Formaldehyde → 1-Ethyl-6-fluoro-1,4-dihydro-7-(4-methyl-1-piperazinyl)-4-oxo-1,8-naphthyridine-3-carboxylic acid

Beteiligte Stoffe

Reaktionsschritte

To a solution of 37% formalin (12 ml) and formic acid (18 ml) was added 6.0 g of 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-1,8-naphthyridine-3-carboxylic acid, and the mixture was heated at 120°-125° C. for 4 hours with stirring. The mixture was then concentrated to dryness under reduced pressure. The residue was adjusted to pH 8 by addition of aqueous 7% sodium bicarbonate, and extracted with chloroform. The extract was dried and the solvent was evaporated. The crystalline residue was recrystallized from a mixture of dichloromethane and ethanol to give 5.0 g of 1-ethyl-6-fluoro-1,4-dihydro-7-(4-methyl-1-piperazinyl)-4-oxo-1,8-naphthyridine-3-carboxylic acid, m.p. 228°-230° C.

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