[Br:1][C:2]1[CH:3]=[N:4][N:5]2[CH:10]=[CH:9][C:8]([CH2:11][CH3:12])=[CH:7][C:6]=12.C1C(=O)N([Br:20])C(=O)C1.C(OOC(=O)C1C=CC=CC=1)(=O)C1C=CC=CC=1.O>C(Cl)(Cl)(Cl)Cl>[Br:1][C:2]1[CH:3]=[N:4][N:5]2[CH:10]=[CH:9][C:8]([CH:11]([Br:20])[CH3:12])=[CH:7][C:6]=12To a stirred solution of 3-bromo-5-ethylpyrazolo[1,5-a]pyridine (I-17, 2.1 g, 0.0094 mmol) in CCl4 (20 mL) at rt was added NBS (2 g, 0.01 mmol) followed by benzoyl peroxide (1.1 g, 0.004 mmol). The resulting reaction mixture was heated to 77° C. After 2 h, the reaction mixture was allowed to cool to rt and subsequently water (20 mL) was added followed by extraction with dichloromethane (2×20 mL). The combined organic layers were washed with water (1×20 mL), sat NaHCO3 solution (1×10 mL), brine (1×10 mL), dried over Na2SO4 and the solvent was removed under reduced pressure. The resulting crude product was purified by column chromatography over silica gel (petroleum ether/EtOAc, 0-5% EtOAc) to afford 820 mg (29%) of 3-bromo-5-(1-bromoethyl)pyrazolo[1,5-a]pyridine (I-18) as a brown solid. 1H NMR (400 MHz, CDCl3) δ 8.45 (d, J=7.91 Hz, 1H), 7.93 (s, 1H), 7.46 (d, J=1.32 Hz, 1H), 6.90-6.92 (dd, J=1.76, 5.71 Hz, 1H), 5.19-5.24 (m, 2H), 2.08 (d, J=7.04 Hz, 3H); ESI-LC/MS (m/z): [M+H]+ 302.9, [(M+2)+H]+ 304.9, [(M+4)+H]+ 306.9, RT 2.65 min
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