Cesium carbonate → 6-Chloro-2-methyl-4-(5-methyl-1H-pyrazol-3-ylamino)pyridazin-3(2H)-one

Participants

Reaction Steps

A 100-mL single-neck round-bottomed flask equipped with a magnetic stirrer and a reflux condenser was charged with 1,4-dioxane (20 mL), 5-ethyl-1H-pyrazol-3-amine (971 mg, 10.0 mmol), 4-bromo-6-chloro-2-methylpyridazin-3(2H)-one (2.46 g, 11.0 mmol), and cesium carbonate (6.52 g, 20.0 mmol). After bubbling nitrogen through the suspension for 10 minutes, xantphos (1.74 g, 3.0 mmol) and tris(dibenzylideneacetone)dipalladium(0) (1.37 g, 1.5 mmol) were added. The system was subjected to three cycles of vacuum/argon flush and heated at reflux for 2 h. It was then filtered immediately when the reaction mixture was still hot. The solid was washed with dioxane (3×30 mL) and the combined filtrate was concentrated under reduced pressure. The residue was purified by silica-gel chromatography eluting with 6:1 petroleum ether/ethyl acetate to afford 127a (1.8 g, 75%) as a yellow solid. MS-ESI: [M+H]+ 239.9

Provenance & Evidence