A 500-mL single-neck round-bottomed flask equipped with a magnetic stirrer and a reflux condenser was charged with 1,4-dioxane (100 mL), 1,2,4-triazin-3-amine (1.5 g, 15.6 mmol), 3,5-dibromo-1-methylpyridin-2(1H)-one (4.2 g, 15.6 mmol), Pd2(dba)3 (458 mg, 1.56 mmol), XantPhos (1.8 g, 3.12 mmol), and cesium carbonate (10 g, 31.2 mmol). After three cycles of vacuum/argon flush, the mixture was stirred at 90° C. for 2.5 h. After this time the reaction was filtered and the filtrate was evaporated in vacuo. The resulting residue was recrystalized from ethyl acetate to afford 172a as a yellow solid (1.76 g, 40%). MS-ESI: [M+H]+ 282.
