A 10 mL screw cap vial equipped with a magnetic stir bar was charged with triphosgene (22 mg, 0.233 mmol, 0.35 equiv) and dichloromethane (1 mL) under nitrogen and cooled to 0° C. 1,1,1,3,3,3-Hexafluoroisopropanol (29 uL, 0.23 mmol) was added via syringe over 1 min followed by addition of 2,6-lutidine, (52 uL, 0.44 mmol, 2.1 equiv) over 1 min. The latter addition is exothermic and the internal temperature was maintained below 5° C. during the addition. N,N-dimethylaminopyridine (2 mg, 0.1 equiv) was then added to the reaction mixture. The solution remained colorless and the ice bath was removed. The resulting clear solution was allowed to stir at room temperature for 1 h. A separate 10 mL vial, equipped with a magnetic stir bar, was charged with 4-(3-fluoro-4-(piperazin-1-ylmethyl)phenyl)morpholine (59.1 mg, 0.212 mmol) and dichloromethane (1 mL). The chloroformate solution was re-cooled to 0° C. and the amine solution was added to the chloroformate solution over 1 min via syringe. The amine-containing flask was rinsed with dichloromethane (0.25 mL) and the rinsing solution was added to the reaction flask. The ice bath was removed and the clear, colorless reaction was stirred at room temperature overnight. Saturated aqueous sodium bicarbonate (1 mL) was added and the layers were separated. The aqueous layer was washed with dichloromethane (1 mL). The organic layers were combined, concentrated and applied to a 40 g silica gel column to afford 1,1,1,3,3,3-hexafluoropropan-2-yl 4-(2-fluoro-4-morpholinobenzyl)piperazine-1-carboxylate, 54 mg (58%). 1H NMR 400 MHz (CDCl3) δ 7.18 (t, J=8.5 Hz, 1H), 6.65 (dd, J=8.5, 2.2 Hz, 1H), 6.56 (dd, J=13.0, 2.2 Hz, 1H), 5.73 (hep, J=6.2 Hz, 1H), 3.88-3.81 (m, 4H), 3.53 (bs, 6H), 3.18-3.07 (m, 4H), 2.52-2.43 (m, 4H). LCMS (ESI, m/z): 194.1 (4-morpholino-2-fluorobenzyl cation).
