A mixture of N′-[(3,4-difluorophenyl)acetyl]-3-methoxy-4-(2-methyl-1,3-oxazol-5-yl)benzohydrazide (4.69 g), carbon tetrachloride (2.24 mL) and triphenylphosphine (12.3 g) in acetonitrile (117 mL) was stirred at 80° C. for 2 hr. The mixture was allowed to cool to room temperature, the precipitate was filtered off, and the filtrate was concentrated. Water was added to the residue, and the mixture was extracted with ethyl acetate. The extract was dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (ethyl acetate). Ethyl acetate was added to the obtained crude product, the precipitate was filtered off, and the filtrate was concentrated. Acetonitrile was added to the obtained residue, and the resultant precipitate was collected by filtration to give the title compound (2.41 g).
