To a suspension of 5-bromopyridine-2-carbonyl chloride (10.11 g, 46 mmol), N-phenyl-1,2-diaminobenzene (8.46 g, 46 mmol) in anhydrous dichloromethane (DCM) (100 mL), was added triethylamine (TEA) at 0° C. Then the whole was stirred at room temperature (RT) for about 20 hours. The mixture was poured into water, extracted with dichloromethane (100 mL×2). The organic phase was collected, dried over sodium sulfate (Na2SO4), and passed through a pad of silica gel (hexanes/ethyl acetate 4:1). After removal of solvent, a brown oil was obtained, which was dissolved in dioxane (150 mL), phosphoryl chloride (POCl3) (25 mL) was added at 0° C., and the mixture was then heated at about 100° C. under argon overnight. Then the whole was poured into ice (200 g) after being cooled to RT, then neutralized by sodium carbonate (Na2CO3), and extracted with dichloromethane (DCM) (200 mL×2). The organic phase was dried over Na2SO4, absorbed on silica gel, and purified by a silica gel column (hexanes/ethyl acetate 4:1). The desired fraction was collected, concentrated, and reprecipitated with hexanes. After filtration and being washed with methanol, an off-white crystalline solid (Compound 1) was obtained, 4.02 g, with an overall 25% yield.
