Potassium tert-butoxide → Ethyl 1-cyclopropyl-6,7-difluoro-4-oxo-1,4-dihydroquinoline-3-carboxylate

A solution of 7.2 g (22 mmol) of ethyl 2-(2,4,5-trifluoro-5-methylbenzoyl)-3-cyclopropylaminoacrylate in 100 ml of dry t-butanol was treated portionwise with 2.8 g (25 mmol) of potassium t-butoxide, and the reaction mixture was stirred at 60° C. for five hours. The suspension was cooled to room temperature and concentrated. The residue was partitioned between dichloromethane and 1N hydrochloric acid; the organic phase was washed with water, dried over magnesium sulfate, and concentrated. The crude product was slurried in boiling ethanol, filtered, and air-dried to give 4.2 g of the title compound.