Synthesis of Schiff bases and oxazolidines from 2-amino-4-phenylthiazole

Article abstract of DOI:10.1134/S107042800812018X

Reactions of 2-amino-4-phenylthiazole with aromatic aldehydes gave the corresponding Schiff bases which were reduced with sodium tetrahydridoborate to amines. Reactions of the Schiff bases with 2-methyloxirane, 2- chloromethyloxirane, and 2-phenoxymethylo

Full text of DOI:10.1134/S107042800812018X

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 12, pp. 1821–1823. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © S.E. Sadigova, A.M. Magerramov, M.A. Allakhverdiev, 2008, published in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 12,
pp. 1848–1850.
Synthesis of Schiff Bases and Oxazolidines
from 2-Amino-4-phenylthiazole
S. E. Sadigova, A. M. Magerramov, and M. A. Allakhverdiev
Baku State University, ul. Z. Khalilova 23, Baku, Az1048, Azerbaidjan
e-mail: s_sevinj@mail.ru
Received October 23, 2007
Abstract—Reactions of 2-amino-4-phenylthiazole with aromatic aldehydes gave the corresponding Schiff
bases which were reduced with sodium tetrahydridoborate to amines. Reactions of the Schiff bases with
2-methyloxirane, 2-chloromethyloxirane, and 2-phenoxymethyloxirane led to the formation of 2,5-disubstituted
3-(4-phenylthiazol-2-yl)oxazolidines.
DOI: 10.1134/S107042800812018X
Schiff bases derived from 2-amino-4-arylthiazoles
[1] are important for analytical chemistry and chemo-
therapy [2–4]. In particular, these compounds are used
for the concentration and photometric determination of
some transition metals. It is known that reactions of
various amines with aldehydes give rise to a new C=N
bond. We synthesized Schiff bases I–III by reaction of
2-amino-4-phenylthiazole with benzaldehyde, salicyl-
aldehyde, and 2-hydroxynaphthalene-1-carbaldehyde
(Scheme 1). Schiff bases II and III were reduced with
sodium tetrahydridoborate under mild conditions to
2-(2-hydroxybenzylamino)- and 2-(2-hydroxynaphtha-
len-1-ylmethylamino)-4-phenylthiazoles IV and V, re-
spectively, and compounds IV and V were converted
into the corresponding hydrochlorides VI and VII by
treatment with hydrogen chloride (Scheme 2).
The IR spectra of Schiff bases I–III resembled
those of initial 2-amino-4-phenylthiazole with the dif-
ference that a broad band appeared at about 3450 cm–1
in the spectra of II and III due to OH group involved
in intramolecular hydrogen bond with the N=CH frag-
ment. No absorption typical of primary amino group
was observed. The OH proton signal appeared in the
1H NMR spectra of II and III at δ 3.25 ppm, and the
N=CH proton resonated in the region δ 7.85–7.90 ppm.
Four nonequivalent protons in the 2-hydroxyphenyl
fragment of II gave a multiplet at δ 7.2–7.5 ppm.
Scheme 1.
Ph
Ph
N
N
RCHO
–H2O
CHR
NH2
N
S
S
I–III
I, R = Ph; II, R = 2-HOC6H4; III, R = 2-HOC10H6.
The UV spectra of Schiff bases II and III sharply
differed from those of their hydrogenated derivatives
IV and V. Compound II displayed absorption maxima
at λ 208 and 278 nm due to electron transitions in the
aromatic ring, and the long-wave absorption maximum
(λ 385 nm) was assigned to π–π* transition in the con-
jugated azomethine fragment. No band in the region of
λ 385 nm was present in the UV spectrum of IV.
Insofar as the benzene rings in molecule IV are not
conjugated, the spectrum of IV contained two maxima
at λ 260 and 282 nm instead of one maximum at
λ 278 nm as in the spectrum of II; these maxima are
likely to belong to the 4-phenyl and hydroxyphenyl
rings, respectively.
Scheme 2.
Ph
Ph
NaBH4
N
N
CHR
HCl
CH2R
N
N
S
S
H
II, III
IV, V
Ph
N
CH2R
N
S
·HCl
H
VI, VII
II, IV, VI, R = 2-HOC6H4; III, V, VII, R = 2-HOC10H6.
1821

SADIGOVA et al.
1822
Scheme 3.
Ph
Ph
N
HCl
N
·HCl
N
N
S
S
HO
III
HO
VIII
2-(2-Hydroxynaphthalen-1-ylmethylideneamino)-4-
phenylthiazole (III) was converted into hydrochloride
VIII (Scheme 3). Schiff bases I–III reacted with
2-methyloxirane, 2-chloromethyloxirane, and 2-phen-
oxymethyloxirane in carbon tetrachloride in the pres-
ence of SnCl4 to give 2,5-disubstituted 3-(4-phenyl-
thiazol-2-yl)oxazolidines IX–XIII (Scheme 4).
2-(4-Phenyl-1,3-thiazol-2-yliminomethyl)phenol
(II) was synthesized in a similar way. Yield 11.21 g
(86%), mp 143°C. Found, %: C 68.76; H 4.13; N 9.74;
S 11.28. C16H12N2OS. Calculated, %: C 68.55; H 4.32;
N 9.99; S 11.44.
1-(4-Phenyl-1,3-thiazol-2-yliminomethyl)naph-
thalen-2-ol (III). A solution of 4.4 g (0.025 mol) of
2-amino-4-phenylthiazole in 15 ml of ethanol was
added to 4.3 g (0.025 mol) of 2-hydroxynaphthalene-1-
carbaldehyde in 12 ml of ethanol, and the mixture was
stirred for 3 h at 75°C. After cooling to room tempera-
ture, the precipitate was filtered off. Yield 5.1 g (74%),
mp 156–157°C. Found, %: C 72.52; H 4.43; N 8.78;
S 9.51. C20H14N2OS. Calculated, %: C 72.70; H 4.30;
N 8.50; S 9.70.
Scheme 4.
Ph
R'
N
+
CHR
O
N
S
I–III
R'
Ph
N
O
2-(4-Phenyl-1,3-thiazol-2-ylaminomethyl)phenol
(IV). Compound II, 5.6 g (0.02 mol), was dispersed in
30 ml of ethanol under stirring at 30–40°C, sodium
tetrahydridoborate was added until the mixture turned
white, and the mixture was stirred for 30 min, diluted
with 100 ml of water, and acidified to pH 7.5. The
colorless precipitate was filtered off and recrystallized
from benzene. Yield 3.9 g (70%), mp 155°C. Found,
%: C 67.93; H 5.14; N 9.86; S 11.49. C16H14N2OS.
Calculated, %: C 68.06; H 5.00; N 9.92; S 11.36.
N
S
R
IX–XIII
IX, R = 2-HOC10H6, R′ = Me; X, R = Ph, R′ = ClCH2; XI, R =
2-HOC10H6, R′ = ClCH2; XII, R = 2-HOC6H4, R′ = PhOCH2;
XIII, R = 2-HOC10H6, R′ = PhOCH2.
EXPERIMENTAL
The IR spectra (700–3700 cm–1) were recorded on
a Specord 75IR spectrometer from samples prepared as
1-(4-Phenyl-1,3-thiazol-2-ylaminomethyl)naph-
thalen-2-ol (V) was synthesized in a similar way.
Yield 4.5 g (68%), mp 171–172°C. Found, %: C 72.41;
H 4.63; N 8.27; S 9.79. C20H16N2OS. Calculated, %:
C 72.26; H 4.85; N 8.43; S 9.65.
1
thin films or dispersed in mineral oil. The H NMR
spectra were measured from solutions in DMSO-d6 on
a Varian VXR-400S spectrometer (400 MHz) relative
to TMS as internal reference. Analytical thin-layer
chromatography was performed on Silufol UV-254
plates using propan-2-ol–heptane (1:1) as eluent; spots
were visualized by treatment with iodine vapor.
2-(4-Phenyl-1,3-thiazol-2-ylaminomethyl)phenol
hydrochloride (VI). Dry hydrogen chloride was
passed through a solution of 2.8 g (0.01 mol) of com-
pound IV in isopropyl alcohol cooled to 0°C. The
colorless precipitate was filtered off, washed with
several portions of anhydrous diethyl ether, and recrys-
tallized from ethanol. Yield 3.0 g (93%), mp 177–
178°C. Found, %: C 60.35; H 4.57; N 8.92; S 10.26.
C16H15ClN2OS. Calculated, %: C 60.28; H 4.74;
N 8.79; S 10.06.
N-Benzylidene-4-phenyl-1,3-thiazol-2-amine (I).
A mixture of 5.3 g (0.05 mol) of benzaldehyde and
8.8 g (0.05 mol) of 2-amino-4-phenylthiazole was vig-
orously stirred for 30 min and poured into 15 ml of
ethanol. After several minutes, the colorless crystalline
product was filtered off. Yield 9.4 g (71%), mp 155–
156°C, Rf 0.74. Found, %: C 72.61; H 4.73; N 10.75;
S 12.02. C16H12N2S. Calculated, %: C 72.80; H 4.58;
N 10.60; S 12.12.
Compounds VII and VIII were obtained in a simi-
lar way.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 12 2008

SYNTHESIS OF SCHIFF BASES AND OXAZOLIDINES
1823
1-(4-Phenyl-1,3-thiazol-2-ylaminomethyl)naph-
thalen-2-ol hydrochloride (VII). Yield 3.3 g (90%),
mp 193–194°C. Found, %: C 65.47; H 4.53; N 7.68;
S 8.37. C20H17ClN2OS. Calculated, %: C 65.12; H 4.65;
N 7.59; S 8.69.
Found, %: C 65.13; H 4.72; N 6.47; S 7.79.
C23H19ClN2O2S. Calculated, %: C 65.32; H 4.53;
N 6.62; S 7.58.
2-[5-Phenoxymethyl-3-(4-phenyl-1,3-thiazol-2-
yl)oxazolidin-2-yl]phenol (XII). A solution of 0.23 ml
(0.002 mol) of tin(IV) chloride in 5 ml of carbon tetra-
chloride was added dropwise over a period of 1 h to
a solution of 3.3 ml (0.022 mol) of 2-phenoxymethyl-
oxirane and 5.6 g (0.02 mol) of Schiff base II in 8 ml
of carbon tetrachloride. The organic phase was dried
over Na2SO4. Yield 5.76 g (67%), mp 128–129°C.
Found, %: C 69.56; H 5.37; N 6.42; S 7.66.
C25H22N2O3S. Calculated, %: C 69.74; H 5.15; N 6.51;
S 7.45.
1-(4-Phenyl-1,3-thiazol-2-yliminomethyl)naph-
thalen-2-ol hydrochloride (VIII). Yield 0.5 g (72%),
mp 115°C. Found, %: C 65.13; H 4.32; N 7.46; S 8.81.
C20H15ClN2OS. Calculated, %: C 65.48; H 4.12;
N 7.64; S 8.74.
1-[5-Methyl-3-(4-phenyl-1,3-thiazol-2-yl)oxazoli-
din-2-yl]naphthalen-2-ol (IX). A solution of 0.23 ml
(0.002 mol) of tin(IV) chloride in 2.4 ml of carbon
tetrachloride was added dropwise over a period of 1 h
to a solution of 1.69 ml (0.022 mol) of 2-methyl-
oxirane and 3.3 g (0.01 mol) of Schiff base III in 4 ml
of carbon tetrachloride. The organic phase was dried
over Na2SO4. Yield 2.52 g (65%), mp 85–86°C. Found,
%: C 71.26; H 5.32; N 7.43; S 8.03. C23H20N2O2S.
Calculated, %: C 71.11; H 5.19; N 7.21; S 8.25.
1-[5-Phenoxymethyl-3-(4-phenyl-1,3-thiazol-2-
yl)oxazolidin-2-yl]naphthalen-2-ol (XIII) was syn-
thesized in a similar way. Yield 6.9 g (72%), mp 171–
172°C. Found, %: C 72.31; H 5.18; N 5.97; S 6.79.
C29H24N2O3S. Calculated, %: C 72.48; H 5.03; N 5.83;
S 6.67.
5-Chloromethyl-2-phenyl-3-(4-phenyl-1,3-thia-
zol-2-yl)oxazolidine (X). A solution of 0.23 ml
(0.002 mol) of tin(IV) chloride in 5 ml of carbon tetra-
chloride was added dropwise over a period of 1 h to
a solution of 1.69 ml (0.022 mol) of 2-chloromethyl-
oxirane and 5.60 g (0.02 mol) of Schiff base I in 8 ml
of carbon tetrachloride. The organic phase was dried
over Na2SO4. Yield 5.2 g (75%), mp 78–79°C. Found,
%: C 63.72; H 4.96; N 7.68; S 8.66. C19H17ClN2OS.
Calculated, %: C 63.95; H 4.80; N 7.85; S 8.99.
REFERENCES
1. Sadigova, S.E., Magerramov, A.M., Allakhverdiev, M.A.,
Alieva, R.A., Chyragov, F.M., and Vekilova, T.M., Russ.
J. Gen. Chem., 2003, vol. 73, p. 1932.
2. Samus’, N.M., Mel’nik, S.V., and Tsapkov, V.I., Russ. J.
Gen. Chem., 2000, vol. 70, p. 281.
3. Aptekar’, M.D., Traplika, E., and Savich, I.A.,
Zh. Obshch. Khim., 1972, vol. 42, p. 2555.
1-[5-Chloromethyl-3-(4-phenyl-1,3-thiazol-2-yl)-
oxazolidin-2-yl]naphthalen-2-ol (XI) was synthe-
sized in a similar way. Yield 5.92 g (70%), mp 106°C.
4. Samus’, N.M., Nauzat Al’-Nabgali, Shlyakhov, E.N.,
and Tsapkov, V.I., Khim.-Farm. Zh., 1991, vol. 25,
no. 3, p. 37.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 12 2008