Hydrochloric Acid → 6-chloro-4-(5-methyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazin-2-ylamino)pyridazin-3(2H)-one

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Reaction Steps

A 50-mL single-neck round-bottomed flask equipped with a magnetic stirrer, reflux condenser and nitrogen inlet was charged with 1,4-dioxane (5.0 mL), 5-methyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazin-2-amine 101l (152 mg, 1.00 mmol), 4-bromo-6-chloropyridazin-3(2H)-one (209 mg, 1.00 mmol) and a 1 M THF solution of LiHMDS (5.0 mL, 5.00 mmol). After bubbling nitrogen through the resulting solution for 30 min, Xantphos (49 mg, 0.05 mmol) and tris(dibenzylideneacetone)dipalladium(0) (59 mg, 0.085 mmol) were added, and the reaction mixture was heated at reflux for 3 h. After this time, the reaction was cooled to room temperature, and water (10 mL) was added. The pH was adjusted to 6.5 with 2 N hydrochloric acid. The resulting precipitate was collected by vacuum filtration, washed with water (2×25 mL), absorbed on silica gel and purified by flash chromatography to afford a 74% yield (210 mg) of 6-chloro-4-(5-methyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazin-2-ylamino)pyridazin-3(2H)-one 101m as a light brown solid: 1H NMR (300 MHz, DMSO-d6) δ 12.94 (s, 1H), 9.55 (s, 1H), 7.68 (s, 1H), 5.96 (s, 1H), 4.04 (t, 1H, J=5.7 Hz), 3.53 (s, 2H), 2.82 (t, 2H, J=5.7 Hz), 2.36 (s, 3H); MS (ESI+) m/z 281.1 (M+H).

Provenance & Evidence