Potassium Carbonate → 2-(4-Ethyloxycarbonyl-butylsulfanyl)-5-fluoro-benzoimidazole

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A suspension of 5-fluoro-1H-benzoimidazole-2-thiol (168 mg, 1 mmol), 5-bromo-pentanoic acid ethyl ester (188 mg, 0.9 mmol, 145 μl) and K2CO3 (276 mg, 2 mmol) in acetone (2 ml) is refluxed for 3 h. It is cooled down and filtered over a short plug of silica gel and rinsed with AcOEt. The solvent is removed in vacuo. The crude is purified by flash chromatography on silica-gel (AcOEt/heptane, 1:2), yielding the title compound (190 mg) in 64% as a brown oil: tR=1.87 min (LC-2), ESI-MS (pos.): m/z 297.28 [M+H]+, ESI-MS (neg.): m/z 295.30 [M−H]+; 1H-NMR (CDCl3): δ (ppm) 1.25 (t, 3H, CH3), 1.79 (br. t, 4H), 2.36 (br. t, 2H, CH2CO), 3.28 (br. t, 2H, SCH2), 4.14 (q, 2H, CH2O), 6.93 (dt, 1Harom), 7.20 (dd, 1Harom), 7.41 (dd, 1Harom).

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