To a dry Shlenck tube equipped with a magnetic stir bar was added 3-(1H-indazol-1-yl)phenol 2 (630 mg, 3.0 mmol, 1.0 eq), 9-(4-tert-butylpyridin-2-yl)-2-bromo-9H-carbazole (1365 mg, 3.6 mmol, 1.2 eq), CuI (57 mg, 0.3 mmol, 0.1 eq), picolinic acid (74 mg, 0.6 mmol, 0.2 eq) and K3PO4 (1273 mg, 6.0 mmol, 2.0 eq). The tube was evacuated and backfilled with nitrogen. The evacuation and backfill procedure was repeated another two times. Then solvent DMSO (9 mL) was added under the protection of nitrogen. The mixture was stirred in an oil bath at a temperature of 90-100° C. for 3 days and then cooled down to ambient temperature. Water was added to dissolve the solid. The mixture was extracted with ethyl acetate three times. The combined organic layer was washed with water three time, dried over sodium sulfate, and then filtered. The solvent was removed under reduced pressure, and the residue was purified through column chromatography on silica gel using hexane/ethyl acetate (10:1-5:1) as eluent to obtain the desired product Ligand ON12-tBu as a colorless solid 1378 mg in 90% yield. 1H NMR (DMSO-d6, 400 MHz): δ 1.17 (s, 9H), 7.05-7.08 (m, 1H), 7.13 (dd, J=8.4, 2.0 Hz, 1H), 7.19 (t, J=7.6 Hz, 1H), 7.29 (t, J=7.6 Hz, 1H), 7.34 (dd, J=5.6, 1.2 Hz, 1H), 7.37-7.42 (m, 4H), 7.53-7.54 (m, 2H), 7.57 (s, 1H), 7.73 (d, J=8.0 Hz, 1H), 7.78 (d, J=8.8 Hz, 1H), 7.81 (d, J=8.4 Hz, 1H), 8.18 (d, J=7.6 Hz, 1H), 8.25 (d, J=8.8 Hz, 1H), 8.29 (s, 1H), 8.50 (d, J=4.8 Hz, 1H). 13C NMR (DMSO-d6, 100 MHz): 529.93, 34.74, 101.50, 110.41, 111.15, 111.77, 113.13, 115.70, 116.34, 116.37, 119.21, 119.82, 120.12, 121.11, 121.53, 121.78, 121.84, 123.20, 125.19, 125.90, 127.58, 131.12, 136.01, 137.97, 139.42, 139.91, 141.08, 149.34, 150.61, 155.25, 158.09, 162.96.
