Dimethylformamide → 6-(2-(2,4-Difluorophenyl)-6,7-dihydro-5H-pyrrolo[1,2-a]imidazol-3-yl)-3-isopropyl-[1,2,4]triazolo[4,3-b]pyridazine

Participants

Reaction Conditions

Reaction Steps

A 250 mL three-neck round bottom flask was charged with 2-(2,4-difluorophenyl)-3-iodo-6,7-dihydro-5H-pyrrolo[1,2-a]imidazole (5.00 g, 14.4 mmol) in THF (38 mL) to give a brown suspension. The suspension was cooled to about −30° C., followed by the drop-wise addition of a i-PrMgCl (2.0 M in THF, 8.70 mL, 17.3 mmol) over about 8 min. The reaction mixture was then stirred at about −20° C. for about 30 min. In a separate 50 mL round bottom flask were combined zinc chloride (2.56 g, 18.8 mmol) and THF (23 mL) with stirring. The clear, colorless solution was added drop-wise to the reaction mixture over about 10 min. The resulting suspension was stirred at about −20° C. for about 30 min. A third round bottom flask was charged with 6-iodo-3-isopropyl-[1,2,4]triazolo[4,3-b]pyridazine (4.16 g, 14.4 mmol, Preparation #H.1) and DMF (38 mL). The mixture was heated in order to fully dissolve the crystalline solid. The resulting yellow solution was rapidly added in one portion to the vigorously stirred reaction mixture, followed by the addition of Pd(PPh3)4 (0.67 g, 0.58 mmol) to the reaction mixture. Upon addition of this hot solution, the reaction mixture was immediately heated to about 80° C. Heating at about 80° C. was continued for about 30 min at which point the mixture was cooled to ambient temperature. The solvents were removed under reduced pressure to give a dark brown residue, which was then dissolved into a minimal volume of DCM (about 100 mL). The organic solution was washed with 1 N HCl (about 300 mL) and the remaining organic solution was then discarded. The aqueous solution containing the product was back-extracted once with DCM (about 75 mL) and then basified with solid Na2CO3. The yellow precipitate that formed was collected by vacuum filtration. The filtrate was then adjusted from pH ˜6 to pH ˜8 with additional solid Na2CO3, resulting in precipitation of additional solid that was also collected by vacuum filtration. The wet filter cake was partially dissolved into DCM and the solid that would not dissolve was removed by filtration and discarded. The organic solution was dried over MgSO4, filtered, and concentrated to dryness to give a dark yellow oil that was purified by flash silica gel chromatography (stepwise gradient, DCM/MeOH/NH4OH 990:9:1 to 980:18:2 to 970:27:3). The product-containing fractions were combined and concentrated to dryness to give a viscous yellow oil. Et2O was added to dissolve the oil and the resulting solution was re-concentrated to give the title compound as a yellow foam (1.4 g, 26%): LC/MS (Table 1, Method a) Rt=2.21 min; MS m/z 381.2 (M+H)+; 1H NMR (400 MHz, DMSO-d6) δ 8.20 (d, 1 H), 7.66 (m, 1 H), 7.34 (m, 1 H), 7.22 (m, 1 H), 6.96 (d, 1 H), 4.38 (m, 2 H), 3.55 (m, 1 H), 2.92 (m, 2 H), 2.64 (m, 2 H), 1.41 (d, 6 H).

Provenance & Evidence