Hydrochloric Acid → (RS)-7-fluoro-1-methyl-4-oxo-8-(3-phenyl-1-piperazinyl)-1,4-dihydrobenzo[b][1,8]naphthyridine-3-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

A solution of (RS)-3-ethoxycarbonyl-7-fluoro-1-methyl-4-oxo-8-(3-phenyl-1-piperazinyl)-1,4 -dihydrobenzo[b][1,8]naphthyridine (1.07 g) in acetic acid (10 cc) and 17.5% strength aqueous hydrochloric acid solution (10 cc) is heated to a temperature in the region of 100° C. for 40 minutes. The reaction mixture is concentrated to dryness under reduced pressure (20 kPa) at approximately 60° C. The dry extract is taken up with ethanol (10 cc), drained and washed with ethanol (2×10 cc) and ethyl ether (2×10 cc). The solid obtained is suspended in water (30 cc) and heated to a temperature in the region of 95° C. After the addition of 2 N aqueous potassium hydroxide (1.35 cc) and stirring for 30 minutes, the solid is drained at approximately 95° C. and washed with water (3×20 cc) at approximately 80° C., ethanol (3×15 cc) at approximately 60° C. and ethyl ether (3×20 cc). After 1 recrystallization in a mixture of dimethylformamide (12 cc) and ethanol (6 cc), (RS)-7-fluoro-1-methyl-4-oxo-8-(3-phenyl-1-piperazinyl)-1,4-dihydrobenzo[b][1,8]naphthyridine-3-carboxylic acid (0.7 g) is obtained in the form of a yellow solid, m.p. 265° C.

Provenance & Evidence