Hydrochloric Acid → Nadifloxacin

Participants

Reaction Conditions

Reaction Steps

A mixture of 6.6 g of 5-(4-hydroxy-1-piperidyl)-6-fluoro-2-methyl-1,2,3,4-tetrahydroquinaldine and 6.0 g of diethyl ethoxymethylenemalonate was reacted by heating at 160° C. for 30 minutes. Then, 48 g of polyphosphoric acid prepared from 24 g of phosphorus pentoxide and 24 g of phosphoric acid was added thereto and the resulting mixture was reacted by heating at 150°-160° C. for 1 hour. After completion of the reaction the reaction mixture was poured into 150 g of ice water. Precipitations which formed were collected by filtration, washed with water and dried. To the crystals thus obtained were added 70 ml of a 10% aqueous sodium hydroxide solution and the mixture was reacted at 100°-110° C. for 1 hour. After cooling, the reaction mixture was rendered acidic with concentrated hydrochloric acid to precipitate crystals, which then were collected by filtration, washed with water and recrystallized from ethanol-water to give 440 mg of 8-(4-hydroxy-1-piperidyl)-9-fluoro-5-methyl-6,7-dihydro-1-oxo-1H,5H-benzo[ij]quinolizine-2-carboxylic acid. m.p. 244°-247° C.

Provenance & Evidence