Cl.[F:2][C:3]1([F:9])[CH2:8][CH2:7][NH:6][CH2:5][CH2:4]1.C(N(CC)CC)C.Cl[C:18]([O:20][C:21]1[CH:26]=[CH:25][C:24]([N+:27]([O-:29])=[O:28])=[CH:23][CH:22]=1)=[O:19]>ClCCl.C(OCC)(=O)C>[F:2][C:3]1([F:9])[CH2:8][CH2:7][N:6]([C:18]([O:20][C:21]2[CH:22]=[CH:23][C:24]([N+:27]([O-:29])=[O:28])=[CH:25][CH:26]=2)=[O:19])[CH2:5][CH2:4]1
To a solution of 4,4-difluoropiperidin hydrochloride (2.15 g, 14 mmol) in 30 mL of dichloromethane was added triethylamine (5.7 ml, 41 mmol), followed by 4-nitrophenyl chloroformate 40 (3.0 g, 15 mmol). After 1 h, the reaction was diluted with ethyl acetate and was washed with 3×30 mL of sat. NaHCO3, and 1×30 mL brine. The organic layer was dried over MgSO4, filtered, and concentrated to afford 4-nitrophenyl 4,4-difluoropiperidin-1-carboxylate 41 (3.9 g, 100% yield). 1H-NMR (400 MHz, CDCl3): δ 8.26 (m, 2H), 7.30 (m, 2H), 3.76 (m, 4H), 2.09 (m, 4H). MS 286.1 (calc'd) 287.1 (M+H, found).
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