 (c = 0.5, MeOH). The salt was hydrolysed by
shaking in HCl (20%) and the desired atropisomer was extracted
with EtOAc (2×20 mL), dried over MgSO4, filtered and evapo-
2,2Ј-Dimethyl-6,6Ј-dinitrobiphenyl (3): 2-Bromo-3-nitrotoluene (2,
30 g, 0.14 mol) and freshly activated copper powder[9] (30 g) were
heated under inert atmosphere to 200 °C for 2 hours. The mixture
was filtered through celite and washed thoroughly with diethyl
ether. After evaporation of the solvent, biphenol 3 (16.4 g, 86%,
1
60 mmol) was obtained. – m.p. 100–102 °C. H NMR (CDCl3): δ
rated in vacuo to afford (+)-(P)-6 (0.41 g, 35%, 1.5 mmol), [α]2D0
=
= 1.98 (s, 6 H), 7.47 (dd, J = 8.0 and 7.5 Hz, 2 H), 7.58 (ddd, J = +162 (c = 0.5, MeOH). – NMR spectra were identical to those of
7.4, 0.9 and 0.5 Hz, 2 H), 7.99 (ddd, J = 8.0, 0.9 and 0.5 Hz, 2
rac-6.
H) ppm. 13C NMR (CDCl3): δ = 19.9, 122.4, 128.6, 131.5, 135.2,
6,6Ј-Dimethylbiphenyl-2,2Ј-diol [(+)-(M)-5 and (–)-(P)-5]: LiAlH4
(20 mg, 0.5 mmol) was added to a solution of the hydrogenphos-
phate (–)-(M)-6 or (+)-(P)-6 (50 mg, 0.18 mmol) in THF (5 mL) at
0 °C. The mixture was heated at reflux for 3 h and was then hydro-
lysed with HCl (20%, 1 mL) and extracted with EtOAc. The or-
ganic layer was washed with brine, dried over MgSO4 and filtered,
and the solvent was evaporated under vacuum to provide the de-
sired atropisomer (38 mg, 99%, 0.18 mmol). (+)-(M)-5: [α]2D0 = +84
138.3, 148.1 ppm. IR (KBr): ν = 743, 799, 811, 1217, 1351, 1455,
˜
1518, 1738, 2864–3087 cm–1.
6,6Ј-Dimethylbiphenyl-2,2Ј-diamine (4): A catalytic amount of Pd
(5% on carbon) in a solution of dinitrobiphenyl 3 (3.0 g, 11 mmol)
in methanol (50 mL) was stirred at room temp. under hydrogen
atmosphere (30–50 bar) for 5 hours. Filtration of the mixture over
silica gel, followed by evaporation of the solvent, afforded diamine
4 (2.31 g, 99%, 10.9 mmol). H NMR (CDCl3): δ = 1.98 (s, 6 H), (c = 1, EtOH), (ref.[4] +91 (c = 0.5, MeOH). (–)-(P)-5: [α]2D0 = –83
1
3.46 (broad s, 4 H), 6.65 (dd, J = 7.8 and 0.7 Hz, 2 H), 6.73 (ddd,
J = 7.5, 7.2 and 0.7 Hz, 2 H), 7.09 (dd, J = 7.8 and 7.5 Hz, 2
H) ppm. 13C NMR (CDCl3): δ = 19.5, 113.2, 120.5, 122.3, 128.6,
(c = 1, EtOH). – m.p. 159–160 C. IR and NMR spectra were iden-
tical to those of rac-5.
6,6Ј-Dimethylbiphenyl-2,2Ј-diyl Bis[4Ј-(octyloxy)biphenyl-4-carbox-
ylate] [(–)-(M)-7a and (+)-(P)-7a]: A solution of 4Ј-(octyloxy)bi-
phenyl-4-carboxylic acid (165 mg, 0.50 mmol), triethylamine
(0.13 mL, 0.92 mmol) and methanesulfonyl chloride (35 μL,
0.45 mmol) in THF (2 mL) was stirred between –25 °C and –35 °C
for 1 h. Biphenol (+)-(M)-5 or (–)-(P)-5 (40 mg, 0.19 mmol) and
DMAP (4 mg) dissolved in THF (1 mL) were added. The mixture
was stirred at room temperature for 5 days, filtered through celite
and purified by preparative TLC (ethyl acetate/hexane, 20:80) to
provide 75 mg (0.09 mmol, 48%) of (–)-(M)-7a: [α]2D0 = –211 (c =
1, CH2Cl2); pitch = +2.1 μm (1% in ROTN 3010) or (+)-(P)-7a:
[α]2D0 = +208 (c = 1, CH2Cl2); pitch = –2.0 μm (1% in ROTN
138.2, 144.5 ppm. IR (KBr): ν = 746, 779, 787, 1297, 1460, 1581,
˜
1607, 3345, 3421, 3440 cm–1.
6,6Ј-Dimethylbiphenyl-2,2Ј-diol (rac-5):
A solution of NaNO2
(3.38 g, 49 mmol) in water (50 mL) was added slowly at 0 °C to a
solution of diamine 4 (5.2 g, 25 mmol) in concentrated H2SO4
(17 mL) and water (150 mL). The mixture was stirred for a further
10 minutes at 0 °C and was then added dropwise at 105–110 °C to
a solution of H2SO4 (50%, 450 mL). As soon as the addition had
been finished the mixture was cooled to r.t. and extracted with
diethyl ether. The desired biphenol was extracted from the organic
phase with NaOH (1 m); this aqueous phase was acidified by ad-
dition of H2SO4 (1 m) in order to precipitate biphenol 5. The solid
1
3010). – m.p. 52–54 °C; H NMR (CDCl3): δ = 0.91 (t, J = 5.5 Hz,
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R. Holzwarth, R. Bartsch, Z. Cherkaoui, G. Solladié
FULL PAPER
6 H), 1.2–1.9 (m, 24 H), 2.15 (s, 6 H), 4.00 (t, J = 6.4 Hz, 4 H),
brucine salt (2.6 g, 33%) [α]2D0 = –38 (c = 1, MeOH) was obtained.
6.98 (d, J = 8.6 Hz, 4 H), 7.1–7.3 (m, 6 H), 7.55 (2d, J = 8.6 Hz, 8 The two obtained salts were each hydrolysed by shaking in a mix-
H), 7.88 (d, J = 8.3 Hz, 4 H) ppm. 13C NMR (CDCl3): δ = 14.1, ture of EtOAc/HCl (1 m, 1:1) in a separation funnel. The organic
19.5, 22.6, 26.0, 29.2, 29.3, 29.4, 31.8, 68.1, 114.8, 119.8, 126.3,
127.3, 127.5, 128.3, 129.0, 130.4, 132.0, 138.7, 145.5, 148.7, 159.4,
layer was washed with saturated aqueous NaHCO3 and brine, dried
over MgSO4 and filtered, and the solvent was evaporated under
vacuum to afford the desired atropisomers. (+)-(P)-8: 1.4 g (38%,
3.5 mmol) [α]2D0 = +21 (c = 1, MeOH), (ref.[7] +22, c = 1, MeOH);
(–)-(M)-8: 1.1 g (32%, 3.4 mmol) [α]2D0 = –20 (c = 1, MeOH) of the
desired atropisomer (99%, 0.18 mmol); m.p. 208–210 °C. IR and
NMR spectra were identical to those of rac-8.
164.7 ppm. IR (KBr): ν = 826, 1077, 1182, 1220, 1247, 1264, 1465,
˜
1497, 1604, 1732, 2855, 2924 cm–1.
6,6Ј-Dimethylbiphenyl-2,2Ј-diyl Bis[4Ј-(8-acryloyloxyoctyloxy)bi-
phenyl-4-carboxylate] [(–)-(M)-7b and (+)-(P)-7b]: A solution of 4Ј-
(8-acryloyloxyoctyloxy)biphenyl-4-carboxylic acid (600 mg,
1.45 mmol), triethylamine (0.38 mL, 2.7 mmol) and methanesulfo-
nyl chloride (100 μL, 1.33 mmol) in THF (7 mL) was stirred be-
tween –25 °C and –35 °C for 1 h. Biphenol (+)-(M)-5 or (–)-(P)-5
(130 mg, 0.6 mmol) and DMAP (15 mg) dissolved in THF (7 mL)
were added. The mixture was stirred at room temperature for 4
days, filtered through celite and purified by preparative TLC (ethyl
acetate/hexane, 50:50) to provide 115 mg (0.12 mmol, 20%) of (–)-
(M)-7b: [α]2D0 = –216 (c = 1, CH2Cl2); pitch = +2.4 μm (1% in
ROTN 3010) or (+)-(P)-7b: [α]2D0 = +212 (c = 1, CH2Cl2); pitch =
Bis(4-ethoxyphenyl) 6,6Ј-Dimethylbiphenyl-2,2Ј-dicarboxylate [(–)-
(M)-9a]: A solution of diacid (–)-(M)-8 (257 mg, 0.95 mmol), tri-
ethylamine (0.56 mL, 4.0 mmol) and methanesulfonyl chloride
(0.15 mL, 1.9 mmol) in THF (4 mL) was stirred between –25 °C
and –35 °C for 1 h. p-Ethoxyphenol (276 mg, 2.0 mmol) and
DMAP (5 mg) dissolved in THF (2 mL) were added. The mixture
was stirred at room temperature for 5 days, filtered through celite
and purified by preparative TLC (ethyl acetate/hexane, 50:50) to
provide (–)-(M)-9a as a viscous liquid (220 mg, 0.43 mmol, 45%).
[α]2D0 = –111 (c = 1, CH2Cl2); pitch = +10.2 μm (1% in ROTN
1
–2.1 μm (1% in ROTN 3010). H NMR (CDCl3): δ = 1.3–1.9 (m,
1
24 H), 2.13 (s, 6 H), 4.00 (t, J = 6.5 Hz, 4 H), 4.16 (t, J = 6.7 Hz,
4 H), 5.82 (B of ABX, J = 10.2 and 1.6 Hz, 2 H), 6.30 (X of ABX,
J = 17.5 and 10.2 Hz, 2 H), 6.41 (A of ABX, J = 17.2 and 1.6 Hz,
2 H), 6.97 (d, J = 8.9 Hz, 4 H), 7.1–7.4 (m, 6 H), 7.53 (d, J =
8.9 Hz, 4 H), 7.55 (d, J = 8.6 Hz, 4 H), 7.86 (d, J = 8.7 Hz, 4
H) ppm. 13C NMR (CDCl3): δ = 19.5, 25.8, 25.9, 28.5, 29.1, 29.2,
64.6, 68.0, 114.8, 119.8, 126.3, 127.3, 128.3, 128.6, 130.4, 127.5,
128.9, 130.5, 132.0, 138.7, 145.4, 148.6, 159.4, 164.6, 166.3 ppm.
3010). H NMR (CDCl3): δ = 1.37 (t, J = 7.0 Hz, 6 H), 2.02 (s, 6
H), 3.96 (q, J = 7.0 Hz, 4 H), 6.76 (d, J = 3.0 Hz, 8 H), 7.38 (dd,
J = 7.5 Hz, 2 H), 7.49 (d, J = 7.0 Hz, 2 H), 8.00 (d, J = 7.2 Hz, 2
H) ppm. 13C NMR (CDCl3): δ = 14.7, 20.1, 63.7, 114.8, 122.1,
127.2, 128.1, 129.3, 134.0, 136.9, 140.9, 143.9, 156.4, 166.1 ppm.
IR (KBr): ν = 761, 1116, 1192, 1247, 1282, 1506, 1744, 2927, 2980,
˜
3066 cm–1. C32H30O6 (510.6): calcd. C 75.3, H 5.9; found C 74.6,
H 6.3.
IR (KBr): ν = 829, 1084, 1187, 1222, 1249, 1269, 1295, 1604, 1732,
˜
2857, 2933 cm–1. C62H66O10 (971.2): calcd. C 76.7, H 6.9; found C
76.4, H 6.8.
Bis[4Ј-(octyloxy)biphenyl-4-yl] 6,6Ј-Dimethylbiphenyl-2,2Ј-dicarbox-
ylate [(–)-(M)-9b]: A solution of diacid (–)-(M)-8 (129 mg,
0.48 mmol), triethylamine (0.28 mL, 2.0 mmol) and methanesulfo-
nyl chloride (74 μL, 0.95 mmol) in THF (2 mL) was stirred be-
tween –25 °C and –35 °C for 1 h. 4Ј-Octyloxy-biphenyl-4-ol
(300 mg, 1.0 mmol) and DMAP (7 mg) dissolved in THF (2 mL)
were added. The mixture was stirred at room temperature for 4
days, filtered through celite and purified by preparative TLC (ethyl
acetate/hexane, 50:50) to provide (–)-(M)-9b (210 mg, 0.25 mmol,
52%). [α]2D0 = –154 (c = 1, CH2Cl2). pitch = +3.9 μm (1% in ROTN
6,6Ј-Dimethylbiphenyl-2,2Ј-dicarboxylic Acid (rac-8): NaNO2 (7.8 g,
113 mmol) was added at 0 °C to a solution of 3-methylanthranylic
acid (17 g, 113 mmol) in aqueous NaOH (10%, 60 mL) and the
mixture was stirred for 30 minutes. HCl (4 m, 240 mL) was added
slowly, the temperature being kept below +7 °C. In another flask
(NH2OH)2·H2SO4 (17.6 g, 107 mmol) was added at 0 °C to a solu-
tion of concentrated ammonia (55 mL, 0.35 mol) and
CuSO4·5H2O (28 g, 0.11 mol) in water (90 mL) and stirring was
continued for 30 minutes at 0 °C.
1
3010). m.p. 56–64 °C. H NMR (CDCl3): δ = 0.91 (t, J = 6.5 Hz,
6 H), 1.1–1.5 (m, 20 H), 1.7–1.9 (m, 4 H), 2.02 (s, 6 H), 3.99 (t, J
= 6.4 Hz, 4 H), 7.93 (2×d, J = 8.0 Hz, 8 H), 7.4–7.6 (m, 12 H),
8.01 (d, J = 7.5 Hz, 2 H) ppm. 13C NMR (CDCl3): δ = 14.1, 20.2,
22.6, 26.0, 29.2, 29.7, 31.8, 68.0, 114.7, 121.6, 127.4, 127.6, 128.0,
128.3, 129.1, 132.8, 134.2, 137.0, 138.5, 141.1, 149.5, 158.7,
The freshly prepared solution containing the diazonium salt was
added to this mixture by addition funnel, the temperature being
kept between 0 and +10 °C. As soon as the addition was finished
the mixture was heated at reflux for 30 minutes. It was then allowed
to cool down to r.t., concentrated HCl (75 mL) was added, and
stirring was continued for 12 h. Filtration of the mixture over celite,
followed by washing of the organic layer with water and brine,
drying over MgSO4 and evaporation of the solvent, afforded diacid
165.9 ppm. IR (KBr): ν = 759, 1001, 1114, 1167, 1203, 1246, 1268,
˜
1497, 1609, 1745, 2855, 2926 cm–1. C56H62O6 (831.1): calcd. C 80.9,
H 7.5; found C 80.8, H 8.2.
1
rac-8 (11 g, 72%, 44 mmol); m.p. 236–237 °C. H NMR (CDCl3):
δ = 1.83 (s, 6 H), 7.29(dd, J = 7.5 Hz, 2 H), 7.43 (d, J = 7.5 Hz, 2
H), 7.91 (d, J = 7.5 Hz, 2 H) ppm. 13C NMR (CDCl3): δ = 20.0,
Acknowledgments
126.8, 127.5, 129.0, 134.6, 136.2, 142.3, 172.6 ppm. IR (KBr): ν =
˜
753, 1158, 1186, 1271, 1295, 1402, 1689, 2558, 1654, 2500–
This work was enabled and financed by ROLIC Research Ltd.,
Allschwil, Switzerland. Dr. Richard Buchecker, Dr. M. Schadt and
Prof. Zoubair M. Cherkaoui are acknowledged both for fruitful
discussions and for material support. We thank Dr. Klaus Schmitt
for his kind technical collaboration.
3200 cm–1.
6,6Ј-Dimethylbiphenyl-2,2Ј-dicarboxylic Acid [(+)-(P)-8 and (–)-
(M)-8]: Diacid rac-8 (3.22 g, 11.9 mmol) and brucine (4.71 g,
11.9 mmol) were dissolved at reflux in a mixture of methanol
(5 mL) and acetone (10 mL). The solution was allowed to cool
down slowly to r.t. and the ((+)-(P)-8)-brucine salt crystallised
(3.1 g, 39%) [α]2D0 = +38 (c = 1, MeOH). The mother liquor was
evaporated and the residue was dissolved at a minimum of acetone
at reflux. After cooling down to r.t. the crystallised ((–)-(M)-8)-
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2005, 3536–3541

New Biphenyls Inducing Strong Helical Twisting Power in Liquid Crystals
FULL PAPER
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Received February 7, 2005
Published Online: June 30, 2005
Eur. J. Org. Chem. 2005, 3536–3541
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3541