Triethylamine → Ethyl 1-(2,4-difluorophenyl)-6-fluoro-1,4-dihydro-7-(2-nitrobenzenesulfonyloxy)-4-oxo-1,8-naphthyridine-3-carboxylate

Participants

Reaction Steps

In 30 ml of methylene chloride was suspended 3.00 g of ethyl 1-(2,4-difluorophenyl)-6-fluoro-1,4-dihydro-7-hydroxy-4-oxo-1,8-naphthyridine-3-carboxylate, and 1.02 g of triethylamine and 2.20 g of ortho-nitrobenzenesulfonyl chloride were added thereto with ice-cooling, after which the resulting mixture was subjected to reaction at the same temperature for 30 minutes and then at room temperature for 6 hours. The reaction mixture was washed with three 50-ml portions of water and then dried over anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure, and to the residue thus obtained was added a mixture of 6 ml of ethyl acetate and 12 ml of diethyl ether, after which the crystals thus despotied were collected by filtration to obtain 4.40 g (yield 97.2%) of ethyl 1-(2,4-difluorophenyl)-6-fluoro-1,4-dihydro-7-(2-nitrobenzenesulfonyloxy)-4-oxo-1,8-naphthyridine-3-carboxylate having a melting point of 157°-160° C.

Provenance & Evidence