2-Chloro-3-[2,2,2-trifluoro-1-(pyridin-3-yl)ethoxy]-quinoxaline (Compound BJ) (73 mg, 0.21 mmol) was dissolved in dimethyl sulfoxide (2 mL). To this, benzenesulfonamide (33 mg, 0.21 mmol) and potassium carbonate (29 mg, 0.21 mmol) were added at room temperature and the mixture was stirred at 150° C. for 2 hours. The reaction mixture was allowed to cool down to room temperature, a 1% aqueous acetic acid solution (20 mL) was added thereto, and the precipitate was collected by filtration. The obtained solid was subjected to slurry purification using methanol, to give N-{3-[2,2,2-trifluoro-1-(pyridin-3-yl)ethoxy]quinoxalin-2-yl}benzenesulfonamide (Compound 137) (31 mg, 320).
