The synthesis and transition temperatures of 2-(4-alkyl- and 4-alkoxy-phenyl)-5-cyano-1-benzofurans and related diaryl-1-benzofurans - An assessment of how deviations from linearity and conformational effects in a core unit affect mesogenicity

Article abstract of DOI:10.1039/b102837p

The synthesis and transition temperatures are reported for several 2-(4-alkyl- and 4-alkoxy-phenyl)-5-cyano-1-benzofurans, 2-(4′-alkylbiphenyl-4-yl)-5-cyano- and 5-(4′-alkylbiphenyl-4-yl)-2-cyano-1-benzofurans, and for compounds with other combinations of terminal alkyl and cyano groups in 2,5-disubstituted-1-benzofurans containing two phenyl units, some isolated examples of related cyclohexane systems are also presented. The mesogenic behaviour of these compounds and several intermediates (e.g. amides, acids and esters) is discussed and the transition temperatures are rationalised on the following basis (a) 1-benzofuran is a superior core unit to benzene, (b) 2,5-disubstitution in 1-benzofuran gives a bent core which adversely affects mesogenicity, to an extent which depends on its position in the core, (c) antiparallel associations in terminal cyano compounds can eliminate the disadvantage of a bent core structure, (d) 2-aryl-1-benzofurans have negligible inter-annular twist but 5-aryl-1-benzofurans have similar inter-annular twist to that in biphenyls.

Full text of DOI:10.1039/b102837p

View Article Online / Journal Homepage / Table of Contents for this issue
The synthesis and transition temperatures of 2-(4-alkyl- and
4-alkoxy-phenyl)-5-cyano-1-benzofurans and related diaryl-1-
benzofurans—an assessment of how deviations from linearity and
conformational effects in a core unit affect mesogenicity{{
Mark R. Friedman, Kenneth J. Toyne,* John W. Goodby and Michael Hird
Liquid Crystals and Advanced Organic Materials Research Group, The Department of
Chemistry, The University, Hull, UK HU6 7RX. E-mail: K.J.Toyne@chem.hull.ac.uk
Received 1st March 2001, Accepted 1st May 2001
First published as an Advance Article on the web 1st October 2001
The synthesis and transition temperatures are reported for several 2-(4-alkyl- and 4-alkoxy-phenyl)-5-cyano-1-
benzofurans, 2-(4’-alkylbiphenyl-4-yl)-5-cyano- and 5-(4’-alkylbiphenyl-4-yl)-2-cyano-1-benzofurans, and for
compounds with other combinations of terminal alkyl and cyano groups in 2,5-disubstituted-1-benzofurans
containing two phenyl units; some isolated examples of related cyclohexane systems are also presented. The
mesogenic behaviour of these compounds and several intermediates (e.g. amides, acids and esters) is discussed
and the transition temperatures are rationalised on the following basis (a) 1-benzofuran is a superior core unit
to benzene, (b) 2,5-disubstitution in 1-benzofuran gives a bent core which adversely affects mesogenicity, to an
extent which depends on its position in the core, (c) antiparallel associations in terminal cyano compounds can
eliminate the disadvantage of a bent core structure, (d) 2-aryl-1-benzofurans have negligible inter-annular twist
but 5-aryl-1-benzofurans have similar inter-annular twist to that in biphenyls.
The initial suggestion for any new development or application
of liquid crystals usually originates from the work of physical
scientists who outline the general specifications of the material
properties required. Chemists with the appropriate interdisci-
plinary knowledge may then, in collaboration with physicists,
device engineers etc., attempt to propose molecular structures
which meet the required specification as closely as possible. In
proposing a structure the chemist has to choose what he
regards as the most suitable combination of molecular units to
achieve as many as possible of the required properties. The
variety of factors to consider for a molecular unit is immense,
and includes core units, linking groups, terminal groups, lateral
groups, length of chains, etc. At this point we are conscious
of the severe limitations faced in devising suitable molecules
and we have to acknowledge the deficiencies in predicting
with accuracy how the range of crucial physical properties
is revealed by the proposed molecular structure. In general,
the prime targets for the physical properties are a specific
mesophase type or a mesophase sequence, acceptable meso-
phase range(s), desirable viscosity (almost without exception,
low), dielectric, optical properties etc. In some areas, other
criteria need to be met; for example, with thermochromic
systems, pitch lengths leading to a colour play temperature
range or a specific colour may be the aim, or for ferroelectrics/
antiferroelectrics, spontaneous polarisations and tilt angles
over a working temperature range need to be controlled. There
is no hope of achieving an ‘ideal’ compound (or mixture)
because there is always room for improvement—the tempera-
ture range can always be greater, the viscosity lower, the
switching time shorter, the colour brighter or the colour change
sharper or broader. Given the above limitations, it is quite
remarkable that in the majority of areas of liquid crystals,
adequate materials have been provided for the desired
application.
One structural parameter that has not been so extensively
examined is how deviations from linearity of a core unit affect
mesogenicity and to what extent they can be tolerated before
mesogenicity is lost. The problem faced in considering this issue
is that it is not possible to control the precise deviation from
linearity one wishes to consider because the units of the
molecular core only give certain ‘quantised’ possibilities. When
a benzene ring is used as a core unit, for example, 1,4-
disubstitution gives linearity, but 1,3- or 1,2-disubstitution give
a 60u or 120u deviation respectively from linearity and it is
impossible to choose intermediate values. A core system such
as indene, 1-benzothiophene or 1-benzofuran allows di-
substitution with a greater variety of deviation from linearity.
However, the methylene group in indene prevents efficient
molecular associations and, although discotic examples have
been reported,1 no calamitic examples have appeared. For
1-benzothiophenes and 1-benzofurans, only a few discotic and
calamitic examples have been reported, but our preliminary
comparison (see compounds 75 and 78 below) showed that
the sulfur system had a significantly higher melting point,
which may mask mesophase formation; we therefore chose
1-benzofuran (see Fig. 1) as the core unit for the basis of this
study. In this unit there are several positions for disubstitution
which are not linear and these allow some judgement to be
made on how smaller deviations from linearity than those
which arise in benzene systems, affect mesogenicity. X-Ray
crystallography of 2-(4-methoxybenzoyl)-1-benzofuran2 and
{Basis of a presentation given at Materials Discussion No. 4, 11–14
September 2001, Grasmere, UK.
{Electronic supplementary data information (ESI) available: experi-
mental details for 5, 6, 8, 9, 21, 24, 34, 36, 40, 41, 47, 50, 52, 54, 57, 58,
61, 62, 63, 64, 72, 73 and 74. For direct electronic access see http://
www.rsc.org/suppdata/jm/b1/b102837p/
Fig. 1 Deviations from linearity arising from various substitution
patterns in 1-benzofuran. Calculated from the X-ray crystallography
results given in ref. 2.
DOI: 10.1039/b102837p
J. Mater. Chem., 2001, 11, 2759–2772
This journal is # The Royal Society of Chemistry 2001
2759

View Article Online
Scheme 1 1a, BrCH2CH(OMe)2, K2CO3, KI, solvent; 1b, PPA, chlorobenzene; 1c, (i) n-BuLi, THF, (ii) ‘Cardice’, THF, (iii) AcOH; 1d, (i) thionyl
chloride, benzene, (ii) ammonia, THF; 1e, thionyl chloride, DMF; 1f, CuCN?H2O, N-methylpyrrolidin-2-one; 1g, (i) n-BuLi, THF, (ii) trimethyl
borate, (iii) HCl; 1 h, Pd(PPh3)4, Na2CO3, DME, H2O.
subsequent geometrical calculations give the transposed bond
angles shown in Fig. 1. The 2,5-example has the smallest
deviation from linearity of y15u, the 2,6- and 3,6- have similar
deviations (approximately 40u) and the 3,5-disubstitution has a
severe deviation of almost 90u; the 2,6- and 3,6- cases differ in
that in the former case the oxygen atom is on the inside of the
bend whereas for the latter case the oxygen is on the outside.
Further novel features offered by the 1-benzofuran system are
that 6,7-difluoro-substitution gives three electron attracting
atoms on the ‘edge’ of the molecule, and these may be on the
exposed, outside (2,5-disubstituted core) or the sheltered, inside
(2,6-disubstituted core) of the bent molecule.
We have begun a series of studies of the different substitu-
tion patterns in 1-benzofurans and have started with 2,5-
disubstituted compounds. The aims of the investigation are
to consider polar (cyano) and non-polar (alkyl, alkoxy)
terminal groups with the 1-benzofuran at the centre or side
of an extended core unit. We have already reported some
results for 5-substituted-2-cyano-1-benzofurans3 and in this
paper we present results for related 5-cyano-2-substituted-1-
benzofurans and related compounds and we give some
examples to elucidate the effect of altering the position of
the benzofuran unit in a core system.
acetal (4–6) from a p-substituted phenol. Protonation of the
acetal generates an acylium ion which cyclises by electrophilic
aromatic substitution and gives a good method of synthesis for
benzofurans with a 5-substituent, since the cyclisation process
gives a single product.8 The second method was used to
synthesise 2-aryl-1-benzofurans with a 5-cyano- or a 5-carboxy
group and was developed by Hercouet;9 the process is
effectively an intramolecular Wittig reaction of an ester
carbonyl group. The third procedure involves the reaction of
a suitably substituted salicylaldehyde with diethyl bromo-
malonate10 (see compound 61, and compound 8 in ref. 3).
Lithiation at the 2-position of the benzofuran [either by
n-butyllithium (11, 21 and 41) or by lithium diisopropylamide
(44)] allows a 2-boronic acid, a 2-carboxylic acid (18) or 2-alkyl
derivatives (49 and 50) to be created. The route to the
thiophene compound (75) is based on the preparation of com-
pound 70 11 (cf. compound 8) and the subsequent steps are
similar to those in other schemes.
Confirmation of the structures of intermediates and products
was obtained by 1H NMR spectroscopy (JEOL Lambda 400 or
a JEOL JNM-GX270 spectrometer; tetramethylsilane was used
as the internal standard for all samples; J values are given in
Hz), infrared spectroscopy (Perkin-Elmer 457 grating spectro-
photometer or a Perkin-Elmer 1000 FT-IR Fourier transform
spectrophotometer) and mass spectrometry (Finnigan-MAT
1020 GC/MS spectrometer or a ThermoQuest Finnigan-MAT
GCQ ion-trap GC/MS). The progress of reactions was
frequently monitored using a Chrompack 9001 capillary gas
chromatograph fitted with a WCOT fused silica column (CP-
Sil 5 CB 0.12 m, 10 m long 0.25 mm internal diameter), using
nitrogen as the carrier gas. Elemental analyses of products were
carried out using a Fisons EA 1108 CHN analyzer. Transition
temperatures were measured using a Mettler FP52 heating
stage and FP5 control unit in conjunction with an Olympus
BH2 polarizing microscope and were confirmed using differ-
ential scanning calorimetry (Perkin-Elmer 7 Series/Unix DSC
with an indium standard and IBM data station). The purities of
all final compounds were checked by GLC analysis (see above)
and by HPLC analysis (Microsorb C18 80-215-C5 RP column)
Experimental
The synthetic routes to the compounds reported are shown in
Schemes 1–6. In general the compounds are not part of a
homologous series but are examples of different core systems
and therefore require specific routes, although some features of
the syntheses are common. Frequently connections are made
between aryl rings by palladium-catalysed cross-coupling of
arylboronic acids and an aryl halide [bromide (15–17, 40, 43, 48
and 51) or iodide (24, 25, 47 and 53)] or aryl triflate§ (56).4-7
The formation of the benzofuran unit was achieved in three
different ways as illustrated for compounds 7–9, 31 and 32, and
61 respectively. The first method involves the formation of an
§The IUPAC name for triflate is trifluoromethanesulfonate.
2760
J. Mater. Chem., 2001, 11, 2759–2772

View Article Online
The acronyms used are DCC (N,N’-dicyclohexylcarbo-
diimide), DCM (dichloromethane), DMAP (4-dimethyl-
aminopyridine),
(N,N-dimethylformamide), THF (tetrahydrofuran).
DME
(1,2-dimethoxyethane),
DMF
Representative syntheses are given below and other pre-
parations are given as Electronic Supplementary Information.{
Preparations
2-[4-(trans-4-Pentylcyclohexyl)phenoxy]acetaldehyde dimethyl
acetal 4. 4-(trans-4-Pentylcyclohexyl)phenol (1) (10.0 g,
41 mmol), bromoacetaldehyde dimethyl acetal (10.1 g,
60 mmol), potassium carbonate (11.1 g, 80 mmol) and potas-
sium iodide (0.5 g, 3 mmol) in cyclopentanone (60 ml) were
heated under reflux under nitrogen with stirring (48 h). The
mixture was allowed to cool, poured into water (200 ml) and
was washed with ether (26200 ml). The combined organic
layers were washed with sodium hydroxide solution (10%),
water, dried (Na2SO4), and the solvent removed in vacuo. The
crude product was purified by flash chromatography [neutral
alumina, petroleum fraction (bp 40–60 uC)–DCM 1 : 1],
followed by distillation. Yield 10.1 g (75%), bp 195 uC at
0.01 mmHg. 1H NMR (CD2Cl2) d: 7.11(2H, d, J 8.5), 6.82(2H,
d, J 8.5), 4.66(1H, t, J 5.2), 3.94(2H, d, J 5.2), 3.41(6H, s), 2.83–
2.80(1H, m), 1.73–1.66(4H, m), 1.45–1.38(1H, m), 1.35–
1.20(10H, m), 1.08–1.02(2H, m), 0.89(3H, t, J 7.1). IR (KBr)
Scheme 2 2a, Paraformaldehyde, conc. HCl; 2b, triphenylphosphine,
chloroform; 2c, for 31: (i) DCC, DMAP, DCM, (ii) Et3N, toluene; for
32: (i) 30 and thionyl chloride, (ii) Et3N, toluene; 2d, (i) KOH, EtOH,
(ii) aq. HCl; 2e, (i) thionyl chloride, benzene, (ii) ammonia, THF; 2f,
thionyl chloride, DMF.
n
max/cm21 2928, 2860, 1709, 1644, 1514, 1139, 1081, 828. MS
m/z: 334(Mz), 260, 176, 133, 75(100%).
and were found to be w99.5% pure. Flash (pressurised) or
gravity column chromatography was carried out using Merck
Kieselgel 60 (230–400 mesh) silica gel or Aldrich Brockmann 1
Standard Grade 150 mesh neutral alumina; the eluents were as
detailed in the text.
Tetrakis(triphenylphosphine)palladium(0) was prepared
according to the literature procedure.12 Arylboronic acids are
difficult to obtain pure because of the possibility of anhydride
formation and they were used without purification in the cross-
coupling reactions.
Compounds 2, 22, 26, 29, 30, 42, 45, 60, 66, and 68 were
obtained from Aldrich, 3 from Lancaster, and 1 was supplied
by Merck (Darmstadt). The syntheses of compound 12, 13, 14,
39 and 71 are described in ref. 3 and 23 in ref. 13.
Molecular modelling was carried out using (a) Cerius,2
Version 3.5, with the Smart minimiser and a UFF parameter
set;14 quantum effects were not included, (b) CS Chem3DStd2
Version 3.5.2.
5-(trans-4-Pentylcyclohexyl)-1-benzofuran 7. Compound 4
(10.1 g, 31 mmol) was added dropwise to polyphosphoric
acid (13.0 g) in chlorobenzene (130 ml) under reflux with
stirring and the mixture was heated under reflux overnight. The
solvent was removed in vacuo and sodium hydroxide solution
(10%) (20 ml) and ether (100 ml) were added; the separated
aqueous layer was washed with ether (26200 ml) and the
combined organic layers washed with water, brine, and dried
(MgSO4). The solvent was removed in vacuo and the crude
product was purified by flash chromatography [silica gel,
petroleum fraction (bp 40–60 uC)], followed by distillation.
Yield 4.1 g (48%), bp 165 uC at 0.01 mmHg. 1H NMR (CD2Cl2)
d: 7.51(1H, d, J 2.2), 7.34(1H, d, J 2.0), 7.31(1H, d, J 8.5),
7.07(1H, dd, J 2.0 and 8.5), 6.64(1H, dd, J 2.0 and 2.2),
2.48(1H, tt, J 3.2 and 12.2), 1.84–1.77(4H, m), 1.44(1H, dd, 3.2
and 12.7), 1.38(1H, dd, J 3.2 and 12.7), 1.26–1.14(9H, m),
Scheme 3 3a, Pd(PPh3)4, Na2CO3, DME; 3b, (i) n-BuLi, THF, (ii) trimethyl borate, (iii) aq. HCl; 3c, (i) n-BuLi, Pri2NH, THF, (ii) trimethyl borate,
(iii) aq. HCl; 3d, (i) pentanoyl chloride, anhydrous AlCl3, DCM, (ii) PMHS.
J. Mater. Chem., 2001, 11, 2759–2772
2761

View Article Online
Scheme 4 4a, (i) n-BuLi, Pri2NH, THF, (ii) RI; 4b, Pd(PPh3)4, Na2CO3, DME, H2O; 4c, (i) Mg, THF, (ii) trimethyl borate, (iii) aq. HCl; 4d, Tf2O,
pyridine; 4e, (i) n-BuLi, THF, (ii) ‘Cardice’, THF, (iii) AcOH; 4f, (i) thionyl chloride, benzene, (ii) ammonia, THF; 4g, thionyl chloride, DMF.
1.02(1H, dd, J 4.2 and 13.7), 0.95(1H, dd, J 4.2 and 13.7),
0.83(3H, t, J 7.0). IR (KBr) nmax/cm21 2927, 2856, 1514, 1455,
1197, 877, 809, 735. MS m/z: 270(Mz), 199, 171, 157(100%),
131.
ether was added (200 ml). The separated aqueous layer was
washed with ether (26300 ml) and the combined ethereal
layers were washed with water, brine, dried (MgSO4), and the
solvent removed in vacuo. The residue was recrystallised
(cyclohexane). Yield 6.6 g (45%), mp 82–83 uC. 1H NMR
(CD2Cl2) d: 7.98(1H, dd, J 1.0 and 1.6), 7.78(1H, d, J 2.2),
7.61(1H, d, J 8.8), 7.60(1H, dd, J 1.6 and 8.8), 6.89(1H, dd, J
1.0 and 2.2). IR (KBr) nmax/cm21: 3150, 2200, 1755, 1600, 1550,
1185, 1010, 885, 760, 610. MS m/z: 143(Mz, 100%), 88, 62, 50.
5-Cyano-1-benzofuran 10. A mixture of compound 8 (20.0 g,
102 mmol) and cuprous cyanide monohydrate (22.0 g,
204 mmol) in N-methylpyrrolidin-2-one (700 ml) was heated
under reflux (24 h) with stirring. The reaction mixture was
allowed to cool and was filtered through a pad of ‘Hyflo
Supercel’. The filtrate was then poured into water (200 ml) and
Scheme 5 5a, Diethyl bromomalonate, K2CO3, MEK; 5b, (i) KOH,
H2O, EtOH, (ii) aq. HCl; 5c, (i) thionyl chloride, benzene, (ii)
ammonia, THF; 5d, thionyl chloride, DMF; 5e, Py?HCl; 5f, (i) DCC,
DMAP, DCM.
Scheme 6 6a, NaOEt, BrCH2CH(OMe)2, EtOH; 6b, PPA, chloro-
benzene; 6c, Pd(PPh3)4, Na2CO3, DME, H2O; 6d, (i) n-BuLi, THF, (ii)
‘Cardice’, THF, (iii) AcOH; 6e, (i) thionyl chloride, benzene, (ii)
ammonia, THF; 6f, thionyl chloride, DMF.
2762
J. Mater. Chem., 2001, 11, 2759–2772

View Article Online
5-Cyano-1-benzofuran-2-boronic acid 11. Compound 10
(6.5 g, 45 mmol) in dry THF (150 ml) was degassed and
flushed with nitrogen. It was cooled (290 uC) and
n-butyllithium (2.5 M in hexanes, 19.1 ml, 48 mmol) was
added dropwise with stirring. The mixture was stirred for a
further 0.5 h, and trimethyl borate (9.4 g, 90 mmol) was added
at 2100 uC; the mixture was stirred (20 min), hydrochloric acid
(2 M, 137 ml) was added. The mixture was stirred for a further
15 min, allowed to return to room temperature, poured into
water (150 ml) and ether was added (150 ml). The separated
aqueous layer was washed with ether (26200 ml) and the
combined organic layers were washed with water, brine, dried
(MgSO4), and the solvent removed in vacuo. Yield 7.2 g (86%).
MS m/z: 187(Mz), 160, 145, 117, 43(100%).
of ‘Cardice’ in dry THF (200 ml), allowed to reach room
temperature with continuous stirring, and the solvent was
removed in vacuo. The residue was dissolved in glacial acetic
acid and the resulting solution was poured into water. The solid
was filtered off, washed with water and dried in vacuo (KOH) to
give a white solid. Yield 0.2 g (10%). Transitions/uC Cryst 191.5
N 217.5 Iso liq. 1H NMR (CD2Cl2) d: 7.47(1H, d, J 1.7),
7.44(1H, d, J 8.8), 7.39(1H, s), 7.27(1H, dd, J 1.7 and 8.8),
2.54(1H, tt, J 3.4 and 12.0), 1.89–1.83(4H, m), 1.49(1H, dd, J
3.2 and 12.7), 1.42(1H, dd, J 3.2 and 12.7), 1.31–1.19(9H, m),
1.07(1H, dd, J 3.9 and 13.9), 1.10(1H, dd, J 3.9 and 13.9),
0.86(3H, t, J 7.3); the acidic proton was not detected. IR (KBr)
n
max/cm21: 3100, 2926, 2853, 1692, 1580, 1425, 943, 828. MS
m/z: 314(Mz), 260, 201, 188(100%), 175.
5-Cyano-2-(4-propylphenyl)-1-benzofuran 15. Compound 15
was prepared in a similar manner to that described for the
preparation of compound 9 in ref. 3. Quantities: compound 12
(1.0 g, 5.0 mmol), compound 11 (1.1 g, 5.9 mmol), sodium
carbonate (1.3 g, 13 mmol), tetrakis(triphenylphosphine)palla-
dium(0) (0.3 g, 0.3 mmol), DME (15 ml) and water (15 ml). The
product was purified by flash chromatography [neutral
alumina, hexane–propionitrile 40 : 1] and recrystallisation
(hexane). Yield 0.1 g (8%). Transitions/uC Cryst 98.0 Iso liq.
(Found: C, 82.5; H, 5.7; N, 5.4; C18H15NO requires C, 82.7; H,
5.8; N, 5.4%). 1H NMR (CD2Cl2) d: 7.93(1H, dd, J 0.7 and 1.7),
7.79(2H, d, J 8.1), 7.61(1H, d, J 8.6), 7.55(1H, dd, J 1.7 and
8.6), 7.31(2H, d, J 8.1), 7.06(1H, d, J 0.7), 2.65(2H, t, J 7.6),
5-(trans-4-Pentylcyclohexyl)-1-benzofuran-2-carboxamide 19.
Compound 19 was prepared in a similar manner to that
described for the preparation of compound 14 in ref. 3.
Quantities: compound 18 (0.2 g, 0.6 mmol), thionyl chloride
(0.2 g, 1.8 mmol), ammonia (d 0.880, 0.4 ml), dry benzene
(7 ml) and dry THF (6 ml). Yield 0.08 g (50%), mp 214–
1
215 uC. H NMR (CD2Cl2) d: 7.51(1H, d, J 1.7), 7.43(1H, d, J
8.8), 7.41(1H, d, J 0.8), 7.31(1H, dd, 1.7 and 8.8), 6.51(1H, s,
br), 5.69(1H, s, br), 2.59(1H, tt, J 3.2 and 12.2), 1.93–1.88(4H,
m), 1.55–1.45(2H, m), 1.33–1.21(9H, m), 1.36–1.03(2H, m),
0.90(3H, t, J 7.1). IR (KBr) nmax/cm21: 3424, 3167, 2926, 2854,
1659, 1613, 1449, 1198, 939, 888. MS m/z: 313(Mz), 200,
187(100%), 115.
1.68(2H, sextet, J 7.6), 0.96(3H, t, J 7.6). IR (KBr) nmax/cm21
:
2966, 2225, 1505, 1463, 1118, 818, 794, 738. MS m/z: 261(Mz),
232(100%), 202, 176, 58.
2-Cyano-5-(trans-4-pentylcyclohexyl)-1-benzofuran 20. Com-
pound 20 was prepared in a similar manner to that described for
the preparation of compound 16 in ref. 3. Quantities: compound
19 (0.05 g, 0.2 mmol), thionyl chloride (0.2 g, 1.4 mmol) and dry
DMF (1 ml). Yield 0.03 g (60%). Transitions/uC Cryst 77.6
(N 58.5) Iso liq. (Found: C, 81.1; H, 8.3; N, 4.6; C20H25NO
requires C, 81.3; H, 8.5; N, 4.7%). 1H NMR (CD2Cl2) d: 7.51(1H,
dd, J 0.7 and 2.0), 7.47(1H, ddd, J 0.7, 0.7 and 8.6), 7.45(1H, d,
J 0.7), 7.39(1H, dd, J 2.0 and 8.6), 2.60(1H, tt, J 3.2 and 12.2),
1.93–1.87(4H, m), 1.52–1.43(2H, m), 1.33–1.21(9H, m), 1.14–
1.03(2H, m), 0.90(3H, t, J 7.3). IR (KBr) nmax/cm21: 2924, 2852,
2230, 1557, 1465, 1198, 950, 874, 845, 815.
5-Cyano-2-(4-pentylphenyl)-1-benzofuran 16. Compound 16
was prepared in a similar manner to that described for the
preparation of compound 15. Quantities: compound 13 (1.1 g,
4.8 mmol), compound 11 (1.1 g, 5.9 mmol), sodium carbonate
(1.3 g, 13 mmol), tetrakis(triphenylphosphine)palladium(0)
(0.3 g, 0.3 mmol), DME (15 ml) and water (15 ml). Yield
0.2 g (14%). Transitions/uC Cryst 99.7 (N 86.5) Iso liq. (Found:
C, 82.9; H, 6.7; N, 4.9; C20H19NO requires C, 83.0; H, 6.6; N,
4.8%). 1H NMR (CD2Cl2) d: 7.92(1H, dd, J 0.8 and 1.6),
7.89(2H, d, J 8.3), 7.61(1H, d, J 8.5), 7.55(1H, dd, J 1.6 and
8.5), 7.31(2H, d, J 8.3), 7.05(1H, d, J 0.8), 2.66(2H, t, J 7.7),
1.65(2H, quintet, J 7.7), 1.35(4H, m), 0.90(3H, t, J 7.3). IR
(KBr) nmax/cm21: 2933, 2865, 2224, 1504, 1461, 1185, 1115,
890, 800, 740. MS m/z: 289(Mz, 100%), 245, 232, 222, 219, 203.
2-(4’-Cyanobiphenyl-4-yl)-5-pentyl-1-benzofuran 25. Com-
pound 25 was prepared in a similar manner to that described
for the preparation of compound 39 in ref. 3. Quantities:
compound 24 (1.0 g, 3 mmol), compound 21 (0.8 g, 4 mmol),
sodium carbonate (0.9 g, 8 mmol), tetrakis(triphenylphos-
phine)palladium(0) (0.1 g, 0.1 mmol) and DME (20 ml). The
product was recrystallised (ethanol). Yield 36 mg (2%).
Transitions/uC Cryst 150.8 CrB 167.0 N 280.3 Iso liq.
(Found: C, 85.6; H, 6.3; N, 3.7; C26H23NO requires C,
5-Cyano-2-(4’-pentylbiphenyl-4-yl)-1-benzofuran 17. Com-
pound 17 was prepared and purified in a similar manner to
that described for the preparation of compound 15. Quantities:
compound 14 (1.5 g, 5.0 mmol), compound 11 (1.5 g,
8.0 mmol), sodium carbonate (1.3 g, 13 mmol), tetrakis(tri-
phenylphosphine)palladium(0) (0.6 g, 0.6 mmol), DME (15 ml)
and water (15 ml); the product was recrystallised (ethanol–
DCM 5 : 1). Yield 0.3 g (16%). Transitions/uC Cryst 187.1 N
284.2 Iso liq. (Found: C, 85.4; H, 6.3; N, 3.6; C26H23NO
requires C, 85.45; H, 6.3; N, 3.8%). 1H NMR (CD2Cl2) d:
7.96(1H, m), 7.95(2H, d, J 8.5), 7.73(2H, d, J 8.5), 7.63(1H, d, J
8.5), 7.58(2H, d, J 8.3), 7.56(1H, dd, J 1.7 and 8.5), 7.30(2H, d,
J 8.3), 7.13(1H, d, J 0.7), 2.66(2H, t, J 7.5), 1.66(2H, quintet, J
7.5), 1.36(4H, m), 0.91(3H, t, J 7.3). IR (KBr) nmax/cm21: 2933,
2859, 2229, 1497, 1122, 913, 803, 746. MS m/z: 365(Mz), 308,
277, 165, 43(100%).
1
85.45; H, 6.3; N, 3.8%); H NMR (CD2Cl2) d: 7.97(2H, d, J
8.8), 7.79–7.75(4H, m), 7.72(2H, d, J 8.8), 7.44(1H, d, J 8.3),
7.42(1H, m), 7.15(1H, dd, J 2.0 and 8.3), 7.09(1H, d, J 0.8),
2.71(2H, t, J 7.5), 1.67(2H, quintet, J 7.5), 1.38–1.33(4H, m),
0.91(3H, t, J 6.8). IR (KBr) nmax/cm21: 2927, 2858, 2229, 1603,
1493, 1465, 1189, 825, 802. MS m/z: 365(Mz), 322, 308(100%),
264, 154.
Methyl 3-(chloromethyl)-4-hydroxybenzoate 27. A suspen-
sion of methyl 4-hydroxybenzoate (26) (15.2 g, 100 mmol)
in conc. hydrochloric acid (130 ml) was cooled (5 uC) with
stirring. Paraformaldehyde (3.3 g, 11 mmol) was added, and
the mixture was heated (50–55 uC) for 6 hours and then left
overnight at room temperature. The solid was filtered off,
washed with water, dried in vacuo (CaCl2), and recrystallised
(CHCl3). Yield 8.0 g (40%), mp 144–145 uC (lit.,15 147–149 uC).
5-(trans-4-Pentylcyclohexyl)-1-benzofuran-2-carboxylic acid
18. Compound 7 (1.7 g, 6.3 mmol) in dry THF (70 ml) was
flushed with nitrogen, degassed, flushed again with nitrogen
and cooled (270 uC). n-Butyllithium (2.5 M in hexanes, 2.7 ml,
6.7 mmol) was then added dropwise with stirring and kept at
270 uC for 0.5 h. The mixture was poured into a stirred slurry
J. Mater. Chem., 2001, 11, 2759–2772
2763

View Article Online
1H NMR (CDCl3) d: 8.03(1H, d, J 1.5), 7.93(1H, dd, J 1.5 and
8.0), 6.90(1H, d, J 8.0), 6.18(1H, s), 4.68(2H, s), 3.90(3H, s). IR
(KBr) nmax/cm21: 3241, 2958, 1688, 1605, 1287, 1152, 844, 754,
705. MS m/z: 202, 200(Mz), 165(100%), 149, 133, 119.
J 8.0), 2.61(2H, t, J 7.1), 1.59(2H, quintet, J 7.1), 1.26(8H, m),
0.85(3H, t, J 7.1). IR (KBr) nmax/cm21: 3450, 2926, 2849, 2361,
1674, 1612, 1507, 1168, 912, 836. MS m/z: 336(Mz), 264,
251(100%), 206, 178.
[2-Hydroxy-5-(methoxycarbonyl)benzyl]triphenylphosphonium
chloride 28. A mixture of compound 27 (7.9 g, 39 mmol) and
triphenylphosphine (9.8 g, 37 mmol) in chloroform (100 ml)
was heated under reflux (1 h). The mixture was allowed to cool,
the solvent was removed in vacuo and on addition of a small
volume of toluene, the residue solidified. The solid was filtered
off and dried in vacuo (100 uC, 1 h) and recrystallised (H2O).
Yield 13.8 g (81%), mp 256–257 uC. 1H NMR (CDCl3) d:
11.37(1H, s), 7.76(3H, dt, J 1.4 and 7.0), 7.66(1H, ddd, J 2.2,
2.2 and 8.4), 7.59(12H, m), 7.38(1H, d, J 2.2), 7.38(1H, d, J 8.4),
4.71(2H, d, J 14.0), 3.76(3H, s). IR (KBr) nmax/cm21: 3400,
1693, 1606, 1435, 1291, 1113, 770, 745, 690. MS m/z: 427,
425(Mz2Cl), 395, 349, 262(100%), 183.
2-(4-Heptylphenyl)-1-benzofuran-5-carboxamide 35. Com-
pound 35 was prepared in a similar manner to that described
for the preparation of compound 14 in ref. 3. Quantities:
compound 33 (1.0 g, 3 mmol), thionyl chloride (1.1 g, 9 mmol),
ammonia (d 0.880, 2.0 ml), dry benzene (35 ml) and dry THF
(50 ml). Yield 0.6 g (60%), mp 242–243 uC. 1H NMR (DMSO-
d6) d: 8.10(1H, d, J 1.0), 7.78(2H, d, J 8.0), 7.77(1H, d, J 8.0),
7.54(1H, d, J 8.0), 7.28(2H, d, J 8.0), 7.06(1H, d, J 1.0),
6.81(1H, s), 5.85(1H, s), 2.64(2H, t, J 7.0), 1.63(2H, quintet, J
7.0), 1.25(8H, m), 0.87(3H, t, J 7.0). IR (KBr) nmax/cm21: 3419,
3192, 2922, 1646, 1608, 1391, 912, 801. MS m/z: 335(Mz),
250(100%), 217, 206, 178.
5-Cyano-2-(4-heptylphenyl)-1-benzofuran 37. Compound 37
was prepared in a similar manner to that described for the
preparation of compound 16 in ref. 3. Quantities: compound
35 (0.6 g, 1.6 mmol), thionyl chloride (1.9 g, 16 mmol) and dry
DMF (11 ml). Yield 0.2 g (39%). Transitions/uC Cryst 86.5 N
87.5 Iso liq. (Found: C, 83.0; H, 7.3; N, 4.3; C22H23NO requires
Methyl 2-(4-heptylphenyl)-1-benzofuran-5-carboxylate 31.
DCC (1.8 g, 8.7 mmol) in dry DCM (20 ml) was added to a
stirred mixture of DMAP (0.2 g, 1.6 mmol), compound 28
(3.2 g, 6.8 mmol) and 4-heptylbenzoic acid (29) (1.8 g, 8 mmol)
in dry DCM (80 ml). The mixture was stirred for 24 h, dry
toluene (350 ml) was added, the DCM was distilled off and dry
triethylamine (2.0 g, 20 mmol) was added and the mixture was
heated (85 uC) with stirring under nitrogen (14 h). The mixture
was allowed to cool, filtered and the solvent removed from
the filtrate in vacuo. The residue was then chromatographed
[silica gel, petroleum fraction (bp 40–60 uC)–DCM 6 : 4],
and recrystallised (hexane). Yield 1.3 g (55%). Transitions/uC
Cryst 101.0 SmF 104.5 SmA 114.9 Iso liq. 1H NMR (CD2Cl2)
d: 8.30(1H, dd, J 1.0 and 1.7), 7.98(1H, dd, J 1.7 and 8.5),
7.79(2H, d, J 8.4), 7.55(1H, d, J 8.5), 7.30(2H, d, J 8.4),
7.07(1H, d, J 1.0), 3.92(3H, s), 2.66(2H, t, J 7.4), 1.65(2H,
1
C, 83.2; H, 7.3; N, 4.4%). H NMR (CD2Cl2) d: 7.92(1H, d, J
1.3), 7.79(2H, d, J 8.0), 7.61(1H, d, J 8.4), 7.55(1H, dd, J 1.3
and 8.4), 7.31(2H, d, J 8.0), 7.05(1H, s), 2.66(2H, t, J 7.9),
1.65(2H, quintet, J 7.9), 1.30(8H, m), 0.89(3H, t, J 7.1). IR
(KBr) nmax/cm21: 2920, 2840, 2229, 1616, 1504, 1119, 881, 741.
MS m/z: 317(Mz), 245, 232(100%), 203, 176.
2-(4-Nonyloxyphenyl)-5-cyano-1-benzofuran 38. Compound
38 was prepared and purified in a similar manner to that
described for the preparation of compound 37. Quantities:
compound 36 (0.2 g, 0.5 mmol), thionyl chloride (0.6 g,
5 mmol) and dry DMF (4 ml). Yield 0.04 g (22%). Transi-
tions/uC Cryst 103.0 SmA 119.7 Iso liq. (Found: C, 79.5; H, 7.5;
N, 4.0; C24H27NO2 requires C, 79.7; H, 7.5; N, 3.9%); 1H NMR
(CD2Cl2) d: 7.90(1H, dd, J 0.8 and 1.7), 7.80(2H, d, J 9.0),
7.59(1H, d, J 8.6), 7.53(1H, dd, J 1.7 and 8.6), 7.00(2H, d, J
9.0), 6.96(1H, d, J 0.8), 4.02(2H, t, J 6.6), 1.80(2H, quintet,
J 6.6), 1.47(2H, m), 1.34–1.26(10H, m), 0.89(3H, t, J 6.8). IR
(KBr) nmax/cm21: 2921, 2850, 2225, 1609, 1504, 1175, 1010,
875, 802. MS m/z: 361(Mz), 235(100%), 206, 190, 164.
quintet, J 7.4), 1.32(8H, m), 0.89(3H, t, J 6.8). IR (KBr) nmax
/
cm21: 2927, 2852, 1717, 1590, 1300, 1160, 1086, 838, 766. MS
m/z: 350(Mz), 319, 278, 265(100%), 206.
Methyl 2-(4-nonyloxyphenyl)-1-benzofuran-5-carboxylate 32.
A suspension of 4-nonyloxybenzoic acid (30) (3.2 g, 12 mmol)
in thionyl chloride (16.4 g, 138 mmol) was stirred overnight
with exclusion of moisture. The solution was then heated under
reflux (1 h), and allowed to cool. The excess of thionyl chloride
was removed in vacuo and residual hydrogen chloride was
removed by addition of dry toluene, followed by removal
in vacuo. The acid chloride was then added to compound 28
(4.6 g, 10 mmol) and dry triethylamine (3.0 g, 30 mmol) in dry
toluene (45 ml) under nitrogen, and the mixture was heated
under reflux with stirring for 18 h. The mixture was allowed to
cool, the precipitate was removed by filtration, and the solvent
was removed from the filtrate in vacuo. The residue was purified
by flash chromatography [silica gel, petroleum fraction (bp 40–
60 uC)–DCM 7 : 3], followed by recrystallisation (hexane).
Yield 0.9 g (22%). Transitions/uC Cryst 151.5 SmA 152.0 Iso
liq. 1H NMR (CD2Cl2) d: 8.19(1H, d, J 1.5), 7.87(1H, dd, J 1.5
and 8.5), 7.72(2H, d, J 8.8), 7.45(1H, d, J 8.5), 6.90(2H, d,
J 8.8), 6.89(1H, s), 3.93(2H, t, J 6.6), 3.83(3H s), 1.72(2H,
quintet, J 7.5), 1.39(2H, quintet, J 7.5), 1.22(10H, m), 0.81(3H,
t, J 7.1). IR (KBr) nmax/cm21: 2920, 1722, 1612, 1506, 766. MS
m/z: 394(Mz), 268(100%), 237, 210, 182.
2-(4-Cyanophenyl)-5-(4-pentylphenyl)-1-benzofuran 43. Com-
pound 43 was prepared in a similar manner to that described
for the preparation of compound 39 in ref. 3. Quantities:
compound 42 (0.7 g, 4 mmol), compound 41 (1.1 g, 4 mmol),
sodium carbonate (1.1 g, 10 mmol), tetrakis(triphenylphos-
phine)palladium(0) (0.2 g, 0.2 mmol) and DME (14 ml). The
product was recrystallised (carbon tetrachloride). Yield 0.4 g
(30%). Transitions/uC Cryst 139.0 N 252.6 Iso liq. (Found: C,
85.2; H, 6.1; N, 3.9; C26H23NO requires C, 85.45; H, 6.3; N,
3.8%); 1H NMR (CD2Cl2) d: 7.99(2H, d, J 8.3), 7.83(1H, dd, J
1.2 and 1.2), 7.76(2H, d, J 8.3), 7.61–7.59(2H, m), 7.55(2H, d, J
8.5), 7.29(2H, d, J 8.5), 7.27(1H, d, J 1.2), 2.66(2H, t, J 7.6),
1.66(2H, quintet, J 7.6), 1.38–1.34(4H, m), 0.92(3H, t, J 6.8).
IR (KBr) nmax/cm21: 2968, 2854, 2224, 1607, 1155, 842, 802.
MS m/z: 365(Mz), 308(100%), 277, 252, 154.
5-Bromo-1-benzofuran-2-boronic acid 44. Dry diisopropyl-
amine (2.0 g, 20 mmol) was added to n-butyllithium (2.5 M in
hexanes, 8 ml, 20 mmol) at 210 uC, and the mixture was stirred
under nitrogen (20 min). Compound 8 (3.5 g, 18 mmol) in dry
ether (35 ml) was added and the mixture stirred (2 h) at
210 uC. Trimethyl borate (3.7 g, 36 mmol) was added at
210 uC, and the mixture was allowed to return to room
temperature with stirring under nitrogen. Hydrochloric acid
(5 M, 15 ml) was added with stirring and the mixture was then
2-(4-Heptylphenyl)-1-benzofuran-5-carboxylic acid 33. Com-
pound 33 was prepared in a similar manner to that described
for the preparation of compound 11 in ref. 3. Quantities:
compound 31 (4.2 g, 12 mmol), potassium hydroxide (1.4 g,
24 mmol), ethanol (110 ml) and water (11 ml). Yield 3.7 g
(92%). Transitions/uC Cryst 200.3 SmC 255.8 Iso liq. 1H NMR
(DMSO-d6) d: 12.87(1H, s), 8.25(1H, s), 7.90(1H, d, J 8.3),
7.83(2H, d, J 8.0), 7.68(1H, d, J 8.3), 7.47(1H, s), 7.34(2H, d,
2764
J. Mater. Chem., 2001, 11, 2759–2772

View Article Online
poured into water (100 ml) and ether added (50 ml). The
separated aqueous layer was washed with ether (2650 ml)
and the combined organic layers were washed with sodium
hydroxide solution (10%, 30 ml). The separated aqueous layer
was washed with light petroleum (bp 40–60 uC) and acidified
to pH 3 with hydrochloric acid (5 M). It was then washed with
ether (2650 ml) and the combined organic layers were washed
with water, brine, dried (MgSO4), and the solvent removed
in vacuo. A pale-orange solid was obtained. Yield 3.4 g (78%).
1H NMR (DMSO-d6) d: 8.62(2H, s), 7.92(1H, d, J 2.0),
7.56(1H, d, J 8.8), 7.46(1H, dd, J 2.0 and 8.8), 7.42(1H, s). MS
m/z: 197, 195(Mz2B(OH)2), 165, 151, 117, 89(100%).
2-Pentyl-5-(4’-cyanobiphenyl-4-yl)-1-benzofuran 53. Com-
pound 53 was prepared in a similar manner to that described
for the preparation of compound 9 in ref. 3. Quantities:
compound 52 (1.7 g, 7 mmol), compound 24 (1.7 g, 6 mmol),
sodium carbonate (1.5 g, 14 mmol), tetrakis(triphenylphos-
phine)palladium(0) (0.2 g, 0.2 mmol), DME (25 ml) and water
(7 ml). The reaction was carried out with exclusion of light and
the product was recrystallised (ethanol). Yield 0.1 g (5%).
Transitions/uC Cryst 94.8 N 236.7 Iso liq. (Found: C, 85.6; H,
1
6.4; N, 3.9; C26H23NO requires C, 85.45; H, 6.3; N, 3.8%); H
NMR (CD2Cl2) d: 7.77–7.68(9H, m), 7.48(1H, dd, J 2.0 and
8.6), 7.47(1H, d, J 8.6), 6.45(1H, s), 2.78(2H, t, J 7.4), 1.76(2H,
quintet, J 7.4), 1.40–1.34(4H, m), 0.90(3H, t, J 6.8). IR (KBr)
n
max/cm21: 2935, 2860, 2228, 1604, 1466, 1120, 948, 829, 802.
1-Iodo-4-pentylbenzene 46. Compound 46 was prepared in
a similar manner to that described for the preparation of
compound 3 in ref. 3. Quantities: iodobenzene (45) (20.4 g,
100 mmol), pentanoyl chloride (14.5 g, 120 mmol), aluminium
chloride (14.7 g, 110 mmol), PMHS (polymethylhydrosiloxane;
16.0 g 267 mmol) and dry DCM (110 ml). A pale-yellow liquid
was obtained which was stored with exclusion of light. Yield
14.4 g (53%), bp 105 uC at 0.01 mmHg (lit.,16 76–78 uC at
MS m/z: 365(Mz), 350, 322, 308(100%), 278.
4-(trans-4-Pentylcyclohexyl)phenyl trifluoromethanesulfonate
55. Trifluoromethanesulfonic anhydride (6.5 g, 23 mmol) was
added dropwise to a stirred, cooled (0 uC) solution of 4-(trans-
4-pentylcyclohexyl)phenol (1) (5.0 g, 20 mmol) in dry pyridine
(80 ml) under dry nitrogen. The mixture was stirred at room
temperature overnight. It was then poured into water (150 ml)
and ether added (100 ml). The separated aqueous layer was
washed with ether (26100 ml). The combined organic layers
were washed with water, hydrochloric acid (10%) (twice), brine,
dried (MgSO4), and the solvent was removed in vacuo. The
product was purified by flash chromatography [silica gel,
petroleum fraction (bp 40–60 uC)–DCM 7 : 3] to give a pale-
1
0.1 mmHg). H NMR (CDCl3) d: 7.58(2H, d, J 8.0), 6.93(2H,
d, J 8.0), 2.54(2H, t, J 7.0), 1.58(2H, m), 1.31(4H, m), 0.89(3H,
t, J 7.0). IR (KBr) nmax/cm21: 2962, 2862, 1486, 1118, 1065,
825, 795. MS m/z: 274(Mz), 217(100%), 203, 175, 89.
5-(4-Cyanophenyl)-2-(4-pentylphenyl)-1-benzofuran 48. Com-
pound 48 was prepared in a similar manner to that described
for the preparation of compound 9 in ref. 3. Quantities: com-
pound 47 (0.3 g, 0.9 mmol), compound 23 (0.2 g, 1.0 mmol),
sodium carbonate (0.2 g, 2 mmol), tetrakis(triphenylphosphine)-
palladium(0) (0.03 g, 0.03 mmol) and DME (9 ml). The product
was purified by flash chromatography (silica gel, hexane–
propionitrile 40 : 1), followed by recrystallisation (ethanol).
Yield 0.04 g (12%). Transitions/uC Cryst 133.8 N 230.5 Iso liq.
(Found: C, 85.3; H, 6.5; N, 3.9; C26H23NO requires C, 85.45; H,
6.3; N, 3.8%). 1H NMR (CD2Cl2) d: 7.74(1H, d, J 2.0), 7.73(2H,
d, J 8.6), 7.69(2H, d, J 8.8), 7.67(2H, d, J 8.8), 7.53(1H, d, J 8.6),
7.45(1H, dd, J 2.0 and 8.6), 7.23(2H, d, J 8.6), 6.99(1H, d, J 0.8),
2.58(2H, t, J 7.6), 1.58(2H, quintet, J 7.6), 1.27(4H, m), 0.83(3H,
t, J 7.1). IR (KBr) nmax/cm21: 2927, 2854, 2226, 1607, 1463,
1153, 1125, 889, 841, 813. MS m/z: 365(Mz), 308(100%), 264,
176, 154.
1
yellow oil. Yield 5.2 g (69%). H NMR (CD2Cl2) d: 7.21(2H,
d, J 8.5), 7.10(2H, d, J 8.5), 2.44(1H, tt, J 3.2 and 12.4),
1.82–1.81(2H, m), 1.78–1.77(2H, m), 1.38–1.36(1H, m), 1.34–
1.31(1H, m), 1.26–1.12(9H, m), 1.02–0.99(1H, m), 0.96–
0.93(1H, m), 0.81(3H, t, J 7.3). IR (KBr) nmax/cm21: 2929,
2858, 1503, 1427, 1143, 1018, 837, 740, 607. MS m/z: 378(Mz),
307, 252, 175, 69(100%).
5-[4-(trans-4-Pentylcyclohexyl)phenyl]-1-benzofuran 56. Com-
pound 56 was prepared in a similar manner to that described
for the preparation of compound 9 in ref. 3. Quantities:
compound 55 (3.4 g, 9 mmol), compound 54 (1.6 g, 10 mmol),
sodium carbonate (2.4 g, 23 mmol), tetrakis(triphenylphos-
phine)palladium(0) (0.3 g, 0.3 mmol), DME (40 ml) and water
(10 ml). Volatiles were removed by heating (95 uC) in vacuo (12 h)
and the residue was recrystallised (hexane). Yield 1.9 g (61%).
Transitions/uC Cryst 116.3 N 153.7 Iso liq. 1H NMR (CD2Cl2)
d: 7.80–7.79(1H, m), 7.67(1H, d, J 2.2), 7.56–7.51(4H, m),
7.30(2H, d, J 8.3), 6.84(1H, dd, J 0.7 and 2.2), 2.53(1H, tt, J 3.2
and 12.4), 1.94–1.88(4H, m), 1.48(2H, ddd, J 3.9, 9.0 and 12.9),
1.35–1.22(9H, m), 1.08(2H, ddd, J 3.9, 9.0 and 12.9), 0.91(3H, t, J
7.0). IR (KBr) nmax/cm21: 3124, 2924, 2853, 1463, 1131, 1027,
883, 742, 697. MS m/z: 346(Mz), 331, 303, 275, 233(100%).
2-Pentyl-5-bromo-1-benzofuran 49. Compound 49 was pre-
pared and purified in a similar manner to that described for the
preparation of compound 50. Quantities: compound 8 (12.0 g,
61 mmol), dry diisopropylamine (6.8 g, 67 mmol), n-butyl-
lithium (2.5 M in hexanes, 26.8 ml, 67 mmol), 1-iodopentane
(24.2 g, 122 mmol) and dry THF (120 ml). Yield 2.6 g (16%),
1
bp 198 uC at 0.6 mmHg. H NMR (CD2Cl2) d: 7.61(1H, dd, J
0.9 and 1.2), 7.29(2H, m), 6.36(1H, dd, J 0.9 and 1.0), 2.76(2H,
dt, J 1.0 and 7.6), 1.74(2H, quintet, J 7.6), 1.37(4H, m),
0.91(3H, t, J 6.8). IR (KBr) nmax/cm21: 2935, 2868, 1599, 1450,
1117, 1050, 948, 867, 671, 579. MS m/z: 268, 266(Mz), 251,
223, 208(100%), 116.
2-Cyano-5-[4-(trans-pentylcyclohexyl)phenyl]-1-benzofuran 59.
Compound 59 was prepared in a similar manner to that des-
cribed for the preparation of compound 16 in ref. 3 using the
quantities stated. Quantities: compound 58 (1.0 g, 2.6 mmol),
thionyl chloride (3.2 g, 26 mmol) and dry DMF (20 ml).
The product was recrystallised (ethanol). Yield 0.5 g (52%).
Transitions/uC Cryst 113.0 N 240.7Isoliq. (Found: C, 83.9; H, 8.0;
N, 3.9; C26H29NO requires C, 84.1; H, 7.9; N, 3.8%); 1H NMR
(CD2Cl2)d: 7.86(1H, dd, J 0.7and 2.0), 7.75(1H, dd, J 2.0 and 8.8),
7.61(1H, ddd, J 0.7, 0.7 and 8.8), 7.55(1H, m), 7.54(2H, d, J 8.0),
7.32(2H, d, J 8.0), 2.53(1H, tt, J 3.2 and 12.2), 1.93–1.87(4H, m),
1.56–1.44(4H, m), 1.35–1.19(7H, m), 1.08(2H, m), 0.90(3H, t, J
7.3). IR(KBr)nmax/cm21:2925, 2854, 2234, 1558, 1515, 1462, 1178,
1128, 950, 887. MS m/z: 371(Mz, 100%), 300, 245, 232, 189.
5-(4-Cyanophenyl)-2-heptyl-1-benzofuran 51. Compound 51
was prepared and purified in a similar manner to that described
for the preparation of compound 15. Quantities: compound 23
(0.2 g, 1.5 mmol), compound 50 (0.4 g, 1.4 mmol), sodium
carbonate (0.4 g, 3.5 mmol), tetrakis(triphenylphosphine)-
palladium(0) (0.05 g, 0.04 mmol), DME (9 ml) and water
(6 ml). Yield 0.03 g (7%). Transitions/uC Cryst 43.0 (N 30.9)
Iso liq. (Found: C, 83.4; H, 7.3; N, 4.4; C22H23NO requires C,
83.2; H, 7.3; N, 4.4%). 1H NMR (CD2Cl2) d: 7.71(5H, m),
7.47(1H, d, J 8.8), 7.43(1H, dd, J 1.9 and 8.8), 6.45(1H, d, J
1.0), 2.77(2H, t, J 7.4), 1.74(2H, quintet, J 7.4), 1.33(8H, m),
0.87(3H, t, J 7.1). IR (KBr) nmax/cm21: 2934, 2861, 2229, 1608,
1468, 844, 808. MS m/z: 317(Mz), 274, 260, 232(100%), 190.
J. Mater. Chem., 2001, 11, 2759–2772
2765

View Article Online
2-Cyano-5-hydroxy-1-benzofuran 65. A mixture of com-
pound 64 (0.7 g, 4 mmol) and pyridinium chloride (4.6 g,
40 mmol) was heated under reflux (3 min). The reaction
mixture was then poured into ice–water (50 ml). The precipitate
was filtered off and dried in vacuo. The product was recry-
stallised (toluene–hexane 1 : 2). Yield 0.2 g (31%), mp 146.5–
147.5 uC (lit.,17 144 uC). 1H NMR (CD2Cl2) d: 7.43(1H, m),
7.40(1H, d, J 0.7), 7.07(1H, m), 7.05(1H, dd, J 2.4 and 8.8),
5.07(1H, s). IR (KBr) nmax/cm21: 3435, 2238, 1558, 1195, 949,
862, 608. MS m/z: 159(Mz, 100%), 130, 103, 82, 76.
Results and discussion
Cyano compounds
In an earlier paper3 we discussed the transition temperatures
of 5-(4-substituted-phenyl)-2-cyano-1-benzofurans (I) and
5-(4-substituted-phenyl)-1-benzofuran-2-carboxylate esters (II)
(some values for 2-cyano compounds related to the compounds
reported here are given in Table 1). In these systems, the
benzene ring at the 5-position of the 1-benzofuran gives a
biphenyl-like situation, with respect to the extent to which
inter-annular twisting occurs. The transition temperatures
for the 2-cyano-5-phenyl-1-benzofurans were similar to, but
consistently higher than (by approximately 10–20 uC), those
for the analogous biphenyls. On the other hand, the
2-carboxylate esters have significantly lower mesophase
stabilities (by approximately 20–40 uC) than the analogous
compounds with phenyl replacing the benzofuran unit. We
interpret these results on the basis of the benzofuran unit being
intrinsically superior to phenyl in supporting mesogenicity, but
the bend in the molecular core adversely affects the terminally
‘non-polar’ ester systems resulting in lower clearing points. For
the antiparallel correlated, terminal cyano compounds,20–25 the
pair-wise associations eliminate the disadvantage of the bent
core and higher clearing points result (see Fig. 3 and comments
below).
2-Cyano-1-benzofuran-5-yl trans-4-pentylcyclohexanecarboxy-
late 67. Compound 65 (0.5 g, 3 mmol) and trans-4-pentyl-
cyclohexanecarboxylic acid (66) (0.6 g, 3 mmol) were dissolved
in dry DCM (30 ml), and DMAP (0.1 g, 1 mmol) was added. The
mixture was stirred and DCC (0.6 g, 3 mmol) was then added,
and stirring was continued (24 h). The precipitate of N,N’-
dicyclohexylurea was filtered off, and the solvent removed
in vacuo. The product was purified by flash chromatography
[silica gel, petroleum fraction (bp 40–60 uC)–DCM 7 : 3] and
recrystallisation (ethanol). Yield 0.3 g (98%). Transitions/uC
Cryst 71.9 N 103.8 Iso liq. (Found: C, 74.0; H, 7.2; N, 4.1;
C21H25NO3 requires C, 74.3; H, 7.4; N, 4.1%). 1H NMR
(CD2Cl2) d: 7.56(1H, d, J 9.0), 7.48(1H, d, J 1.0), 7.40(1H, d, J
2.4), 7.21(1H, dd, J 2.4 and 9.0), 2.50(1H, tt, J 3.7 and 12.2),
2.16–2.12(2H, m), 1.91–1.86(2H, m), 1.59–1.55(1H, m), 1.52–
1.49(1H, m), 1.34–1.19(9H, m), 1.05–1.01(1H, m), 0.99–
0.95(1H, m), 0.89(3H, t, J 7.1). IR (KBr) nmax/cm21: 2858,
2235, 1747, 1557, 982, 884. MS m/z: 339(Mz), 198, 180, 152,
97(100%).
1-Bromo-4-[2,2-(dimethoxy)ethylsulfanyl]benzene 69. Sodium
(13.8 g, 0.6 g atoms) was added to ‘superdry’ ethanol (400 ml)
with stirring under nitrogen. 4-Bromothiophenol (68) (103.3 g,
0.55 mol) was added and stirring was continued (5 min).
Bromoacetaldehyde dimethyl acetal (120.0 g, 0.71 mol) was
then added and the mixture heated under reflux overnight with
stirring under nitrogen. The mixture was then washed with DCM
(36100 ml) and the combined washings were washed with
water, brine, dried (MgSO4), the solvent removed in vacuo and
the residue was distilled. Yield 104.3 g (69%), bp 132 uC at
2 mmHg [lit.,18 142–144 uC (bath temperature) at 10 mmHg]. 1H
NMR (CDCl3) d: 7.39(2H, d, J 8.0), 7.24(2H, d, J 8.0), 4.50(1H,
In this paper we give a few more examples of 5-substituted-2-
cyano- systems (20, 59, 67), but principally we consider the
reversed 5-cyano-2-substituted systems (15–17, 37, 38) and
present reasons for their improved mesogenicity; some other
examples of closely related compounds with alternative core
units are also presented (43, 48, 51, 53), along with one example
of a 1-benzothiophene (75). The transition temperatures for all
the new compounds are given in Table 1 and are arranged to
aid comparisons with the previously reported values.
t, J 7.0), 3.36(6H, s), 3.08(2H, d, J 7.0). IR (KBr) nmax/cm21
:
2930, 2830, 1470, 1120, 1090, 800, 480. MS m/z: 278, 276(Mz),
247, 215, 201, 189, 75(100%).
Comparison of the transition temperatures for the phenyl-
substituted compounds 76 and 15, 77 and 16, 78 and 37, and 79
and 38, and for the biphenyl-substituted compounds 80 and 17
shows that compounds with the cyano group at the 5-position
have higher melting points (by 40.0, 48.6, 55.4, 41.0 and 53.1 uC
respectively) and higher clearing points (by [no mesophase]
30.1, 27.0, 22.7 and 28.6 uC respectively) than compounds with
a 2-cyano group. The types of mesophase which are present are
solely nematic for the lower alkyls (C3H7, C5H11, C7H15), with
a smectic A phase appearing for the C9H19O compound; the
smectic A phase is more strongly enhanced than the nematic
phase for compound 38 in comparison with compound 79.
Although both sets of 2,5-disubstituted systems have a similar
shape, the reason for the higher melting points, smectic A and
nematic phase stabilities for the 5-cyano- systems than for the
2-cyano- counterparts is reasonably explained by the reduced
inter-annular twisting effect in the compounds with a 2-phenyl
substituent. Modelling shows that a 5-phenyl-1-benzofuran is
structurally similar to a biphenyl or terphenyl in the nature of
its connection of the two rings and indicates a dihedral angle of
approximately 40u (see Fig. 2). For a 2-phenyl-1-benzofuran,
the inter-ring linkage is between a phenyl ring and a five-
membered furan unit in which the atoms ortho to the ring
junction are constrained away from interference with the
ortho-region of the phenyl unit (bond angles at the 2-position
5-Bromo-1-benzothiophene 70. Compound 70 was prepared
in a similar manner to that described for the preparation of
compound 7. Quantities: compound 69 (104.3 g, 376 mmol),
polyphosphoric acid (156.2 g) and chlorobenzene (1000 ml).
The product was recrystallised (ethanol). Yield 12.0 g (15%),
1
mp 46–47 uC (lit.,19 47–48 uC). H NMR (CD2Cl2) d: 7.98(1H,
dd, J 0.7 and 2.0), 7.77(1H, m), 7.52(1H, d, J 5.5), 7.44(1H, dd,
J 2.0 and 8.5), 7.30(1H, dd, J 0.7 and 5.5). IR (KBr) nmax/cm21
:
3080, 1576, 1399, 898, 807, 472. MS m/z: 214, 212(Mz),
133(100%), 106, 89, 81.
2-Cyano-5-(4-heptylphenyl)-1-benzothiophene 75. Compound
75 was prepared in a similar manner to that described for the
preparation of compound 16 in ref. 3. Quantities: compound 74
(1.0 g, 3 mmol), thionyl chloride (3.3 g, 28 mmol) and dry DMF
(20 ml). The product was recrystallised (ethanol). Yield 0.4 g
(43%), mp 93.2 uC (Found: C, 79.2; H, 7.1; N, 4.2; S, 9.4;
C22H23NS requires C, 79.2; H, 6.95; N, 4.2; S, 9.6%). 1H NMR
(CD2Cl2) d: 8.10(1H, m), 7.97(1H, d, J 0.7), 7.94(1H, m),
7.80(1H, dd, J 2.0 and 8.6), 7.57(2H, d, J 8.3), 7.31(2H, d, J 8.3),
2.66(2H, t, J 7.5), 1.65(2H, quintet, J 7.5), 1.35–1.30(8H, m),
0.89(3H, t, J 7.1). IR (KBr) nmax/cm21: 2959, 2855, 2214, 1506,
1178, 890, 800. MS m/z: 333(Mz), 290, 261, 248(100%), 221.
2766
J. Mater. Chem., 2001, 11, 2759–2772

View Article Online
Table 1 Transition temperatures/uC for various terminal cyano derivatives of 1-benzofuran and 1-benzothiophene
Compound
Structure
Cryst
CrB
—
SmA
—
Na
Iso liq.
76b
.
58.0
98.0
51.1
—
—
—
—
—
—
(.
48.9)
.
.
.
15
.
.
—
—
—
—
—
—
77b
.
56.4
16
20
.
.
99.7
77.6
—
—
—
—
—
—
—
—
(.
(.
86.5)
58.5)
.
.
78b
.
31.1
—
—
—
—
.
60.5
.
37
51
.
.
86.5
43.0
—
—
—
—
—
—
—
—
.
87.5
.
.
(.
30.9)
79b
.
.
62.0
—
—
—
—
.
.
87.0
.
97.0
.
.
38
103.0
119.7
—
—
17
25
.
.
187.1
150.8
—
—
—
—
—
—
.
.
284.2
280.3
.
.
.
167.0
J. Mater. Chem., 2001, 11, 2759–2772
2767

View Article Online
Table 1 (Continued)
Compound
Structure
Cryst
CrB
—
SmA
—
Na
Iso liq.
53
.
94.8
—
—
.
236.7
.
80b
.
134.0
.
147.3
—
—
.
255.6
.
48
43
59
.
.
.
133.8
139.0
113.0
—
—
—
—
—
—
—
—
—
—
—
—
.
.
.
230.5
252.6
240.7
.
.
.
67
.
71.9
—
—
—
—
.
103.8
.
81c
.
.
47.2
93.2
—
—
—
—
—
—
—
—
.
79.2
.
.
75
—
—
c
a() denotes a monotropic transition. bFrom ref. 3. From ref. 31.
of 2-phenyl-1-benzofuran are 122.4u and 127.0u for the
O–C–C[phenyl] and C–C–C[phenyl] angles respectively); mod-
elling indicates that the inter-ring dihedral angle is approxi-
mately 0–2u. The smaller the inter-annular dihedral angle, the
greater the degree of polarizability between the p-systems of
each ring, giving in effect an extended core region, which leads
to greater mesogenicity; the more efficient packing of the more
planar 2-phenyl systems in the crystal phase would also lead
to higher melting points. Fig. 2 shows the general structures
for the two series and the biphenyl-like structure of (a) will
diminish the mesophase stabilities of these compounds in
comparison with the compounds of structure (b). The
importance of the extent of inter-annular twisting in under-
standing how the mesogenicity of terphenyl systems is
influenced by lateral mono- and di-fluoro substitution has
been extensively demonstrated previously.7
The high clearing point of 5-cyano-2-aryl-1-benzofurans
is also shown for compounds analogous to terphenyls. The
2-cyano compound 80 has a higher clearing point (255.6 uC)
than the terphenyl analogue (240.0 uC),3 but the 5-cyano isomer
(17) has the highest clearing point of 284.2 uC. The justification
for these differences is similar to that given above for the
biphenyl equivalents. Compound 80 has two inter-annular
twists similar to those in terphenyl, but the superior benzofuran
core unit, in pairwise associations, overcomes the deviation
from linearity. For compound 17, only one significant inter-
annular twist is present and the compound has a higher clearing
point than compound 80.
2768
J. Mater. Chem., 2001, 11, 2759–2772

View Article Online
preferred. With these points in mind, compound 17 is the best
structural arrangement (one twist, bend at the end of the
structure) and compound 25, with cyano and pentyl inter-
changed, is similar. Although we do not know the degree to
which these cyano systems overlap in their anti-parallel
associations, Fig. 3 gives an indication of how the pairs can
be quite linear. It is clear from these drawings that another
factor which may influence mesophase stability is the effect of
the position of the oxygen atoms in the core; for example, in the
dimer for compound 17 the hetero atoms are closer to the
centre of the structure than in compound 25. It is also appa-
rent that the dimer for compound 17 has a more extensive
central planar region than that for compound 25. The same
observation can be made for the pairs of compounds 80/53
and 43/48, discussed below, in which the first compound in each
pair has the more extended central area.
Compounds 80 and 53 (two twists, bend at the end) have
lower clearing points than compounds 17 and 25, and the anti-
parallel association of 53 still leaves obvious bends whereas
antiparallel association of 80 masks the deviation from
linearity (see Fig. 3) and has linear terminal regions. Com-
pounds 43 and 48 have one twist, like compounds 17 and 25,
but with a bend in the middle of the structure their clearing
points are much lower than for either compound 17 or 25. The
differences between the values for compounds 43 and 48 may
be justified by the larger central planar region in the dimer for
compound 43.
Fig. 2 The inter-annular twisting in (a) 5-phenyl-, (b) 2-phenyl-
substituted-1-benzofurans.
For compounds with a benzofuran and two phenyl rings, a
greater variety of structural arrangements is possible and the
position in the core of the site for the deviation from linearity
can be changed. All the six possible structural combinations for
pentyl and cyano terminal groups have been prepared
(compounds 17, 25, 43, 48, 53 and 80). This set of compounds
shows relatively simple mesophase types, all are nematogenic
and two of them give a CrB phase, and their mesogenicity can
be rationalised on the basis of the following factors: (a) a 2,5-
disubstituted-1-benzofuran unit is superior to phenyl in
promoting mesogenicity, (b) 2-aryl- is superior to 5-aryl-
substitution in 1-benzofuran because of less inter-annular
twisting, (c) the disadvantage of the bend in the molecule is
more easily masked by anti-parallel associations if it is at the
end of the molecule rather than the middle, and (d) a more
extensive planar region arising from antiparallel correlations is
Compounds 20 and 67 are two further examples of 2-cyano
systems and in each case they conform to the pattern shown by
the related biphenyl systems.3 Compound 20 (a cyclohexyl
system) has a higher TN–I value than the phenyl equivalent (77)
and although the difference is small, the relationship is similar
to that for the analogous cyclohexylphenyl and biphenyl
systems respectively. Compound 67 has a higher TN–I value
than compound 81 and in this case the difference is more in
keeping with the differences previously reported for phenyl and
1-benzofuran systems.
Acids, amides and esters
Several compounds (e.g. some acids, amides, esters) were
prepared as intermediates in the synthesis of the final com-
pounds shown in Table 1, and in many cases they were
mesogenic. Several points are worth noting for these inter-
mediates but there has not been any planned objective to
produce extensive comparisons.
Acids 33/83 and 34/85 confirm that, as for the cyano systems,
the 5-carboxylic acids show greater mesogenicity than the
2-carboxylic acids. These differences can be ascribed to greater
planarity for the 2-aryl compounds (33 and 34) compared to
the 5-aryl analogues (83 and 85 respectively). However, with
one exception, all the 1-benzofurancarboxylic acids have lower
clearing points than the analogous systems with a phenyl ring
replacing the 1-benzofuran unit, but the types of mesophase are
the same in each set (compare 33 and 85 with 84, 34 and 85 with
86, and 18 with 82). One can justify the difference in behaviour
of the acids from that of the nitriles by claiming that anti-
parallel associations of nitriles minimises the effect of the bend
in the molecular core,3 whereas acids have an ‘end-on’
formation of a dimer which does not disguise the deviation
from linearity (see III); the collinear systems 84, 86 and 82
therefore show greater mesogenicity. The one surprising
exception to this pattern is that compound 62 has a much
higher TN–I value than 87.
Fig. 3 Suggested structures for antiparallel associations of cyano
systems. The clearing points are given and the limits of the central
planar region are indicated.
J. Mater. Chem., 2001, 11, 2759–2772
2769

View Article Online
Primary amides usually show very high melting points and
consequently not many examples of calamitic amides are
known. Amides can hydrogen bond to each other26 and if they
associate in a similar way to carboxylic acids (see IV) then the
second hydrogen on each nitrogen atom of a primary amide
can generate a network of hydrogen bonding leading to higher
melting points. The examples in the literature of mesogenic
amides are usually for systems with a bend in the structure (e.g.,
from a Schiffs base linkage,27 a dimethylene link28 or flexible,
non-axially symmetrical end rings29) and this feature may be
necessary to suppress melting points. Two of the amides
encountered in this work {compounds 36 [Cryst 225.0 N 235.0
Iso liq. (uC)] and 58 [Cryst 275.0 N 296.0 Iso liq. (uC)]} are
mesogenic and the bend generated by a 1-benzofuran core unit
may also be responsible for lowering their melting points and
allowing the compounds to produce a mesophase.
The three esters 31, 88 and 89 also demonstrate that, relative
to the biphenyl systems 89, compound 88 has a lower clearing
point (by 38.6 uC) because of the bend in the core unit, whereas
compound 31 has a higher clearing point (by 25.3 uC) which
indicates that the disadvantage of the molecular bend is over-
come by the absence of twisting of the 2-aryl substituent in 31;
in a simplistic analysis, these effects suggest that the bend
decreases mesogenicity by y40 uC and the coplanarity at the 2-
position increases mesogenicity by y60 uC. A similar, but less
precise, comparison can be made for compounds 91 (ethyl ester),
90 (ethyl ester) and 32 (methyl ester); here the bend depresses
the clearing point by 21.4 uC and planarity raises it by 67.4 uC.
Table 2 Transition temperatures/uC for various 1-benzofurancarboxylic acids
Compound
Structure
Cryst
SmC
—
Na
Iso liq.
18
.
191.5
—
.
217.5
.
82b
.
.
180
—
—
.
.
265
.
.
83c
131.0
.
185.0
222.0
33
.
.
200.3
156
.
.
255.8
243
—
—
.
.
84d
.
262
85c
.
212.2
.
223.0
—
—
.
34
.
.
172.0
176
.
.
193.2
256.5
.
.
253.7
258.5
.
.
86e
62
.
.
208.0
184
—
—
—
—
.
221.0
156)
.
.
87f
(.
a( ) denotes a monotropic transition. bFrom ref. 32; entry 5669. cFrom ref. 3. dFrom ref. 33; entry 3013 eFrom ref. 33; entry 3027. fFrom
ref. 33; entry 372.
2770
J. Mater. Chem., 2001, 11, 2759–2772

View Article Online
Table 3 Transition temperatures/uC for various 1-benzofurancarboxylates and related compoundsa
Compound
Structure
31
Cryst 101.0 SmF 104.5 SmA 114.9 Iso liq.
88b
Cryst 76.0 (SmA 51.0) Iso liq.
89b
Cryst 61.0 E 88.5 B/SmA 89.6 Iso liq.
32
Cryst 151.5 SmA 152.0 Iso liq.
Cryst 85.8 (SmA 84.6) Iso liq.
90b
91b
Cryst 78.0 E 81.0 SmB 91.0 SmA 106.0 Iso liq.
56
Cryst 116.3 N 153.7 Iso liq.
92c
Cryst 57.9 SmB 81.9 N 97.9 Iso liq.
c
a( ) denotes a monotropic transition. bFrom ref. 3. From ref. 30.
One example of a mesogenic monosubstituted 1-benzofuran
(56) was noted which is directly comparable with 92.30 Fusing
the furan ring onto compound 92 has not depressed meso-
genicity by creating an angular structure but has significantly
increased the clearing point as though a pseudo-alkoxy
terminal group has been added.
Acknowledgements
The work reported here was supported by the Defence
Evaluation Research Agency (Malvern) and a CASE Student-
ship for M. R. Friedman is gratefully acknowledged; the paper
is published by permission of the Director, HMSO. We thank
Mrs B. Worthington, Dr D. F. Ewing, Mr R. Knight and
Mr A. D. Roberts (deceased) for spectroscopic measurements
and Drs. A. N. Boa, J. D. Crane and T. Stirner for helpful
discussions.
Summary
Transition temperatures have been reported for several 2- and
5-cyano-1-benzofurans with one or two phenyl units or a
biphenyl unit in the molecular core and for esters, amides
and acids etc. involved in their synthesis. The mesomorphic
behaviour of this set of compounds and those reported
previously3 can be explained on the basis of the following
points: (a) 1-benzofuran is superior to benzene as a core unit,
(b) 2,5-disubstitution in 1-benzofuran gives a bent core system
which adversely affects mesogenicity, compared to 1,4-
diphenyl, but the disadvantage can be minimised by the
position of the bend in the core and it is overcome in cyano
compounds by antiparallel correlations, (c) 2-aryl-1-benzo-
furans have negligible inter-annular twist but 5-aryl-1-benzo-
furans have similar inter-annular twist to that in biphenyls.
References
1
V. Vill, in Liquid Crystal Database of liquid crystalline compounds
for Personal Computers’, LCI Publisher GmbH, Eichenstr. 3,
D-20259 Hamburg, Germany, 1999.
2
3
4
5
6
R. Benassi, U. Folli, D. Iarossi, L. Schenetti, F. Taddei, A. Musatti
and M. Nardelli, J. Chem. Soc., Perkin Trans. 2, 1987, 1443.
M. R. Friedman, K. J. Toyne, J. W. Goodby and M. Hird, Liq.
Cryst., 2001, 28, 901.
G. W. Gray, M. Hird, D. Lacey and K. J. Toyne, J. Chem. Soc.,
Perkin Trans. 2, 1989, 2041.
G. W. Gray, M. Hird and K. J. Toyne, Mol. Cryst. Liq. Cryst.,
1991, 195, 221.
G. W. Gray, M. Hird and K. J. Toyne, Mol. Cryst. Liq. Cryst.,
1991, 204, 91.
J. Mater. Chem., 2001, 11, 2759–2772
2771

View Article Online
7
8
M. Hird and K. J. Toyne, Mol. Cryst. Liq. Cryst., 1998, 323, 1.
P. Spagnolo, M. Tiecco, A. Tundo and G. Martelli, J. Chem. Soc.,
Perkin Trans. 1, 1972, 556.
21 G. J. Brownsey and A. J. Leadbetter, J. Phys. Lett., 1981, 42,
135.
22 H. Schad and M. A. Osman, J. Chem. Phys., 1981, 75, 880.
23 H. Schad and M. A. Osman, J. Chem. Phys., 1983, 79, 5710.
24 H. Schad and S. M. Kelly, J. Chem. Phys., 1984, 81, 1514.
25 D. A. Dunmur and K. Toriyama, Liq. Cryst., 1986, 1, 169.
26 L. A. LaPlanche, H. B. Thompson and M. T. Rogers, J. Phys.
Chem., 1965, 69, 1482.
9
A. Hercouet and M. L. Corre, Tetrahedron, 1981, 37, 2867.
10 R. Kurdukar and N. V. S. Rao, Proc. Indian Acad. Sci., Sect. A,
1963, 58, 336.
11 B. D. Tilak, Tetrahedron, 1960, 9, 76.
12 D. R. Coulson, Inorg. Synth., 1972, 13, 121.
13 M. Hird, K. J. Toyne, G. W. Gray, S. E. Day and
D. G. McDonnell, Liq. Cryst., 1993, 15, 123.
27 J. A. Castellano, J. E. Goldmacher, L. A. Barton and J. S. Kane,
J. Org. Chem., 1968, 33, 3501.
14 A. K. Rappe´, C. J. Casewit, K. S. Colwell, W. A. Goddard and
W. M. Skiff, J. Am. Chem. Soc., 1992, 114, 10024.
15 E. Kasztreiner, L. Vargha, Z. Huszti, J. Borsy, G. Szilagyi,
J. Szakaly, S. Elek and I. Polgari, German Patent, 1972, 2,137,538.
16 P. Kaszynski, J. Huang, G. S. Jenkins, K. A. Bairamov and
D. Lipiak, Mol. Cryst. Liq. Cryst., 1995, 260, 315.
17 L. Rene´, J.-P. Buisson and R. Royer, Bull. Soc. Chim. Fr., 1974,
475.
18 K. Rabindran, A. V. Sunthankar and B. D. Tilak, Proc. Indian
Acad. Sci. Sect. A, 1952, 36, 405.
19 A. S. Angeloni and M. Tramontini, Ann. Chim. (Rome), 1963, 53,
1665.
28 Y. Goto, S. Sugimori and T. Ogawa, Japanese Patent, 1985,
JP 85-125489.
29 L. A. Karamysheva, I. F. Agafonova, R. K. Geivandov and
V. F. Petrov, Liq. Cryst., 1991, 10, 875.
30 W. Haase, H. Paulus and H. T. Mu¨ller, Mol. Cryst. Liq. Cryst.,
1983, 97, 131.
31 H.-J. Deutscher, F. Kuschel, S. Ko¨nig, H. Kresse, D. Pfeiffer,
A. Wiegeleben, J. Wulf and D. Demus, Z. Chem., 1977, 17, 64.
32 D. Demus and H. Zaschke, Flussige Kristalle in Tabellen,
Vol II; VEB Deutscher Verlag fur Grundstoffindustrie, Leipzig,
Germany, 1984.
33 D. Demus, H. Demus and H. Zaschke, Flussige Kristalle in
Tabellen, Vol I; VEB Deutscher Verlag fur Grundstoffindustrie,
Leipzig, 1974.
20 A. J. Leadbetter, R. M. Richardson and C. N. Colling, J. Phys. C
Solid State Phys., 1975, 36, 37.
2772
J. Mater. Chem., 2001, 11, 2759–2772