1,3-Dibromo-5,5-dimethylhydantoin → 3'-Bromo-2,2,2-trifluoro-5'-(trifluoromethyl)acetophenone

To a solution of 5.00 g of 2,2,2-trifluoro-5′-(trifluoromethyl)acetophenone in 1 mL of acetic acid and 6 mL of concentrated sulfuric acid, 3.54 g of 1,3-dibromo-5,5-dimethylhydantoin was added and the resultant mixture was stirred at 35° C. for 3.5 hours. After the completion of the reaction, the reaction mixture was charged into 60 mL of ice water and the resultant mixture was extracted with chloroform (30 mL×2). The organic phase was washed with a saturated sodium hydrogen carbonate aqueous solution (50 mL×1) and then dehydrated and dried over saturated saline and anhydrous magnesium sulfate in this order, and the solvent was distilled off under reduced pressure. The resultant residue was dissolved in 20 mL of hexane and an insoluble substance was filtered off, followed by distilling off the solvent under reduced pressure to obtain 6.50 g of the objective substance as a yellow oily substance. This substance was used in the next process as it was without being further purified.