Phosphorus oxychloride → 7-Chloro-1-ethyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylic acid

Participants

Reaction Steps

A mixture containing 16 g of 1-ethyl-6-fluoro-7-hydroxy-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid and 160 ml of phosphoryl chloride was heated under reflux for 20 minutes with stirring. After evaporation of excess phosphoryl chloride under reduced pressure, the residue was triturated with ice-water and the mixture was stirred for 20 minutes. The resulting precipitate was collected by filtration, washed with water, dried, and recrystallized from acetonitrile to give 14 g of 7-chloro-1-ethyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid, m.p. 265°-267° C.

Provenance & Evidence