Piperazine → 7-Fluoro-1-methylamino-4-oxo-8-(1-piperazinyl)-1,4-dihydro-benzo[b][1,8]naphthyridine-3-carboxylic acid

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Reaction Steps

7-Fluoro-1-methylamino-4-oxo-8-(1-piperazinyl)-1,4-dihydro-benzo[b][1,8]naphthyridine-3-carboxylic acid is prepared under the conditions of Reference Example 5 but starting from 2.25 g of 8-chloro- 7-fluoro-1-methylamino-4-oxo-1,4-dihydro-benzo[b][1,8]naphthyridine-3-carboxylic acid and 2.4 g of piperazine in 30 cm3 of pyridine. After recrystallizing 3 times from, in total, 400 cm3 of dimethylformamide, 0.82 g of 7-fluoro-1-methylamino-4-oxo-8-(1-piperazinyl)-1,4-dihydro-benzo[b][1,8]naphthyridine-3-carboxylic acid is obtained in the form of a deep yellow solid melting at 322°-324° C., solvated by 13.6% of dimethylformamide.

Provenance & Evidence