Imidazo[2,1-b][1,3]thiazoles 4a-e, 6a,b, 7 (general method). A. Sulfuric acid (96%, 3.3 mmol) was
added to a solution of 2-mercaptomidazole (3 mmol) and the corresponding ketone (3.3 mmol) in glacial acetic
acid (10-15 ml) and refluxed for 1-1.5 h. The product was cooled to room temperature and diluted with water (5
ml). The precipitate formed was filtered off, washed with water, dissolved in hot alcohol, and the product was
precipitated using aqueous ammonia (15%). Yield 36-72%.
B. Sulfuric acid (3 mmol) was added to a solution of 2-(1H-imidazol-2-ylthio)-1-(R3-phenyl)ethanone (3
mmol) in glacial acetic acid and refluxed for 20-40 min. The product was cooled to room temperature and
diluted with water (5 ml). The precipitate formed was filtered off, washed with water, dissolved in hot alcohol,
and the product was precipitated using aqueous ammonia (15%). Reaction product yields 41-75%.
1
1-(3-Methyl-6-phenylimidazo[2,1-b][1,3]thiazol-2-yl)ethanone (4a). Mp 191-194°C, yield 68%. H
NMR spectrum, δ, ppm : 2.15 (3H, s, CH3); 2.5 (3H, s, Ac); 7.30-7.55 (5H, m, ArH); 8.20 (1H, s, CH).
2-(4-Chlorophenyl)-5,6,7,8-tetrahydrobenzo[d]imidazo[2,1-b][1,3]thiazole (4b). Mp 180-183 C,
yield 58%. 1H NMR spectrum, δ, ppm (J, Hz): 1.6 (4H, s, 2CH2); 2.65 (4H, m, 2CH2); 7.38 (2H, d, J = 9, ArH);
7.60 (2H, d, J = 9, ArH); 8.18 (1H, s, CH).
7-tert-Butyl-2-(4-chlorophenyl)-5,6,7,8-tetrahydroimidazo[2,1-b][1,3]benzothiazole (4c). Mp 160-163 C,
1
yield 45%. H NMR spectrum, δ, ppm (J, Hz): 0.80 (9H, s, 3CH3); 1.25-1.70 (3H, m, CH2); 2.00-2.20 (1H, m,
CH); 2.30-2.80 (4H, m, 2CH2); 7.40 (2H, d, J = 8, ArH); 7.82 (2H, d, J = 8. ArH); 8.16 (1H, s, CH).
2-(4-Chlorophenyl)-7-methyl-5,6,7,8-tetrahydrobenzo[d]imidazo[2,1-b][1,3]thiazole (4d). Mp 164-
165 C, yield 36%. 1H NMR spectrum, δ, ppm (J, Hz): 1.05 (3H, d, CH3); 1.50 (1H, m, CH); 1.75-2.10 (2H, m, CH2);
2.15-2.35 (1H, m, 1/2CH2); 2.55-2.80 (3H, m, 3/2CH2); 7.40 (2H, d, J = 8, ArH); 7.82 (2H, d, J = 8, ArH); 8.16
(1H, s, CH).
6-(4-Bromophenyl)-3-(4-methylphenyl)imidazo[2,1-b][1,3]thiazole (4e). Mp 216-218°C, yield 55%.
1H NMR spectrum, δ, ppm (J, Hz): 2.25 (3H, s, CH3); 7.18 (1H, s, CH); 7.35 (2H, d, J = 10, ArH); 7.53 (2H, d, J
=8, ArH); 7.70 (2H, d, J = 10, ArH); 7.88 (2H, d, J = 8, ArH); 8.21 (1H, s, CH).
1-(3-Methylbenzo[4,5]imidazo[2,1-b][1,3]thiazol-2-yl)-1-ethanone (6a). Mp 198-200 C, yield 70%.
1H NMR Spectrum, δ, ppm (J, Hz): 2.60 (3H, s, Ac); 3.10 (3H, s, CH3); 7.34 (2H, m, ArH); 7.69 (1H, d, J = 8
ArH); 8.08 (1H, d, J = 8, ArH).
1-(6-Bromo-3-methylbenzo[4,5]imidazo[2,1-b][1,3]thiazol-2-yl)-1-ethanone (6b) and 1-(7-Bromo-3-
methylbenzo[4,5]imidazo[2,1-b][1,3]thiazol-2-yl-1-ethanone (7). Yield of the mixture 58%. 1H NMR
spectrum, δ, ppm: 2.55 (6H, s, 2Ac); 3.05 (6H, s, 2CH3); 7.45-7.55 (4H, m, ArH); 7.87 (1H, s, ArH); 8.00 (1H, s,
ArH).
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