To a stirred (30 min) solution of 1-[3-(methyloxy)-4-nitrophenyl]piperazine (3.52 g, 14.9 mmol), 1-Boc-4-piperidone (5.96 g, 29.9 mmol), HOAc (24.0 mL, 1M in DCM, 24.0 mmol) and TEA (2.00 mL, 14.3 mmol) in 1,2-DCE was added in one portion sodium triacetoxyborohydride (4.82 g, 22.7 mmol). The reaction was stirred for 30 min at which time sodium triacetoxyborohydride (2.00 g, 9.40 mmol) and HOAc (10.0 mL, 1M in DCM, 10.0 mmol) was added. The reaction was stirred at rt overnight. The reaction was quenched with saturated NaHCO3 (150 mL) and extracted with DCM. The organic layer was washed with H2O, dried (MgSO4) and concentrated. Purification by flash chromatography provided the title compound of step C (6.09 g, 14.5 mmol, 97%). 1H NMR (400 MHz, DMSO-d6) δ ppm 1.20-1.32 (m, 2H), 1.37 (s, 9H), 1.74 (d, J=10.6 Hz, 2H), 2.41 (tt, J=11.0, 3.2 Hz, 1H), 2.55-2.62 (m, 4H), 2.70 (br. s., 2H), 3.36-3.44 (m, 4H), 3.88 (s, 3H), 3.94 (d, J=13.2 Hz, 2H), 6.50 (d, J=2.6 Hz, 1H), 6.57 (dd, J=9.5, 2.6 Hz, 1H), 7.86 (d, J=9.2 Hz, 1H).
