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

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Reaction Steps

7-Fluoro-1-methylamino-8-(3-methyl-1-piperazinyl)-4-oxo-1,4-dihydro-benzo[b][1,8]naphthyridine-3-carboxylic acid is prepared under the conditions of Reference Example 5 but starting from 3.2 g of 8-chloro-7-fluoro-1-methylamino-4-oxo-1,4-dihydro-benzo[b][1,8]naphthyridine-3-carboxylic acid and 4 g of 2-methylpiperazine in 40 cm3 of pyridine. The crude product obtained is taken up in 30 cm3 of water and 7 cm3 of 2N aqueous potassium hydroxide solution. A very small amount of insoluble matter is removed by filtration through diatomaceous silica. The filtrate is washed with twice 20 cm3 of diethyl ether and the product is then precipitated by adding 3.5 cm3 of 4N methanesulphonic acid. The precipitate obtained is drained and washed with 3 times 20 cm3 of water and 3 times 20 cm3 of ethanol 2.2 g of 7-fluoro-1-methylamino-8-(3-methyl-1-piperazinyl)-4-oxo-1,4-dihydro-benzo[b][1,8]naphthyridine-3-carboxylic acid are obtained in the form of a deep yellow solid melting at 343°-345° C., solvated by 3.7% of water.

Provenance & Evidence