Synthesis of 5-chloro-2-(4-tetradecanoyloxybenzylidenamino)benzoxazole

Article abstract of DOI:10.14233/ajchem.2013.13636

A new compound, 5-chloro-2-(4-tetradecanoyloxybenzylideneamino)benzoxazole was synthesized and characterized by IR, NMR and MS analysis.

Full text of DOI:10.14233/ajchem.2013.13636

Asian Journal of Chemistry; Vol. 25, No. 2 (2013), 1175-1176
http://dx.doi.org/10.14233/ajchem.2013.13636
NOTE
Synthesis of 5-Chloro-2-(4-tetradecanoyloxybenzylidenamino)benzoxazole
1,*
1
2
SIE-TIONG HA , KOK-LEEI FOO and S. SREEHARI SASTRY
1Department of Chemical Science, Faculty of Science, Centre for Biodiversity Research, Universiti Tunku Abdul Rahman, Jln Universiti,
Bandar Barat, 31900 Kampar, Perak, Malaysia
2Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar-522 510, India
*Corresponding author: Fax: +60 54661676; E-mail: hast_utar@yahoo.com; hast@utar.edu.my
(Received: 21 February 2012;
Accepted: 31 August 2012)
AJC-12074
A new compound, 5-chloro-2-(4-tetradecanoyloxybenzylideneamino)benzoxazole was synthesized and characterized by IR, NMR and
MS analysis.
Key Words: 5-Chloro-2-(4-tetradecanoyloxybenzylideneamino)benzoxazole, Liquid crystal, Smectic A.
Liquid crystalline materials have many practical applications
in scientific and technological areas, particularly as display
devices, organic light emitting diodes, anisotropic networks,
photoconductors and semiconductor materials1-3. Strong
demand of new liquid crystals (LCs) for applications has led
to the search for numerous mesogens in particular, thermo-
tropic liquid crystals4,5. A great deal of thermotropic liquid
crystals containing heterocyclic units have been synthesized
and interest in such structures is constantly growing6,7. These
heterocyclic structures basically incorporated unsaturated
atoms, such as O, N, S and/or others and the presence of such
electronegative atoms often resulted in a reduced symmetry
for the overall molecules; and a stronger polar induction6.
However, there are relatively rare examples of benzoxazole-
based liquid crystals reported in the literatuere8 and some of
The Schiff base [5-chloro-2-(4-hydroxybenzyliden-amino)-
benzoxazole] formed was recrystallized with ethanol. Then,
5-chloro-2-(4-hydroxybenzylidenamino)benzoxazole (1.36 g,
5 mmol), tetradecanoic acid (1.28 g, 5 mmol) and 4-dimethyl-
aminopyridine (DMAP, 1 mmol, 0.12 g) were dissolved in 40
mL mixture of dichloromethane and dimethyl formamide and
stirred at 0 ºC. N,N'-dicyclohexylcarbodiimide (DCC, 5 mmol,
1.03 g) dissolved in 10 mL of dichloromethane was added
dropwise into the mixture and continuously stirred for 1 h at
0 ºC. The mixture was then filtered and the filtrate was left to
evaporate. The obtained yellow solid was recrystallized using
hexane and ethanol to give 0.72 g (30 %). EI-MS m/z (rel. int.
%): 483 (9) [M+], 272 (100), IR (KBr, νmax, cm-1): 2917, 2850
(C-H aliphatic); 1751 (C=O ester); 1602 (C=N oxazole); 1449
1
(C=C aromatic); H NMR (400 MHz, CDCl3): δ 0.8 (t, 3H,
them are polymer liquid crystals9-12
.
CH3-), 1.2-1.4 (m, 24H, CH3- (CH2)12-), 1.8 (m, 2H, -CH2-
CH2-COO-), 2.6 (t, 2H, -CH2-COO-), 6.8 (s, 1H, Ar-H), 7.3
(d, 1H, Ar-H), 7.4 (d, 1H, Ar-H), 7.7 (d, 1H, Ar-H), 8.1 (d,
1H,Ar-H), 9.8 (s, 1H, -N=CH-), 13C NMR (100 MHz, CDCl3):
δ 14.12 (CH3), 22.69, 24.84, 29.08, 29.24, 29.36, 29.44, 29.59,
29.65, 29.68, 31.92 for methylene carbons (CH3(CH2)12-), 29.63
(-CH2CH2COO-), 34.43 (-CH2COO-), 104.24, 110.56, 111.27,
119.85, 122.524, 125.34, 131.99, 135.85, 145.73, 155.37,
157.72, 163.03, 165.15 for aromatic carbons, 168.87 (CH=N),
171.64 (COO).
In order to further explore benzoxazole as a mesogenic
core in liquid crystals, here, we report the synthesis of new
benzoxazole liquid crystals. The synthetic route for 5-chloro-
2-(4-tetradecanoyloxybenzylidenamino)benzoxazole is illus-
trated in Scheme-I. The structure of title compound was on
the basis of 1H NMR (Fig. 1), 13C NMR, IR and MS spectral
data. The new compound is smectic A type liquid crystal.
Preparation of 5-chloro-2-(4-tetradecanoyloxybenzyl-
idenamino)benzoxazole (CL14BZX): Firstly, a mixture
of 2-amino-5-chlorobenzoxazole (6.72 g, 40 mmol) and 4-
hydroxybenzaldehyde (4.88 g, 40 mmol) in 60 mL
dichloromethane, with added two drops of acetic acid as
catalyst, was refluxed for 3 h with stirring. The mixture was
then filtered and the filtrate was left evaporated to dryness.
1
Spectral interpretations: In H NMR spectrum of
CL14BZX, a sjnglet corresponding to the azomethine proton
(-N=CH-) appeared at δ = 9.8 ppm. This further supported the
fact that condensation reaction between 2-amino-5-chloro-
benzoxazole and 4-hydroxybenzaldehyde has taken place. The

1176 Ha et al.
Asian J. Chem.
10
9
8
7
6
8
4
3
2
1
ppm
1
Fig. 1. H NMR spectrum of 5-chloro-2-(4-tetradecanoyloxybenzylidenamino)benzoxazole
characteristic resonance peak for other aromatic protons were
observed in relatively downfield region at δ = 6.8-8.1 ppm. As
for the aliphatic protons, it appeared at the upfield region at
δ = 0.8-2.6 ppm.
The prominent molecular ion peak at 483 m/z in the mass
spectrum of CL14BZX established its molecular formula as
C28H35N2O3Cl, supporting the proposed structure.
ACKNOWLEDGEMENTS
The authors thank Universiti Tunku Abdul Rahman and
Ministry of Higher Education (MOHE) for the financial
supports via LRGS (UTAR Account No: 4411/H01) and
research facilities.
Cl
O
H
N
O
OH
NH2
+
DCM
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Scheme-I: Synthetic route towards the formation of 5-chloro-2-(4-
tetradecanoyloxybenzylidenamino)benzoxazole
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