Synthesis and phase behavior of branched esters derived from cyclohexylbenzoic acid

Article abstract of DOI:10.1134/S1070363211110119

A branched aldehyde on the basis of cyclohexylbenzoates and 3,5-dihydroxybenzoates was synthesized. For the characteristic of intermediates and the target substance TLC, elemental analysis, IR, NMR spectroscopy, and differential scanning calorimetry were

Full text of DOI:10.1134/S1070363211110119

ISSN 1070-3632, Russian Journal of General Chemistry, 2011, Vol. 81, No. 11, pp. 2288–2293. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © U.V. Chervonova, M.S. Gruzdev, A.M. Kolker, 2011, published in Zhurnal Obshchei Khimii, 2011, Vol. 81, No. 11, pp. 1837–1842.
Synthesis and Phase Behavior of Branched Esters Derived
from Cyclohexylbenzoic Acid
U. V. Chervonova, M. S. Gruzdev, and A. M. Kolker
Institute of the Solution Chemistry, Russian Academy of Sciences,
ul. Akademicheskaya 1, Ivanovo, 153045 Russia
e-mail: uch@isc-ras.ru
Received October 10, 2010
Abstract—A branched aldehyde on the basis of cyclohexylbenzoates and 3,5-dihydroxybenzoates was
synthesized. For the characteristic of intermediates and the target substance TLC, elemental analysis, IR, NMR
spectroscopy, and differential scanning calorimetry were used. It was found that at the increase in length and
branching degree of aldehyde the final product acquires the tendency to transfer to the glassy state.
DOI: 10.1134/S1070363211110119
Branched molecules are widely used in dendrimer
chemistry [1, 2]. On their basis the macromolecules
with the controlled structure and properties can be
synthesized [3, 4] that permits to carry out
microsegregation of final products with the formation
of regular structures and giving the molecules
spherical or the disk-like form [5, 6]. As a rule for this
purpose the derivatives of gallic acid containing the
long-chain aliphatic radicals (C10H21, C12H25, C18H37)
are used. For the regular branching of the 1:3 type [7]
the scheme of double increase in the dimensions of
molecule is used taking 3,5-dihydroxybenzyl alcohol
and its derivatives [8,9] as the branching center.
Compounds of mixed nature containing cyclohexyl
and aromatic fragment permit to give final products the
new properties [10] which can not be acquired by the
products constructed on the basis of classic approach
using mono, di-, and trialkoxybenzoic acids. Due to
that it presents interest to prepare aldehyde derived
from cyclohexylbenzoic acid with the 1:2 branching on
the basis of 3,5-dihydroxybenzoic acid. Such
compounds, the derivatives of mono- and trialkoxy-
benzoates, are used for preparing of rare earth metal
complexes with the luminescence and magnetic
properties [11–13].
For the subsequent branching of the target aldehyde
3,5-dihydroxybenzoic acid was chosen. The hydroxyl
group location is sterically favorable for the further
growth of molecules, and the carboxyl group can be
easily exposed to chemical modifying. It permits to
introduce benzyl fragment with the purpose of
protecting the carboxyl group while preparing the
branched molecule. Branching is achieved by forma-
tion of esterial groups. Protecting group is easily
introduced in the molecule and easily removed from it
without any alterations in the structure of the
compound formed. Protected function is stable in
presence of large number of reagents used for further
transformations.
It was already mentioned previously that benzyl
3,5-dihydroxybenzoate can be used for the formation
and removing protecting fragment in the course of
synthesis of benzophenone fragments of medicinal
remedies [14].
Benzyl 3,5-dihydroxybenzoate by itself can be the
center of subsequent branching due to formation of
esterial bonds between its hydroxyl groups and the
carboxyl groups of any other reagents. It can be also
the protecting block in the course of subsequent
branching and chain elongation (Scheme 2).
In the course of synthesis of 3,5-di(4-cyclo-
hexylbenzoyl)oxybenzoyl-4-oxy-2-hydroxybenzaldehyde
IV according to the scheme 1 the intermediates were
prepared and studied.
Benzyl 3,5-dihydroxybenzoate I was prepared by
us by means of alkylation of carboxyl group of 3,5-
dihydroxybenzoic acid with benzyl bromide in dry
2288

SYNTHESIS AND PHASE BEHAVIOR OF BRANCHED ESTERS
2289
CH2Br
HO
HO
HO
O
O
Na2CO3, DMF
12 h, 25oC
O
H2
C
+
OH
HO
I
O
Dicyclohexylcarbodiimide,
Dimethylaminopyridine
СH2Сl2
H
O
25oC, 12 h
O
H2
C
OH
O
O
H
2
O
O
H
II
O
O
H
H
1,4-Dioxane,
40oC
O
OH
5% Pd/C, H2,10 atm
O
O
III
Dicyclohexylcarbodiimide,
Dimethylaminopyridine
СHСl3
O
O
H
H
25oC, 24 h
O
O
O
O
HO
OH
O
O
H
OH
OH
IV
Scheme 1. Synthesis of 3,5-di[(4-cyclohexylbenzoyl)oxybenzoyl]-4-oxy-2-hydroxybenzaldehyde IV.
DMF. This compound was used further for the
synthesis of branched benzyl 3,5-(cyclohexylbenzoyl-
oxy)benzoate II. Removing of protecting group as
toluene (debenzylation by hydrogenolysis) yielded free
acid III. Esterification of the obtained 3,5-di(4-
cyclohexylbenzoyl)oxybenzoic acid III with p-hyd-
roxysalicylic aldehyde permitted to prepare the
aldehyde IV.
carboxylic acids and toluene. Using of palladium
catalyst for debenzylation in hydrogen medium gives
good result, but this method is comparatively
expensive and technologically complicated because it
needs palladium salts, hydrogen of high purity, and the
reactor with regulated pressure. That is why for
removing the protective group we have tried to use the
procedures reported by the workers [16–18]. Hence,
for the case of 4-hydroxy-3-methoxyhydrocynnamic
acid debenzylation accompanied by hydrogenation of
the olefin double bond by treating with the HCl–
Benzyl carboxylates are splitt with hydrogen on a
palladium catalyst to form the corresponding
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 11 2011

2290
CHERVONOVA et al.
above-described proposal is confirmed also by the
Тm 135.22°С
behavior of sample in the second heating. At the
repeated heating from the glass-like state (Tg 17.38°C)
the substance crystallizes at Tcr 78.39°C and melts
subsequently at 135.22°C.
Compound II (Fig. 2) melts at 105.16°C with the
subsequent vitrification at about 21.51°C on cooling.
At the subsequent heating of the sample no glass-
crystal transfer is observed. Phase behavior of the
compound III is analogous to II with melting point
215.62°C and vitrification point ~65.51°C. Aldehyde
IV is the hard white powder. Despite of that it
demonstrates interesting phase behavior in the cycles
of heating and cooling (Fig. 3).
Тg 17.38°С
Тg 17.70°С
Тcr 78.39°С
Тcr 68.89°С
Т, °С
Fig. 1. Differential scanning calorimetry curves of benzyl
3,5-dihydroxybenzoate I in the cycles of heating and
cooling. (1) Second heading and (2) first cooling.
In the first cycle of heating and cooling compound
IV begins to crystallize at ~2.95°C with the subsequent
malting at 64.91°C. Note that this compound does not
remain in a melt, but transforms to the vitrified state at
168.34°C at the increase in temperature [19]. In the
cycle of cooling the substance under study undergoes
vitrification at 66.79°C giving the glass-glass transfer.
In the second cycle of heating the aldehyde IV reveals
only vitrification at 73.76°C. Such phase behavior can
be explained probably by formation of intramolecular
hydrogen bonds between the proton of hydroxyl group
and the aldehyde group in the salicylic aldehyde
fragment [20], and also by interaction of cyclohexane
fragments.
CH3COOH mixture was reported about [16]. In our
case no reaction was observed even under the
prolonged refluxing. Removing of benzyl group in a
form of toluene by treating macrocycle esters with zinc
powder and hydrochloric acid was described by the
workers [17], but in the case of compound II this
system occurred to be ineffective. Traditional
hydrolysis of carboxylate by heating it in ethanolic
KOH solution [18] was unsuccessful. Hence, using of
Pd/H2 system was the only suitable method for
debenzylation of benzyl carboxylates in our case.
Phase behavior of compounds I–IV was studied by
means of the differential scanning calorimetry. For the
compound I (Fig. 1) its melting point was found to be
136.02°C. Note that while cooling the sample no
crystallization was observed. Compound I remains in a
glass-like state and demonstrates the melt–glass
transfer unusual for the crystalline organic compounds
(see the table). Such thermal behavior of compound
can be explained by formation of stable intermolecular
hydrogen bonds due to the interaction of the hydroxyl
group protons of the 3,5-disubstituted aromatic ring. In
the IR spectrum of this substance broad intense band in
the range of the OH group vibrations is present. The
EXPERIMENTAL
All the reagents and solvents were of “chemically
pure” grade. They were used without the additional
purification. IR spectra of compounds were recorded
on a Bruker Vertex 80V device in the ranges 7500–
370 cm–1 and 670–190 cm–1 in KBr and CsBr pellets.
13
1H NMR (500.17 MHz) and C NMR (125.78 MHz)
spectra were taken on a Bruker Avance-500 spec-
trometer. Elemental analysis of crystalline substances
was carried out on a FlashEA 1112 analyzer.
Differential scanning calorimetry measurements were
carried out on a NETZCH DSC 204 F1 device in the
aluminum capsules. Mass of the batch ~10 mg, heating
rate 10°C/min. Operations were performed under the
nitrogen atmosphere. TLC was carried out on the
PolyGRAM and Sil G/UV 254 plates, elution with
chloroform. Chromatograms were developed by the
UV irradiation at 254 nm.
1
HO
2
O
H2
C
O
HO
Benzyl 3,4-dihydroxybenzoate (I). Freshly
distilled benzyl bromide (25.33 ml) was mixed with
Scheme 2. Benzyl 3,5-dihydroxybenzoate I.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 11 2011

SYNTHESIS AND PHASE BEHAVIOR OF BRANCHED ESTERS
2291
Temperatures of phase transfers according to the differential scanning calorimetry data
Vitrification
ΔСeq, J g–1 K–1
Crystallizatio
Melting
Comp. no.
Tg, °C
Тcr, °C
–ΔHcr, J g–1
Тm, °C
ΔHm, J g–1
Heating
17.38
–
0.48
–
78.39
61.16
–
135.22
105.16
215.62
64.91
121.70
I
–
54.22
85.77
0.19
II
72.06
158.34
0.21
0.17
–
–
III
IV
–2.95
0.92
Cooling
17.70
21.51
65.51
66.79
0.41
0.23
0.23
0.16
68.89
5.71
–
–
–
–
–
I
–
–
–
–
–
–
–
–
–
II
III
IV
the solution of 3,5-dihydroxybenzoic acid (30 g) in dry
DMF, and the batch of anhydrous Na2CO3 (20.64 g)
was added to it. The mixture obtained was stirred for
12 h at room temperature under nitrogen. After that
resulting brown solution was poured in 200 ml of
distilled water and extracted with diethyl ether (5×
25 ml). Combined organic fractions were washed with
water (3×25 ml), then with brine (20 ml), dried over
the anhydrous Na2SO4 and concentrated in a vacuum.
Solid residue was purified by crystallization from 1:6
dichloromethane-hexane mixture to give white
crystals. Yield 42.49 g (89.3%), mp 135–136°C. IR
spectrum, ν, cm–1: 3387 s (OH group vibrations),
3028–3094 s (aromatic C–H), 2957 s (aliphatic CH2),
1699 s (C=O), 1613 s (esterial –COO–), 1003 (flat
deformational CH-vibrations of monosubstituted
aromatic ring), 851 (1,3,5-substituted aromatic ring,
1
non-planar deformational C–H vibrations). H NMR
spectrum [(CD3)2CO, TMS], δ, ppm: 5.33 s, (2H,
CH2), 6.61 s (1H, Ph–H), 7.06 s (2H, Ph–H), 7.41 m
13
(5H, Ph–H), 8.94 s (2H, Ph–OH). C NMR spectrum
[(CD3)2CO, TMS], δC, ppm: 67.02 (–CH2–), 108.78
(CHarom, C4,C6), 128.87 (CHarom, C12), 129.23 (CHarom
,
C11, C13, C19, C14), 132.90 (CHarom, C9, C2), 137.27
Тm 105.16°С
Тm 64.91°С
Тg 158.34°С
Тcr –2.95°С
Тg 73.76°С
Тg 66.79°С
3
Тg 21.51°С
Т, °С
Т, °С
Fig. 2. Differential scanning calorimetry curves of benzyl
3,5-dicyclohexylbenzoyloxybenzoate in the cycles of
heating and cooling. (1) First heading and (2) first cooling.
Fig. 3. Differential scanning calorimetry curves of the
compound IV in the cycles of heating and cooling. (1) First
heading, (2) second heating, and (3) first cooling.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 11 2011

2292
CHERVONOVA et al.
(CHarom, C5), 159.56 (CHarom, C1, C3), 166.76 (C=O).
Calculated, %: C 68.85, H 4.95, O 26.20. C14H12O4.
Found, %: C 66.487, H 4.359, O 23.769.
formation of white crystals. Yield 0.7 g (70.1%), mp
216.26°C. IR spectrum, ν, cm–1: 3461 w (OH bond
vibrations), 3090 w (C–H aromatic bond vibrations),
2923–2650, 2599 s (CH2 vibrations), 1742–1695 s
(C=O vibrations), 1609 a ( esterial –COO vibrations),
1256 s (asymmetric bond C–O–C vibrations), 1132 s
(flat deformational C–H vibrations of the 1,4-
disubstituted aromatic ring), 1057 s (flat deformational
C–H vibrations of the 1,3,5-trisubstituted aromatic
ring), 1016, 753–704 (m, cyclohexane –CH2– vibra-
tions). 1H NMR spectrum (CDCl3, TMS), δ, ppm: 1.22
d (2H, H-cyclohexyl), 1.38 m (8H, CH22,6-cyclohexyl),
Benzyl
3,5-di(4-cyclohexylbenzoyl)oxybenzoic
acid (II). Batches of cyclohexylbenzoic acid (4 g), of
compound I (2.39 g), and of dicyclohexylcarbodiimide
(3.26 g) were dissolved in 100 ml of methylene
chloride and stirred for 30 min. After that the catalytic
amount of dimethylaminopyridine was added and the
reaction mixture was stirred for 12 h. The urea formed
was filtered off on a glass filter, and solvent was
removed on a rotor evaporator. Dry yellow residue was
chromatographed on silica gel, elution with chloro-
form. The target product is yellow oil crystallizing
from 2:1 acetonitrile-chloroform mixture. Yield 3.73 g
(30.88%), mp 105.16°C. IR spectrum, ν, cm–1: 3096–
3004 s (bond vibrations of the aromatic ring hydrogen
atoms), 2924–2853 s (CH-aliphatic), 1742–1718 s
(C=O vibrations), 1605 s (esterial –COO– vibrations),
1262–1218 s (asymmetric bond C–O–C vibrations),
1016–997 (–CH2– vibrations of cyclohexane). 1H
NMR spectrum (CDCl3, TMS), δ, ppm: 1.42 m (8H,
CH22,6-cyclohexyl), 1.88 m (8H, CH23,5-cyclohexyl),
4
1.82 m (8H, CH23,5-cyclohexyl), 2.54 m (4H, CH2 -
cyclohexyl), 7.19 d (2H, Ph–H2,6), 7.37 s (2H, Ph–H4),
13
7.82 d (4H, Ph–H3,5), 8.04 d (4H, Ph–H2,6). C NMR
spectrum (CDCl3, TMS), δC, ppm: 25.85 (CH2-cyclohexyl
C18, C31), 26.91 (CH2-cyclohexyl, C19, C17, C32, C30), 34.29
(CH2-cyclohexyl, C20, C16, C33, C29), 44.93 (CH2-cyclohexyl
,
,
C15, C28), 121.06 (CHarom, C5), 121.57 (CHarom, C7, C3,
C14, C10, C27, C23), 126.37 (CHarom, C13, C11, C26, C24),
127.26 (CHarom, C9, C22), 130.54 (CHarom, C2), 151.46
(CHarom, C12, C25), 154.75 (CHarom, C6, C4), 164.56
(C=O, C8, C21), 169.90 (C=O C1). Calculated, %: C
75.26, H 18.23, O 5.51. C33H34O8. Found, %: C
75.512, H 6.907, O 18.26.
4
2.1 m (4H, CH2 -cyclohexyl), 5.36 s (2H, CH2), 7.33 d
(4H, H2,5–Ph), 7.36 s (2H, H4,4'–Ph), 7.38 m (2H, H2,6-
Ph), 7.42 d (2H, H2,6-Ph), 7.83 m (2H, H3,5-Ph), 8.09 d
(4H3,5–Ph). 13C NMR spectrum (CDCl3,TMS), δC,
ppm: 25.95 (CH2-cyclohexyl, C25, C38), 26.33 (CH2-cyclohexyl
C26, C24, C39, C37), 33.97 (CH2-cyclohexyl,C27, C23, C40,
C36), 44.60 (CH2-cyclohexyl, C22, C35), 67.20 (CH2),
120.51 (CHarom C12), 120.75 (CHarom, C14, C10, C21,C34,
C30), 126.33(CHarom,C16, C29), 127.14 (CHarom, C20, C18,
C33,C31), 128.31 (CHarom, C2, C6), 128.57 (CHarom, C4),
130.32 (CHarom,C3, C5), 132.23 (CHarom,C9), 151.23
(CHarom, C13, C11) 154.55 (CHarom, C19, C32), 164.52
(C=O, C8, C15, C28). Calculated, %: C 77.90, H 6.54, O
15.57. C40H38O6. Found, %: C 75.432, H 7.725, O
15.545.
3,5-Di[(4-cyclohexylbenzoyloxy)benzoyl]-4-oxy-
2-hydroxybenzaldehyde (IV). The batches of 4-
hydroxysalicylic aldehyde, 0.47 g, of compound III,
1.8 g, and of dicyclohexylcarbodiimide, 1.92 g, were
dissolved in 100 ml of chloroform during 30 min under
stirring. After that the catalytic amount of dimethyl-
aminopyridine was added, and the reaction mixture
was stirred for 24 h. Precipitated urea was filtered off
on a glass filter, solvent was removed on a rotor
evaporator, and dry yellow residue was chromato-
graphed on silica gel, elution with chloroform. The
product, yellow oil, was crystallized from 10:1 aceto-
nitrile–chloroform mixture. White powder, 0.96 g
(43.37%) was obtained, mp 226°C. IR spectrum, ν,
cm–1: 3423 s (O–H bond vibrations), 2925 w (C–H
bond vibrations of the aromatic rings), 2846, 2679-
2534 w (CH2-vibrations), 1729 s (Ar-COO vibrations),
1613 s (vibrations of the aromatic ring), 1388 s
(vibrations of the aromatic aldehyde group), 1264 s
(asymmetric bond C–O–C vibrations), 1131 s (flat
deformational C–H vibrations of the 1,4-disubstituted
aromatic ring), 1073 s (flat deformational C–H
vibrations of the 1,3,5-trisubstituted aromatic ring),
3,5-Di(4-cyclohexylbenzoyloxy)benzoic acid (III).
The calculated amount of catalyst, 5% Pd/C (0.36 g),
was mixed with dioxane in a steel hydrogenation
reactor and activated with hydrogen. After that a
solution of 1 g of compound II in 100 ml of dioxane
was added, and the reaction mixture was stirred at 40°C
under hydrogen (10 ta) until the necessary amount of
hydrogen, 16.2 mmol, was consumed. The reaction
mixture was twice filtered through a glass filter, and
solvent was removed on a rotor evaporator. The
residue was crystallized from the 1:6 dioxane-hexane
mixture. The solution was left on air until the
1
998 w (CH2 vibrations in cyclohexane). H NMR
spectrum, (CDCl3, TMS), δ, ppm: 1.25 d (2H, H-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 11 2011

SYNTHESIS AND PHASE BEHAVIOR OF BRANCHED ESTERS
2293
cyclohexyl), 1.42 m (8H, CH22,6-cyclohexyl), 1.91 m
Angew. Chem., Int. Ed. Engl., 1990, vol. 29, p. 138.
8. Tully, D.C., Wilder, K., Frechet, J.M.J., Trimble, A.R.,
4
(8H, CH23,5-cyclohexyl), 2.60
m
(4H, CH2 -
cyclohexyl), 6.89 d (2H, Ph–H2,6), 7.44 s (2H, Ph–H4),
7.87 d (4H, Ph–H3,5), 8.10 d (4H, Ph–H2,6), 9.88 s (1H,
CHO), 11.27 s (1H, Ph-OH). 13C NMR spectrum
(CDCl3, TMS), δC, ppm: 25.85 (CH2-cyclohexyl, C25, C38),
26.77 (CH2-cyclohexyl, C26, C24, C39, C37), 34.23(CH2-
cyclohexyl, C27, C23, C40, C36), 44.94 (CH2-cyclohexyl, C22,
C31), 120.98 (CHarom, C6, C4), 121.20 (CHarom, C12),
126.35 (CHarom, C13, C11), 127.00 (CHarom, C21, C17,
C34, C30), 127.21 (CHarom,C20, C18, C33, C31), 130.50
(CHarom, C9, C16, C29), 131.65 (CHarom, C7), 151.43
(CHarom, C19, C32), 154.67 (CHarom, C5), 164.90 (C=O,
C15, C28), 169.76 (C=O, C8), 171.87 (CHarom, C14, C10),
195.57 (CHO). Calculated, %: C 74.29; H 5.92, O
16.79. C40H38O8. Found, %: C 75.03, H 7.16, O 18.9.
and Quate, C.F., Adv. Mater., 1999, vol. 11, no. 4, p. 314.
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11. Galyametdinov, Yu., Athanassopoulou, M.A., Griesar, K.,
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ACKNOWLEDGMENTS
13. Barbera, J., Cavero, E., Lehmann, M., Serrano, J.-L.,
Sierra, T., and Vasquez, J.T., J. Am. Chem. Soc., 2003,
vol. 125, p. 4527.
The work was carried out with the financial support
of grant of President of Russian Federation no MK-
1625.2009.3 and of Russian Fundation for Basic
Research (grant no. 08-03-00513).
14. Denieul, M.P., Laursen, B., Hazell, R., and Skrydstrup, T.,
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