Hydrochloric Acid → 6-(2-(2,4-Difluorophenyl)-5,6-dihydro-4H-pyrrolo[1,2-b]pyrazol-3-yl)-3-isopropyl-[1,2,4]triazolo[4,3-b]pyridazine

Participants

Reaction Steps

A mixture of 1-(2,4-difluorophenyl)-2-(3-isopropyl-[1,2,4]triazolo[4,3-b]pyridazin-6-yl)ethanone (0.20 g, 0.63 mmol, Preparation #K.1), 1-aminopyrrolidin-2-one hydrochloride (0.13 g, 0.95 mmol, prepared according to WO02/094833 Preparation #38), pyridine (0.15 mL, 1.9 mmol), and HOAc (1.2 mL) was sonicated to give a solution in a sealed vial. After stirring for about 16 h, additional 1-aminopyrrolidin-2-one hydrochloride (0.086 g, 0.632 mmol) was added and the resulting solution was stirred at ambient temperature for about 2 d. The reaction was then concentrated under reduced pressure and purified via silica gel chromatography eluting with a gradient of 0-5% MeOH in DCM to give impure 1-(1-(2,4-difluorophenyl)-2-(3-isopropyl-[1,2,4]triazolo[4,3-b]pyridazin-6-yl)ethylideneamino)pyrrolidin-2-one (0.16 g) as an oil that was carried on without further purification. A 10 mL round-bottomed flask equipped with reflux condenser and outfitted with a nitrogen inlet adapter was charged with 1-(1-(2,4-difluorophenyl)-2-(3-isopropyl-[1,2,4]triazolo[4,3-b]pyridazin-6-yl)ethylideneamino)pyrrolidin-2-one (0.060 g, 0.15 mmol) in toluene (1.5 L) to give a yellow solution. Sodium ethoxide (0.020 g, 0.30 mmol) was added in one portion to give a yellow suspension. The reaction mixture was heated to reflux for about 5 h. The reaction mixture was allowed to cool to ambient temperature and continued stirring for about 2 d. The reaction mixture was diluted with water (5 mL) adjusted to about pH 2 with 6 N HCl. The aqueous layer was extracted with EtOAc. The combined organic extracts were dried with MgSO4, filtered, and concentrated under reduced pressure. The resulting residue was purified via silica gel chromatography eluting with a gradient of 0-10% MeOH in DCM. The product-containing fractions were concentrated under reduced pressure and the resulting material was crystallized from EtOAc/heptane to give the title compound (0.031 g, 54%) as orange needles: LC/MS (Table 1, Method b) Rt=2.44 min; MS m/z: 381.4 (M+H)+.

Provenance & Evidence