F[C:2]1[CH:12]=[CH:11][C:5]([C:6]([O:8]CC)=[O:7])=[CH:4][C:3]=1[N+:13]([O-:15])=[O:14].[NH:16]1[CH2:21][CH2:20][CH2:19][CH2:18][CH2:17]1.[OH-].[Li+]>CN(C=O)C.O.C1COCC1>[N+:13]([C:3]1[CH:4]=[C:5]([CH:11]=[CH:12][C:2]=1[N:16]1[CH2:21][CH2:20][CH2:19][CH2:18][CH2:17]1)[C:6]([OH:8])=[O:7])([O-:15])=[O:14]A mixture of ethyl 4-fluoro-3-nitrobenzoate (Chontech 01072; 500 mg; 2.35 mmol; 1 eq.) and piperidine (Fluka 80640; 599.18 mg; 7.04 mmol; 3 eq.) in DMF (2 mL) was stirred at 50° C. for 3 hours. The reaction was then allowed to cool to room temperature and diluted with water. Extraction with ethyl acetate, drying over sodium sulfate and concentration in vacuo gave a yellow oil. The oil was taken up in THF (15 mL) and lithium hydroxide (280.86 mg; 11.73 mmol; 5 eq.) was added, followed by water (15 mL). The reaction mixture was then stirred at room temperature for 5 hours. THF was evaporated and the residue diluted with water. The aqueous phase was washed with Et2O and acidified to pH 5 with acetic acid. Extraction with Et2O followed by drying over magnesium sulfate and concentration in vacuo afforded the title compound (562 mg, 96%) as a yellow solid.
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