8-Chloro-3-ethoxycarbonyl-7-fluoro-1-methyl-4-oxo-1,4-dihydro-benzo[b][1,8]naphthyridine → 8-Chloro-7-fluoro-1-methyl-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine-3-carboxylic acid

Beteiligte Stoffe

Reaktionsschritte

A suspension of 15 g of 8-chloro-3-ethoxycarbonyl-7-fluoro-1-methyl-4-oxo-1,4-dihydro-benzo[b][1,8]naphthyridine in 150 cm3 of acetic acid and 150 cm3 of hydrochloric acid as a 17.5% aqueous solution is heated at a temperature close to 100° C., with stirring, for 4 hours. After cooling to a temperature close to 20° C., the product is drained and washed with twice 150 cm3 of ethanol and then twice 100 cm3 of diethyl ether. 12.7 g of 8-chloro-7-fluoro-1-methyl-4-oxo-1,4-dihydro-benzo[b][1,8]naphthyridine-3-carboxylic acid are obtained in the form of a beige solid which sublimes at 400°-405° C. and is used for the subsequent steps without further purification.

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