Water (0.60 mL), 2-thiopheneboronic acid (34 mg), sodium carbonate (70 mg), and tetrakis(triphenylphosphine)palladium(0) (13 mg) were added to an ethylene glycol dimethyl ether (2.0 mL) suspension of tert-butyl 4-bromo-2-(5-phenylpyridine-3-carboxamido)benzoate (0.10 g), followed by heating to reflux under a nitrogen atmosphere for 2 hours. The reaction mixture was cooled to room temperature, and then ethyl acetate and a 10% aqueous solution of citric acid were added thereto. The organic layer was separated, washed with a saturated aqueous solution of sodium chloride, and dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The obtained residue was purified by silica gel column chromatography [Kanto Chemical Co., Inc., silica gel 60 (spherical), eluent: 95-85% hexane/ethyl acetate] to obtain tert-butyl 2-(5-phenylpyridine-3-carboxamido)-4-(thiophen-2-yl)benzoate.
