Reaction SMILES: [NH:1]1[C:5]2[NH:6][CH:7]=[CH:8][C:9](=O)[C:4]=2[CH:3]=[N:2]1.P(Cl)(Cl)(Cl)(Cl)[Cl:12]>O=P(Cl)(Cl)Cl>[Cl:12][C:9]1[CH:8]=[CH:7][N:6]=[C:5]2[NH:1][N:2]=[CH:3][C:4]=12
Reactant: ClP(Cl)(Cl)(Cl)Cl
Reactant: O=c1cc[nH]c2[nH]ncc12
Solvent: O=P(Cl)(Cl)Cl
Product: Clc1ccnc2[nH]ncc12
Reaction time: 1 h
Yield: 53396.2 %

Procedure:
A solution of 3-styryl-1-(2-triethylsilanyl-ethoxymethyl)-6-trimethylstanny]-1H-indazole (1.0 g, 1.90 mmol), 1-(4-iodo-pyrazolo[3,4-b]pyridin-1-yl)-ethanone (0.56 g, 1.90 mmol), AsPh3 (116 mg, 0.38 mmol), and Pd2 dba3 (87 mg, 0.09 mmol) in degassed dioxane (10 ml) was heated at 110° C. for 3 h. The solution was then diluted with ethyl acetate (50 ml), washed with brine (2×10 ml), dried over MgSO4, and concentrated under reduced pressure. Purification by silica gel chromatography gave Example 52(a) as a white solid (412 mg, 46%). 1H NMR (300 MHz, CDCl3) δ 8.82 (d, 1H, J=5.8 Hz), 8.52 (s, 1H), 8.29 (d, 1H, J=8.2 Hz), 8.05 (s, 1H), 7.73-7.32 (m, 10H), 5.86 (s, 2H), 3.69 (t, 2H, J=8.2 Hz), 0.97 (t, 2H, J=8.2 Hz), 0.03 (s, 9H). A solution of 6-iodo-3-styryl-1-(2-trimethylsilanyl-ethoxymethyl)-1H-indazole (2.90 g, 6.10 mmol), hexamethylditin (2.00 g, 6.12 mmol), and Pd(Ph3)4 (282 mg, 0.24 mmol) in degassed dioxane (10 ml) was heated at 110° C. for 3 h. The solution was then diluted with ethyl acetate (200 ml), washed with brine (2×21 ml), dried over MgSO4, and evaporated under reduced pressure. Purification by silica gel chromatography gave 3-styryl-1-(2-trimethylsilanyl-ethoxymethyl)-6-trimethylstannyl-1H-indazole as a yellow oil (3 g, 96%). 1H NMR (300 MHz, CDCl3) δ 8.02 (d, 1H, J=7.4 Hz), 7.71 (s, 1H), 7.71-7.29 (m, 8H), 5.77 (s, 2H), 3.65 (t, 2H, J=16.3 Hz), 0.95 (t, 2H, J=16.4 Hz), 0.38 (s, 9H), −0.03 (s, 9H). A mixture of 4-chloro-1H-pyrazolo[3,4-b]pyridine (820 mg, 5.30 mmol), sodium iodide (2.4 mg, 16.0 mmol), and acetyl chloride (0.8 ml) in acetonitrile (6 rid) was refluxed 8 h. The mixture was then treated with a 10% aqueous solution of NaCO3 (10 ml), and a 10% aqueous solution of NaHSO3 (10 ml), and held 10 min. The mixture was extracted with ethyl acetate (50 ml), and the organics were washed with brine (10 ml), dried over MgSO4, and evaporated under reduced pressure. Purification by silica gel chromatography gave 12-(5-iodo-pyrazolo[3,4-b]pyridin 1-yl)ethanone as a brown solid (650 mg, 42%). 1H NMR (300 MHz, CDCl3) δ 8.39 (d, 1H, J=5.0 Hz), 8.04 (s, 1H), 7.76 (d, 1H, J=5.0 Hz), 2.88 (s, 3H). 1,7-Dihydro-pyrazolo[3,4-b]pyridin-4-one (1.2 g, 8.8 mmol) (Dorn, H. et al., Prakt. Chem., 324, 557-62 (1982)) in POCl3 (15 ml) at 0° C. was treated with PCl5 (2.5 mg, 0.01 mmol). The solution was allowed to warn to rt over 1 h, then heated to 90°c and held 3 h. The solution was concentrated under reduced pressure, then treated with ice and water (50 ml). The resulting mixture was extracted with ethyl acetate (100 ml), and the organic layer was washed with a saturated aqueous solution of sodium bicarbonate (30 ml). The organic layer was dried over MgSO4, then evaporated under reduced pressure to give 4-chloro-1H-pyrazolo[3,4-b]pyridine as a yellow solid (820 mg, 60%). 1H NMR (300 MHz, CDCl3) δ 8.57 (d, 1H, J=52 Hz), 8.25 (s, 1H), 7.28 (d, 1H, J=5.2 Hz).