A solution of 4-(3-(dimethylamino)propyl)-3,4-dihydro-2H-benzo[b][1,4]thiazin-7-amine (0.22 g, 0.875 mmol) in dry ethanol (10 mL) was treated with methyl thiophene-2-carbimidothioate hydroiodide (0.499 g, 1.750 mmol) at room temperature, and the resulting mixture was stirred over night (18 hours) at room temperature. The reaction was diluted with saturated NaHCO3 solution (25 mL), and the product was extracted into CH2Cl2 (3×20 mL). The combined CH2Cl2 layers were washed with brine (15 mL) and dried (Na2SO4). The solvent was evaporated, and the crude material was purified by column chromatography (5:95 (2M NH3 in MeOH):CH2Cl2) on silica gel to obtain the title product 22 (0.27 g, 86%) as a solid. 1H NMR (DMSO-d6) δ 7.68 (d, 1H, J=3.0 Hz), 7.56 (d, 1H, J=5.1 Hz), 7.06 (dd, 1H, J=3.9, 4.8 Hz), 6.69 (d, 1H, J=8.7 Hz), 6.52-6.45 (m, 2H), 6.33 (brs, 2H), 3.51-3.48 (m, 2H), 3.25 (t, 2H, J=7.2 Hz), 3.04-3.01 (m, 2H), 2.25 (t, 2H, J=6.9 Hz), 2.14 (s, 6H), 1.70-1.61 (m, 2H); ESI-MS (m/z, %): 361 (MH+, 93), 276 (100); HPLC purity: 98.23% by area.
