Acetic Acid → (RS)-7,9-difluoro-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 suspension of (RS)-3-ethoxycarbonyl-7,9-difluoro-1-methyl-4-oxo-8-(3-phenyl-1-piperazinyl)-1,4-dihydrobenzo[b][1,8]naphthyridine (2 g) in ethanol (25 cc) and N aqueous potassium hydroxide (15 cc) is heated with stirring to a temperature in the region of 75° C. for 2 hours. The solution obtained, at approximately 75° C., is treated with 10% strength aqueous acetic acid solution (9 g). The insoluble matter obtained is drained at a temperature in the region of 75° C. and washed with water (3×30 cc) at approximately 20° C. After 1 recrystallization in dimethylformamide (40 cc), (RS)-7,9-difluoro-1-methyl-4-oxo-8-(3-phenyl-1-piperazinyl)-1,4-dihydrobenzo[b][1,8]naphthyridine-3-carboxylic acid (1.5 g) is obtained in the form of an orange-colored solid, m.p. 298° C.

Provenance & Evidence