Under argon atmosphere, a solution of tert-butyl 6-bromo-2H-1-benzopyran-3-carboxylate (5.00 g), 4-methylphenyl borate (2.62 g) and potassium carbonate (4,44 g) in toluene-ethanol-water (160-16-16 ml) was stirred at room temperature for 1 hour. To the reaction mixture was added tetrakistriphenylphosphinepalladium (0.56 g), and the mixture was refluxed for 14 hours and cooled to room temperature. The organic layer was washed with saturated sodium chloride solution, dried with magnesium sulfate and concentrated. The residue was separated and purified with column chromatography (ethyl acetate/hexane=1:19) to give pale yellow crystals, which were recrystallized from ethanol to give tert-butyl 6-(4-methylphenyl)-2H-1-benzopyran-3-carboxylate (3.84 g) as pale yellow crystals.
