Synthesis and Mesomorphic Properties of Novel Bent-shaped Naphthyl Diketones

Article abstract of DOI:10.5562/cca3541

The synthesis and liquid-crystalline properties are reported for novel naphthyl-based diketones incorporating variant terminal chains and lateral fluoro- substitution. Newly prepared materials exhibit a broad temperature range of the nematic phase. The study demonstrates how subtle structural modifications can be exploited to alter the efficiency of molecular packing and consequently the thermal behaviour.

Full text of DOI:10.5562/cca3541

O R I G I NA L S C I E N T I F I C P A P E R
Croat. Chem. Acta 2019, 92(2)
Published online: October 21, 2019
DOI: 10.5562/cca3541
Synthesis and Mesomorphic Properties of Novel
Bent-shaped Naphthyl Diketones
Anđela Buljan, Anamarija Knežević, Irena Dokli, Andreja Lesac*
Ruđer Bošković Institute, Bijenička cesta 54, HR-10000 Zagreb, Croatia
Corresponding author’s e-mail address: Andreja.Lesac@irb.hr
*
RECEIVED: July 1, 2019
REVISED: July 12, 2019
ACCEPTED: July 14, 2019
TH
THIS PAPER IS DEDICATED TO PROF. KATA MLINARIĆ-MAJERSKI ON THE OCCASION OF HER 70 BIRTHDAY
Abstract: The synthesis and liquid-crystalline properties are reported for novel naphthyl-based diketones incorporating variant terminal chains
and lateral fluoro- substitution. Newly prepared materials exhibit a broad temperature range of the nematic phase. The study demonstrates
how subtle structural modifications can be exploited to alter the efficiency of molecular packing and consequently the thermal behaviour.
Keywords: liquid crystals, bent-shaped dimers, naphthyl diketones.
numbered spacer, the mesogenic groups are inclined with
respect to each other giving a bent-shaped motif. The
INTRODUCTION
HE liquid-crystalline state of matter, which exists
between the crystalline solid and amorphous liquid
recent discovery of a twist-bend nematic phase (NTB) found
in odd-membered dimers has sparked a great interest in
this class of materials.[5,6] The reason for such interest is not
only its promising technological applications, but also the
fact that the NTB phase is one of the most recent examples
of spontaneous chirality. Unlike the uniaxial nematic phase
in which a preferred direction of molecules is parallel to the
main molecular axis (Figure 1a), the NTB phase is charac-
terized by a spontaneous twist-bend distortion of the
nematic director, which is organized on a conical helix
(Figure 1b). Formation of degenerate helices does not
require molecular chirality, instead, it is facilitated by
the shape of bent molecules.[7–10] Initially proposed as
a theoretical possibility,[11] the NTB phase has been
identified[6,7,12] and intensively studied aiming to
understand its structural characteristics and macroscopic
properties.[7–9,13–17] Although predominantly exhibited by
liquid crystal dimers having odd-number of methylene units
in the spacer, the NTB phase has also been reported for
trimers and tetramers[18–22] including a semi-flexible bent-
core liquid crystal.[10,23]
T
states, share the anisotropic (direction dependent)
properties of crystalline state and fluid properties of iso-
tropic liquids. Molecular shape, "microphase segregation"
and specific molecular interactions are important factors
that drive the formation of various LC phases in the
matter.[1,2] Though liquid crystals are primarily known for
their technological applications in the liquid-crystal displays
(LCDs) their domain spans across multiple disciplines of
pure and applied science including bioscience and materials
science.[3]
For many years liquid crystalline dimers, in which
two mesogenic units are linked by a flexible spacer, have
been studied due to their ability to serve as model
compounds for liquid-crystalline polymers and their rich
and unusual mesomorphism, which differs from that of the
corresponding monomers[4] One of the main characteristics
of this class of materials is that their mesomorphic
properties depend on the parity of the flexible spacer and
the nature of the link between the spacer and the
mesomorphic units. Thus, in dimers with an even-
numbered spacer, the mesogenic groups are disposed to
give an overall rod-like shape, whereas, with an odd-
The structure-property relation essential for the
emergence of the NTB phase has been intensively studied.
To date, the work involved modifications of the mesogenic
This work is licensed under a Creative Commons Attribution 4.0 International License.

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A. BULJAN et al.: Mesomorphic Bent-shaped Naphthyl Diketones
prepared from corresponding hydroxybenzoic acids by
Williams reaction. Esterification of 4 with appropriate
benzoyl chlorides using 4-dimethylaminopyridine (DMAP)
and triethylamine (Et3N) provided target molecules in 69–
77 % yield.
The mesomorphic behaviour of new compounds was
investigated by polarising optical microscopy and
differential scanning calorimetry. The phase transition
temperatures and the corresponding enthalpy changes are
collected in Table 1. The DSC traces of the heating and
cooling cycles are given in Supplementary Information.
The data listed in Table 1 shows that all dimers
exhibit a wide temperature range enantiotropic nematic
phase. The nematic phase was identified according to
characteristic schlieren texture containing both two and
four brush point singularities observed through the
polarising microscope, and which flashed when subjected
to mechanical stress (Figure 2).
Figure 1. Cartoon illustration of the molecular organization
in (a) uniaxial nematic phase, (b) NTB phase.
Comparison of transition temperatures between
newly prepared compounds and BNC-72 revealed that
structural modifications result in a general reduction of the
clearing point while the melting temperatures are variable,
with no N to NTB transition being detected. Due to the
supercooling effect, all materials show a very large
temperature range of the nematic phase. The effects of
structural modifications on the thermodynamic behaviour
of parent ethoxy analogue BNC-72[34] is illustrated in Figure
3. Since both, ethyloxy and butyloxy homologues display
the monotropic NTB phase,[34] the absence of the NTB phase
in propoxy and propargyloxy homologues is rather
surprising. Also, these results are in contradiction to those
observed for methylene-linked dimers which have shown
that terminal chains of odd parity give more stable NTB
phases than those of even parity.[28] It appears that the
initial elongation of the chain disrupts the molecular
packing required for the NTB phase formation, while
subsequently increased chains may be accommodated
within this particular arrangement.
The entropy of the N-Iso transition, measured for
propoxy homologue is lower than that reported for BNC-
72[34] suggesting that the odd parity contributes to the
greater effective molecular curvature and consequently
reduces isotropization temperature. Combined experimen-
tal and computational studies showed that a bend angle in
the region of 125 ° is the optimum for a material to exhibit
the twist-bend nematic phase.[38] Thus, a small fluctuation
in the bend angle of 6a may disrupt the formation of the
NTB phase, which even in ethoxy homologues appears on
cooling just 1 °C before crystallization. The reduction in
clearing and melting temperatures but also supercooling
effect are the most pronounced for the dimer with
propargyloxy terminal chains. This may be attributed to the
joined contribution of the increased effective molecular
units and the terminal groups attached to them,[24–27]
variation of linkage groups and the length of the
spacer.[28,29] It has been reported that the stability of the
NTB phase is affected by molecular bending defined as
the angle between the two mesogenic arms,[24,30,31]
conformational distribution,[32,33] the bend angle fluctuat-
ion,[14] intramolecular torsion,[28,29] π-π interactions[34] and
the effect of free volume.[25,35] The recent study of the
electroclinic effect in the NTB phase (ECENTB) discussed the
improvements of the physical properties of NTB materials
that might lead to possible technological applications of the
fast NTB electro-optic effects.[36] Despite the growing
number of compounds exhibiting the NTB phase, diverse
libraries of materials are required to optimize meso-
morphic and other physical properties necessary for a
potential application.
Previously we have shown that naphthyl-based
diketones with ethoxy and butyloxy terminal chains exhibit
the nematic and the monotropic NTB phase. Tuning the
mesomorphic properties of naphthyl-based diketones, we
explore the effect of propargyl terminal chain and position
of lateral fluoro substituent inserted in the outer-ring of the
mesogenic core. Propargyl group is attractive substituent
due to its ability to undergo polymerization while lateral
fluorination may offer improved electro-optical properties
as demonstrated for a vast number of fluorinated calamitic
liquid crystals.[37]
RESULTS AND DISCUSSION
The target materials were prepared according to the
synthetic route described in Scheme 1. The main precursor
4 was successfully prepared following the procedures
reported earlier.[34] 4-O-substituted benzoic acid 5a–d were
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A. BULJAN et al.: Mesomorphic Bent-shaped Naphthyl Diketones
3
CHO
Table 1. Transition temperatures (°C), enthalpies (kJ mol–1)
in italics and the dimensionless value of ΔS/R in [] for dimers
6a–d.
TBSO
1
Dimer
6a
Cr
N
Iso
1.
7Br,
Et
2O
Mg,
Br(CH2)
2. Et
2O
165
222
•
•
•
65.25[17.91]
1.82[0.44]
OH OH
6b
146
67.05[19,2]
205
1.91[0.48]
•
•
•
•
•
•
•
•
•
6c(a)
6d
155
50.94[14.30]
227
2.42[0.58]
7
TBSO
TBSO
2
OTBS
OTBS
170
62.10[16.84]
220
1.49[0.36]
Jones
acetone
reagent,
Cr–Cr transition at 137 °C, ∆H = 10.28 kJ mol–1; N, nematic phase; Iso,
isotropic liquid.
(a)
O
O
O
7
3
TBAF,
THF, H
2O
O
7
4
HO
OH
DMAP, Et3N
CH2Cl2
RCOCl
5a-d
O
O
O
O
7
Figure 2. Schlieren and marbled textures characteristic for
the nematic phase obtained on cooling at 186 °C for (a) 6a,
(b) 6b, (c) 6c and (d) 6d.
R
R
O
=
O
6
O
O
O
decreases both clearing and melting temperatures
resulting in the wide range nematogen material. Fluoro-
substitution in the meta position (6d), lowers the clearing
point further but increases the melting temperature for 10
°C. However, on cooling, it crystalizes at even lower
temperature than parent BNC-72 and yet does not show
the NTB phase. Despite several studies on the laterally
fluorinated bimesogens suggested that the position of
fluoro-substituent is not critical for the formation of the NTB
phase,[38–40] non-of the prepared dimers exhibit the NTB
phase. Since a fluoro-substituent is not very different in size
as compared to the hydrogen it replaces, its effect on the
overall shape is negligible. However, the high polarity of the
fluoro-substituent and its position within the mesogenic
core, cause the changes in conformational distribution.
This affects the efficiency of molecular packing and
6a
6b
R
O
F
F
6c
6d
Scheme 1. Synthesis of naphthyl-based diketones 6a–d.
curvature and the incompatibility of propargyloxy terminal
chains and the aliphatic spacer.
As expected, the inclusion of a lateral fluoro substit-
uent reduces the N-Iso transition temperatures. The
magnitude of the reduction depends on the position of the
lateral fluoro substituent in the outer-ring of the meso-
genic core. Fluoro-substitution in the ortho position (6c)
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transition properties. In perspective, modification can be
employed in tailoring specific electro-optical properties
that might lead to possible technological applications.
EXPERIMENTAL
All the solvents were either puriss p.a. quality or distilled
over appropriate drying reagents. All other reagents were
purchased from commercial sources and used without
purifications. For the chromatographic separations silica
gel (Fluka Analytical, 35–75 μm) was used. Analytical thin-
layer cromatography was performed on silica gel plates
(DC-Alufolien-Kieselgel F254, Sigma Aldrich). Visualization
was carried out under ultra-violet irradiation (254 nm).
NMR spectra were recorded on Bruker AV 600 MHz and 300
MHz spectrometers, operating at 150.92 or 75.47 MHz for
1
13C and 600.13 or 300.13 MHz for H nuclei. The NMR
spectra were taken in CDCl3 or DMSO-d6 at ambient
temperature using TMS as a reference. Multiplets are
abbreviated as follows: br – broad; s – singlet; d – doublet;
t – triplet; q – quartet; m – multiplet. CHN analysis were
done on Perkin Elmer 2400 Series II CHNS analyser. Infrared
spectra were recorded with a Bruker ABB Bomem FTIR
spectrometer. Melting points were determined using an
Electrothermal 9100 apparatus in open capillaries and are
uncorrected. Textures were examined using an Olympus
BX51 polarising microscope equipped with a Linkam TH600
hot stage and PR600 temperature controller and the
Olympus C 5050 ZOOM digital camera. Phase transition
temperatures and corresponding enthalpies were
determined from thermograms recorded on Perkin-Elmer
Diamond DSC, operated at scanning rates of 5 °C min–1.
The compounds 1–4 were prepared following the
procedures described earlier.[34] The NMR spectra of new
compounds are given in Supplementary Information.
Figure 3. (a) Chemical structure and transition temperatures
of BNC-72,[34] (b) marbled texture of the nematic phase, (c)
blocky texture characteristic for the N-NTB phase transition,
(d) plots of the difference in transition temperatures
between newly prepared compounds 6a–d and ethoxy
analogue obtained on cooling.
consequently alter transition properties. These results
show that the mesomorphic behaviour of bent-shaped
dimers can be altered by a small change in molecular
curvature, by the introduction of the incompatible parts,
which obstruct microphase separation, and by the change
in conformational distribution.
General Procedure for the Synthesis of
4-O-Substituted Benzoic Acids 5a-d
CONCLUSION
To a solution of 4-hydroxybenzoic acid (1 equiv.) in absolute
MeOH (40 mL) concentrated sulfuric acid was added (0.1
equiv.). The reaction mixture was heated at reflux for 24 h,
and then cooled to rt. The solvent was removed under
reduced pressure. A saturated aqueous solution of NaHCO3
(40 mL) was added and the aqueous layer was extracted
with diethyl eter (3 × 15 mL). The organic extracts were
dried over anhydrous Na2SO4, filtered, and the solvent was
removed under reduced pressure. Crude ester was
dissolved in acetone (30 mL) and potassium carbonate (1.5
equiv.) and 1-bromoethane (3 equiv.) were added. The
reaction mixture was heated at reflux for 48 h, and then
cooled to rt. The solvent was removed under reduced
pressure and water was added. The aqueous layer was
extracted with CH2Cl2 (3 × 15 mL). The organic extracts were
In the presented study we have reported the synthesis
and mesomorphic properties of novel naphthyl-based
diketones, having variant terminal chains and lateral fluoro-
substitution positioned on the outer-ring of the mesogenic
core. Investigation of mesomorphic properties showed that
all newly prepared materials exhibit a broad temperature
range of the nematic phase with no nematic to NTB
transition being observed. In general, structural modif-
ications, either by changing the type of the terminal chain
or by the introduction of lateral fluoro-atom, result in the
reduction of the clearing temperatures while the melting
temperatures are variable. Overall our study demonstrates
how subtle changes in chemical structure can be used to
tune the efficiency of molecular packing and consequently
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General Procedure for the Synthesis of
Naphthyl-based Diketones 6a-d
dried over anhydrous Na2SO4, filtered, and the solvent was
removed under reduced pressure. The obtained crude
product was then dissolved in 96 % EtOH (35 mL) and
aqueous solution of NaOH (15 mL, 40 %) was added. The
reaction mixture was heated at reflux overnight. Mixture
was cooled, and pH was adjusted to 1 by addition of
concentrated HCl to the reaction mixture. The precipitate
was filtered, washed with water and dried to yield crude
5a–d. The compounds 5a–d were purified by crystallization
from boiling 96 % EtOH.
4-O-substituted benzoic acid 5a–d (5 equiv.) was suspen-
ded in toluene. Oxalyl chloride (6.5 equiv.) and 1 drop of
DMF were added and the reaction mixture was stirred for
1.5 h at room temperature. The solvent was removed
under reduced pressure. The residue was dissolved in
CH2Cl2 (4 mL) and was added dropwise to a cooled mixture
(0 °C) of compound 4 (1 equiv.), Et3N (10 equiv.) and DMAP
(0.15 equiv.) in CH2Cl2 (10 mL). After the addition was
complete, the reaction mixture was stirred at room
temperature for 24 h. The solvent was removed under
reduced pressure. The residue was purified by column
chromatography on silica gel (CH2Cl2/MeOH = 30/1). The
compounds 6a–d were crystallized from acetone/CH2Cl2
(3/1) to give a white solid (69–77 %).
4-PROPOXYBENZOIC ACID (5a)
Prepared according to the general procedure from 4-hydroxy-
benzoic acid (2.00 g) and obtained as a white solid (2.20 g,
85 %).
1H NMR (CDCl3, 600 MHz) δ/ppm: 1.05 (t, J = 7.4 Hz,
3H), 1.81–1.87 (m, 2H), 3.99 (t, J = 6.6 Hz, 3H), 6.94 (d, J =
8.9 Hz, 2H), 8.06 (d, J = 8.9 Hz, 2H); 13C (CDCl3, 151 MHz)
δ/ppm: 10.6, 22.6, 69.9, 114.3, 121.5, 132.5, 163.8, 172.3.
Mp 144–145 °C.
1,9-BIS[6-(4-PROPOXYBENZOYLOXY)NAPHTHALEN-2-YL]-
NONANE-1,9-DIONE (6a)
According to the general procedure, the 4-propoxybenzoyl
chloride was prepared from 4-propoxybenzoic acid 5a (0.25
g, 1.13 mmol), oxalyl chloride (0.13 mL, 1.50 mmol) and
catalytic amount of DMF in toluene (4 mL). In the reaction
with the compound 4 (0.10 g, 0.23 mmol) the product 6a
(0.14 g, 77 %) was obtained as a white solid, phase
transition temperatures (°C): Cr⦁166⦁ N ⦁227⦁ I.
1H NMR (CDCl3, 300 MHz) δ/ppm: 1.07 (t, J = 7.4 Hz,
6H), 1.41–1.53 (m, 6H), 1.75-1.92 (m, 8H), 3.11 (t, J = 7.4 Hz,
4H), 4.02 (t, J = 6.6 Hz, 4H), 7.00 (d, J = 8.9 Hz, 4H), 7.43 (dd,
J = 8.9, 2.3 Hz, 2H), 7.72 (d, J = 2.3 Hz, 2H), 7.87 (d, J = 8.7
Hz, 2H), 8.02 (d, J = 9.0 Hz, 2H), 8.06 (dd, J = 8.7, 1.8 Hz, 2H),
8.18 (d, J = 9.0 Hz, 4H), 8.52 (s, 2H); 13C (CDCl3, 75 MHz)
δ/ppm: 10.4, 22.5, 24.4, 29.2, 29.4, 38.6, 69.8, 114.4, 118.8,
121.2, 122.5, 124.7, 128.2, 129.4, 130.5, 131.1, 132.4,
134.3, 136.2, 150.7, 163.7, 164.9, 200.3. IR (KBr) ṽmax/cm–1:
2936, 1726, 1680, 1609, 1512, 1474, 1248, 1168, 1071, 766.
Anal. Calcd. mass fractions of elements, w/%, for C49H48O8
(Mr = 764.923) are: C 76.94, H 6.33, found: C 76.59, H 6.27.
4-(PROP-2-YN-1-YLOXY)BENZOIC ACID (5b)
Prepared according to the general procedure from 4-hydroxy-
benzoic acid (2.00 g) and obtained as a white solid (2.13 g,
82 %).
1H NMR (DMSO-d6, 300 MHz) δ/ppm: 3.61 (t, J = 2.4
Hz, 1H), 4.88 (d, J = 2.4 Hz, 2H), 7.07 (d, J = 8.9 Hz, 3H), 7.90
(d, J = 9.0 Hz, 3H), 12.67 (bs, 1H); 13C (DMSO-d6, 75 MHz)
δ/ppm: 55.6, 78.7, 78.8, 114.7, 123.7, 131.3, 160.7, 166.9.
Mp 215–217 °C.
4-ETOXY-2-FLUOROBENZOIC ACID (5c)
Prepared according to the general procedure from 4-hydroxy-
2-fluorobenzoic acid (2.22 g) and obtained as a white solid
(2.31 g, 88 %).
1H NMR (DMSO-d6, 600 MHz) δ/ppm: 1.32 (t, J = 7.0
Hz, 3H), 4.10 (q, J = 6.7 Hz, 2H), 6.80–6.87 (m 2H), 7.80 (t, J
= 8.7 Hz, 1H), 12.83 (bs, 1H); 13C (DMSO-d6, 151 MHz)
δ/ppm: 14.3, 64.1, 102.7 (2JCF = 25.8 Hz), 110.9 (4JCF = 2.9
Hz), 111.0, 133.3 (4JCF = 2.9 Hz), 162.8 (1JCF = 257.4 Hz, C–F),
163.4 (3JCF = 11.5 Hz), 164.7 (3JCF = 3.7 Hz). Mp 187–189 °C.
1,9-BIS[6-(4-PROP-2-YN-1-YLOXY)BENZOYLOXY)-
NAPHTHALEN-2-YL]NONANE-1,9-DIONE (6b)
According to the general procedure, the 4-(prop-2-yn-1-
yloxy)benzoyl chloride was prepared from 4-(prop-2-yn-1-
yloxy)benzoic acid 5b (0.21 g, 1.15 mmol), oxalyl chloride
(0.13 mL, 1.50 mmol) and catalytic amount of DMF in
toluene (4 mL). In the reaction with the compound 4 (0.10
g, 0.23 mmol) the product 6b (0.13 g, 77 %) was obtained
as a white solid, phase transition temperatures (°C):
Cr⦁145⦁ N ⦁211⦁ I.
1H NMR (CDCl3, 300 MHz) δ/ppm: 1.40–1.52 (m, 6H),
1.76–1.89 (m, 4H), 2.58 (t, J = 2.4 Hz, 2H), 3.11 (t, J = 7.4 Hz,
4H), 4.80 (d, J = 2.4 Hz, 4H), 7.09 (d, J = 8.9 Hz, 4H), 7.42 (dd,
J = 8.9, 2.3 Hz, 2H), 7.72 (d, J = 2.3 Hz, 2H), 7.87 (d, J = 8.7
4-ETOXY-3-FLUOROBENZOIC ACID (5d)
Prepared according to the general procedure from 4-hydroxy-
3-fluorobenzoic acid (2.20 g) and obtained as a white solid
(1.50 g, 57 %).
1H NMR (DMSO-d6, 300 MHz) δ/ppm: 1.36 (t, J = 7.0
Hz, 3H), 4.18 (q, J = 7.0 Hz, 2H), 7.24 (t, J = 8.6 Hz, 1H), 7.66
(dd, J = 11.9, 2.0 Hz, 1H), 7.74 (ddd, J = 8.6, 2.0, 0.9 Hz, 1H);
13C (DMSO-d6, 75 MHz) δ/ppm: 14.4, 64.6, 114.1, 116.5,
123.2 (3JCF = 6.0 Hz), 126.8 (3JCF = 3.2 Hz), 150.3 (2JCF = 10.4
Hz), 150.9 (1JCF = 244.6 Hz, C–F), 166.2 (4JCF = 2.5 Hz). Mp
193–195 °C.
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A. BULJAN et al.: Mesomorphic Bent-shaped Naphthyl Diketones
Hz, 2H), 8.02 (d, J = 8.9 Hz, 2H), 8.06 (dd, J = 8.6, 1.7 Hz, 2H),
8.22 (d, J = 8.9 Hz, 4H), 8.49 (s, 2H); 13C NMR (CDCl3, 75
MHz) δ/ppm: 24.5, 29.4, 29.5, 38.8, 56.1, 76.4, 114.9,
118.9, 122.5, 122.6, 124.9, 128.3, 129.5, 130.7, 131.2,
132.5, 134.4, 136.3, 150.8, 162.0, 164.8, 200.4, CH-alkynyl
not visible. IR (KBr) ṽmax/cm–1: 3286, 2936, 2123, 1726,
1680, 1609, 1512, 1474, 1248, 1168, 1071, 766. Anal. Calcd.
mass fractions of elements, w/%, for C49H40O8 (Mr =
756.859) are: C 77.76, H 5.33; found: C 76.77, H 5.40.
151 MHz) δ/ppm: 14.7, 24.6, 29.4, 29.5, 38.8, 65.2, 113.59
(4JCF = 1.9 Hz), 118.02 (2JCF = 20.1 Hz), 118.8, 121.78 (3JCF
=
6.5 Hz), 122.3, 124.9, 127.64 (3JCF = 3.3 Hz), 128.3, 129.5,
130.7, 131.3, 134.5, 136.3, 150.6, 152.0 (1JCF = 247.3 Hz, C–
F), 152.1 (2JCF = 10.7 Hz), 164.1, 200.3. IR (KBr) ṽmax/cm–1:
2936, 1726, 1680, 1609, 1512, 1474, 1248, 1168, 1071,
766. Anal. Calcd. mass fractions of elements, w/%, for
C47H42F2O8 (Mr = 772.853) are: C 73.04, H 5.48; found: C
73.08, H 5.87.
1,9-BIS[6-(4-ETOXY-2-FLUOROBENZOYLOXY)NAPHTHALEN-
2-YL]NONANE-1,9-DIONE (6c)
Acknowledgment. The authors thank the Croatian Science
Foundation (grant ref. IP-2014-09-1525) for financial
support.
According to the general procedure, the 4-etoxy-2-
fluorobenzoyl chloride was prepared from 4-etoxy-2-
fluorobenzoyl acid 5c (0.20 g, 1.15 mmol), oxalyl chloride
(0.13 mL, 1.50 mmol) and catalytic amount of DMF in
toluene (4 mL). In the reaction with the compound 4 (0.10
g, 0.23 mmol) the product 6c (0.14 g, 77 %) was obtained
as a white solid, phase transition temperatures (°C):
Cr⦁139⦁ Cr ⦁157⦁ N ⦁232⦁ I.
Supplementary Information. Supporting information to the
paper is attached to the electronic version of the article at:
https://doi.org/10.5562/cca3541.
PDF files with attached documents are best viewed with Adobe Acrobat
Reader which is free and can be downloaded from Adobe's web site.
1H NMR (CDCl3, 300 MHz) δ/ppm: 1.41–1.55 (m,
12H), 1.76–1.92 (m, 4H), 3.10 (t, J = 7.4 Hz, 4H), 4.12 (q, J =
7.0 Hz, 4H), 6.70 (dd, J = 12.7, 2.4 Hz, 2H), 6.79 (dd, J = 8.9,
2.4 Hz, 2H), 7.43 (dd, J = 8.9, 2.3 Hz, 2H), 7.74 (d, J = 2.3 Hz,
2H), 7.87 (d, J = 8.7 Hz, 2H), 8.01 (d, J = 9.0 Hz, 2H), 8.03–
8.13 (m, 4H), 8.51 (s, 2H); 13C NMR (CDCl3, 75 MHz) δ/ppm:
14.7, 24.6, 29.4, 29.5, 38.8, 64.5, 103.1 (2JCF = 25.6 Hz),
109.8 (2JCF = 9.7 Hz), 111.1 (3JCF = 2.8 Hz), 118.9, 122.5,
124.8, 128.3, 129.5, 130.7, 131.2, 134.0 (4JCF = 2.3 Hz),
134.5, 136.3, 150.5, 162.5 (2JCF = 9.0 Hz), 164.2 (1JCF = 256.9
Hz, C–F), 164.9 (3JCF = 11.7 Hz), 200.4. IR (KBr) ṽmax/cm–1:
2936, 1726, 1680, 1609, 1512, 1474,1248, 1168, 1071, 766.
Anal. Calcd. mass fractions of elements, w/%, for
C47H42F2O8 (Mr = 772.853) are: C 73.04, H 5.48; found: C
72.93, H 5.69.
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