Ethanol → Ethyl 6-fluoro-7-(3-trifluoroacetylamino-1-pyrrolidinyl)-1,4-dihydro-4-oxo-1-vinyl-1,8-naphthyridine-3-carboxylate

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Reaction Steps

A mixture of 3-trifluoroacetylaminopyrrolidine (5.46 g), ethanol (60 ml) and triethylamine (3 g) was added to ethyl 7-chloro-6-fluoro-1,4-dihydro-4-oxo-1-vinyl-1,8-naphthyridine-3-carboxylate (5.93 g) obtained according to Reference Example 1. The mixture was heated under reflux for one hour. After ice-cooling, the resulting crystals were collected by filtration and washed with ethanol. Recrystallization of the crude crystals from ethanol-chloroform gave 7.5 g of ethyl 6-fluoro-7-(3-trifluoroacetylamino-1-pyrrolidinyl)-1,4-dihydro-4-oxo-1-vinyl-1,8-naphthyridine-3-carboxylate, m.p. 280°-282° C. A solution of the compound (4.4 g) thus obtained in 1 N sodium hydroxide (80 ml) was stirred for 2 hours at 60° C. At the same temperature the mixture was adjusted to pH 7-8 by addition of acetic acid. After ice-cooling, the resulting crystals were collected by filtration, washed with water, and dissolved in hot 10% acetic acid, followed by treating with charcoal.

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