[1,1′-Bis(diphenylphosphino)ferrocene]dichloropalladium(II) (69.0 mg, 0.0950 mmol) was added to a stirred solution of 5a (1.45 g, 3.16 mmol), 3,6-dichloropyridazine (660 mg, 4.43 mmol) and sodium carbonate (3.20 mL of a 2.0 M aqueous solution, 6.32 mmol) in EtOH:toluene (10.0 mL of an 80:20 mixture, respectively) at rt. The resulting solution was heated to 95° C. for approximately 4 h. After cooling to rt, the reaction mixture was filtered through a short column of CELITE®, eluting with EtOAc. The filtrate was washed with water, brine, dried (sodium sulfate) and concentrated in vacuo. The crude residue was purified by flash chromatography on silica gel (gradient elution; 20%-80% EtOAc/hexanes as eluent) to furnish the title compound 5b. m/z (ES) 445 (MH)+. 1HNMR (500 MHz, CDCl3): δ 8.63 (d, 1H, J=4.1 Hz), 8.41 (d, 1H, J=1.8 Hz), 7.96 (d, 2H, J=8.7 Hz), 7.80 (d, 1H, J=8.9 Hz), 7.76 (dt, 1H, J=1.7, 7.7 Hz), 7.53 (m, 4H), 7.27 (dd, 1H, J=5.1, 7.1 Hz), 7.19 (m, 2H), 5.24 (s, 2H), 3.11 (m, 1H, J=6.7 Hz), 1.61 (s, 3H), 0.89 (d, 3H, J=6.6 Hz), 0.83 (d, 3H, J=6.9 Hz).
