Cesium carbonate → 5-Bromo-3-(6,7-dihydro-4H-pyrazolo[5,1-c][1,4]oxazin-2-ylamino)-1-methylpyridin-2(1H)-one

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Reaction Steps

A 50-mL three-neck round-bottomed flask equipped with a magnetic stirrer, reflux condenser and nitrogen inlet was charged with 1,4-dioxane (20 mL), 131b (600 mg, 4.31 mmol), 3,5-dibromo-1-methylpyridine-2(1H)-one (1.44 g, 5.40 mmol) and cesium carbonate (3.08 g, 9.48 mmol). After bubbling nitrogen through the resulting solution for 30 min, Xantphos (300 mg, 0.52 mmol) and tris(dibenzylideneacetone)dipalladium(0) (320 mg, 0.35 mmol) were added, and the reaction mixture was heated at reflux for 2 h. After this time the reaction was cooled to room temperature, partitioned between ethyl acetate (75 mL) and water (75 mL) and filtered. The aqueous layer was separated and extracted with ethyl acetate (2×25 mL). The organic layers were combined and washed with brine (50 mL) and dried over sodium sulfate. The drying agent was removed by filtration and the filtrate concentrated under reduced pressure. The resulting residue was purified by column chromatography using 500 cc of silica gel and eluting with 1% methanol in methylene chloride. The fractions were collected to afford, after concentrating under reduced pressure, a 31% yield (433 mg) of 131c as a green solid: mp 195-197° C.; 1H NMR (300 MHz, CDCl3) 7.92 (d, 1H, J=2.4 Hz), 7.44 (s, 1H), 6.90 (d, 1H, J=2.4 Hz), 5.65 (s, 1H), 4.80 (s, 2H), 4.13 (s, 2H), 3.61 (s, 5H); MS (ESI+) m/z 324.9 (M+H).

Provenance & Evidence