Methyl chloroformate → Dimethyl 2-(2-fluoro-4-(trifluoromethyl)phenyl)piperidine-1,4-dicarboxylate

Methyl 2-(2-fluoro-4-(trifluoromethyl)phenyl)piperidine-4-carboxylate hydrochloride (5.50 g, 16.09 mmol) was dissolved in DCM (100 mL), then DIPEA (7.03 mL, 40.23 mmol) was added. Methyl carbonochloridate (1.774 mL, 22.53 mmol) was added dropwise to the solution. The mixture was stirred at room temperature for 4 h. The mixture was washed with 0.1 M HCl (100 mL) and satd NaHCO3 (100 mL), then dried through a phase-separator and evaporated yielding dimethyl 2-(2-fluoro-4-(trifluoromethyl)phenyl)piperidine-1,4-dicarboxylate (5.33 g, 91%) as a brown oil.