[CH3:1][C:2]1[CH:10]=[C:5]2[CH:6]=[CH:7][CH:8]=[CH:9][N:4]2[N:3]=1.C([Li])CCC.[Br:16]C(Cl)(Cl)C(Br)(Cl)Cl.[Cl-].[NH4+]>O1CCCC1.C(OCC)(=O)C.O>[Br:16][C:9]1[N:4]2[N:3]=[C:2]([CH3:1])[CH:10]=[C:5]2[CH:6]=[CH:7][CH:8]=1
To a solution of 2-methylpyrazolo[1,5-a]pyridine (Reference; Chem. Pharm. Bull., 1983, 31, 4568–5572) (1.0 g) dissolved in tetrahydrofuran (20 mL) was added n-butyllithium (2.66 M hexane solution; 3.7 mL) dropwise at −78° C. under a nitrogen stream, and the reaction mixture was stirred for 30 minutes. To the reaction mixture was added a solution of 1,2-dibromo-1,1,2,2-tetrachloroethane (2.7 g) in tetrahydrofuran (5 mL) dropwise, and stirring was continued for 30 minutes. After adding saturated aqueous ammonium chloride to the obtained reaction mixture, the temperature was raised to room temperature, water was added to the reaction mixture and extraction was performed with ethyl acetate. The organic extract was separated, then washed with brine, dried over anhydrous magnesium sulfate and filtered. The solvent was evaporated under reduced pressure, the residue was purified by silica gel column chromatography and the title compound (1.34 g) was obtained as a yellow oil from the n-hexane:ethyl acetate (10:1) fraction.
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