Ethyl 6,7-difluoro-8-methoxy-4-oxo-1-(2,2,2-trifluoroethyl)-1,4-dihydroquinoline-3-carboxylate → 6,7-Difluoro-8-methoxy-4-oxo-1-(2,2,2-trifluoroethyl)-1,4-dihydroquinoline-3-carboxylic acid

Participants

Reaction Steps

800 mg (2.19 mmol) of the compound of Example 23A are provided in a mixture of 25 ml of acetic acid-water-sulfuric acid 12:8:1 and stirred over night under reflux. For the work-up the solvent is removed to a large extent on a rotary evaporator, the residue is adjusted carefully to pH 3 while cooling with ice with a saturated sodium hydrogen carbonate solution, the suspension is diluted with water, the precipitate is collected by suction filtration and after drying the filter residue under high vacuum, 575 mg of the title compound are obtained.

Provenance & Evidence