A 50-mL single-neck round-bottomed flask equipped with a magnetic stirred and a reflux condenser was charged with 5-ethylisoxazol-3-amine (250 mg, 2.23 mmol), 3,5-dibromo-1-methylpyridin-2(1H)-one (893 mg, 3.35 mmol), Pd2(dba)3 (102 mg, 0.112 mmol), Xantphos (129 mg, 0.223 mmol), Cs2CO3 (1.45 g, 4.46 mmol), and dioxane (20 mL). The system was subjected to three cycles of vacuum/nitrogen flush and heated at 100° C. under N2 protection for 3 h. Analysis of the reaction mixture by LCMS showed complete conversion to the desired product. It was then cooled to room temperature and filtered. The filtrate was concentrated under reduced pressure and the residue was purified by reverse-phase prep-HPLC to afford 158a (300 mg, 45%) as a white solid. MS-ESI: [M+H]+ 297.8
