5-Bromo-1-(phenylsulfonyl)-1H-pyrrole-3-carbaldehyde (2.67 g), (2-chloropyridin-3-yl)boronic acid (2.00 g), sodium hydrogen carbonate (2.15 g) and tetrakis(triphenylphosphine)palladium (738 mg) were added to a deaerated mixture of 1,2-dimethoxyethane (40 mL) and water (10 mL), and the mixture was stirred under a nitrogen atmosphere at 80° C. for 5 hr. The reaction mixture was allowed to cool, saturated aqueous sodium hydrogen carbonate solution was added, and the mixture was extracted with ethyl acetate. The extract was washed with saturated brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: hexane-ethyl acetate=4:1→1:1). The obtained pale-yellow oil was dissolved in methanol (15 mL) and tetrahydrofuran (15 mL), 8 mol/L aqueous sodium hydroxide solution (15 mL) was added dropwise at room temperature and the mixture was stirred for 30 min. The reaction mixture was diluted with saturated brine, and extracted with ethyl acetate. The extract was washed with saturated brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. Ethyl acetate was added to the residue and insoluble crystals were collected by filtration to give the title compound as brown crystals (yield 578 mg, 33%).
