6-Bromo-2-cyclopropyl-7-fluoro-5-methyl-1,3-benzoxazole-4-carbonitrile (I-77) (8.88 g, 30.08 mmol) was dissolved in toluene (130 ml), then tributyl(1-ethoxyvinyl)tin (11.2 ml, 33.09 mmol) and 2,6-di-tert-butylcresol (66 mg, 0.30 mmol) and bis(triphenylphosphine)palladium(II) dichloride (1.06 g, 1.50 mmol) were added, followed by heating under reflux for 17 hours under nitrogen atmosphere. The reaction liquid was cooled, the insoluble matter was separated by filtration through Celite, the solvent was concentrated under reduced pressure. The resulting residue was subjected to silica gel column chromatography, followed by removing tin-derived side products with n-hexane and by elution with a mixed solvent of n-hexane/ethyl acetate (7:1, v/v) to obtain the a crude product (9.34 g, quant.) as a yellow white solid.
