[F:1][C:2]1[CH:7]=[C:6]([C:8]2[C:9]([CH2:17][CH2:18][CH3:19])=[N:10][N:11]3[CH:16]=[CH:15][CH:14]=[CH:13][C:12]=23)[CH:5]=[CH:4][N:3]=1.C([Li])CCC.C(Cl)(Cl)(Cl)[Cl:26]>O1CCCC1>[Cl:26][C:16]1[N:11]2[N:10]=[C:9]([CH2:17][CH2:18][CH3:19])[C:8]([C:6]3[CH:5]=[CH:4][N:3]=[C:2]([F:1])[CH:7]=3)=[C:12]2[CH:13]=[CH:14][CH:15]=1A solution of 3-(2-fluoropyridin-4-yl)-2-propylpyrazolo[1,5-a]pyridine (109 mg, 0.42 mmol) in tetrahydrofuran (5 mL) was cooled to −78° C. Butyllithium (0.4 mL, 1.6 M in hexane, 0.64 mmol) was added dropwise and the resultant solution was stirred at −78° C. for 45 minutes. Carbon tetrachloride (0.3 mL) was added and the mixture was stirred at −78° C. for 30 minutes and then quenched byt the addition of methanol while cold. Upon warming to room temperature water and ether were added and the layers separated. The organic layer was washed with brine. The aqueous layer was extracted with ether and the combined organics were dried over magnesium sulfate. Filtration and concentration followed flash chromatography on silica gel (4:1 to 2:1 hexane-ethyl acetate) provided 7-chloro-3-(2-fluoropyridin-4-yl)-2-propylpyrazolo[1,5-a]pyridine (77 mg, 63%) as an orange solid. 1H NMR (CDCl3) δ 8.33 (d, 1H), 7.58 (d, 1H), 7.30 (m, 1H), 7.22 (t, 1H), 7.02–6.98 (m, 2H), 2.99 (t (m, 2H), 1.01 (t, 3H); 19F NMR (CDCl3) δ −68.11; MS m/z 290 (M+1).
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