Reaction Steps
Ethyl 1-[(6-methyl-2,3′-bipyridin-5-yl)methyl]-4-thioxo-1,4-dihydropyrido[2,3-c]pyridazine-3-carboxylate [(Example 6, Step 2), 125 mg, 0.299 mmol], (±)-tetrahydro-2H-pyran-3-ylhydrazine hydrochloride (91.0 mg, 0.599 mmol, 2 equiv) and potassium carbonate (414 mg, 2.99 mmol, 10 equiv) were combined in ethanol (10 mL), N,N′-dimethylformamide (3 mL) and dioxane (5 mL) at ambient temperature and after 5 minutes, were warmed to 80° C. for 4 hours. The mixture was cooled to ambient temperature, poured into sodium bicarbonate (100 mL, aqueous saturated) and extracted with ethyl acetate (2×100 mL). The combined organic extracts were dried with sodium sulfate, filtered and concentrated in vacuo. The residue was purified by silica gel gradient chromatography (100:0 to 0:100; hexanes:ethyl acetate containing 10% methanol), providing the titled compound as a deep red solid: 1H-NMR (400 MHz, CDCl3) δ 9.02 (1H, d, J=2.1 Hz), 8.93 (1H, d, J=2.3 Hz), 8.75 (1H, dd, J=4.6, 1.8 Hz), 8.51 (1H, dd, J=8.1, 1.8 Hz), 8.16 (1H, dd, J=8.1, 2.4 Hz), 7.97 (1H, dd, J=8.2, 2.3 Hz), 7.66 (1H, dd, J=8.2, 0.6 Hz), 7.50 (1H, dd, J=7.9, 4.6 Hz), 7.24 (1H, d, J=8.1 Hz), 5.97 (1H, br s), 4.70-4.62 (1H, m), 4.01-3.94 (2H, m), 3.74 (1H, ap t, J=10.7 Hz), 3.49 (1H, br m), 3.45 (1H, dd, J=11.1, 3.4 Hz), 2.60 (3H, s), 2.21-2.05 (3H, m) ppm; high resolution mass spectrometry (ES+) m/z 454.1984 [(M+H)+; calculated for C25H24N7O2: 454.1986].
