To a suspension of 3-iodo-1H-indazole-5-carboxaldehyde (200 mg, 0.74 mmol) and 4-pyridineboronic acid (110 mg, 0.89 mmol) in toluene/EtOH (1:1, 8 mL) in a sealed tube was added Na2CO3 (2 N, 1 mL) followed by Pd(PPh3)4 (85 mg, 0.074 mmol). The reaction mixture was put under vacuum, and re-charged with N2 three times, then kept at ca. 100-110° C. for ca. 4-5 hr. The reaction mixture was cooled to rt, diluted with water, and extracted with EtOAc. The organic phase was washed with brine, and dried. Concentration followed by purification by flash chromatography afforded 3-(4-pyridinyl)-1H-indazole-5-carboxaldehyde (106 mg, 64%).
