To a solution of 4-fluoro-1-nitro-2-(trifluoromethyl)benzene (5 g, 24 mmol) in DMSO (50 ml) was added tert-butyl 4-aminopiperidine-1-carboxylate (4.78 g, 23.9 mmol, 1 eq.) and potassium carbonate (9.9 g, 72 mmol, 3 eq.). The resulting mixture was stirred with heating overnight at 100° C. (oil bath) and then diluted with water (300 ml). The solids were collected by filtration to afford tert-butyl 4-[[4-nitro-3-(trifluoromethyl)phenyl]amino]piperidine-1-carboxylate as a yellow powder (8 g, 86%); (ES, m/z): [M+H]+ 390.0; 1H NMR (300 MHz, DMSO-d6): δ 8.06 (d, J=9.3 Hz, 1H), 7.47 (d, J=7.8 Hz, 1H), 7.08 (d, J=2.1 Hz, 1H), 6.89 (dd, J=2.4, 9.3 Hz, 1H), 3.87 (d, J=13.5 Hz, 2H), 3.68 (m, 1H), 2.95 (m, 2H), 2.54 (s, 0.6H), 1.89 (m, 2H), 1.39 (s, 9H), 1.28 (m, 2H).
