Cl.[F:2][C:3]1[CH:4]=[C:5]([CH:10]2[CH2:15][CH:14]([C:16]([O:18][CH3:19])=[O:17])[CH2:13][CH2:12][NH:11]2)[CH:6]=[CH:7][C:8]=1[F:9].CCN(C(C)C)C(C)C.Cl[C:30]([O:32][CH3:33])=[O:31]>C(Cl)Cl>[F:2][C:3]1[CH:4]=[C:5]([CH:10]2[CH2:15][CH:14]([C:16]([O:18][CH3:19])=[O:17])[CH2:13][CH2:12][N:11]2[C:30]([O:32][CH3:33])=[O:31])[CH:6]=[CH:7][C:8]=1[F:9]Methyl 2-(3,4-difluorophenyl)piperidine-4-carboxylate hydrochloride (6.1 g, 20.91 mmol) and DIPEA (9.13 mL, 52.28 mmol) were dissolved in DCM (30 mL). Methyl chloroformate (1.944 mL, 25.09 mmol) was added and the reaction stirred at room temperature for 1.5 h. DCM (170 mL) was added. The organic phase was washed with 0.1 M HCl (2×200 mL), satd NaHCO3 (200 mL), dried with a phase separator and evaporated in vacuo yielding dimethyl 2-(3,4-difluorophenyl)piperidine-1,4-dicarboxylate (6.58 g, 100%) as a dark oil. MS m/z 314 (M+H)+.
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