New schiff bases derived from 2,5-dihydroxybenzaldehyde and amino-substituted 2-phenyl-1,3-benzothiazoles. Mesogenic monomers for liquid crystalline polyethers

Full text of DOI:10.1134/S1070428011100307

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2011, Vol. 47, No. 10, pp. 1604–1605. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.V. Chernienko, Yu.N. Nikiforova, L.I. Rudaya, S.M. Ramsh, V.V. Shamanin, 2011, published in Zhurnal Organicheskoi Khimii,
2011, Vol. 47, No. 10, p. 1574.
SHORT
COMMUNICATIONS
New Schiff Bases Derived from 2,5-Dihydroxybenzaldehyde
and Amino-Substituted 2-Phenyl-1,3-benzothiazoles. Mesogenic
Monomers for Liquid Crystalline Polyethers
A. V. Chernienkoa, Yu. N. Nikiforovaa, L. I. Rudayaa, S. M. Ramsha, and V. V. Shamaninb
a St. Petersburg State Institute of Technology, Moskovskii pr. 26, St. Petersburg, 190013 Russia
e-mail: 9241890@mail.ru
b Institute of High-Molecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia
Received December 10, 2010
DOI: 10.1134/S1070428011100307
(7.2 mmol) of 2,5-dihydroxybenzaldehyde (I) in 40 ml
of methanol containing 0.02 ml of concentrated hydro-
chloric acid was added dropwise to a solution of 1.6 g
(7.2 mmol) of compound II in 90 ml of methanol. The
mixture was stirred for 5 h at 50°C, and the precipitate
was filtered off, washed, and dried. Yield 1.58 g
(63%), mp 237–240°C (from propan-2-ol), Rf 0.86. IR
Condensation of 2,5-dihydroxybenzaldehyde (I)
with amino-substituted 2-phenyl-1,3-benzothiazoles II
and III in methanol in the presence of HCl gave new
Schiff bases IV and V which can be used as mesogenic
heteroaromatic monomers for the synthesis of poten-
tially mesogenic rigid–flexible polyethers.
1
spectrum (KBr): ν 1621 cm–1 (CH=N). H NMR spec-
OH
trum (DMSO-d6), δ, ppm: 6.80 d (1H, CH, J = 8.0 Hz),
7.45 t (1H, CH, J = 7.8 Hz), 7.48 d (1H, Harom, J =
8.8 Hz), 7.60–7.68 m (4H, Harom), 7.85 d (1H, CH, J =
8.8 Hz), 7.89 s (1H, CH), 8.20 d (2H, CH, J = 7.0 Hz),
9.05 s (1H, HC=N), 10.48 s (1H, OH), 12.9 s (1H,
OH). 13C NMR spectrum (DMSO-d6), δC, ppm: 117.4
(CH), 118.3 (C), 119.5 (CH), 120.2 (CH), 121.8 (CH),
121.9 (CH), 122.4 (CH), 122.9 (CH), 125.6 (CH),
126.3 (CH), 128.5 (CH), 128.8 (CH), 133.8 (C), 134.6
(C), 149.8 (C), 151.2 (C), 153.3 (COH), 153.7 (COH),
163.9 (CH=N), 166.7 (C). Found, %: C 69.66; H 4.20;
N 8.38. C20H14N2O2S. Calculated, %: C 69.39; H 4.05;
N 8.09.
S
N
N
HO
IV
HO
S
N
N
OH
V
4-(1,3-Benzothiazol-2-yl)aniline (II) was synthe-
sized by condensation of 2-aminobenzenethiol with
4-aminobenzoic acid in 112% polyphosphoric acid at
145°C [1], and 2-phenyl-1,3-benzothiazol-5-amine
(III) was obtained by condensation of 2,4-diamino-
benzenethiol with benzoic acid under analogous condi-
tions [1]. 2,4-Diaminobenzenethiol was prepared by
reduction of 2,2′,4,4′-tetranitrodiphenyl disulfide [2]
with tin(II) chloride in hydrochloric acid according to
the procedure described in [3].
2-{(E)-[(2-Phenyl-1,3-benzothiazol-5-yl)imino]-
methyl}benzene-1,4-diol (V) was synthesized in
a similar way from amine III. Yield 2.08 g (83%),
mp 228–230°C (from propan-2-ol), Rf 0.84. IR spec-
1
trum (KBr): ν 1618 cm–1 (CH=N). H NMR spectrum
(DMSO-d6), δ, ppm: 6.98 d (1H, CH, J = 8.0 Hz),
7.43 t (1H, CH, J = 7.8 Hz), 7.49 d (1H, Harom, J =
8.8 Hz), 7.62–7.68 m (4H, Harom), 7.84 d (1H, CH, J =
8.8 Hz), 7.88 s (1H, CH), 8.20 d (2H, CH, J = 7.0 Hz),
9.03 s (1H, HC=N), 10.18 s (1H, OH), 13.01 s (1H,
OH). 13C NMR spectrum (DMSO-d6), δC, ppm: 116.6
2-{(E)-[4-(1,3-Benzothiazol-2-yl)phenylimino]-
methyl}benzene-1,4-diol (IV). A solution of 1.0 g
1604

NEW SCHIFF BASES DERIVED FROM 2,5-DIHYDROXYBENZALDEHYDE
1605
(CH), 117.4 (CH), 119.2 (C), 119.4 (CH), 120.2 (CH),
120.4 (CH), 125.6 (CH), 127.4 (CH), 129.4 (CH),
129.6 (CH), 132.2 (CH), 132.6 (CH), 133.3 (C), 142.5
(C), 145.7 (C), 149.2 (C), 151.2 (COH), 153.7 (COH),
160.2 (CH=N), 163.7 (C). Found, %: C 65.23; H 4.04;
N 7.60. C20H14N2O2S·H2O. Calculated, %: C 65.93;
H 4.39; N 7.69.
toluene–ethyl acetate (1 : 1) as eluent; spots were
detected by UV irradiation. Compounds IV and V
showed luminescence upon irradiation at λ 365 nm
(Spectroline ENF-260C/FE). The elemental composi-
tions were determined on a Leco CHNS(O)-932
analyzer.
The 13C NMR spectra were recorded on a Bruker
CXP-100 spectrometer at 25 MHz using tetramethyl-
silane as internal reference. The 1H NMR spectra were
measured on a Bruker AC-400 spectrometer relative to
TMS. The IR spectra were obtained on a Shimadzu
FTIR-8400S instrument from samples pelleted with
KBr. The progress of reactions and the purity of prod-
ucts were monitored by TLC on Sorbfil plates using
REFERENCES
1. Preston, J., De Winter, W.F., and Hofferbert, W.L.,
J. Heterocycl. Chem., 1969, vol. 6, p. 119.
2. Lukashevich, V.O. and Sergeeva, M.M., Zh. Obshch.
Khim., 1949, vol. 19, p. 1493.
3. Hodgson, H.H. and Dodgson, D.P., J. Chem. Soc., 1948,
p. 1002.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 10 2011