[Cl:1][C:2]1[C:10](I)=[C:5]2[CH:6]=[CH:7][CH:8]=[CH:9][N:4]2[N:3]=1.[CH3:12]B(O)O.C(=O)([O-])[O-].[Cs+].[Cs+].C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1>O1CCCC1.C([O-])(=O)C.[Pd+2].C([O-])(=O)C>[Cl:1][C:2]1[C:10]([CH3:12])=[C:5]2[CH:6]=[CH:7][CH:8]=[CH:9][N:4]2[N:3]=1
A mixture of 2-chloro-3-iodopyrazolo[1,5-a]pyridine (27-3; 0.8 g, 2.87 mmol), methyl boronic acid (0.345 g, 5.7 mmol), and cesium carbonate (2.8 g, 8.61 mmol) in tetrahydrofuran (15 mL) was degassed for 10 min. Then triphenylphosphine (0.15 g, 0.574 mmol) and palladium acetate (0.064 g, 0.287 mmol) were added and heated in a sealed tube at 100° C. for 18 h. The reaction mixture was then cooled to room temperature, filtered and concentrated under reduced pressure. Purification of the resulting residue by flash chromatography on silica gel (0-5% ethyl acetate in hexanes) provided 2-chloro-3-methylpyrazolo[1,5-a]pyridine. 1H NMR (400 MHz, DMSO-d6) δ 8.55-8.53 (d, J=8 Hz, 1 H), 7.61-7.59 (d, J=8 Hz, 1 H), 7.25-7.21 (t, J=8 Hz, 1 H), 6.89-6.86 (t, J=8 Hz, 1 H), 2.19 (s, 3 H). MS (M+1): 167.1.
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