CYCLIZATION OF 2-AMINO-4-METHYL-3-[2-ARYL(HETARYL)-2-OXOETHYL]...
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3-methyl and 6-aryl(hetaryl) substituents. The IR
spectra contained absorption bands due to bending
vibrations of the heterocyclic fragment in the region
1601–1067 cm–1.
1236, 1092, 995, 815. H NMR spectrum, δ, ppm:
2.11 s (3H, CH3), 2.53 s (3H, SCH3), 5.77 s (2H,
CH2CO), 6.78 s (1H, 5-H), 7.48 d (2H, 3′-H, 5′-H, J =
8.5 Hz), 7.98 d (2H, 2′-H, 6′-H, J = 8.5 Hz), 9.55 br.s
(2H, NH2). Found, %: C 43.48; H 4.25; N 7.76.
C13H15BrN2OS2. Calculated, %: C 43.46; H 4.21;
N 7.80.
Thus, we have proposed a simple “green” proce-
dure for the two-step synthesis of 6-arylimidazo-
[2,1-b]thiazoles in high yields.
2-Amino-3-[2-(4-chlorophenyl)-2-oxoethyl]-
4-methylthiazolium bromide (IIe). Yield 89%,
mp 264–265°C (decomp.). IR spectrum, ν, cm–1: 3140,
3017, 1693 (C=O), 1628, 1557, 1406, 1227, 995, 826.
1H NMR spectrum, δ, ppm: 2.13 s (3H, CH3), 5.78 s
(2H, CH2CO), 6.79 s (1H, 5-H), 7.87 d (2H, 3′-H,
5′-H, J = 8.5 Hz), 8.08 d (2H, 2′-H, 6′-H, J = 8.5 Hz),
9.53 br.s (2H, NH2). Found, %: C 41.43; H 3.51;
N 8.11. C12H12BrClN2OS. Calculated, %: C 41.46;
H 3.48; N 8.06.
2-Amino-4-methyl-3-[2-aryl(hetaryl)-2-oxo-
ethyl]thiazolium bromides IIa–IIh (general proce-
dure). A mixture of 30 mmol of 4-methylthiazol-2-
amine and 30 mmol of α-bromo ketone Ia–Ih in 40 mL
of anhydrous acetone was stirred for 12 h at room
temperature. The precipitate was filtered off, washed
with diethyl ether (2×15 mL), and dried in air.
2-Amino-4-methyl-3-(2-oxo-2-phenylethyl)-
thiazolium bromide (IIa). Yield 92%, mp 210–211°C
(decomp.); published data [15]: mp 216°C. IR spec-
trum, ν, cm–1: 3110, 3014, 1687 (C=O), 1627, 1556,
2-Amino-3-[2-(4-bromophenyl)-2-oxoethyl]-
4-methylthiazolium bromide (IIf). Yield 88%,
mp 258–260°C (decomp.). IR spectrum, ν, cm–1: 3140,
3110, 3016, 1694 (C=O), 1628, 1557, 1408, 1227, 995,
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1404, 1231, 998, 765. H NMR spectrum, δ, ppm:
2.14 s (3H, CH3), 5.82 s (2H, CH2CO), 6.79 s (1H,
5-H), 7.51 t (1H, 4′-H, J = 7.9 Hz), 7.65 t (2H, 3′-H,
5′-H, J = 7.9 Hz), 8.08 d (2H, 2′-H, 6′-H, J = 7.9 Hz),
9.57 br.s (2H, NH2). Found, %: C 45.96; H 4.21;
N 8.99. C12H13BrN2OS. Calculated, %: C 46.02;
H 4.18; N 8.94.
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826. H NMR spectrum, δ, ppm: 2.12 s (3H, CH3),
5.77 s (2H, CH2CO), 6.78 s (1H, 5-H), 7.88 d (2H,
3′-H, 5′-H, J = 8.6 Hz), 7.99 d (2H, 2′-H, 6′-H, J =
8.5 Hz), 9.53 br.s (2H, NH2). Found, %: C 36.74;
H 3.12; N 7.21. C12H12Br2N2OS. Calculated, %:
C 36.76; H 3.08; N 7.14.
2-Amino-4-methyl-3-[2-(4-methylphenyl)-2-oxo-
ethyl]thiazolium bromide (IIb). Yield 96%, mp 254–
256°C (decomp.). IR spectrum, ν, cm–1: 3109, 3013,
1687 (C=O), 1628, 1559, 1408, 1232, 818, 557.
1H NMR spectrum, δ, ppm: 2.11 s (3H, CH3), 2.43 s
(3H, CH3), 5.76 s (2H, CH2CO), 6.78 s (1H, 5-H),
7.45 d (2H, 3′-H, 5′-H, J = 8.6 Hz), 7.97 d (2H, 2′-H,
6′-H, J = 7.9 Hz), 9.53 br.s (2H, NH2). Found, %:
C 47.66; H 4.65; N 8.62. C13H15BrN2OS. Calculated,
%: C 47.71; H 4.60; N 8.56.
2-Amino-4-methyl-3-[2-(3-nitrophenyl)-2-oxo-
ethyl]thiazolium bromide (IIg). Yield 89%, mp 254–
255°C (decomp.). IR spectrum, ν, cm–1: 3116, 3025,
1706 (C=O), 1627, 1556, 1527, 1353, 1223, 1085, 819,
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735. H NMR spectrum, δ, ppm: 2.09 s (3H, CH3),
5.92 s (2H, CH2CO), 6.80 s (1H, 5-H), 7.75 t (1H,
5′-H, J = 7.9 Hz), 8.14–8.16 m (1H, 4′-H), 8.29 d (1H,
6′-H, J = 7.9 Hz), 8.66–8.68 m (1H, 2′-H), 9.59 br.s
(2H, NH2). Found, %: C 40.20; H 3.41; N 11.78.
C12H12BrN3O3S. Calculated, %: C 40.24; H 3.38;
N 11.73.
2-Amino-3-[2-(4-ethoxyphenyl)-2-oxoethyl]-
4-methylthiazolium bromide (IIc). Yield 95%,
mp 211–212°C (decomp.). IR spectrum, ν, cm–1: 3119,
3017, 1681 (C=O), 1630, 1600, 1560, 1408, 1233,
1178, 1040, 919, 840. 1H NMR spectrum, δ, ppm: 1.37 t
(3H, OCH2CH3, J = 7.0 Hz), 2.11 s (3H, CH3), 4.18 q
(2H, OCH2, J = 7.3 Hz), 5.75 s (2H, CH2CO), 6.79 s
(1H, 5-H), 7.15 d (2H, 3′-H, 5′-H, J = 8.5 Hz), 8.03 d
(2H, 2′-H, 6′-H, J = 9.2 Hz), 9.54 br.s (2H, NH2).
Found, %: C 47.01; H 4.83; N 7.87. C14H17BrN2O2S.
Calculated, %: C 47.07; H 4.80; N 7.84.
2-Amino-4-methyl-3-[2-oxo-2-(thiophen-2-yl)-
ethyl]thiazolium bromide (IIh). Yield 91%, mp 232–
234°C (decomp.). IR spectrum, ν, cm–1: 3116, 3025,
1706 (C=O), 1627, 1556, 1527, 1353, 1223, 1085, 819,
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735. H NMR spectrum, δ, ppm: 2.14 s (3H, CH3),
5.73 s (2H, CH2CO), 6.77 s (1H, 5-H), 7.40 t (1H,
5′-H, J = 4.2 Hz), 7.89 d (1H, 4′-H, J = 4.9 Hz), 8.21–
8.19 m (1H, 3′-H), 9.57 br.s (2H, NH2). Found, %:
C 37.58; H 3.51; N 8.81. C10H11BrN2OS2. Calculated,
%: C 37.63; H 3.47; N 8.77.
2-Amino-4-methyl-3-[2-(4-methylsulfanyl-
phenyl)-2-oxoethyl]thiazolium bromide (IId). Yield
91%, mp 204–206°C (decomp.). IR spectrum, ν, cm–1:
3115, 3014, 1683 (C=O), 1631, 1585, 1556, 1405,
3-Alkyl-6-aryl(hetaryl)imidazo[2,1-b]thiazoles
IIIa–IIIh (general procedure). A mixture of 10 mmol
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 12 2014