Synthesis and study of new rod-like mesogens containing 2-aminothiophene unit

Article abstract of DOI:10.1016/j.tet.2012.07.075

We present a synthesis and mesomorphic properties of a new series of rod-like mesogens. All the compounds possess a substituted 2-aminothiophene unit as a main element in the structure attached to a stilbene moiety with a terminal alkyloxy chain (OR¹, OR² where R ¹=C_nH_2n+1, R²=C_mH _2m+1; n, m ranging from 6 to 12). The synthesis of alkyloxybiphenyl substituted 2-aminothiophenes was carried out by the Gewald reaction and the appropriate reaction conditions were investigated. The liquid-crystalline properties were studied via polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. These materials exhibit nematic and/or smectic A phases. The influence of structural changes (variation in alkyloxy chain length and symmetry of the molecule) on mesogenic behaviour is discussed. Evaluation of UV-vis, fluorescent and electrochemical properties are also included.

Full text of DOI:10.1016/j.tet.2012.07.075

Tetrahedron 68 (2012) 8172e8180
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and study of new rod-like mesogens containing 2-aminothiophene unit
*
ꢀ
Zita Puterova , Jerzy Romiszewski, Jozef Mieczkowski, Ewa Gorecka
ꢁ
Department of Chemistry, University of Warsaw, Al. Zwirki i Wigury 101, 02-089 Warsaw, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
We present a synthesis and mesomorphic properties of a new series of rod-like mesogens. All the
compounds possess a substituted 2-aminothiophene unit as a main element in the structure attached to
a stilbene moiety with a terminal alkyloxy chain (OR1, OR2 where R1¼CnH2nþ1, R2¼CmH2mþ1; n, m ranging
from 6 to 12). The synthesis of alkyloxybiphenyl substituted 2-aminothiophenes was carried out by the
Gewald reaction and the appropriate reaction conditions were investigated. The liquidecrystalline
properties were studied via polarizing optical microscopy, differential scanning calorimetry and X-ray
diffraction. These materials exhibit nematic and/or smectic A phases. The influence of structural changes
(variation in alkyloxy chain length and symmetry of the molecule) on mesogenic behaviour is discussed.
Evaluation of UVevis, fluorescent and electrochemical properties are also included.
Received 15 February 2012
Received in revised form 25 June 2012
Accepted 23 July 2012
Available online 31 July 2012
Keywords:
2-Aminothiophene
Gewald reaction
Liquid crystals
Nematic
Ó 2012 Elsevier Ltd. All rights reserved.
Smectic A
1. Introduction
materials is one of the promising approaches to control the mo-
lecular self-organization processes and can lead to the de-
The area of liquid crystals (LCs) arguably belongs to the one of
the most extensive and dynamic fields of present-day materials
research. The first observations on compounds possessing meso-
genic phase behaviour are dated 150 years ago1 and are related to
scientific works of Planer,2 Reinitzer3 and Lehmann.4 Liquid crystals
combine order and mobility and form well-organized supramo-
lecular assemblies that exhibit a variety of physical properties,
which makes them attractive for utilization in the fields of nano-
science.5e7 Since 1989, when Hitachi Ltd. presented the first type of
LCD (low-power flat-panel liquidecrystal display),8 liquid crystals
became essential materials of the modern era. Important for dis-
play applications are thermotropic liquid crystals, which change
phase with temperature. They usually represent classical rod-like
molecules built up from the aromatic rigid core with one or two
alkyl terminal chains possessing mainly nematic and/or smectic
phase.9
velopment of new electro- and photofunctional metamaterials.10
The versatility of thiophene chemistry and the
p-donating char-
acter of the thiophene moiety (electronic affinity: EA¼ꢀ1.17 eV,
ionization potential: IP¼8.87 eV) provides the basis for the syn-
thesis of most conjugated
p-systems with a high degree of func-
tionalization.11 Generally, thiophene containing compounds having
donoreacceptor character are known as active components in or-
ganic electronic devices and optoelectronics.12 Several examples
show, that liquid crystals containing a thiophene moiety in the
structure exhibit, besides thermotropic behaviour, also interesting
photoconductive,13 fluorescent14 and charge-transfer properties.15
We report herein a rapid and simple synthesis of model rod-like
mesogens with the functionalized aminothiophene moiety as part
of the central rigid core linked to a fluorescent stilbene segment
with an alkyloxy tail on both ends. These compounds exhibit ne-
matic and smectic A phases and show interesting fluorescent
properties. Towards the synthesis of the 2-aminothiophene part in
the designed compounds, the Gewald reaction was explored.16 As
we have shown previously, the free amino group allows its re-
placement in a manner usable for the preparation of thiophene-
containing structures with the possibility to be integrated into
polymers with tunable electronic and optical properties.17 How-
ever, this approach has not been applied in a design and synthesis
of liquidecrystals so far. The present synthesis and physical study
can provide a new approach in the development of liquidecrystal-
line materials with a thiophene-based central unit.
Nowadays, the increasing scientific interest is focused on the
prediction and monitoring of the properties of the liquid crystals at
a nanoscale level. As an effective way much work has been done on
molecular design and synthesis leading to well-defined supra-
molecules. The key criteria among such design processes are the
yields achievable in each synthetic step and the nature of the ter-
minal groups. The induction of liquid crystallinity in p-conjugated
* Corresponding author. Tel.: þ48 22 8220211x387; e-mail addresses: z.puter-
ꢀ
ova@chem.uw.edu.pl, zita.puterova@gmail.com (Z. Puterova).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.07.075

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Z. Puterova et al. / Tetrahedron 68 (2012) 8172e8180
8173
2. Results and discussion
2.1. Synthesis
a second step with methylmagnesium iodide prepared in situ un-
der Grignard reaction conditions. Formed ketones 3a,b with
a scrambled alkyloxyl tail represent an CH-active oxo-components
suitable for the Gewald thiophene synthesis, which encompasses
a Knoevenagel condensation and cyclization reaction sequence. The
reaction conditions leading to a new type of substituted 2-
aminothiophenes 5a and 5b were slightly modified and are de-
scribed below (Scheme 2, Table 2).
The synthesis of target thiophene containing mesogens 10aef is
described in Scheme 1. The 2-aminothiophene core in 5a and 5b
was formed via a four step reaction sequence. The hydroxy group in
40-hydroxybiphenyl-4-carbonitrile (1) was initially reacted with
a halogenated alkane, 1-bromohexane or 1-bromooctane, re-
spectively, using potassium carbonate in DMF. Under these condi-
tions the corresponding 40-(alkyloxy)-biphenyl-4-carbonitriles
(2a,b) were isolated.18 The carbonyl group was introduced in
The four-step procedure was employed for the synthesis of the
stilbene
part
9aed
(Scheme
1).
Treatment
of
4-
hydroxybenzaldehyde (6) with corresponding alkylbromide in
DMF using potassium carbonate led to 4-alkyloxy-benzaldehydes
7aed.19 Reaction of 7aed with Wittig salt in
a dichlor-
omethaneeTHF mixture in the presence of 18-crown-6 and po-
tassium carbonate afforded 4-[2-(4-alkyloxy-biphenyl)-vinyl]-
benzoic acid methyl esters 8aed.20 The ester moiety was sub-
sequently hydrolyzed with an aqueous solution of KOH in ethanol
and the carboxylic acid salt obtained was converted into acyl
chloride 9aed with oxalyl chloride in dichloromethane.21 The de-
scribed synthesis represents a convenient and easy route to 4-[2-
(4-alkyloxy-phenyl)-vinyl]-benzoyl chlorides (9aed) requiring
only one purification stepdthe crystallization of methyl esters
8aed after the Wittig reaction.
The acyl chlorides 9aed were finally reacted with 2-amino-
thiophenes 5a or 5b, respectively, in boiling toluene using DMAP as
nucleophilic catalyst to afford the final thiophene-containing
mesogenic compounds (Scheme 1). Final products 10aef were
isolated from the dark slurry in acceptable yields 35e45% (Table 1).
Table 1
Thiophene-containing rod-like mesogens 10aef
Compound
R1(¼CnH2nþ1
)
R2(¼CmH2mþ1
)
Yield (%)
10a
10b
10c
10d
10e
10f
C6H13
C6H13
C8H16
C8H16
C8H16
C8H16
C6H13
C8H16
C6H13
C8H16
C10H21
C12H24
42%
45%
40%
42%
38%
35%
The Gewald synthesis is probably the most versatile reaction for
the preparation of highly substituted 2-aminothiophenes, where by
choosing suitable substrates the functionalization of the final
thiophene derivative is precisely predicted.22 Our initial effort to
synthesize 2-aminothiophenes 5a and 5b employing the simplest
one-pot procedure resulted in complicated mixtures that were
difficult to purify. Generally, the one-pot Gewald method has lim-
ited scope in the synthesis of 2-aminothiophenes with an unsub-
stituted
Accordingly, the two-step variation of the Gewald reaction was
performed. The -unsaturated nitriles (so called ylidenes or ac-
a
-position or provide products in very poor yields.23
a,b
rylonitriles) 4a and 4b were obtained via Knoevenagel condensa-
tion by heating the respective ketone 3a or 3b with
methylcyanoacetate (2.0 equiv) in toluene at 80 ꢁC using ammo-
nium acetate as a promoter for the reaction. Because of the low
reactivity of the starting ketones 3a,b, NH4OAc was used in equi-
molar amounts.24 The use of DeaneStark apparatus was replaced
by trimethylsilylacetate as an organic desiccant (TMSOAc, in
1.5 equiv relative to ketone). Employment of TMSOAc also prevents
the possible side-reactiondthe self-condensation of the formed
ylidene.25 The conversion of starting compounds into condensation
products never proceeded to completion even if the reaction time
was extended to 12 h. The yields of ylidenes 4a,b after isolation and
purification from unreacted substrates were about 60% (Table 2).
The ylidenes were subsequently reacted with sulfur (1.5 equiv)
Scheme1. Synthesis of thiophene-containing rod-like mesogens 10aef. Reagents and
conditions: (i) alkylbromide (1.2 equiv), K2CO3 (2.0 equiv), DMF, 120 ꢁC, 16 h; (ii) Mg
(1.5 equiv), CH3I (1.5 equiv), Et2O, 36 ꢁC, 6 h; (iii) Knoevenagel condensation: see
Scheme 2 and Table 2; (iv) Gewald cyclization: see Scheme 2 and Table 2; (v) alkyl-
bromide (1.2 equiv), K2CO3 (1.2 equiv), DMF, 80 ꢁC, 8 h; (vi) Wittig salt (1.5 equiv),
K2CO3 (2.0 equiv), 18-crown-6 (cat. amount), DCM/THF (1:1), reflux, 40 h; (vii) KOH aq
(10.0 equiv), H2O/EtOH (1:1), reflux, 5 h; (vii) oxalyl chloride (4.0 equiv), DCM, reflux
3 h; (ix) DMAP, TEA (cat. amount), toluene, reflux 12e24 h.

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Z. Puterova et al. / Tetrahedron 68 (2012) 8172e8180
Table 3
Phase transitions, transition enthalpies and layer thickness in SmA phase of studied
compounds
C H
O
S
Scheme 2. The Gewald synthesis of 5a,b.
H3COOC
NH
O
O
C
H
10a-f
Table 2
Base and solvent screen for the Gewald reaction (Scheme 2)
Compound
n
m
Phase transition
(ꢁC), transition
Layer
thickness
in SmA (A)
Compound
Reaction conditions (reagents,
temperature, time)
Yield (%)
enthalpies (kJ molꢀ1
)
ꢂ
10a
10b
6
6
6
8
Iso 229.8 (0.62) N 144.6
(40.94) Cr
Iso 211.1 (0.70)
d
Knoevenagel
condensation (iii)
4a
4b
40.0
NH4OAc (1.0 equiv), TMSOAc
(1.5 equiv), toluene, 80 ꢁC, 12 h
58%
61%
N 161.7 (0.10)
SmA 144.0 (36.40) Cr
Iso 212.4 (0.40) N 163a
SmA 130.3 (35.93) Cr
Iso 221.5 (0.87)
N 196.6 (0.37)
SmA 124.9 (25.21) Cr
Iso 150.66 (1.06) N 143.25
(5.65) Cr 108.3 (17.35)
Iso 111.7 (0.25)
Cyclization (iv)
5a
10c
10d
8
8
6
8
40.8
42.2
A: Et3N (2.2 equiv), S8 (2.0 equiv),
Methanol, 45 ꢁC, 12 h
B: Morpholine (2.2 equiv), S8
(2.0 equiv), Methanol, 45 ꢁC, 12 h
C: Morpholine (2.2 equiv),
28%
40%
60%
10e
10f
8
8
10
12
d
d
S
8 (2.0 equiv), Tetrahydrofuran,
50 ꢁC, 12 h
5b
A: Et3N (2.2 equiv), S8 (2.0 equiv),
Methanol, 45 ꢁC, 12 h
B: Morpholine (2.2 equiv),
30%
39%
N 96.7 (19.06) Cr
Abbreviations used: Cr¼crystal, N¼nematic, SmA¼smectic A, Iso¼isotropic.
a
S
8 (2.0 equiv), Methanol,
Value taken from X-ray measurements, not detectable on DSC.
45 ꢁC, 8 h
C: Morpholine (2.5 equiv),
64%
S
8 (2.0 equiv), Tetrahydrofuran,
50 ꢁC, 12 h
under basic conditions to give the 2-aminothiophenes 5a,b
(Scheme 2).26 In order to increase the yields and purity of the de-
sired 2-aminothiophenes 5a,b a brief solvent and base screen was
investigated for the cyclization step. The reaction carried out in
methanol at 45 ꢁC with triethylamine (2.2 equiv)27 gave the cor-
responding compounds 5a,b in approximately 30% yield after 12 h
(Table 2).
Neither extension of the reaction time or increasing the reaction
temperature did not give better results. Using morpholine
(2.2 equiv) as a base in methanol28 showed an increase in product
yield to 40% (Table 2). The highest reactivity was observed when
the reaction was carried out in THF at 50 ꢁC with morpholine
(2.2 equiv). The products 5a and 5b were obtained in 60% and 64%
yield, respectively, after 12 h (Table 2). Compounds 5a and 5b
represent novel types of 2-aminothiophenes where the alkyl-
Fig. 1. Optical texture of a nematic phase of compound 10c at 207 ꢁC (on cooling).
biphenyl substituent in the
b-position is established during the
synthetic procedure and no other modifications of the final struc-
ture are required.
2.2. Mesomorphic properties
Mesomorphic properties of compounds 10aef were in-
vestigated by polarizing optical microscopy (POM), differential
scanning calorimetry (DSC) and X-ray measurements. Phase types,
their thermal stability, transition enthalpies and layer thickness in
smectic A phase are given in Table 3. Chosen POM image of rep-
resentative nematic phase and characteristic images from X-ray
measurements are shown in Figs. 1 and 2.
Fig. 2. X-ray diffraction patterns for compound 10c in: (a) nematic phase at 187 ꢁC and
(b) smectic A phase at 158 ꢁC.
All compounds 10aef display thermotropic liquid crystalline
properties forming nematic and/or smectic A mesophases, which
are determined by the length of the terminal alkyl groups and
symmetry of the molecule. For compounds with total alkyl chain
length (nþm) of 14 carbon atoms (10b, c) and of 16 carbon atoms
(10d) nematic and smectic A phases are observed. Whereas for
compounds 10a (nþm¼12), 10e and 10f (nþm¼18 and 20, re-
spectively) only a nematic phase is observed. Compounds 10b and
10c, with interchanged alkyl tails on both sides of the molecule

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Z. Puterova et al. / Tetrahedron 68 (2012) 8172e8180
8175
(nþm¼14 carbon atoms), exhibit enantiotropic nematic and mon-
otropic smectic A phase. The transition temperatures in SmA for
10b with n¼6, m¼8 and for 10b with n¼8, m¼6 are very close. For
compound 10d, with nþm¼16 carbon atoms, where n¼m¼8, both
enantiotropic nematic and enantiotropic smectic A phase are ob-
served. The layer thickness in smectic A for 10bed is almost equal
to the molecule length, therefore it can be assumed that layers are
built from almost entirely stretched molecules and do not in-
tercalate. This type of behaviour is typical for rod-like molecules
built of an aromatic core with aliphatic tails. For less symmetric
compounds 10e and 10f, when the number of alkyl chain is in-
creased from m¼8 to m¼10, 12 (nþm¼18 carbon atoms in 10e and
nþm¼20 carbon atoms in 10f), the formation of smectic A phase is
completely suppressed and only the nematic phase is observed.
We can conclude, that in the series of presented mesogens
10aef, the compounds with medium sized alkyl chains and higher
symmetry (10b, 10c where nþm¼14, n¼6 or 8, m¼6 or 8, 10d with
nþm¼16, n¼m¼8) exhibit both, nematic and smectic A phase,
while shortening of alkyl chains (10a, nþm¼12, n¼m¼6) or elon-
gation and symmetry breaking (10e, 10f, nþm¼18, 20) favours only
the nematic phase.
Typical schlieren texture of nematic phase of 10c compound is
presented in Fig. 1. The X-ray data were collected for all synthesized
mesogenic compounds. The X-ray pattern for nematic phase con-
sists of two diffused signals related to the short range positional
order along director (averaged long axes direction) and perpen-
dicular to it (Fig. 2a). With lowering temperature the low angle
signal narrows, showing increasing positional order in the system.
In smectic A phases low angle signals become resolution limited
(Fig. 2b).
1.76 ns, respectively). This is opposite behaviour to usual, in which
quenching of the fluorescence is much faster in the crystal phase
because of strong interactions between molecules. However it
should be noted that, for stilbene compounds in solution relaxation
from the excited state involves twisting of the phenyl rings of the
stilbene unit, while in solid state this relaxation channel is closed as
the twisting of phenyl rings becomes frozen.29 The optical band gap
derived from the onset of absorption spectrum is equal 3.0 eV.
2.4. Electrochemistry
The electrochemical and electronic properties of compounds
were investigated by means of cyclic voltammetry and differential
pulse voltammetry. Resolution of cyclic voltammetry was too low
to obtain the value of the first oxidation potential Eox therefore we
used differential pulse voltammetry and obtained Eoxz1.47 V ver-
sus NHE and the first reduction potential Eredzꢀ1.56 V versus NHE.
The measured electrochemical band gap is therefore almost equal
with the value of the optical band gap. It should be mentioned that
during cyclic voltammetry measurements we observed a gradual
shift of the signals towards higher potentials in the positive po-
tential range and a decrease in current intensity. At the same time
on the surface of the carbon electrode a shiny blue film developed.
This behaviour was not observed while measurements were per-
formed in the negative potentials range. On this basis we conclude,
that studied compounds are capable of electropolymerisation.
3. Conclusion
A convenient synthesis of 4-alkyloxy-biphenyl substituted 2-
aminothiophenes was described. The final products were meso-
genic materials. It was found that these compounds exhibit nematic
and smectic A phases and mesomorphic behaviour is dependent on
the length of the alkyloxy tails and on the symmetry of the molecule.
The compounds with short terminal alkyloxy chains and less sym-
metric molecules with one prolonged alkyloxy chain favours only
the formation of nematic phase. For symmetric compounds with
middle sized terminal alkyloxy chains also smectic A phase occurs.
Investigated compounds exhibit interesting fluorescence related to
the presence of stilbene unit in the molecular structure. The elec-
trochemical band gap for this material was found to be ca. 3.0 eV.
2.3. UVevis and fluorimetry
The spectroscopic properties of the compounds show very little
dependence on the alkyl chain length. The absorption and fluores-
cence spectrum of 10c as the representative for this group of com-
pound is shown in Graph 1. All compounds exhibit two absorption
peaks
in
the
UVevis
region:
with
l1max¼280 nm
(
3
¼3ꢂ104 Mꢀ1 cmꢀ1) and l2max¼363 nm (
3
¼4.5ꢂ104 Mꢀ1 cmꢀ1) and
a single slightly asymmetric fluorescence signal with a maximum at
450 nm. The fluorescence quantum yield in solution for this com-
pound 10c was found to be ca. 6%. The fluorescence of compound is
related to the presence of the stilbene unit in the molecular struc-
ture, the thiophene part is fluorescence inactive, as checked for the
5a semiproduct. The fluorescence decay time is shorter for com-
pound dissolved in organic solvent than in solid state (0.96 ns and
4. Experimental section
4.1. General
All chemicals were purchased from SigmaeAldrich and used
without further purification. All solvents were HPLC grade and used
as supplied. Compositions of the synthesized compounds were
determined by elemental analysis (FlashEA 1112, Thermo Finnigan).
ESI-MS spectra were recorded on Mass Quattro LC. 1H NMR
(500 MHz) and 13C NMR (125 MHz) spectra were recorded on
a Varian Unity Plus instrument at 25 ꢁC. The measurements were
done using protiated solvent CDCl3 with TMS as the internal stan-
dard. Two dimensional spectra gs-H,H-COSY, 1D-gs-NOESY, gs-
HSQC and gs-HMBC were measured using standard software pro-
grams provided by Varian. Coupling constants (J) are quoted to the
50000
40000
30000
20000
10000
0
nearest 0.1 Hz and chemical shifts (d-scale) are quoted in parts per
million (ppm). The following abbreviations: s¼singlet, d¼doublet,
t¼triplet, q¼quartet, m¼multiplet and br¼broad, are used in
reporting the spectra. Infrared spectra were obtained using a JASCO
FTIR-460 PLUS spectrometer. Column chromatography was per-
250
300
350
400
450
500
550
600
Wavelength/nm
formed using Silica gel Kiesegel 60 with particle size 40e63 mm
(230e400 mesh) by preparing the slurry with the eluent mixture
and packing into a chromatography column. The collected samples
Graph 1. Absorption (red line) and fluorescence (blue line) spectra for 10c dissolved in
chloroform at 25 ꢁC (c¼3.2ꢂ10ꢀ5 mol dmꢀ3).

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Z. Puterova et al. / Tetrahedron 68 (2012) 8172e8180
8176
were analysed by TLC. Compounds are numbered according to
Schemes 1 and 2.
Identification of the liquid crystalline phases was based on the
type of texture exhibited by the compound. The textures were
observed with a polarizing optical microscope Zeiss Axio Imager
A2m equipped with a Linkam hot stage.
The identification was confirmed by X-ray studies carried out on
a Bruker GADDS system equipped with Vantec 2000 area detector
and hot stage controlled by Linkam controller, and on a Bruker D8
Discover system equipped with Anton Paar DCS-350 heating stage.
alkyloxy-4-carbonitrile 2a or 2b (9.1 g for 2a, 10.0 g for 2b,
0.0325 mol) in diethylether (400 mL) was added to a mixture of
methylmagnesium iodide and heated at the boiling temperature of
diethylether for 6 h, then the flask was cooled and distilled water
(300 mL) was added slowly. The mixture was left to stir for an
additional 30 min. The aqueous and etheric layers were separated,
water phase was extracted with diethylether (2ꢂ250 mL). The
combined organic phase was dried with MgSO4 and evaporated.
The crude product was purified by column chromatography on
silica gel eluting with dichloromethane.
In both systems Cu Ka radiation was used.
Phase transition temperatures, enthalpies and melting points
were determined by differential scanning calorimetry measure-
ments performed on TA Instruments DSC Q 200. Only for com-
pound 10c, the temperature of the nematic to smectic A phase
transition was determined on the basis of polarizing optical mi-
croscopy and X-ray measurements. This phase transition was not
detectable by the DSC measurement.
Absorption spectra were recorded on a Shimadzu UV-3101PC
spectrometer. Emission spectra were measured with FluoroLog FL3-
2-IHR320 HORIBA Jobin Yvon spectrofluorometer equipped with
4.3.1. 1-(40-Hexyloxy-biphenyl-4-yl)-ethanone 3a. Yield: 52% (5.0 g),
white crystals; mp¼135e140 ꢁC; Rf (CH2Cl2) 0.68; dH (500 MHz
CDCl3): 7.99 (d, J¼8.6 Hz, 2H), 7.64e7.52 (m, 4H), 6.87 (d, J¼8.6 Hz,
2H), 3.97 (t, J¼6.2 Hz, 2H, CH2), 2.61 (s, 3H, COCH3),1.76 (q, J¼6.2 Hz,
2H, CH2), 1.24 (br s, 6H, 3ꢂ CH2), 0.89 (t, J¼6.2 Hz, 3H, CH3); dC
(125 MHz CDCl3): 197.6, 159.6, 145.4, 135.5, 132.0, 128.7, 128.1, 127.7,
115.1, 69.9, 31.4, 30.1, 26.3, 24.1, 22.7,13.9; nmax(KBr) 3124, 2928,1705
(C]O), 1615, 1455, 782, 647 cmꢀ1; Anal. Calcd for C20H24O2 (296.4):
C, 81.04; H, 8.16%. Found: C, 81.12; H, 8.22%. Mass (ESI) m/z (%) 296.2.
a
TBX-04
PMT
detector.
Both
chloroform
solutions
4.3.2. 1-(40-Octyloxy-biphenyl-4-yl)-ethanone
3b. Yield:
50%
(c¼3.2ꢂ10ꢀ5 mol dmꢀ3) and solid state samples were excited at
360 nm. For fluorescence quantum yield measurements an ethanol
solution of anthracene was used as a standard.30 Fluorescence decay
was measured by time-correlated single-photon counting system us-
ing the same FluoroLog fluorometer and Horiba-Jobin Yvon NanoLED
340 pulse diode light source with peak wavelength at 335 nm.
Electrochemical datawere obtained with cyclic voltammetryand
differential pulse voltammetry techniques using a three-electrode
cell and an electrochemical workstation CH instruments 750 B.
The working electrode was a glass carbon electrode, the auxiliary
electrode was a Pt wire, and Ag/Agþ was used as a reference elec-
trode. Tetrabutylammonium hexafluorophosphate (TBAHFP) 0.1 M
was used as supporting electrolyte in CH2Cl2. Ferrocenium/ferro-
cene (Fc/Fcþ) redox couple was used as a potential reference. The
potentials versusNormalHydrogenElectrode (NHE)werecalculated
by addition of 700 mV to the potentials versus Fc/Fcþ.31
(5.3 g), white crystals; mp¼115e118 ꢁC; Rf (CH2Cl2) 0.70; dH
(500 MHz CDCl3): 7.95 (d, J¼8.4 Hz, 2H), 7.62e7.56 (m, 4H), 6.84 (d,
J¼8.4 Hz, 2H), 3.89 (t, J¼6.4 Hz, 2H, CH2), 2.58 (s, 3H, COCH3), 1.72
(q, J¼6.4 Hz, 2H, CH2), 1.30 (q, J¼6.4 Hz, 2H, CH2), 1.27 (br s, 8H, 4ꢂ
CH2), 0.84 (t, J¼6.4 Hz, 3H, CH3); dC (125 MHz CDCl3): 196.9, 158.4,
146.0, 135.7, 131.9, 129.0, 128.6, 128.2, 127.4, 114.7, 70.2, 31.5, 30.4,
29.9, 26.6, 23.8, 22.4, 14.0; nmax(KBr) 3099, 2943, 1715 (C]O), 1607,
1454, 764, 632 cmꢀ1; Anal. Calcd for C22H28O2 (324.46): C, 81.44; H,
8.70%. Found: C, 81.70; H, 8.92%. Mass (ESI) m/z (%) 324.60.
4.4. Knoevenagel condensation of 3a and 3b
1-(40-Alkyloxy-biphenyl-4-yl)-ethanone 3a or 3b (3.0 g for 3a,
3.2 g for 3b, 10.0 mmol) and methylcyanoacetate (2.0 g, 1.8 mL,
20.0 mmol) were dissolved in dry toluene (100 mL). Trimethylsilyla-
cetate (2.0 g, 2.2 mL,15.0 mmol) and NH4OAc (0.8 g,10.0 mmol) were
added and the mixture was heated at 80 ꢁC for 12 h. After the reaction
was complete, the mixture was cooled to room temperature and di-
luted with water (80 mL). The aqueous layer was separated and
extracted with toluene (2ꢂ50 mL). The combined organic extracts
were dried with MgSO4 and evaporated. Products 4a and 4b were
isolated and purified by column chromatography on silica gel eluting
with dichloromethane and isolated as a mixture of E/Z isomers.
4.2. Typical procedure for the alkylation of 1
40-Hydroxybiphenyl-4-carbonitrile (1) (20.0 g, 0.1 mol), potas-
sium carbonate (28.0 g, 0.2 mol) and DMF (600 mL) were placed in
a 1000 mL flask and stirred. The corresponding alkylbromide
(20.0 g for 1-bromohexane, 23.0 g for 1-bromo-octane, 0.12 mol)
was added and the reaction mixture was heated at 120 ꢁC for 48 h.
The mixture was then cooled to room temperature and poured onto
ice water (1000 mL) and left to stand overnight. The precipitated
product was isolated by filtration and crystallized from ethanol.
4.4.1. (E/Z) 2-Cyano-3-(40-hexyloxy-biphenyl-4-yl)-but-2-enoic acid
methyl ester 4a. Yield: 58% (2.2 g), yellow solid; mp¼82e86 ꢁC; Rf
(CH2Cl2) 0.82; dH (500 MHz CDCl3): 8.01 (d, J¼8.2 Hz, 2H),
7.66e7.50 (m, 4H), 6.84 (d, J¼8.2 Hz, 2H), 4.02 (t, J¼6.6 Hz, 2H, CH2),
3.96 (s, 3H, COOCH3), 1.83 (s, 3H, CH3), 1.77 (q, J¼6.6 Hz, 2H, CH2),
1.27 (br s, 6H, 3ꢂ CH2), 0.88 (t, J¼6.6 Hz, 3H, CH3); dC (125 MHz
CDCl3): 172.0, 161.9, 157.6, 135.1, 132.8, 127.9, 127.2, 126.1, 125.3,
117.6, 113.9, 101.9, 67.1, 51.7, 31.3, 30.9, 28.6, 25.0, 18.2, 13.1;
nmax(KBr) 3116, 2956, 2247 (C^N), 1694 (C]Oester), 1628 (C]C),
1216 (CeOester), 1467, 782, 588 cmꢀ1; Anal. Calcd for C24H27NO3
(377.48): C, 76.36; H, 7.21; N, 3.71%. Found: C, 76.48; H, 7.15; N,
3.84%. Mass (ESI) m/z (%) 378.40 [MþH]þ.
4.2.1. 40-Hexyloxybiphenyl-4-carbonitrile 2a. Yield: 85% (24.0 g),
white crystals. Analytical data corresponds to those published for
40-hexyloxybiphenyl-4-carbonitrile, C19H21NO (279.38).32
4.2.2. 40-Octyloxybiphenyl-4-carbonitrile 2b. Yield: 88% (27.0 g),
white crystals. Analytical data corresponds to those published for
40-octyloxybiphenyl-4-carbonitrile, C21H25NO (307.43).32
4.3. The Grignard reaction of 2a and 2b
4.4.2. (E/Z) 2-Cyano-3-(40-octyloxy-biphenyl-4-yl)-but-2-enoic acid
methyl ester 4b. Yield: 61% (2.5 g), yellow solid; mp¼74e77 ꢁC; Rf
(CH2Cl2) 0.80; dH (500 MHz CDCl3): 8.12 (d, J¼8.6 Hz, 2H), 7.72e7.54
(m, 4H), 6.87 (d, J¼8.6 Hz, 2H), 3.98 (t, J¼6.6 Hz, 2H, CH2), 3.88 (s,
3H, COOCH3), 1.87 (s, 3H, CH3), 1.74 (q, J¼6.6 Hz, 2H, CH2), 1.38 (q,
J¼6.6 Hz, 2H, CH2), 1.30 (br s, 8H, 3ꢂ CH2), 0.86 (t, J¼6.6 Hz, 3H,
CH3); dC (125 MHz CDCl3): 169.7, 162.2, 156.9, 135.3, 133.0, 128.1,
To an evacuated 1000 mL three necked round bottomed flask
magnesium (1.2 g, 0.05 mol) and dry diethylether (15 mL) were
placed. To the stirred mixture a 2.0 M solution of methyl iodide
(7.1 g, 3.0 mL, 0.05 mol) in diethylether was added dropwise over
40 min. The resulting solution of methylmagnesium iodide was
stirred at room temperature for 1 h. The solution of starting 40-

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Z. Puterova et al. / Tetrahedron 68 (2012) 8172e8180
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127.9, 127.1, 124.8, 117.4, 114.0, 102.0, 68.2, 52.1, 32.0, 31.1, 30.6, 29.9,
28.7, 24.6, 17.8, 13.9; nmax(KBr) 3129, 2944, 2239 (C^N), 1698 (C]
Oester), 1642 (C]C), 1214 (CeOester), 1457, 776, 596 cmꢀ1; Anal.
Calcd for C26H31NO3 (405.53): C, 77.01; H, 7.71; N, 3.45%. Found: C,
77.23; H, 7.66; N, 3.52%. Mass (ESI) m/z (%) 406.24 [MþH]þ, 428.30
[MþNa]þ.
(C]Oester), 1209 (CeOester), 1465, 872, 577 cmꢀ1; Anal. Calcd for
C26H31NO3S (437.59): C, 71.36; H, 7.14; N, 3.20; S, 7.33%. Found: C,
71.40; H, 7.15; N, 3.25; S, 7.36%. Mass (ESI) m/z (%) 438.2 [MþH]þ.
4.6. Typical procedure for the synthesis of 4-alkylox-
ybenzaldehydes 7aed
4.5. Gewald reaction: synthesis of
substituted 2-aminothiophenes 5a, 5b
b
-alkyloxybiphenyl
4-Hydroxybenzaldehyde (12.5 g, 0.1 mol), potassium carbonate
(16.5 g, 0.12 mol) and dimethylformamide (300 mL) were placed in
a three-necked 1 L round bottomed flask. The reaction mixture was
heated to 80 ꢁC and stirred. To the warm solution the appropriate
alkylbromide (19.8 g for 1-bromohexane; 23.2 g for 1-bromooctane;
26.5 g for 1-bromodecane; 29.9 g for 1-bromododecane; 0.12 mol)
was added dropwise over 1 h. The mixture was then heated at 80 ꢁC
for 8 h. After cooling down to room temperature the mixture was
diluted with water (300 mL). The aqueous phase was extracted with
dichloromethane (3ꢂ300 mL). The combined organic layer was
washed twice with aq NaOH (10%mol), water and dried with MgSO4.
After evaporation of solvent on a rotary evaporator the corre-
sponding products were obtained as pale yellow oils, which were
subsequently used without purification.
General procedure A. To a solution of (E/Z) 2-cyano-3-(40-hex-
yloxy-biphenyl-4-yl)-but-2-enoic acid methyl ester 4a (2.0 g,
5.5 mmol) or (E/Z) 2-cyano-3-(40-octyloxy-biphenyl-4-yl)-but-2-
enoic acid methyl ester 4b (2.2 g, 5.5 mmol) in methanol
(30 mL), sulfur (350 mg, 11.0 mmol) and triethylamine (1.22 g,
1.70 mL, 12.1 mmol) were added. After stirring at 45 ꢁC for 12 h,
the reaction mixture was evaporated and the crude product was
purified by column chromatography on silica gel (absorbed with
1% triethylamine) eluting with a mixture of hexanes/ethylacetate
(80:20).
General procedure B. To a solution of (E/Z) 2-cyano-3-(40-hex-
yloxy-biphenyl-4-yl)-but-2-enoic acid methyl ester 4a (2.0 g,
5.5 mmol) or (E/Z) 2-cyano-3-(40-octyloxy-biphenyl-4-yl)-but-2-
enoic acid methyl ester 4b (2.2 g, 5.5 mmol) in methanol (30 mL),
sulfur (350 mg, 11.0 mmol) and morpholine (1.10 g, 1.10 mL,
12.1 mmol) were added. After stirring at 45 ꢁC for 8e12 h, the re-
action mixture was evaporated and the crude product was purified
by column chromatography on silica gel (absorbed with 1% trie-
thylamine) eluting with a mixture of hexanes/ethylacetate (80:20).
General procedure C. To a solution of (E/Z) 2-cyano-3-(40-hex-
yloxy-biphenyl-4-yl)-but-2-enoic acid methyl ester 4a (2.0 g,
5.5 mmol) or (E/Z) 2-cyano-3-(40-octyloxy-biphenyl-4-yl)-but-2-
enoic acid methyl ester 4b (2.2 g, 5.5 mmol) in tetrahydrofuran
(30 mL), sulfur (350 mg, 11.0 mmol) and morpholine (1.20 g,
1.20 mL, 14.0 mmol) were added. After stirring at 50 ꢁC for 12 h, the
reaction mixture was evaporated and the crude product was pu-
rified by column chromatography on silica gel (absorbed with 1%
triethylamine) eluting with a mixture of hexanes/ethylacetate
(80:20).
4.6.1. 4-Hexyloxybenzaldehyde 7a. Yield: 94% (19.4 g), yellow
oil. Analytical data corresponds to those published for
4-hexyloxybenzaldehyde, C13H18O2 (206.28).33
4.6.2. 4-Octyloxybenzaldehyde 7b. Yield: 91% (21.3 g), yellow
oil. Analytical data corresponds to those published for
4-octyloxybenzaldehyde, C15H22O2 (234.33).19
4.6.3. 4-Decyloxybenzaldehyde 7c. Yield: 89% (23.4 g), yellow
oil. Analytical data corresponds to those published for
4-decyloxybenzaldehyde, C17H26O2 (262.39).33
4.6.4. 4-Dodecyloxybenzaldehyde 7d. Yield: 90% (26.1 g), yellow oil;
dH (500 MHz CDCl3): 9.65 (s, 1H, CHO), 7.78 (d, J¼8.3 Hz, 2H), 7.34
(d, J¼8.3 Hz, 2H), 4.12 (t, J¼6.6 Hz, 2H, CH2), 1.88e1.74 (m, 2H, CH2),
1.48e1.42 (m, 2H, CH2), 1.26 (br s, 16H, 8ꢂ CH2), 0.88 (t, J¼6.6 Hz,
3H, CH3); dC (125 MHz CDCl3): 189.8, 159.7, 130.6, 130.1, 128.4, 112.6,
69.7, 32.1, 30.2, 29.7, 29.4, 29.0, 28.6, 28.4, 26.1, 22.8, 14.2; nmax(KBr)
2956, 2920, 2812, 1698 (C]O), 1600, 1468, 675 cmꢀ1; Anal. Calcd
for C19H30O2 (290.44): C, 78.57, H,10.41%. Found: C, 78.31, H, 10.70%.
Mass (ESI) m/z (%) 290.8.
4.5.1. 2-Amino-4-(40-hexyloxy-biphenyl-4-yl)-thiophene-3-
carboxylic acid methyl ester 5a. Yield: 28% (630 mg)dMethod A;
40% (900 mg)dMethod B; 60% (1.4 g)dMethod C; white solid,
mp¼120e124 ꢁC; Rf (hexanes/EtOAc/80:20) 0.46; dH (500 MHz
CDCl3): 7.56e7.49 (m, 4H), 7.35 (d, J¼8.4 Hz, 2H), 6.97 (d, J¼8.4 Hz,
2H), 6.12 (s,1H, Hthiophene), 6.08 (br s, 2H, NH2), 4.00 (t, J¼6.5 Hz, 2H,
CH2), 3.60 (s, 3H, COOCH3), 1.81 (q, J¼6.5 Hz, 2H, CH2), 1.48e1.44
(m, 2H, CH2), 1.27 (br s, 4H, 2ꢂ CH2), 0.884 (t, J¼6.5 Hz, 3H, CH3); dC
(125 MHz CDCl3): 163.5, 156.7, 140.3, 136.6, 134.8, 130.0, 128.6,
128.0, 127.5, 127.1, 122.0, 115.2, 105.8, 74.3, 49.5, 33.1, 30.9, 26.4,
24.4, 12.8; nmax(KBr) 3343 (NH2), 3115, 2952, 1691 (C]Oester), 1222
4.7. Wittig reaction: synthesis of substituted stilbenes 8aed20
To a solution of methyl (4-triphenylphosphoniummethyl)-ben-
zoate bromide34 (6.0 g, 12.0 mmol), dissolved in dry dichloro-
methane (70 mL) and tetrahydrofuran (70 mL), anhydrous
potassium carbonate (8.4 g, 61.0 mmol) followed by 18-crown-6
(20 mg, 0.07 mmol) were added. The reaction mixture was stirred
at room temperature for 1 h. The appropriate 4-alkylox-
ybenzaldehyde 7aed (3.7 g for 7a, 4.2 g for 7b, 4.7 g for 7c, 5.2 g for
7d, 18.0 mmol) was added and the reaction mixture was heated at
the boiling temperature of dichloromethaneeTHF solvent mixture
for 20 h. After filtration of inorganic salts formed during reaction,
the mixture was evaporated and the crude product was crystallized
from ethanol. According to spectral data, only (E)-stilbene was
crystallized from the reaction mixture in all cases.
(CeOester), 1478, 840, 603 cmꢀ1
; Anal. Calcd for C24H27NO3S
(409.54): C, 70.39; H, 6.65; N, 3.42; S, 7.83%. Found: C, 70.77; H,
6.50; N, 3.72; S, 7.66%. Mass (ESI) m/z (%) 409.3.
4.5.2. 2-Amino-4-(40-octyloxy-biphenyl-4-yl)-thiophene-3-
carboxylic acid methyl ester 5b. Yield: 30% (722 mg)dMethod A;
39% (940 mg)dMethod B; 64% (1.5 g)dMethod C; white solid,
mp¼105e108 ꢁC; Rf (hexanes/EtOAc/80:20) 0.48; dH (500 MHz
CDCl3): 7.99 (d, J¼8.4 Hz, 2H), 7.67e7.59 (m, 4H), 6.97 (d, J¼8.4 Hz,
2H), 6.10 (s,1H, Hthiophene), 6.04 (br s, 2H, NH2), 4.00 (t, J¼6.6 Hz, 2H,
CH2), 3.60 (s, 3H, COOCH3), 1.81 (q, J¼6.6 Hz, 2H, CH2), 1.32 (q,
J¼6.6 Hz, 2H, CH2), 1.29 (br s, 8H, 4ꢂ CH2), 0.89 (t, J¼6.6 Hz, 3H,
CH3); dC (125 MHz CDCl3): 162.2, 155.9, 141.0, 137.1, 135.0, 129.7,
129.1, 128.0, 127.6, 125.6, 121.6, 114.8, 105.9, 72.3, 50.1, 31.8, 27.1,
29.6, 29.3, 26.6, 24.2, 14.1; nmax(KBr) 3321 (NH2), 3067, 2943, 1696
4.7.1. (E) 4-[2-(4-Hexyloxy-phenyl)-vinyl]-benzoic acid methyl ester
8a. Yield: 63% (3.8 g), pale yellowish solid; mp¼144e146 ꢁC; dH
(500 MHz CDCl3): 8.03 (d, J¼8.1 Hz, 2H), 7.66 (d, J¼8.3 Hz, 2H),
7.59 (d, J¼8.1 Hz, 2H), 7.55 (d, J¼16.2 Hz, 1H), 7.51 (d, J¼16.2 Hz,
1H), 6.95 (d, J¼8.3 Hz, 2H), 4.06 (t, J¼6.6 Hz, 2H, CH2), 3.95 (s, 3H,
COOCH3), 1.57 (t, J¼6.6 Hz, 2H, CH2), 1.26 (br s, 6H, 3ꢂ CH2), 0.882

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(t, J¼6.6 Hz, 3H, CH3); dC (125 MHz CDCl3): 167.1, 156.7, 140.2,
129.7, 128.8, 127.9, 126.7, 126.4, 124.1, 123.8, 113.5, 71.0, 52.2, 32.1,
30.0, 26.1, 22.9, 14.2; nmax(KBr) 2925, 2864, 1715 (C]Oester), 1596
(C]C), 1475, 1286 (CeOester), 1468, 822, 654 cmꢀ1; Anal. Calcd for
C22H26O3 (338.44): C, 78.07; H, 7.74%. Found: C, 78.2; H, 7.83%.
Mass (ESI) m/z (%) 338.2.
4.8.1. 4-[2-(4-Hexyloxy-phenyl)-vinyl]-benzoyl chloride 9a. Yield
96% (2.3 g), bright yellow solid, C21H23ClO2 (342.86).
4.8.2. 4-[2-(4-Octyloxy-phenyl)-vinyl]-benzoyl chloride 9b. Yield
98% (2.5 g), bright yellow solid, C23H27ClO2 (370.91).
4.8.3. 4-[2-(4-Decyloxy-phenyl)-vinyl]-benzoyl chloride 9c. Yield
4.7.2. (E) 4-[2-(4-Octyloxy-phenyl)-vinyl]-benzoic acid methyl ester
8b. Yield: 59% (3.9 g), pale yellowish solid; mp¼132e130 ꢁC; dH
(500 MHz CDCl3): 8.00 (d, J¼8.1 Hz, 2H), 7.66 (d, J¼8.1 Hz, 2H), 7.56
(d, J¼8.1 Hz, 2H), 7.48 (d, J¼16.2 Hz, 1H), 7.35 (d, J¼16.2 Hz, 1H),
6.91 (d, J¼8.1 Hz, 2H), 3.98 (t, J¼6.2 Hz, 2H, CH2), 3.92 (s, 3H,
COOCH3), 1.66 (t, J¼6.2 Hz, 2H, CH2), 1.35 (q, J¼6.2 Hz, 2H, CH2),
1.29 (br s, 8H, 4ꢂ CH2), 0.91 (t, J¼6.2 Hz, 3H, CH3); dC (125 MHz
CDCl3): 166.9, 157.9, 139.8, 129.6, 128.7, 128.0, 127.5, 126.4, 125.8,
123.9, 123.1, 114.0, 73.1, 51.9, 31.5, 30.8, 29.9, 26.1, 23.0, 13.8;
nmax(KBr) 2936, 2879, 1723 (C]Oester), 1602 (C]C), 1451, 1269
(CeOester), 1454, 856, 692 cmꢀ1; Anal. Calcd for C24H30O3 (366.49):
C, 78.65; H, 8.25%. Found: C, 79.0; H, 8.32%. Mass (ESI) m/z (%)
366.2.
94% (2.6 g), bright yellow solid, C25H31ClO2 (398.97).
4.8.4. 4-[2-(4-Dodecyloxy-phenyl)-vinyl]-benzoyl chloride 9d. Yield
90% (2.7 g), bright yellow solid, C27H35ClO2 (427.02).
4.9. Synthesis of final 2-aminothiophene-stilbene containing
mesogens 10aef
To a solution of 2-amino-4-(40-alkyloxy-biphenyl-4-yl)-thio-
phene-3-carboxylic acid methyl ester 5a or 5b (614 mg for 5a,
660 mg for 5b,1.5 mmol), DMAP (20 mg, 0.16 mmol), triethyl-
amine (few drops) in toluene (50 mL) the appropriate 4-[2-(4-
alkyloxy-phenyl)-vinyl]-benzoyl chloride 9aed (1030 mg for 9a,
1110 mg for 9b, 1200 mg for 9c, 1300 mg for 9d, 3.0 mmol) was
added. The reaction mixture was stirred at the boiling tempera-
ture of toluene for 12e24 h, then the excess of solvent was
evaporated and the remaining oil was purified by column chro-
matography on silica gel (absorbed with 1% triethylamine) eluting
with dichloromethane. The range of product yields in this step
varied from 35 to 45 %.
4.7.3. (E) 4-[2-(4-Decyloxy-phenyl)-vinyl]-benzoic acid methyl ester
8c. Yield: 54% (3.8 g), yellowish solid; mp¼124e126 ꢁC; dH
(500 MHz CDCl3): 8.06 (d, J¼8.4 Hz, 2H), 7.70 (d, J¼8.3 Hz, 2H),
7.54 (d, J¼8.3 Hz, 2H), 7.60 (d, J¼16.4 Hz, 1H), 7.41 (d, J¼16.4 Hz,
1H), 7.00 (d, J¼8.4 Hz, 2H), 4.00 (q, J¼6.4 Hz, 2H, CH2), 3.96 (s, 3H,
COOCH3), 1.72 (t, J¼6.4 Hz, 2H, CH2), 1.41e1.37 (m, 2H, CH2), 1.27
(br s, 12H, 6ꢂ CH2), 0.87 (t, J¼6.4 Hz, 3H, CH3); dC (125 MHz CDCl3):
167.3, 158.2, 141.0, 130.6, 129.1, 128.5, 127.3, 126.7, 126.0, 124.0,
123.3, 113.7, 71.2, 50.5, 32.0, 30.1, 29.9, 29.5, 26.9, 26.0, 22.8, 15.1;
nmax(KBr) 2944, 2860, 1718 (C]Oester), 1612 (C]C), 1468, 1264
(CeOester), 1476, 822, 665 cmꢀ1; Anal. Calcd for C26H34O3 (394.55):
C, 79.15; H, 8.69%. Found: C, 79.3; H, 8.30%. Mass (ESI) m/z (%)
394.1.
4.9.1. 4-(40-Hexyloxy-biphenyl-4-yl)-2-{4-[2-(4-hexyloxy-phenyl)-
vinyl]-benzoylamino}-thiophene-3-carboxylic acid methyl ester
10a. Yield: 42% (451 mg), yellow solid; mp¼169e172 ꢁC; Rf
(CH2Cl2) 0.80; dH (500 MHz CDCl3): 12.36 (br s, 1H, NH), 8.03 (d,
J¼8.6 Hz, 2H), 7.63 (d, J¼8.6 Hz, 2H), 7.59 (d, J¼8.0 Hz, 2H), 7.57 (d,
J¼8.0 Hz, 2H), 7.49 (d, J¼8.0 Hz, 2H), 7.38 (d, J¼8.0 Hz, 2H), 7.21 (d,
J¼16.2 Hz, 1H), 7.01 (d, J¼16.2 Hz, 1H), 6.99 (d, J¼8.0 Hz, 2H), 6.91
(d, J¼8.0 Hz, 2H), 6.70 (s, 1H, Hthiophene), 4.00 (t, J¼6.6 Hz, 4H, 2ꢂ
CH2), 3.69 (s, 3H, COOCH3), 1.85 (q, J¼6.6 Hz, 4H, 2ꢂ CH2), 1.50 (q,
J¼6.6 Hz, 4H, 2ꢂ CH2), 1.37 (br s, 8H, 4ꢂ CH2), 0.92 (t, J¼6.6 Hz, 6H,
3ꢂ CH3); dC (125 MHz CDCl3): 167.1, 163.5, 158.8, 153.2, 151.0, 145.2,
139.4, 135.9, 133.0, 132.2, 130.0, 128.6, 128.2, 127.9, 127.5, 127.1,
126.5, 126.1, 125.7, 124.3, 122.7, 114.8, 113.0, 111.4, 110.6, 71.1, 69.1,
51.4, 32.2, 31.9, 29.7, 26.0, 25.4, 23.0, 22.7, 14.1, 13.8; nmax(KBr) 3485
(NH), 3184, 3079, 2950, 2933, 2864, 1705 (C]Oester), 1665 (C]
Oamide), 1638 (C]C), 1456, 1317, 1270 (CeOester), 905, 780, 694,
633 cmꢀ1; Anal. Calcd for C45H49NO5S (715.94): C, 75.49, H, 6.90, N,
1.96, S, 4.48%. Found: C, 75.60, H, 6.72, N, 2.05, S, 4.50%. Mass (ESI)
m/z (%) 716.4 [MþH]þ.
4.7.4. (E) 4-[2-(4-Dodecyloxy-phenyl)-vinyl]-benzoic acid methyl
ester 8d. Yield: 45% (3.4 g), pale grey solid; mp¼112e115 ꢁC; dH
(500 MHz CDCl3): 7.97 (d, J¼8.2 Hz, 2H), 7.70 (d, J¼8.2 Hz, 2H), 7.61
(d, J¼8.1 Hz, 2H), 7.36 (d, J¼16.5 Hz, 1H), 7.21 (d, J¼16.5 Hz, 1H),
6.85 (d, J¼8.1 Hz, 2H), 3.99 (s, 3H, COOCH3), 3.96 (t, J¼6.6 Hz, 2H,
CH2), 1.74e1.70 (m, 2H, CH2), 1.31 (q, J¼6.6 Hz, 2H, CH2), 1.26 (br s,
16H, 8ꢂ CH2), 0.86 (t, J¼6.6 Hz, 3H, CH3); dC (125 MHz CDCl3):
166.9, 157.9, 139.8, 129.6, 128.7, 128.0, 127.5, 126.4, 125.8, 123.9,
123.1, 114.0, 73.1, 51.9, 31.6, 30.8, 30.4, 29.9, 29.6, 29.4, 28.2, 26.1,
23.0, 13.8; nmax(KBr) 2952, 2842,1702 (C]Oester), 1625 (C]C), 1480,
1245 (CeOester), 1482, 890, 676 cmꢀ1; Anal. Calcd for C28H38O3
(422.60): C, 79.58; H, 9.06%. Found: C, 79.9; H, 9.25%. Mass (ESI) m/z
(%) 422.3.
4.9.2. 4-(40-Hexyloxy-biphenyl-4-yl)-2-{4-[2-(4-octyloxy-phenyl)-
vinyl]-benzoylamino}-thiophene-3-carboxylic acid methyl ester
10b. Yield: 45% (502 mg), yellow solid; mp¼162e165 ꢁC; Rf
(CH2Cl2) 0.76; dH (500 MHz CDCl3): 12.29 (br s, 1H, NH), 7.92 (d,
J¼8.4 Hz, 2H), 7.60e7.54 (m, 4H), 7.36 (d, J¼8.4 Hz, 2H), 7.32 (d,
J¼8.2 Hz, 2H), 7.27 (d, J¼8.2 Hz, 2H), 7.21 (d, J¼16.0 Hz, 1H), 7.08 (d,
J¼16.0 Hz, 1H), 6.97 (d, J¼8.0 Hz, 2H), 6.91 (d, J¼8.0 Hz, 2H), 6.67 (s,
1H, Hthiophene), 4.02 (t, J¼6.4 Hz, 2H, CH2), 3.99 (t, J¼6.4 Hz, 2H,
CH2), 3.69 (s, 3H, COOCH3), 1.85 (q, J¼6.2 Hz, 4H, 2ꢂ CH2), 1.33 (q,
J¼6.4 Hz, 2H, CH2), 1.27 (br s, 6H, 3ꢂ CH2), 1.24 (br s, 8H, 4ꢂ CH2),
0.92 (t, J¼6.2 Hz, 3H, CH3), 0.89 (t, J¼6.2 Hz, 3H, CH3); dC (125 MHz
CDCl3): 166.8, 162.9, 158.2, 153.4, 150.3, 146.1, 139.0, 135.5, 132.8,
131.9, 130.2, 129.0, 128.4, 128.1, 127.8, 126.9, 126.4, 127.5, 127.1,
126.1, 124.6, 123.2, 114.6, 112.9, 111.7, 110.3, 72.3, 70.2, 52.2, 32.1,
30.9, 30.3, 29.7, 26.6, 26.0, 23.3, 22.8, 14.4, 13.7; nmax(KBr) 3476
(NH), 3205, 3099, 2966, 2948, 2886, 1724 (C]Oester), 1678 (C]
Oamide), 1644 (C]C), 1460, 1326, 1274 (CeOester), 894, 755, 672,
650 cmꢀ1; Anal. Calcd for C47H53NO5S (743.99): C, 75.87, H, 7.18, N,
4.8. Standard procedure for the synthesis of acyl chlorides
9aed21
To a solution of the appropriate (E) 4-[2-(4-alkyloxy-phenyl)-
vinyl]-benzoic acid methyl ester 8aed (2.4 g for 8a, 2.6 g for 8b,
2.8 g for 8c, 3.0 g for 8d, 7.0 mmol) in ethanol (200 mL), a solution
of potassium hydroxide (1.6 g, 28.0 mmol) in water (20 mL) was
added and the mixture was heated at the boiling temperature of
ethanol for 12 h. After cooling the solution, the crude product was
isolated by suction filtration as the potassium salt. After drying
under vacuum, the obtained salt was suspended in toluene
(200 mL) and treated with an excess of oxalyl chloride (6.0 mL). The
reaction mixture was heated at 110 ꢁC for 8 h. After filtration of the
precipitated potassium chloride, the remaining solution was
evaporated to dryness. The products slowly solidified at room
temperature and were subsequently used without further purifi-
cation and characterization in the next step.

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Z. Puterova et al. / Tetrahedron 68 (2012) 8172e8180
8179
1.88, S, 4.31%. Found: C, 76.01, H, 7.31, N, 1.75, S, 4.60%. Mass (ESI)
m/z (%) 743.50.
(CH2Cl2) 0.76; dH (500 MHz CDCl3): 12.35 (br s, 1H, NH), 8.04 (d,
J¼8.1 Hz, 2H), 7.63 (d, J¼8.0 Hz, 2H), 7.58 (d, J¼8.0 Hz, 2H), 7.56 (d,
J¼8.0 Hz, 2H), 7.38 (d, J¼8.0 Hz, 2H), 7.17 (d, J¼16.2 Hz, 1H), 6.99 (d,
J¼8.0 Hz, 2H), 6.98 (d, J¼8.1 Hz, 2H), 6.90 (d, J¼16.2 Hz, 1H), 6.88 (d,
J¼8.0 Hz, 2H), 6.70 (s, 1H, Htihophene), 4.06 (t, J¼6.4 Hz, 2H, CH2),
4.01 (t, J¼6.4 Hz, 2H, CH2), 3.70 (s, 3H, COOCH3), 1.82 (q, J¼6.4 Hz,
4H, 2ꢂ CH2), 1.51 (q, J¼6.4 Hz, 4H, 2ꢂ CH2), 1.27 (br s, 24H, 12ꢂ
CH2), 0.90 (t, J¼6.4 Hz, 3H, CH3), 0.88 (t, J¼6.4 Hz, 3H, CH3); dC
(125 MHz CDCl3): 166.8, 163.0, 158.7, 153.2, 151.1, 148.1, 145.4, 139.6,
136.7,135.7,133.0,132.4,130.0,129.7,128.8,128.4,128.1,127.5,127.0,
126.4, 124.1, 123.0, 116.3, 115.0, 114.5, 112.1, 71.1, 70.9, 51.6, 32.6,
32.2, 31.8, 31.4, 31.0, 30.7, 29.8, 29.5, 27.0, 26.8, 26.5, 26.1, 23.8, 23.4,
14.4, 13.9; nmax(KBr) 3460 (NH), 3152, 3098, 2944, 2920, 2845, 1706
(C]Oester), 1671 (C]Oamide), 1634 (C]C), 1470, 1319, 1251
(CeOester), 908, 799, 685, 619 cmꢀ1; Anal. Calcd for C53H65NO5S
(828.15): C, 76.87, H, 7.91, N, 1.69, S, 3.87%. Found: C, 77.05, H, 7.95,
N, 1.72, S, 3.93%. Mass (ESI) m/z (%) 827.5.
4.9.3. 2-{4-[2-(4-Hexyloxy-phenyl)-vinyl]-benzoylamino}-4-(40-oc-
tyloxy-biphenyl-4-yl)-thiophene-3-carboxylic acid methyl ester
10c. Yield: 40% (446 mg), yellow solid; mp¼165e167 ꢁC; Rf (CH2Cl2)
0.74; dH (500 MHz CDCl3): 12.35 (br s, 1H, NH), 8.03 (d, J¼8.3 Hz, 2H),
7.64 (d, J¼8.3 Hz, 2H), 7.59e7.55 (m, 4H), 7.48 (d, J¼8.1 Hz, 2H), 7.38 (d,
J¼8.1 Hz, 2H), 7.20 (d, J¼16.5 Hz, 1H), 7.02 (d, J¼16.5 Hz, 1H), 6.98 (d,
J¼8.1 Hz, 2H), 6.92 (d, J¼8.1 Hz, 2H), 6.69 (s, 1H, Hthiophene), 4.01 (t,
J¼6.4 Hz, 2H, CH2), 3.99 (t, J¼6.4 Hz, 2H, CH2), 3.69 (s, 3H, COOCH3),1.81
(q, J¼6.6 Hz, 4H, 2ꢂ CH2), 1.48 (q, J¼6.6 Hz, 2H, CH2), 1.27 (br s, 6H, 3ꢂ
CH2),1.25 (br s, 8H, 4ꢂ CH2), 0.93 (t, J¼6.4 Hz, 3H, CH3), 0.89 (t, J¼6.4 Hz,
3H, CH3); dC (125 MHz CDCl3): 167.0, 163.1, 158.6, 153.1, 146.1, 139.4,
135.7, 133.0, 132.3, 130.1, 129.4, 128.4, 128.1, 127.6, 127.1, 126.5, 126.1,
125.7, 124.9, 122.6, 114.7, 113.9, 111.6, 110.2, 71.4, 70.7, 51.6, 32.1, 31.0,
30.5, 30.1, 29.6, 29.4, 26.2, 25.9, 23.4, 22.5, 14.4, 13.9; nmax(KBr) 3472
(NH), 3202, 3094, 2944, 2929, 2881, 1712 (C]Oester), 1681 (C]Oamide),
1624 (C]C),1468,1324,1257 (CeOester), 898, 776, 657, 609 cmꢀ1; Anal.
Calcd for C47H53NO5S (743.99): C, 75.87, H, 7.18, N,1.88, S, 4.31%. Found:
C, 75.55, H, 7.24, N, 1.94, S, 4.20%. Mass (ESI) m/z (%) 745.00 [MþH]þ.
Acknowledgements
This research is supported by Foundation for Polish Science
under TEAM programme No. TEAM 2010-5/4.
4.9.4. 4-(40-Octyloxy-biphenyl-4-yl)-2-{4-[2-(4-octyloxy-phenyl)-vi-
nyl]-benzoylamino}-thiophene-3-carboxylic acid methyl ester
10d. Yield: 42% (486 mg), yellow solid; mp¼168e172 ꢁC; Rf
(CH2Cl2) 0.69; dH (500 MHz CDCl3): 12.36 (br s, 1H, NH), 8.03 (d,
J¼8.3 Hz, 2H), 7.63 (d, J¼8.6 Hz, 2H), 7.60 (d, J¼8.2 Hz, 2H), 7.56 (d,
J¼8.2 Hz, 2H), 7.49 (d, J¼8.3 Hz, 2H), 7.38 (d, J¼8.4 Hz, 2H), 7.20 (d,
J¼16.4 Hz, 1H), 7.03 (d, J¼8.0 Hz, 2H), 7.02 (d, J¼16.4 Hz, 1H), 6.91
(d, J¼8.4 Hz, 2H), 6.70 (s, 1H, Hthiophene), 4.00 (t, J¼6.6 Hz, 4H, 2ꢂ
CH2), 3.69 (s, 3H, COOCH3), 1.82 (q, J¼6.6 Hz, 4H, 2ꢂ CH2), 1.50 (q,
J¼6.6 Hz, 4H, 2ꢂ CH2), 1.30 (br s, 16H, 8ꢂ CH2), 0.90 (t, J¼6.6 Hz, 6H,
3ꢂ CH3); dC (125 MHz CDCl3): 167.2, 162.5, 158.5, 157.4, 152.9, 145.7,
141.8, 139.6, 136.6, 135.2, 132.4, 131.9, 130.0, 129.3, 128.0, 127.4,
127.0, 126.3, 125.5, 124.1, 122.3, 115.5, 114.6, 114.0, 112.1, 71.4, 70.8,
50.6, 32.3, 31.8, 31.4, 30.6, 30.3, 29.9, 26.7, 26.4, 26.0, 23.1, 22.8, 14.4,
13.9; nmax(KBr) 3486 (NH), 3195, 3104, 2961, 2935, 2855, 1708 (C]
Oester), 1675 (C]Oamide), 1634 (C]C), 1460, 1319, 1243 (CeOester),
885, 769, 663, 619 cmꢀ1; Anal. Calcd for C49H57NO5S (772.05): C,
76.23, H, 7.44, N, 1.81, S, 4.15%. Found: C, 76.40, H, 7.67, N, 1.88, S,
4.10%. Mass (ESI) m/z (%) 771.10.
Co-author J.R. acknowledges support of the Foundation for
Polish Science under MPD programme cofinanced by the EU Eu-
ropean Regional Development Fund.
References and notes
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p
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4.9.5. 2-{4-[2-(4-Decyloxy-phenyl)-vinyl]-benzoylamino}-4-(40-oc-
tyloxy-biphenyl-4-yl)-thiophene-3-carboxylic acid methyl ester
10e. Yield: 38% (456 mg), yellow solid; mp¼144e148 ꢁC; Rf
(CH2Cl2) 0.67; dH (500 MHz CDCl3): 12.35 (br s, 1H, NH), 8.01 (d,
J¼8.0 Hz, 2H), 7.85 (d, J¼8.0 Hz, 2H), 7.56 (d, J¼8.0 Hz, 2H), 7.52 (d,
J¼8.0 Hz, 2H), 7.46 (d, J¼8.0 Hz, 2H), 7.38 (d, J¼8.0 Hz, 2H), 7.16 (d,
J¼16.0 Hz, 1H), 7.00 (d, J¼8.0 Hz, 2H), 6.98 (d, J¼16.0 Hz, 1H), 6.90
(d, J¼8.0 Hz, 2H), 6.69 (s, 1H, Hthiophene), 4.01 (t, J¼6.2 Hz, 2H, CH2),
3.98 (t, J¼6.4 Hz, 2H, CH2), 3.69 (s, 3H, COOCH3), 1.80 (q, J¼6.4 Hz,
4H, 2ꢂ CH2), 1.45 (q, J¼6.2 Hz, 4H, 2ꢂ CH2), 1.28 (br s, 20H, 10ꢂ
CH2), 0.88 (t, J¼6.2 Hz, 3H, CH3), 0.86 (t, J¼6.2 Hz, 3H, CH3); dC
(125 MHz CDCl3): 166.4, 161.5, 157.9, 153.3, 151.7, 147.4, 146.2, 140.2,
138.6, 135.8, 133.2, 132.0, 130.3, 129.5, 128.4, 127.6, 127.2, 126.4,
126.1, 124.4, 123.3, 116.5, 114.8, 112.4, 111.7, 71.5, 69.9, 51.3, 32.6,
32.0, 31.8, 30.9, 30.6, 30.3, 30.1, 29.7, 27.1, 26.6, 26.4, 24.0, 23.6, 14.2,
14.0; nmax(KBr) 3474 (NH), 3168, 3116, 2952, 2935, 2861, 1719 (C]
Oester), 1669 (C]Oamide), 1625 (C]C), 1458, 1342, 1249 (CeOester),
902, 794, 676, 604 cmꢀ1; Anal. Calcd for C51H61NO5S (800.10): C,
76.56, H, 7.68, N, 1.75, S, 4.01%. Found: C, 76.80, H, 7.90, N, 1.83, S,
4.05%. Mass (ESI) m/z (%) 799.89.
€
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