F[C:2]1[C:7]([F:8])=[CH:6][C:5]([F:9])=[C:4]([F:10])[N:3]=1.[C:11]([N:18]1[CH2:23][CH2:22][NH:21][CH2:20][CH2:19]1)([O:13][C:14]([CH3:17])([CH3:16])[CH3:15])=[O:12].C(N(CC)C(C)C)(C)C.O>CN1C(=O)CCC1>[C:14]([O:13][C:11]([N:18]1[CH2:23][CH2:22][N:21]([C:2]2[C:7]([F:8])=[CH:6][C:5]([F:9])=[C:4]([F:10])[N:3]=2)[CH2:20][CH2:19]1)=[O:12])([CH3:17])([CH3:15])[CH3:16]A mixture of 2,3,5,6-tetrafluoropyridine (755 mg, 5 mmol, Aldrich), 1-Boc-piperazine (558 mg, 3 mmol, Aldrich) and N,N-diisopropylethylamine (1 mL, 5.8 mmol, Aldrich) in NMP (5 mL) was heated at 150° C. for 16 h. The reaction mixture was cooled to room temperature, water (25 mL) was added, and the mixture was extracted with EtOAc (2×40 mL). The combined organic phases were washed with brine (50 mL), then dried over Na2SO4 and filtered. The filtrate was concentrated in vacuo and the residue was purified by silica gel column chromatography, eluting with 20% EtOAc/hexane to give the title compound as a white solid. MS (ESI, pos. ion) m/z: 318 (M+1).
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