A suspension of tert-butyl 4-(6-nitro-2H-benzo[b][1,4]thiazin-4(3H)-yl)piperidine-1-carboxylate (468 mg, 1.233 mmol) and palladium, 10 wt. % on activated carbon (131 mg, 0.123 mmol) in ethanol (10 mL) and tetrahydrofuran (1 mL) was stirred under an atmosphere of hydrogen (balloon pressure) for 2 hours. During this time, the reaction mixture turned colorless. To the mixture was then added methyl thiophene-2-carbimidothioate hydroiodide (528 mg, 1.850 mmol), and the resulting suspension was stirred at room temperature overnight. The mixture was then diluted with ethyl acetate and filtered through a pad of Celite. The filtrate was washed with saturated sodium carbonate (3×). The organic phase was dried, filtered, concentrated, and then chromatographed in 1:5 ethyl acetate:dichloromethane to give the desired product (403 mg, 71.2%). 1H NMR (DMSO-d6) δ 7.72 (d, J=3.0 Hz, 1H), 7.59 (d, J=5.1 Hz, 1H), 7.10-7.06 (m, 1H), 6.86 (d, J=8.1 Hz, 1H), 6.42-6.28 (m, 3H), 6.13 (d, J=8.1 Hz, 1H), 4.06-3.95 (m, 2H), 3.85-3.76 (m, 1H), 3.40-3.33 (m, 2H), 2.99-2.93 (m, 2H), 2.92-2.75 (m, 2H), 1.69-1.48 (m, 4H), 1.39 (s, 9H); ESI-MS (m/z, %): 459 (MH+, 100).
