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[CH2:20][CH2:19][CH2:18][CH2:17]1.[OH-].[Li+].O>CN(C=O)C.C1COCC1>[N+:13]([C:3]1[CH:4]=[C:5]([CH:11]=[CH:12][C:2]=1[N:16]1[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 pyrrolidine (Fluka 83240; 500.48 mg; 7.04 mmol; 3 eq.) in DMF (2 mL) was stirred at 60° C. for 4 hours. The reaction mixture was then partitioned between ethyl acetate and aq. NH4Cl. The organic layer was washed three times with aq. NH4Cl then brine, dried over magnesium sulfate and concentrated in vacuo to give a yellow oil. The latter was taken up in THF (5 mL) and lithium hydroxide (280.86 mg; 11.73 mmol; 5 eq.) then water (5 mL) were added. The reaction mixture was stirred at room temperature for 16 hours then the THF was evaporated and the residue was diluted with water. After acidification with AcOH, the formed precipitate was filtered and dried under high vacuum to afford the title compound (497 mg, 90%) as a yellow solid.
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