Hydrochloric Acid → 5-Amino-1-cyclopropyl-6,7-difluoro-8-methyl-4-oxo-1,4-dihydroquinoline-3-carboxylic acid

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Reaction Steps

A mixture of 14.8 g of ethyl 5-amino-1-cyclopropyl-6,7-difluoro-1,4-dihydro-8-methyl-4-oxoquinoline-3-carboxylate, 150 ml of 90% acetic acid, and 37.2 ml of conc. hydrochloric acid was heated under reflux for 2 hours. The crystals precipitated were collected by filtration and washed with water to give 11.8 g of yellow crystals. The crystals were recrystallized from N,N-dimethylformamide to give yellow crystals, m.p. 290.5° C. (decomp.).

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