Water (15 mL), sodium carbonate (4.6 g), 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)isoquinoline (5.1 g), and bis(triphenylphosphine)palladium(II) dichloride (0.24 g) were added to an ethylene glycol dimethyl ether (50 mL) solution of tert-butyl 4-bromo-2-nitrobenzoate (5.0 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 water 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 [eluent: 85-75% hexane/ethyl acetate] to obtain 5.8 g of tert-butyl 4-(isoquinolin-4-yl)-2-nitrobenzoate as a brown oily substance.
