F[C:2]1[CH:3]=[C:4]([CH:19]=[CH:20][C:21]=1[N+:22]([O-])=O)[CH:5]=[C:6]1[CH2:11][CH2:10][N:9]([C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])[CH2:8][CH2:7]1.N>C(O)C.ClCCl.O.O.O.O.O.O.O.O.S([O-])([O-])(=O)=O.[Fe+2]>[NH2:22][C:21]1[CH:20]=[CH:19][C:4]([CH:5]=[C:6]2[CH2:7][CH2:8][N:9]([C:12]([O:14][C:15]([CH3:16])([CH3:17])[CH3:18])=[O:13])[CH2:10][CH2:11]2)=[CH:3][CH:2]=1tert-Butyl 4-(3-fluoro-4-nitrobenzylidene)piperidine-1-carboxylate (2.97 mmol, 1 g), iron(II) sulfate heptahydrate (20.42 mmol, 5.68 g) and ammonia (10.02 mmol, 11.39 ml) were combined in ethanol (20 mL) and heated at 85° C. overnight. The reaction mixture was diluted with dichloromethane and water then filtered through celite. The organic phase of the filtrate was dried and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (eluting with dichloromethane to 3% methanol/dichloromethane) to afford the intermediate tert-butyl 4-(4-aminobenzylidene)piperidine-1-carboxylate (600 mg).
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